Assisted Migration (Assisted Colonization, Managed Relocation, Translocation) and Rewilding of Plants and Animals in an Era of Rapid Climate Change


EDITOR'S NOTE: This annotated and linked list of online-accessible papers, articles, and news reports on assisted migration (aka: assisted colonization / colonisation, translocation, managed relocation, facilitated migration, and "neo-natives") aims to further professional and popular understanding of the substance and history of debate and actions regarding one of the most significant developments in conservation biology, forestry, and natural resources management. This lengthy list is continually updated; entries are ordered by topic, with longer excerpts given for papers of high academic importance, insight into shifting conservation values, expansive treatment of the issue, and provision of background understanding.

The FORESTRY section differs from the CONSERVATION BIOLOGY section in that foresters are accustomed to "managing" landscapes, so there has been little debate about whether to engage in assisted migration (which is their preferred term). Rather, the focus is on species-by-species details of how to accomplish it. For readers focused on forestry in the USA, go directly to the excerpts here of the Assisted Migration subsection of a 289-page (77 scientist contributors) 2016 technical report of the U.S. Forest Service.

Note: The volunteer editor and webmaster, Connie Barlow (founder of Torreya Guardians), urges authors, agencies, and publishers to remove paywall barriers. Contributions, such as those listed below, to improve climate adaptation methods must become freely available to researchers, managers, and citizen activists in all nations and to the public at large.

Click to advance to each theme (or do an internal "Find" for a topic or year of your choice).

  • Key Charts and Papers (short list for all to begin here)
  • Society, Values, and Communications (incl. Science & Society field)
  • Ethics, Law, and History
  • Urban Ecology Assisted Migration (emphasis on trees)
  • Paleoecology and Biogeography (focus on Pleistocene range shifts as guidance for assisted migration)
  • Conservation Biology Assisted Colonization (this is a lengthy section)
  • Vertebrate Assisted Migration / Translocation
  • Pleistocene Rewilding and Taxon Substitution for Ecological Restoration

  • FORESTRY Assisted Migration (focus on North America; this is a very lengthy section).
          • KEY REVIEW ARTICLES in forestry    • Paleoecology Specific to Forestry
          • Canada    • Europe     • USA    • Mexico
          • Maps of USA Tree Species Future Ranges (US Forest Service)
          • MapleSpruceLarchDouglas Fir & Ponderosa PineYellow CedarBlack Ash
          • Brewer SpruceRedwood + SequoiaArizona CypressJoshua TreeChestnutMagnolia sp.
          • AspenWhite PineOyamel Fir

  • Inspiration: classic 30-minute allegorical tale, VIDEO: "The Man Who Planted Trees" (by Jean Giono, 1953)

    * * * * *

    HISTORY OF THIS WEBPAGE: This annotated scholarly links webpage was initiated in 2007, when journalist Douglas Fox published in Conservation Magazine a cover story: "When World's Collide". The citizen-led assisted migration actions of Torreya Guardians was the introductory example in that article, but our effort was presented as just the preview of what would follow as climate change pressed on. Nearly simultaneously, the New York Times posted a story by science writer Carl Zimmer: "A Radical Step to Preserve Species: Assisted Migration". Through 2014, volunteer editor (and founder of Torreya Guardians) Connie Barlow could barely keep up on all the papers and news reports dealing with this utterly new and (to many) disturbing conservation strategy. Using "Google Alerts" to ongoingly learn of new publications has been a great help in recent years for keeping this page up to date, while preserving its complex history.
        As of July 2016 the debate and the publications arising from it have tapered off enormously. "Assisted migration" (by whatever term used) is now a standard entry in revisions to management plans for continuing to conserve lands, waters, and biodiversity in this century of rapid climate change. Assisting native species in moving upslope, poleward, and toward climate refugia is now just one more acceptable tool for moving ahead with "climate adaptation." By far, public and private forestry professionals have moved the fastest and farthest in forecasting when and where native tree species should be given a boost, and implementation is well underway in the forests of Alaska and western Canada (hardest hit by climate change on this continent.) Hence, the above linked table of contents singles out assisted migration as it pertains to forestry.
        Henceforth (from 2016 onward) the occasional highly substantive article will be added within the above list of topics (that blend together all past years). But there will now be an additional category to draw attention to the truly significant papers, analyses, or reports, filed year by year, beginning with . . .

  • 2016



  • IPCC Climate Change Report 2014

    "Impacts, Adaptation, and Vulnerability"

       In the 44-page "SUMMARY FOR POLICYMAKERS" of this multi-volume report, Figure SPM.5, along with its caption and a summary paragraph, refer not only to the possible need for "assisted species migration", which ongoing climate change could necessitate to avert extinction and ecological disruptions, but also points to trees as being the most vulnerable of all life forms — and thus the most in need of human assistance to keep pace with climate zone changes. Trees are represented in the left-most vertical bar in image left, "Maximum speed at which species can move (km per decade)".

    (p. 15) "Many species will be unable to track suitable climates under mid- and high-range rates of climate change during the 21st century (medium confidence). Lower rates of change will pose fewer problems. Some species will adapt to new climates. Those that cannot adapt sufficiently fast will decrease in abundance or go extinct in part or all of their ranges. Management actions, such as maintenance of genetic diversity, assisted species migration and dispersal, manipulation of disturbance regimes (e.g., fires, floods), and reduction of other stressors, can reduce, but not eliminate, risks of impacts to terrestrial and freshwater ecosystems due to climate change, as well as increase the inherent capacity of ecosystems and their species to adapt to a changing climate (high confidence)."

    Editor's Note: The diagram above is generic; specific examples will vary, eg., this troubling report published in a top science journal in July 2015: "Climate change impacts on bumblebees converge across continents", by Jeremy Kerr et al., Science 20 July 2015. DESCRIPTION: "Responses to climate change have been observed across many species. There is a general trend for species to shift their ranges poleward or up in elevation. Not all species, however, can make such shifts, and these species might experience more rapid declines. Kerr et al. looked at data on bumblebees across North America and Europe over the past 110 years. Bumblebees have not shifted northward and are experiencing shrinking distributions in the southern ends of their range. Such failures to shift may be because of their origins in a cooler climate, and suggest an elevated susceptibility to rapid climate change." EXCERPT: "Bumblebee species' range losses from their historical southern limits have been pronounced in both Europe and North America, with losses growing to 300 km in southern areas on both continents. Mean elevations of observations for southern species have risen 300 m since 1974." IMPLICATIONS FOR ASSISTED MIGRATION are included as author quotes in a Christian Science Monitor summary article:

    "An advantage of assisted migration is that maybe we can give them a hand to catch up with climate change," Kerr says. "They're just not doing it by themselves. And bumblebee species, in a practical sense, are not really a group you want to try to do without."
         But assisted migration is a controversial measure, especially when it means introducing foreign species to new ecosystems. But in Kerr's view, these ethical questions are small when compared to the ethical and practical implications of extinction. "Is it ethically correct of us to introduce species to places they were never historically present in? In a sense, it's kind of like creating an invasive species," Kerr says. "But these are areas that are adjacent to the places where these species are found normally. So you're extending their range. It's not like we're taking species from Europe and introducing them to Hawaii, which would be crazy."


    The "IUCN Guidelines for Reintroductions and Other Conservation Translocations" 2012 update makes a distinction between two forms of "translocations" that would be characterize conservation actions responsive to the ecological upsets of climate change (see also 2013 final):

      
  • ASSISTED COLONIZATION is the intentional movement and release of an organism outside its indigenous range to avoid extinction of populations of the focal species.

  • ECOLOGICAL REPLACEMENT is the intentional movement and release of an organism outside its indigenous range to perform a specific ecological function.

    See the 3-fold chart immediately below for distinctions between three forms of climate-responsive assisted colonization, as set forth by foresters.


  •     "Assisted Migration: What It Means to Nursery Managers and Tree Planters", intended for landscapers and their clients, urges that planting for climate change become integral to the profession. Three types of climate assistance are:

    (1) Assisted population migration
    (2) Assisted range expansion
    (3) Assisted species migration (species rescue)

    Note: Species examples for each: Western Larch, Ponderosa Pine, Florida Torreya


        Considerations for restoring temperate forests of tomorrow: forest restoration, assisted migration, and bioengineering.

    This 2015 paper by Dumroese et al. sorts through the plethora of terms in conservation biology, forestry, and restoration ecology that refer to new management tools for climate adaptation.

    Notice that the 3 columns of bright green at the bottom of the chart offer nuances for the 3-category scheme depicted in the image directly above.

    This chart provides the key definitions for one of the three management tools specified in the title: assisted migration. This paper also deals with ecological restoration and bioengineering (genetic manipulation).


  • Editor's note:
    The historical sequence of the controversy over terminology can be accessed here: "Assisted Migration or Assisted Colonization: What's in a Name?"



  • SOCIETY, VALUES, and COMMUNICATIONS

      
  • "Reconstructing a Deconstructed Concept: Policy Tools for Implementing Assisted Migration for Species and Ecosystem Management" - by Roxane Sansilvestre et al., 2015, Environmental Science and Policy. EDITOR'S NOTE: This important paper distinguishes the Precautionary Principle, which restrains assisted migration actions (owing to hypothetical risks of invasiveness), from the Prevention Principle, which in this case means prevention of extinction or prevention of loss of ecosystem services.

    EXCERPTS: "Despite the fierce debate that AM [assisted migration] has recently produced between opposing actors who see more risks than benefits in AM initiatives and those seeking to act in the face of climate change threats, AM could be nevertheless seen simply as an extension of the practices of translocation and reintroduction of endangered species. In fact, the distinction between translocations and AM is becoming increasingly artificial because climate change makes parts of the historic ranges of many species unsuitable as reintroduction recipient sites.

  • "The inclusion of AM as an explicit climate adaptation option in environmental policies will involve integrating clearly climate change constraints in regulations and by consequence allowing for increased flexibility, while improving at the same time the management of associated risks. This means that the risks of invasiveness, for example, would be considered not more important than the risks of extinction, so regulations could open windows to experimental translocations under controlled semi-natural environments. Here, the complexity is that policy-makers should implement regulations for two-fold precautionary actions, for extinction risks and AM risks. Probable extinctions could be avoided by facilitating appropriate management actions even if risky, and management risks should be decreased by a responsible, reactive and reasonable biodiversity management.
        "Thus, experimentation must remain a first essential step to be able to measure the real extent of the risks involved. Concerning the risk of genetic pollution, management guidelines must consider integrating new ecological and genetic interactions because of the translocations. Even if genetic pollution could damage ecosystems it could also represent an opportunity for adaptation. Policy-makers and managers must accept that some degree of maladaptation could be the first step before natural selection adjusts populations to the new environmental conditions
        "Degraded forests could be used as an experimental opportunity for AM by bringing new genetic material from lower latitudes and/or altitudes to reinforce local populations. This type of forest restored through AM would be managed for optimality in biomass production or carbon sequestration while other better conserved areas would be managed for biodiversity conservation. In turn, people using plants for restoring different habitats can follow the experimental approach example from the forestry community and set up seed certification schemes based on networks of reciprocal transplant tests to understand the functional limits of common species used in restoration."

  • Scientists, Managers, and Assisted Colonization: Four contrasting perspectives entangle science and policy, by Mark W. Neff and Brendon M. H. Larson, 2014, Biological Conservation
    "Here, we treat scientific opinion of this conservation controversy as a subject of empirical social research in order to provide a richer understanding of the terms of the debate. . . The debate over assisted colonization has largely been framed by academic conservation scientists, so the views of other stakeholders remain underrepresented. To begin to redress this lacuna, we examine the views of the managers who would enact assisted colonization and evaluate its consequences on the ground. There is reason to suspect that managers' views will differ from those of scientists because their direct engagement with conservation practice makes them more intimately familiar with constraints to the application of ecological theory in conservation decision-making."

    HIGHLIGHTS (posted by authors): (1) We use Q method [blend of quantitative and qualitative] to identify axes of dissent regarding assisted colonization amongst scientists and managers; (2) Four groups emerged with distinct ideas about assisted colonization; (3) Disagreements centered on non-technical aspects of the problem; (4) Assisted colonization is a trans-scientific and wicked problem; (5) Lack of shared values may preclude successful implementation of assisted colonization.

    POPULAR SUMMARY BY NEFF: "Using Q method, a technique that blends aspects of quantitative and qualitative social science research, Brendon Larson and I examined the scientific controversy surrounding proposals to move species to new areas as a climate change adaptation strategy. Some conservation biologists see assisted colonization, as the proposal is called, as a necessary evil; to others it is akin to apostasy. Our research systematically evaluates the scientific, policy strategic, and value-based considerations that underlie ongoing disputes that have filled the pages of recent issues of conservation biology and forestry journals. Research such as this exposes where the protagonists in current debates are talking past one another based on different technical understandings, as well as elements of the dispute that are fundamentally about differing values. This is a first step to facilitating nuanced discussion of the value disputes, a pre-requisite for progress toward a resolution."

    Editor's note: What follows are extracts from the narrative descriptions of the FOUR DISTINCT PERSPECTIVES that emerged from the survey:

    ECOLOGICAL INTERVENTIONIST: The Ecological Interventionists accepted significant human management of 'nature,' believing conventional conservation strategies to be necessary for the conservation of biodiversity, but not sufficient in an era of climate change, thus necessitating options such as assisted colonization. These respondents did not perceive assisted colonization to be a radical transformation of natural ecosystems, but rather a necessary response to anthropogenic climate change and an extension of natural processes: "Species have been moving around throughout geological time, mostly under the influence of climate change. It is a very anthropocentric and short-term view to believe that all species should remain exactly where they were perceived to be over the past few hundred years." We do not, according to this logic, have the luxury of conducting "a vast research program before assisted colonization can begin." "There is no time!'" one participant responded. Others emphasized that assisted colonization is already occurring. Another suggested that while "more research is always needed, [awaiting a vast research program] creates a situation where we do nothing but throw a bit of money towards monitoring as species and communities slide into functional extinction."
         The Ecological Interventionists were less concerned than their peers by the idea that citizen groups with appropriate expertise might participate in assisted colonization, but still believed in the importance of following approved and reviewed plans. One participant reported, "I view humans as part of nature, and therefore human interests as part and parcel of our interests in sustaining ecosystem productivity and stability." Further indicating some tension about the role of science in assisted colonization decision-making, a manager wrote that we need structured decision-making methods because scientists tend to resort to a biased "natural is best" ideology.

    NATIVIST TECHNOCRATS: The Nativist Technocrats are committed to saving species from potential extinction, but prefer to do so by minimizing human influence on nature rather than by intervening in ecosystems. The 'Technocrat’ portion of the title for this group reflects their strong rejection of movement of species by expert citizens; they believe that scientists should retain decision-making authority and professionals should conduct conservation work. Whereas the other groups felt that assisted colonization had a role to play, the Nativist Technocrats rejected it, not least because of concerns about introducing diseases or invasive species. One scientist asked, "Do we keep moving species further and further poleward or uphill as the climate warms? Until we run out of hill or latitude? If global warming is not mitigated it will be catastrophic for ecosystems and humanity. Assisted colonization is a hopeless strategy for dealing with climate change and may provide the illusion that mitigation is not necessary."

    INTERVENTIONIST TECHNOCRATS: In contrast to the Nativist Technocrats, the Interventionist Technocrats were amenable to assisted colonization as an important and necessary conservation tool. They were technocratic insofar as they strongly disagreed with basing ecological practice on people's preferences. One clarified that these decisions "should be based on science" and another that "bias play[s] too important [a] part of human make up" to rely on people's preferences." They were the only group to disagree that we require "a framework for debates about subjective values surrounding species conservation" and strongly felt that citizen groups with appropriate expertise should not be allowed to move species. They also held the perspective, unique amongst the sampling pool, that endangered species laws are overly restrictive and thus need to be changed to successfully manage ecosystems in the face of climate change.

    RELUCTANT INTERVENTIONISTS: The Reluctant Interventionists were similar to the Ecological Interventionists, but we retained it as a distinct factor because of its unique perspectives on two issues. First, as the name indicates, the Reluctant Interventionists were far more cautious about implementing assisted colonization. Compared to Ecological Interventionists, they were more concerned about potential negative implications of introduced species and less pessimistic about the possibility of maintaining viable populations of native species under future climatic conditions. They did not easily embrace the idea of moving species, and none were optimistic that it will prove to be a panacea. Second, in contrast to the Ecological Interventionists who were neutral on the idea, this group emphatically rejected the statement that well-intentioned and informed citizen groups should be able to undertake assisted colonization activities without government approval and expressed comparative openness to ethical rejections of assisted colonization. In general, this group felt more strongly than the other groups that public values must be considered in assisted colonization decision-making.
         Of the four perspectives, the Reluctant Interventionists most strongly believed that ecosystems will change and species will go extinct regardless of whether we enact assisted colonization. They concluded that the risks of acting should be weighed against those of not acting, with one scientist elaborating that "I don't think there are perfect solutions nor perfect answers, so this approach [weighing risks] represents the best way forward." Despite the significant risks they identify, these respondents did not conclude that we need more research before utilizing assisted colonization, a sentiment shared with the Ecological Interventionists. They noted both that land managers are already doing things that could be considered assisted colonization and that waiting for definitive results would be detrimental.


  • "Agency launches long-term spruce, aspen treatment plan by Dennis Webb, The Daily Sentinel (Grand Junction, Colorado), 6 August 2016.
    EXCERPTS: Responding to habitat shifts resulting from climate change will be one of the considerations for the Grand Mesa, Uncompahgre and Gunnison national forests as the Forest Service embarks on a new forest treatment project over the next eight to 12 years. Its new Spruce Beetle Epidemic and Aspen Decline Management Response project is a response to about 223,000 acres where spruce have died from beetle infestation on the forests, and 229,000 acres that have been affected by what's called Sudden Aspen Decline, over a decade.
         The Forest Service expects mortality in spruce stands "to continue at relatively high levels for several years to come," according to the final environmental impact statement for the project. In 2009 the detection of new areas of aspen decline dropped considerably, but stands already affected continue to decline, and the Forest Service expects the aspen and spruce problems to be exacerbated in the future by climate change.
         While the new forest treatment plan is intended to also address other goals like reducing safety hazards such as falling trees and increased wildfire danger, improving forest resiliency is a key goal. That includes trying to make the forest resilient in the face of a changing climate. "In the climate change world, that's called adaptation measures — basically trying to adapt the forest to a changing climate," said Jim Worrall, a Forest Service forest pathologist who helped do the climate modeling. He said quite a few outcomes of the management response project "could help adapt the forest to a warmer and potentially drier climate."
         Worrall said where logging of beetle-killed spruce occurs, that could provide an opportunity for regenerating those acres with more aspen, or other trees more tolerant of an expected hotter, drier climate, such as Douglas fir, ponderosa pine and blue spruce. "I think at first it's going to be baby steps because people are a little bit cautious, and reasonably so, about completely changing a (forest) cover type," he said. Where there's spruce-fir forest, it might be crazy to start planting pinon-juniper now, even if models say it would be good pinon-juniper habitat by the end of the century, he said.

  • Also by Dennis Webb, 6 August 2016, "Cycle of decline: Estimate portends big changes in makeup of forests".
         EXCERPTS: Lovers of the local high country could find a recent projection of a warming world's impacts on area forests to be chilling. By 2060, according to a U.S. Forest Service estimate, almost all of the Uncompahgre Plateau would no longer be able to sustain growth of new aspen and spruce, meaning that the plateau could be virtually aspen- and spruce-free by century's end after the remaining trees die. On the southern and eastern fringes of Grand Mesa, aspen also could see sizable losses of suitable habitat by 2060, with spruce habitat largely slipping into a threatened category across the mesa, meaning the future climate isn't favorable to sustaining it.
         The modeling used by the Forest Service found that 52 percent of current aspen distribution across the forests would be in the lost habitat category by 2060, and 42 percent in the threatened category, "meaning it is conceivable that 94 (percent) of current aspen distribution may not continue into the next century," the Forest Service says in its final environmental impact statement for the project, released earlier this year. Aspen habitat generally would be lost at low elevations, especially on south-facing slopes, with the western West Elks also sharing in that habitat loss. Some of that habitat loss could be offset by newly emerging habitat at higher elevations. But Samantha Staley, a Forest Service planner, says while the climate may shift to support the species at a higher elevation, that doesn't mean that other ecological components necessary to support the species will be present. Some higher elevations may not be suitable thanks to things such as poor soil conditions or rocky scree slopes. The model projects a 22 percent loss of current spruce distribution, and that 58 percent of distribution will become threatened, meaning that 80 percent of current distribution may not continue into the next century.
         The model is based on an assumption of a continuing warming trend on the forests. The statement says temperatures are expected to rise 5.4 to 7 degrees by 2040-60. Higher temperatures could foster more spruce beetle outbreaks, further stress trees because of increased drought and result in more damage from wildfire. "I think what those maps show is stunning,"Zukoski said. "I think those kind of maps are extremely helpful because they permit people to see in their areas, places that they care about in their backyards, what the world's going to be like for their kids and grandkids, and for themselves if they live long enough. I think giving people that picture over that longer term really helps them understand how dramatic the impacts of climate change could be if we don't work darn hard to get a handle on it."
         Meanwhile, a 2006 model created by researchers led by Gerald Rehfeldt, who worked at the Forest Service's Moscow Forestry Sciences Laboratory in Idaho before retiring, projected a 47 percent drop in suitable spruce habitat in the western United States in the decade around 2060, and a 72 percent loss by 2090. The Forest Service statement says that for the forests, that model was rebuilt using local data, more "topographical predictors," newer global climate models and carbon scenarios, and higher-resolution climate data. Its resulting projections are an average from three climate models and three greenhouse gas emission scenarios. "These are models, which necessarily include some amount of error," Staley said. She said it's based on the best available information today, and the Forest Service understands the science will be a lot better in a decade. "We have to look at it as it's not the gospel, but it's the best available scientific information that we have today about where vegetation may be headed in the future," Staley said.
         Jim Worrall, a forest pathologist with the Forest Service’s Rocky Mountain Region 2, which includes Colorado, said Rehfeldt worked with him and others to localize his methods, and they developed a model for 13 tree species in southwest Colorado, including spruce and aspen. Worrall said one of the biggest uncertainties pertains to the climate models, because there are so many models and carbon scenarios to choose from. He said the forest-habitat predictions the Forest Service came up with concern him and he hopes they're wrong, but they're the best idea researchers now have of what the future holds. "It's really a very objective process. There's really no subjectivity in the model development," he said. Interpreting the results to make them simple and easy to digest can be a little subjective, he said. "But we've been pretty conservative in that," he said, adding that the predictions are based on what the models are telling researchers, and those models are built on a lot of data.
         Staley said the agency is compelled to use that science in its planning and efforts to manage sustainably into the future, and current research acknowledges that warming will result in shifting of not just animals but trees in terms of habitat. "The environment is changing and that's why we're using as much information as we can to make the best decisions," she said. Forests are always changing, thanks to factors such as insect infestation and wildfire, and cycles such as aspen thriving first in disturbed areas and later being succeeded by other types of trees. But now the Forest Service is learning more about how that's happening in the context of "pretty rapid climate change," and what the forest may look like in that context, Staley said.
         While every generation sees a slightly different version of a forest, future forests may be ones that people have never seen locally, she said. Rather than a mid-elevation forest shifting back and forth from aspen to spruce, it may shift to oakbrush. "And that's a new shift," she said. Oakbrush and mixed-mountain shrubs cover about a quarter of the Uncompahgre Plateau now.
         [Jim Worrall] said of the modeling's findings, "I think we need to plan for the worst and hope for the best, is what I suggest. But most likely even if the models are a little off, we're going to be looking at very different conditions in the future for our children and our children's children than we have now."

  • "The assisted migration of western larch in British Columbia: A signal of institutional change in forestry in Canada? by Nicole L. Klenk and Brendon M.H. Larson, Global Environmental Change 2014.
    EXCERPTS: Based on 46 interviews with policy actors across Canada, our results suggest that the deployment of the first assisted migration policy in Canada successfully avoided the controversy surrounding the idea in the scientific community by changing the scientific discourse associated with best forest management practices. The shift from an ecological discourse to a genetics discourse over forest policy in British Columbia signals what we might expect in future forest adaptation policy development in Canada.
        Clearly, a genetics characterization of forests looks back to the distant past for guidance in future 'climate change fitness of species'. This represents a major conceptual shift, which significantly affects the temporal and spatial scales on which forest management planning occurs. This shift can be characterized, furthermore, by the deployment of new normative goals for forest management: rather than trying to recreate current forest composition and functions, the values and norms guiding forest management from a genetics perspective seek to accelerate forest transition to the future, to a 'climate resilient' state. This normative shift has real material consequences, such as enabling the movement of western larch 1000 km north of its current distribution, sidestepping the issue of its ecological appropriateness in the recipient ecological community, because from a 'climate fitness' perspective, western larch may eventually migrate to northern BC.
        Thus given the genetical frame structuring the AM policy coordinative discourse, we argue that there is a major shift in the cognitive and normative content of ideas at the program level. However, when we analyzed the communicative discourse on western larch AM policy, we found that concerted efforts were taken by policy developers to downplay the significance of this program change in their communication to the public. To begin, educational and training outreach activities stressed the low risk associated with population range expansion, as the following interviewee explains: "We are very open and inclusive in talking about AM. I talk about the risk of action and inaction and more importantly the difference between the various forms of AM. We are very clear that we are not testing or interested in exotic translocations."
        To sum up, our analysis suggests that policy analysts, forest geneticists and policy implementers in the BC Tree Improvement Branch characterized forests so as to highlight and diffuse an evolutionary theory of forest ecosystems that is tied to a new set of norms and values associated with a humanistic philosophy that are highly controversial in the conservation community—yet which, in turn, are signals of major institutional change in forest policy in BC. . .  Our results suggest that the deployment of the first AM policy in Canada has successfully avoided the philosophical debates on AM in the conservation scientific community by changing the scientific discourse associated with best forest management practices (i.e., from an ecological point of view to a genetics point of view) and this discursive shift may signal what we might expect in future forest adaptation policy development in Canada.

    Editor's note: For a superb example of Canadian foresters utilizing the best communication skills in reported news stories, see the 14 June 2015 "Canadian scientists help trees adapt to changing climate". Here is the lead quote by researcher Sally Aitken, "Trees are adapted to historical climate and the climate's moving out from under them. We're using genomics to generate answers more quickly than they can." Here is her closing quote: "We have changed things to the point where we really have to foster the future of the environment and the forest. I think it would be very foolish and irresponsible to say, 'Let nature take care of itself.'" As well, see Aitken quoted in 29 January 2014 news story: "New genes for old forests as Canada warms": "So my research is focused on the best way to better match trees with new and future climates, to assist the movement of that genetic material through reforestation." Aitken is also quoted here (for Whitebark Pine, 18 September 2014, NYT): "For Trees Under Threat, Flight May Be Best Response".

    See also; "Opinions on strategies for forest adaptation to future climate conditions in western Canada: Surveys of the general public and leaders of forest-dependent communities", 2014, Reem Hajjar et al., Canadian Journal of Forest Research.


  • "What is Novel About Novel Ecosystems: Managing Change in an Ever-Changing World", 2015, by Amy Truitt et al, Environmental Management
    Editor's note: This 2015 paper is quoted at length because it places "assisted migration" within a tri-fold management regime which the future will necessarily bring to ecological restoration and conservation biology.

    EXCERPTS: While over the past several hundred years most landscapes have been altered by anthropogenic activities, and in many cases outright habitat destruction, the terminologydescribing the resulting ecosystems is inconsistent and inadequate for effective cross-sectoral management. Due to the dynamic nature of ecosystems and the varied disciplines that have evolved in the Anthropocene to study them, it has proven challenging to find a universal language that defines 'novel' ecosystems (e.g., Milton 2003; Hobbs et al.2013;Morse et al.2014; see Table1). Equally challenging is the development of a common set of metrics to quantify ecosystem changes and the functional impacts resulting from those changes (Murcia et al.2014). Neutral, unambiguous, and consistent terminology with a framework for categorizing novel ecosystems is needed to classify, describe, and manage these systems. Such classification can facilitate decision-making in a landscape of diverse management objectives and variable social perceptions around novel systems (but see Murcia et al. 2014).
         Priorities for and approaches to managing novel ecosystems vary based on perspective of the scientists, managers, and policy-makers along the anthropocentric–biocentric continuum. Practitioners with a biocentric perspective are more concerned with impacts that novel ecosystems have on biodiversity, community composition, and ecosystem function, while those with an anthropocentric perspective may be more interested in how novel ecosystems will affect ecosystem services on which humans depend. Management approaches to novel ecosystems range from strategies that actively promote the ability of novel ecosystems to achieve conservation goals (Zedler et al.2012), to active prevention of novel ecosystems (Stromberg et al.2009). These approaches range from accepting irreversible landscape alterations and promoting and accounting for ecosystem services provided by novel assemblages (Melo et al.2013) to active prevention of native species and ecosystem loss (Willis et al.2010; Lindenmayer et al.2008) or land restoration to prioritize ecosystem functions and processes in certain novel ecosystem scenarios (Hobbs et al.2009). On some sites, assisted migration, such as purposeful ymoving species to more climate suitable habitat (Richard-son et al.2009) has been recommended. Some practitioners suggest that novel ecosystems should be recognized as achieving conservation goals and remain where they arise, rather than be managed (Hobbs et al.2006;2011; Martinet al.2012). Others suggest eliminating the term 'novel ecosystems' as it could be a hindrance to ecologically sound restoration efforts (see Murcia et al.2014). Acknowledging the diverse perspectives may facilitate compromise and development of mutually acceptable management approaches. The term itself may be useful in delineating to the public and policy-makers the far-reach-ing effects of anthropogenic activities on proximal and remote ecosystems (e.g., Blight and Ainley 2008; Holt-grieve et al.2011), which may facilitate greater consensus on appropriate management strategies.
         Here we ask whether novel ecosystems are, in fact novel, or whether these systems are a manifestation of ongoing evolutionary change in ecosystem and species assemblages. Given the many definitions of novel ecosystems, we present previous and current definitions, offer a working definition for use in management decision-making, and differentiate the frameworks surrounding each to organize possible management approaches to novel ecosystems. Finally, we propose a categorization scheme and framework (Figs.1,2) for managing novel ecosystems now and in the future.
         We introduce a framework for identifying how to manage novel ecosystems with three alternative directives to address the spectrum of challenges posed by these ecosystems. The directives include managing against, tolerating, and managing for novel ecosystems and can be directly tied to management objectives (Fig.2). We provide examples and discuss the social, economic, and ecological advantages and disadvantages of each.
         There is a threshold in some affected ecosystems at which point either managing against or tolerating is no longer an option (Fig.1). Although this alternative is less common and may be more controversial, we expect the need to manage for novel ecosystems and the services they have evolved to provide will become more prevalent in the future under changing climatic conditions and increased globalization. Where species have been lost or have severely declined and restoration has been unsuccessful, or where land use change has been intensive, managers may find that managing for novel ecosystems provides the only or best alternative. . . Other examples of managing for novel ecosystems include the plethora of introduced plant species that have become important in the agricultural sector; assisted migration of more climate-suitable tree species to managed forests (Gray et al.2010; Duveneck and Scheller 2014); managing non-native species assemblages in parks (e.g., Underwood et al.2004); non-native species used for recreational purposes (e.g., Crawford and Muir 2008; Britton et al.2011) and non-native species for conservation (Schlaepfer et al.2010; but see Vitule et al.2012for rebuttal).

  • "The Fight to Unmuzzle Canada's Scientists" by Stephen Buranyi, Motherboard 27 August 2015
    EXTRACTS: Dr. Phil Burton's work was also far outside what he thought the government might consider hot button. Dr. Burton, a professor at the University of Northern British Columbia, had previously spent 20 years with the Canadian Forest Service studying boreal forests in northern Canada. He recalls getting permission from Ottawa to attend a conference, but his permission came with a paradoxical request: "The conference was a series on disturbance dynamics in boreal forests, and the theme that year was climate change. I was told not to talk about climate change or forestry impacts. Well that's the whole point of the conference!" he said. . . "I work with government scientists every day, literally every single day, and they've just had their legs completely cut out from under them," said Alana Westwood, a graduate student in biology at Dalhousie University.
        The Liberal Party of Canada has indicated it's interested in staking its claim early as the party of science. In May, Liberal MPs introduced a motion to "un-muzzle" Canadian scientists and introduce a parliamentary science officer, and a month later Liberal Leader Justin Trudeau announced that if elected he would review some of the legislative changes to environmental acts under Harper. The Liberal motion was largely symbolic; the Conservative majority sunk it fast. But it was a start, and the campaign promises remain on record.
        Editor's note: A few months after this report was published, the Liberal Party did become the majority party, and Justin Trudeau did oust Stephen Harper from the office of Prime Minister. The muzzles are gone!

  • "Conservation Biology: The End of the Wild" by Emma Marris, Nature 12 January 2011, 469:150-52
    "Climate change means that national parks of the future won't look like the parks of the past. So what should they look like? . . . [National Park Service director Jonathan] Jarvis has suggested the possibility of moving species outside their native ranges to give them a better chance of surviving — just not right away. "The big point here is that we are willing to face these questions," he says. "We are not afraid to talk about them."

    SEE ALSO an Dec 2010 online interview with NPS Director Jonathan Jarvis on climate change and park management, including "assisted migration".

  • "Defining Migration" chapter of Brian Keel's PhD thesis.
    Brian Keel intentionally coined the term "assisted migration." This short chapter will be useful for those engaged in considering whether "assisted migration" or "assisted colonization" is the best term for the kinds of conservation actions now beginning to be considered. Editor's note: The historical sequence of controversy over terminology can be accessed here: "Assisted Migration or Assisted Colonization: What's in a Name?"

  • "Assisted Colonization: CBC Radio Interview"
    A terrific AUDIO exploration of the controversy, which aired 24 July 2008. Part 1 is the supportive side, via an interview with Prof. Camille Parmesan. Part 2 is an interview with an invasive species researcher that is very critical of the idea. Part 3 is a not-to-be-missed radio spoof of the idea.

  • "Tending to Our Rambunctious Garden" Q&A with journalist Emma Marris, OnEarth 28 September 2011
    Emma Marris's 2011 book, Rambunctious Garden, has "Assisted Migration" as the topic and title for chapter 5. The Q&A linked above is an excellent short introduction to the reach of this book in highlighting the shifting norms and values in conservation biology and land management today. Assisted migration advocate Connie Barlow posted a positive review of the book on Amazon: "Rewilding, Assisted Migration, Ecological Restoration, and More". There's also an excellent dot-Earth video interview of Marris on youtube.

  • "The Age of Man Is Not a Disaster" - Op-ed by Emma Marris, Peter Kareiva, Erle C Ellis, New York Times 7 December 2011
    EXCERPT: "We can accept the reality of humanity's reshaping of the environment without giving up in despair. We can, and we should, consider actively moving species at risk of extinction from climate change."

  • "Guardian Angels" article by Janet Marinelli, Audubon Magazine, May/June 2010.
    In-depth exploration of "the biggest controversy in contemporary conservation science." Engagingly written for both a popular and professional audience, journalist Marinelli draws from her interviews with leading scientists, horticulturalists, and activists to present the core arguments for and against assisted migration. A site visit to an endangered plant breeding facility (the Atlanta Botanical Garden) is paired in the article with Marinelli's eye-witness description of "eco-vigilante" action, when the loose-knit citizens group Torreya Guardians intentionally planted into forested landscapes of mountainous North Carolina 31 seedlings of the highly endangered Florida Torreya — an assisted migration of some 400 miles northward of historically known native habitat.

  • "Taking Wildness in Hand: Rescuing Species" article by Michelle Nijhuis, Orion Magazine, May/June 2008.
    A lengthy and elegant feature article that explores the human side of the controversy over assisted migration, with Torreya taxifolia providing the focal point, pro and con, and with actions by the citizen group Torreya Guardians stirring the brew. Comments page accessible through the foregoing link to Orion magazine.

  • 2009 book highlights ASSISTED MIGRATION controversy, Heatstroke: Nature in an Age of Global Warming, by Anthony Barnosky (Island Press)
    Publisher's press release excerpt: Unfortunately, both assisted migration and Pleistocene rewilding would lead to managed ecosystems — the antithesis of wilderness. Just as we manage fisheries to preserve an important food source, we will have to give up some wildness in order to preserve species. "We can't protect all three faces of nature — ecosystem services, like clean water and fisheries; species diversity; and the feeling of wilderness — without somehow separating those three different concepts of nature and working with each one of them differently," [the author] says. "All can be complementary, but you have to do different things for each one. I think there are people who are quite happy to settle for one or two of those, but my personal philosophy and feeling is that we can have all three faces of nature." [The author] foresees two types of preserves, for example: species preserves to protect a species or assemblages of species, but requiring heavy management; and wildland preserves that retain ecological interactions without the influence of humans — the feel of wilderness — but which will see changing species and even extinctions.


        The SUNY College of Environmental Science and Forestry launched in April 2014 Move It?, an online questionnaire that scores the suitability of user-defined species (candidate taxa) for assisted colonization. Questions are divided into three main categories, following Hoegh-Guldberg et al. (2008): (1) need for assisted colonization, (2) technical feasibility of assisted colonization, and (3) biological/ socioeconomical costs versus benefits of assisted colonization.

    Move It? is also a growing database of user-submitted scores, which can then be used to compare candidate taxa and guide decisions about the use of assisted colonization in practice. Although primarily developed in the context of climate change, Move It? can be used to evaluate any proposal to translocate organisms outside their current range. Take the Survey!


        
    Award-winning animated video excerpts the allegorical tale by French author Jean Giono, 1953.

    This is the mythic story to inspire all of us — conservation biologists, forest managers, and involved citizens — to pull ourselves out of despair over the looming impacts of climate change and get on with the great work of planting (and moving!) trees.

  • Wikipedia entry
  • Video (in full) on youtube
  • DVD via Amazon
  • "The true meaning of life is to plant trees,
    under whose shade you do not expect to sit."
    — Nelson Henderson



    ETHICS, LAW, and HISTORY

  • "Commercial trade of federally listed threatened and endangered plants in the United States" (abstract) by Patrick D. Shirey et al., Conservation Letters Sept/Oct 2013, pp. 300-316.
    Note: This paper clearly establishes the legality of non-commercial translocations ("assisted migration", "assisted colonization") of endangered plant species in the USA. The voluntary efforts of citizen-naturalists in Torreya Guardians (assisting the northward movement of Torreya taxifolia) are used as a key example of such legal practices.

    EXCERPTS: "a listed plant could be purchased in one state and then transported to another state without violating the ESA, so long as the plant was taken from and planted on property not under Federal jurisdiction, such as private property. Furthermore, the ESA does not prohibit an individual from giving listed plants as a gift to someone in another state so long as a change in plant ownership is not in the pursuit of gain or profit." . . . In the United States, the structure of the Endangered Species Act, coupled with inadequate funding for endangered plant conservation, has encouraged citizens to undertake plant conservation, especially for charismatic plants threatened by climate change. For example, the Torreya Guardians have obtained plants and seeds of Florida torreya (Torreya taxifolia), and moved seedlings and saplings to the southern Appalachian Mountains, outside of the species' historic range (McLachlan et al. 2007; www.torreyaguardians.org). . . In contrast to accepted ex situ conservation practices (Haskins & Keel 2012), the Torreya Guardians established private experimental populations on the property of cooperative landowners to help preserve the species outside of its historic range because of its decline, lack of federal funding, and the availability of privately owned and commercially available plants and seeds. . . Finally, under U.S. federal law, citizens who move a listed plant are not constrained by the same assessment process as the federal government — their actions are legal under the ESA without a review of their plans. MORE EXCERPTS available in PDF. See also "Scientific American blog" on this topic (July 2013).

    Note: Because the Shirey et al. paper established the legality of Torreya Guardian actions "rewilding" an endangered conifer tree (Torreya taxifolia) far north of its climate-stressed "critical habitat," activist Connie Barlow recorded in November 2013 a 75-minute VIDEO BLOG (right), posted on Youtube, to summarize the group's learnings to date.

    Note: To go directly in the video to the importance of the Shirey et al. paper, click here, or click on the "Show more" link below the Youtube caption and see the full table of contents of the video, hotlinked by time codes.

      

  • "Regulate Trade in Rare Plants" by Patrick D. Shirey and Gary A. Lamberti, Nature 27 January 2011
    A groundbreaking "Comment" paper in one of the top science journals combines data analysis of 753 threatened or endangered PLANTS in the USA with policy and legal analysis of the as-yet largely unregulated trade in seeds and seedlings cultivated in private gardens and nurseries outside of the official native habitat. A very readable and thought-provoking exposition of pros and cons of business as usual, now that climate change is motivating conservationists (individually and in groups outside of government) to consider whether the imperiled plant species that they love might benefit from, or even require, their assistance ("assisted migration") — given that governmentally agencies are still hesitant to (and in some cases, prohibited from) expanding locations for conservation programs beyond so-called native range. The work of Torreya Guardians is highlighted, including a 2010 revision in the official ESA management plan for Torreya taxifolia, directing plan managers to attempt to coordinate activities with Torreya Guardians, where possible. The authors conclude: "Although the redistribution of plant species around the world is nothing new, the ease with which people can now obtain and transfer specimens is unprecedented. This, combined with a growing interest in assisted colonization, makes it more important than ever for federal and local governments to wrest control of illegal Internet trade, develop a policy for hybrids and ensure that genetic diversity is considered when propagating plants. 3 pages in PDF for purchase online.

    News articles on this paper: in Science Daily; Los Angeles Times.

    2012 poster by Shirey et al., 2012 Ecological Society of America's Emerging Issues Conference:


  • U.S. Fish & Wildlife Service "Internal Discussion Draft: Rising to the Urgent Challenges of a Changing Climate: Strategic Plan for Responding to Accelerating Climate Change in the 21st Century". Draft of 12 December 2008.
    "We will review, identify, and work to revise all elements of the Service's legal, policy, and regulatory framework necessary to support effective adaptive responses to changing climate. We will place particular focus on developing necessary new policies (e.g., assisted colonization) and needed revision of existing policies (e.g., what constitutes native, invasive, or exotic species?)." p. 15 "Novel conservation and recovery actions, such as assisted colonization, will be developed and implemented to protect acutely climate-vulnerable species." (p. 16)

  • "Climate Change Science Compendium 2009" by United Nations Environment Program (UNEP). September 2009
    Massive new report that goes beyond the usual IPCC report to make clear how the likely adverse effects of climate change are now thought to be much greater than even the IPCC reported. The section on "Management" contains a subsection on "Assisted Colonization" (p. 46 of the report; p. 4 of the PDF download), that includes these statements: "The reality of a rapidly changing climate has caught many natural-resource managers and policy-makers unprepared. Large-scale translocations might now be needed. Consequently, the conservation community needs to move beyond the preservation or restoration of species and ecosystems in place as the correct approach." and "Assisted colonization will always carry some risk, but these risks must be weighed against those of extinction and ecosystem loss. Already some regions of the Earth such as the Arctic are experiencing high levels of warming. Many others will experience unprecedented heat within the next 100 years, as well as altered precipitation and ocean acidity. The future for many species and ecosystems is so bleak that assisted colonization might be their best chance. These management decisions will require careful thought and will need to be backed up by detailed scientific understanding if they are to succeed."

  • "Species Conservation, Rapid Environmental Change, and Ecological Ethics" by Ben A. Minteer, The Nature Education Knowledge Project 2012
    EXCERPT: "Rapid, large-scale environmental changes are forcing conservationists to consider innovative and often controversial tactics for protecting species in this century, tactics that raise significant ethical and value-laden questions. Given what we already know about changes in species' ranges and abundances in the face of global climate change, it is inevitable that conservation in the post-preservationist era will require more interventionist conservation policies, leading to debates regarding risks, benefits, and likely success of novel practices such as managed relocation."

    See also Minteer's "Restoring the Narrative of American Environmentalism", January 2013, Restoration Ecology.

  • VIDEO: Assisted Migration and Invasive Species: Exploring an Ethical Dilemma" by Jay Odenbaugh, 2013, at U.S. Forest Service conference on assisted migration (38 min)
    VIDEO: (summary) "According to many, we are subject to two duties. First, it is morally wrong for humans to cause a species to go extinct. Second, it is morally wrong to introduce a species into an area in which it is not native. Unfortunately, human-induced climate change will cause species to go extinct unless we relocate those species to areas outside their native range. Thus, we are either causing species to go extinct or creating exotic species both of which are morally wrong. In this talk, I consider ways of dealing with the environmental dilemma."

  • "Move it or lose it? The ecological ethics of relocating species under climate change" by Ben Minteer and James Collins, Ecological Applications October 2010
    Lead author Ben Minteer is an environmental ethicist, and this paper is a strong and compelling piece of well-supported advocacy in favor of "managed relocation" (aka "assisted migration). The final paragraph reads: "If we value wild species and wish to bequeath a significant fraction of global biodiversity to future generations, radical strategies like managed relocation may well be our last best chance. Although risky, such bold efforts to preemptively move threatened species to new environments may offer the only hope to keep them from moving into museums and zoos—and haunting our ecological conscience." 4 pages in PDF.

  • "Future Human Intervention in Ecosystems and the Critical Role for Evolutionary Biology" by Jessica J. Hellmann and M.E. Pfrender, Conservation Biology December 2011
    EXCERPT: "We expect that considerable philosophical and conceptual change will occur within conservation biology over the next 25 years. If we acknowledge that the human population is growing and that the rapid pace of global change, including climate change, will continue, then we need to begin managing systems that are constantly changing — we can no longer look to the past for guidance on how an ecosystem is supposed to be."


    VIDEO ABOVE LEFT: Alejandro Camacho 2011: Redefining Nature through Assisted Migration (Natural Resources Law and Ethics Under Climate Change; 21 minutes)

    29:19 Begins • 31:21 Torreya example • 32:42 "Why do it, and why is this controversial? The existing literature focuses on whether assisted migration can be done — what I call, questions of scientific viability or legality. But I argue that the concerns with it, at their root, are deeply normative. They're really ethical. Assisted migration challenges deeply entrenched ideas about what the purposes are of natural resource law and natural resources management. But I argue that it is these principles and the legal framework that require rethinking." • 40:11 "We need to reinvent resource management to better reflect a dynamic world … "Natural resources management was not designed with climate change in mind." • 47:35 "I argue that climate change necessitates managing for the future." • 51:19 "I think assisted migration illustrates how resource management is not exclusively a scientific or legal inquiry."

    VIDEO ABOVE RIGHT: Alejandro Camacho 2012: Why Federal Climate Change Legislation Shouldn't Stop States from Innovating in Adaptation Efforts (29 minutes)

    00:01 Begins • 01:24 "My claim is that the law in the United States is not well suited to cultivate successful adaptation because it's not designed to foster learning." • 02:12 "U.S. law is not well suited to foster adaptation because it relies on (in fact, promotes) a very static view of nature and natural systems." • 04:45 "Climate change adaptation in particular is problematic because determining what are suitable adaptations is largely affected by the extent of mitigation … And we don't know that … So knowing what adaptation strategies to adopt, to restore certain mangroves, when we don't actually know if 50 to 100 years from now, whether all that work is wasted, is really problematic." • 06:21 "Scientists are really being challenged to reconsider long-held assumptions and long-held methodologies they've relied on. Regulators and managers are being asked to prepare for problems that they haven't ever faced before." • 06:54 "The most important strategies for effective adaptation, therefore, are those that help reduce uncertainty and that promote learning by managers and stakeholders in particular. [He cites 2 problems in the US] (1) Agencies are really slow to adapt to new information or changed circumstances. They aren't required to adjust their strategies over time … They don't gather information as to the effectiveness of their strategies; so the consequences are weak accountability. (2) Natural resources management in the U.S. is very fragmented, with at best weak coordination. It's not designed with climate change in mind. … It also hinders the capacity for learning between agencies." • 11:18 "Natural resources law in the United States is badly fitted for addressing the effects of climate change because of its goal, because of its objectives … grounded in a preservationist or restorationist baseline, a historical baseline . . . shielding nature from active human intervention … minimizing non-native and protecting native … Climate change reveals the limits of both of these versions of preservationism." • 15:23 "There is little ethical foundation for arresting the evolution of pre-existing ecosystems … Some of the reserves that have been set aside may actually become inhospitable to the very resources that they were created to protect." • 16:08 "Finally, climate change really pits these two different types of preservation — wildness preservation and historical preservation — against each other. Climate change makes it impossible to do both. You can't keep things the way they are and also leave them alone." • 22:02 "By not requiring agencies to monitor, to revisit, to adjust their decisions, to learn, this makes agencies less accountable to the public." • 25:15 "What climate change makes clear is that ecology and natural resource management should not be left solely to an expert: an economist, an ecologist. These are democratic decisions." • 29:00 Q&A starts

    See also print versions of these papers:

    2011: Alejandro Camacho's 2011, "A Learning Collaboratory: Improving Federal Climate Change Adaptation Planning"

    2010: "Why Federal Climate Change Legislation Shouldn't Stop States From Innovating in Adaptation Efforts"

    2013 VIDEO by Camacho: "The Law and Ethics of Assisted Migration" (48 min)


    Note: Serious students of assisted migration or, more broadly, the need for profound professional and public reconsideration of ecological norms in a time of rapid climate change will find it important to read the 86-page (freely downloadable) paper by Camacho, quotations from which follow:

  • "Assisted Migration: Redefining Nature and Natural Resource Law Under Climate Change", by Alejandro E. Camacho, 2010, in Yale Journal on Regulation, vol 27, pp 171-255.
    [86-pages in PDF freely downloadable] Argues for the necessity of assisted migration, owing to ongoing and projected climate change, and suggests changes in the U.S. ESA and regulatory policies for making this possible. Boldly addresses ethical concerns and the need for public discussion in the context of how assisted migration is a leading-edge issue that reveals the scope to which ecological preservation, restoration, and management will need to be thoroughly in light of the new awareness of significant climate change. Key quotations:

    Page 189: "Paradoxically, as detailed in the following subsections, under existing law it may often be more difficult for federal agencies to engage in assisted migration than it is for private parties."

    Page 243: "Assisted migration illustrates how climate change compels a reassessment of three key features of modern American natural resource governance. First, assisted migration demonstrates how climate change inevitably compels a reassessment away from baseline goals that seek to preserve or restore historical or existing conditions to a focus on maximizing desirable future conditions, although the particular formulation of such a goal for natural resource management is very much unresolved. Second, while making clear that biotic interactions will change considerably with or without direct human involvement, climate change necessarily reshapes the primary unit to target for management away from individual species or even assemblages of species toward ecological processes. Yet again, concretely steering resource management toward such a focus remains elusive. Third, the swiftness of climate change demonstrates that distinctions previously made in natural resource policy between native and exotic, or between natural and introduced, are overly simplistic and anchored in the flawed notion that the world is inert. Public resource management must explore new management standards for determining what ecological conditions are desirable or acceptable. Each of these necessitates substantial further public discussions to ascertain the future of public natural resource policy — and thus the prospects for assisted migration."

    page 244: "The conflict over assisted migration shows that the goal of preserving or restoring resources to a historic baseline that currently dominates natural resource policy will be increasingly difficult if not impossible to sustain. More than ever, modern anthropogenic climate change emphasizes the necessity of actively managing for the future. Yet the particular shape of such an objective is far from clear. As such, climate change necessitates extensive public discussions and ultimately legislative guidance regarding what is valuable and important to the public about natural resources such as endangered species and existing biotic communities."

    page 245: "Similarly, natural resource management must be transformed away from a primary focus on preserving or restoring historical biotic assemblages. With significant alterations in climatic conditions anticipated for many ecosystems, preservation and restoration goals will be increasingly unsustainable. Accordingly, statutes like the National Park Service Organic Act and Wilderness Act that primarily seek to preserve historical conditions will need to be reconceived away from a strict fidelity to the past toward a greater focus on promoting desirable future conditions in light of climatic changes."

    Page 251: "Lastly, assisted migration demonstrates the flaw in relying on absolute dichotomies such as native/exotic and natural/artificial as core features of managing biological systems under global climate change. Though such complete dualism has the advantage of simplicity, it is neither accurate nor helpful in deliberations over how to manage and choose among resources as ecological systems change with climatic conditions. Dedicating substantial resources to preserving and restoring a particular biological unit because it existed at one point in time in an ecosystem makes little sense if climatic conditions make the landscape inhospitable to that unit. Similarly, what is the ethical or scientific justification for prohibiting or removing any organism simply because it never existed in a particular location, especially if that organism is now well‚Äźmatched with the location due to changes in climatic conditions?"

    Page 253: "Though this Article provides a preliminary framework for assessing both when to allow and how to manage experimentation with assisted migration, it more importantly explains how climate change reveals a host of value questions that remain unexplored in natural resource law and policy. The resolution of these questions will shape not only determinations regarding the acceptability of assisted migration, but more broadly the future of natural resource management."

    Page 255: "In summary, a regulatory framework that fosters open and transparent access, debate, and deliberation can promote agency accountability to democratic representatives and the general public, and more informed public deliberation and action with regard to the management tradeoffs that must be made in devising goals and sandards for natural resource management. Though developing such institutions and processes will be far from easy, such a pursuit unquestionably should be the focus of natural resource law in a world of rapid climate change. The prior account of a pristine and untouched nature may be nearing its end. However, the opportunity to help foster biotic and human communities that truly integrate humanity's collective self-interest in resource conservation and duties of stewardship has really just begun."

    SEE ALSO: "Assisted Migration: A Viable Conservation Srategry to Preserve the Biodiversity of Threatened Island Nations?", by Jessica Wentz, 2011, Columbia Law School Working Paper.


  • "Reframing the Debate Over Assisted Colonization" by Joshua J. Lawler and Julian D. Olen, Frontiers in Ecology 24 March 2011
    EXCERPT: "In light of the difficulty in weighing the consequences of action versus inaction [re assisted colonization], we conclude that focusing the debate on this issue is counterproductive. In fact, we would argue that, given the magnitude of change that is likely to occur in many receiving ecosystems, there is little use in worrying about the effects of introducing one particular species. This is not to say that we should aban- don efforts to assess potential impacts to the receiving ecosystems. However, it does suggest that we consider the amount of change forecast for that ecosystem before conducting detailed experiments on a system that may not exist in the future."

  • "Hope in the Age of Man" by Emma Marris, Peter Kareiva, Joseph Mascaro, and Erle C. Ellis, New York Times 7 December 2011
    EXCERPT: "We can accept the reality of humanity's reshaping of the environment without giving up in despair. We can, and we should, consider actively moving species at risk of extinction from climate change. We can design ecosystems to maintain wildlife, filter water and sequester carbon. We can restore once magnificent ecosystems like Yellowstone and the Gulf of Mexico to new glories — but glories that still contain a heavy hand of man. We can fight sprawl and mindless development even as we cherish the exuberant nature that can increasingly be found in our own cities, from native gardens to green roofs. And we can do this even as we continue to fight for international agreements on limiting the greenhouses gases that are warming the planet. The Anthropocene does not represent the failure of environmentalism. It is the stage on which a new, more positive and forward-looking environmentalism can be built. This is the Earth we have created, and we have a duty, as a species, to protect it and manage it with love and intelligence. It is not ruined. It is beautiful still, and can be even more beautiful, if we work together and care for it."<

    EDITOR'S NOTE: For an opposing viewpoint, see "Conservation in the Anthropocene" by Tim Caro et al., Conservation Biology 2011.


          
  • VIDEO: Native Peoples Consider Assisted Migration of Plants (2012)

    Beginning at 10:18 into this United Nations video (featuring indigenous awareness of climate change around the world), mention is made of how native peoples in the USA are already looking a hundred or more miles south in order "to see what plants are similar to the plants that are thriving today, because those plants may no longer thrive on their reservation tomorrow. They are looking to see what relatives they may be able to move, to assist, from other places."


  • "Review of science-based assessments of species vulnerability: Contributions to decision-making for assisted migration" by Tannis Beardmore and Richard Winder, 2011, The Forestry Chronicle - The following tools (for assessing potential for assisted migration) are discussed in relation to their use in Canada: (1) the NatureServe Climate Change Vulnerability Index; (2) the System for Assessing Vulnerability of Species to Climate Change (SAVS); (3) the Forest Tree Genetic Risk Assessment; (4) the Index for Predicting Tree Species Vulnerability; (5) ecological standards developed for the assisted migration of Torreya taxifolia; and (6) the Seeds of Success Program.
    EXCERPT: "This example [Torreya Guardians] of assisted migration has raised the issue of authorization and oversight as the official federal recovery plan does not identify assisted migration as a conservation strategy for Florida Torreya. The momentum that this group has created resulted in the U.S. Fish and Wildlife Service considering whether assisted migration is an appropriate strategy for this species (U.S. Fish and Wildlife Service 2010). It is yet to be seen if official plans will include a more thorough assess- ment of the ecological impacts of assisted migration, or more extensive monitoring programs. Nonetheless, this is a very interesting example of how a grassroots organization can pro- pel assisted migration into the forefront, causing a govern- mental agency to consider the use of this strategy."

  • "Why We Disagree about Assisted Migration: Ethical Implications of a Key Debate Regarding the Future of Canada's Forests" by I. Aubin et al., 2011, The Forestry Chronicle - "Although human-mediated movements are not a recent phenomenon, assisted migration has lately been the source of debate, in particular within conservation biology circles. In this paper, we outline the major perspectives that help define differing views on assisted migration and shed some light on the ethical roots of the debate in the context of Canadian forests."

  • "Assisted colonization is not a viable conservation strategy"(preprint of 2009 Trends in Ecology and Evolution paper) by Anthony Ricciardi and Daniel Simberloff Editor's note: This paper has often been cited as representative of arguments against assisted colonization.
    Strong argument against assisted migration in top ecological journal. Excerpt: "Until we develop more accurate and general methods of predicting the impact of introduced species, cost-benefit analyses will be dangerously misleading. It is not yet possible to quantify the probability that a given species will go extinct because of climate change, or that a translocated species will harm one or more native species in a recipient community. To compare two such illusory numbers would lead to a false sense of scientific certainty. . . . Given this lack of predictive power, assisted colonization is tantamount to ecological roulette and should probably be rejected as a sound conservation strategy by the precautionary principle."

    Note: A letter to TEE journal commenting on the above is "Assisted colonization is a techno-fix" by Ioan Fazey and Joern Fischer.

  • "Assisted Colonization Under the U.S. Endangered Species Act" by biologists Patrick D. Shirey and Gary A. Lamberti, in Conservation Letters, February 2010 3(1): 45-52 [full text in PDF online free access] ♦ Editor's note: This paper is an excellent summary of the ecological science, the law, the regulatory options, and the actions through 2009. It is clearly written from an objective position, neither pro nor con.
    "The paper represents a call to arms or a call to caution, depending on your perspective," says Gary Lamberti, the chair of the Department of Biological Sciences who is Shirey's advisor and co-author of the article. "When we're thinking about moving organisms around because of climate change or other environmental factors, we need to think about the legal framework that will enable or not enable us to do that. What Patrick did with his analysis was encourage policy makers and legal scholars to examine the statutes before we reach a crisis point." (quotation drawn from the author's online announcement of the paper). Here are several important legal conclusions made in the paper:
        "Current agency regulations impede alternative strategies such as assisted colonization for endangered animals, but do not impede assisted colonization of endangered plants." (p. 3) "On its surface, the statutory language of the ESA appears to provide the legal framework for allowing assisted colonization of endangered populations to new habitats primarily under Section 10(j), the experimental population provision" (p. 3) "In 1982 additions to the ESA, Congress sought to restrict the use of the experimental population provision as a means of removing protection from species and thus imposed procedural limits. Those limits, however, did not restrict the power of the agency to release species into suitable areas without considering historical distribution. The USFWS can authorize release outside the current range if 'release will further the conservation of such species' (citation). However, in promulgating regulations to implement the experimental population provisions, the USFWS added a geographic restriction in 1984 that prohibits an experimental population from being introduced outside the historic range, 'absent a finding. . . in the extreme case that the primary habitat of the species has been unsuitably and irreversibly altered or destroyed' (citation) (p. 5) "Perhaps the most successful case of assisted colonization of a plant listed under the ESA is the Virginia roundleaf birch (Betula uber). The first translocation of roundleaf birch occurred after the species was rediscovered in 1975 as a population of 41 trees (59 FR 59173). After the round-leaf birch was listed in 1978, the USFWS encouraged its distribution to conservation organizations and individuals (59 FR 59173). Despite protection of its habitat by agencies and landowners, the natural population of round-leaf birch declined to eight trees in 2003 (www.fws.gov/northeast/pdf/vabirch.pdf). However, because assisted colonization established 20 populations on U.S. Forest Service land, the USFWS reclassified roundleaf birch from endangered to threatened in 1994 (59 FR 59173)." (p. 6) "Regulatory restrictions placed on assisted colonization might be lesser obstacles to overcome than political and scientific resistance. Political opposition can include concern over costs of managing populations, resistance of landowners and local governments to introducing endangered species, and concern over species invasiveness. The threat of invasive species, in particular, raises legitimate scientific concern about assisted colonization." (p. 6) "Assisted colonization could be a viable management option to offset the human-caused and inseparable problems of habitat fragmentation and rapid climate change." (p. 7)

    To see what is going on in Europe on this topic, see pp 42-43 of Convention on the Conservation of European Wildlife and Natural Habitats: Standing Committee Report of November 2009.

  • "Naturalness and Beyond: Protected Area Stewardship in an Era of Global Environmental Change", by David N. Cole and 15 other coauthors, 2008, in The George Wright Society Forum 25:36-56.
    Highly useful integrative paper geared for managers of natural lands that examines the need for new philosophical and practical perspectives on management of parks and wilderness areas today, especially given rapid climate change. "Assisted migration" is discussed in this report, but in the much wider context, thus making this paper a key reading for background perspective as well as precise philosophical and management options that supplement the criterion of "natural" with more precise understandings of "historical fidelity," biodiversity conservation," "resilience," and "ecological integrity."

  • "Don't Judge Species on Their Origins" comment by Mark Davis et al., Nature, 9 June 2011.
    Excerpt: "Today's management approaches must recognize that the natural systems of the past are changing forever thanks to drivers such as climate change, nitrogen eutrophication, increased urbanization and other land-use changes. It is time for scientists, land managers and policy-makers to ditch this preoccupation with the native v. non-native dichotomy and embrace more dynamic and pragmatic approaches to the conservation and management of species — approaches better suited to our fast-changing planet.

  • "Climate Change Turns Conservationists into Triage Doctors" CBC News (Canada). 30 November 2009
    Survey of a shift in conservationists attitudes: "The point is not to think outside the box, but to recognize that the box itself has moved and, in the 21st century, will continue to move more and more rapidly," University of Colorado ecologist Timothy Seastedt and his colleagues write in the journal Frontiers in Ecology and the Environment. Seastedt and others argue land managers must focus on ecosystem diversity to give plants and animals the best chance to adapt to the change scientists say is coming: The more diversified a system, the more resilient. Trying to return ecosystems to some historic or natural state is no longer possible, they say. "To be honest, the combination of climate and atmospheric chemistries we're experiencing now — you can't find any historical match," Seastedt says.



    URBAN ECOLOGY ASSISTED MIGRATION

        A September 2014 4-page article, "Have Tree, Will Travel" is a superb way to grasp the paleoecological foundation that undergirds projects for which poleward "assisted migration" on the continent of origin is becoming standard practice in this century of rapid climate change. The author, park planner Kevan Williams, weaves the science and policy viewpoints into three sequential narratives:
        (1) a futile recent Nature Conservancy project of attempting to "rewild" a native camellia, Franklinia alatamaha, southward to its "native" (actually, peak-glacial) habitat in southern Georgia from its cultivated (rescue) domain near Philadelphia.
        (2) the ongoing (and thus far successful) attempt by citizen naturalists to work around the Endangered Species Act and thus on their own initiative move a critically endangered Florida conifer, Torreya taxifolia (photo left), from its peak glacial refuge in northern Florida into the southern Appalachians and points farther north.
        (3) the disaster looming large for even common forest trees, as climate shifts rapidly, along with the role that massive projects of assisted migration, on the one hand, and urban forest landscaping, on the other, could play in helping species move north.

  • "Climate change to Philly trees: It's not 1910 anymore" (news article) by Carolyn Beeler, 23 January 2015. Surveys Philadelphia and Chicago urban trees and parks managers who have already begun planting more southerly tree species on municipal lands. Joan Blaustein, head of urban forestry and ecosystem management at the Philadelphia Parks Department, is quoted: "We need to anticipate what the conditions are going to be 100 years from now, rather than trying to restore to 100 years ago." Beeler writes, "In the fall, the city will plant non-native trees suited to warmer climates, including the Southern chestnut oak and bald cypress, and plant some species native to Pennsylvania that are currently at the northern end of their range, such as the Southern red oak and red mulberry. . . In five years, Blaustein hopes the early results of her experimental test plots will give her an idea of which new trees to plant city-wide."

  • "Vancouver trees might not survive climate change", 29 February 2016, by Michael Mui, in 24 Hours Vancouver. Key quote: "[Bill] Stephen said that about 40 years from now, it's predicted the Metro Vancouver's climate would be much like northern California today." Editor's note: That news article is based on the newly released lengthy report: "Urban Forest Climate Adaptation Framework for Metro Vancouver: Tree Species Selection, Planting, and Management", February 2016, submitted to Metro Vancouver (Canada), by Diamond Head Consulting. Note: This is a long pdf. Advance to page 27, where this report begins as an attachment. See excerpts below.

    EXCERPTS: As a regional government, Metro Vancouver has an interest in increasing the resilience of the urban forest to climate change and maximizing the benefits from urban forests in the region. This project was initiated in response to concern that the region's existing urban forest may not be well suited to the changing climate and, if so, the need for practical guidance on how to adapt the urban forest. Healthy urban forests mitigate climate change and can help people and organisms adapt to the changing climate, playing a large role the region's ongoing livability. (p. 31) . . . Trees are a keystone structure of urban ecosystems [6]. Maintaining and enhancing the health and resilience of trees is essential for urban forests to continue producing beneficial services. (p. 32) . . . Tree populations in western North America [already] lag behind their optimal climate niche by approximately 130 km in latitude or 60 m in elevation (p. 49). . . The annual average temperature in Metro Vancouver is projected to warm by about 3°C over the next 40 years (p. 50). . . The longer growing season expected under climate change may expand the diversity of trees that can be planted in Metro Vancouver (p. 53). . . Fewer frosts and milder winters will enable some new tree species to successfully overwinter in Metro Vancouver. It is expected that the dominant extreme minimum temperature zones for the region will shift from USDA Hardiness Zone 7-8, to Zones 8-9. Longer growing seasons may also increase the growth and productivity of some tree species given adequate soil moisture and nutrient availability. However, responses are likely to be species specific due to differing developmental cues related to temperature and photoperiod. Regional evidence for how tree species will respond to a lengthened growing season is limited. Models generally agree that there will be fewer frost days, milder winters and a longer growing season (p. 57). . . Metro Vancouver has developed a "Design Guidebook" to assist people in designing tree plantings that maximize the climate adaptation benefits of urban forests. The guidebook provides the context for selecting an appropriate species across a wide range of tree planting opportunities (p. 60). The pace of climate change may exceed the capacity of native trees to adapt and there may be justification to influence the direction and timing of adaptation through assisted migration of better adapted tree species and seed sources. For native trees, seed provenance choice will be an important consideration because trees are already lagging behind their optimal climate niche. Further research is required to understand how assisted migration may be of relevance to managing native forests within an urban forestry context, and within the context of biotic nativeness in our region (p. 61). Metro Vancouver's heat days are projected to change from an average of 2 days per year to approximately 28 days per year in the 2080s. This represents a change from an average of heat zone 2 to an average of zone 4 or zone 5 at the upper range of variability (p.62).

  • 90 Foot Sequoia Tree in Downtown Seattle (news article) 20 March 2016. This is a news story about a man who damaged a sequoia tree, but the importance here is that this tree has a 34-inch diameter (DBH) and "The Seattle Transportation Department planted the sequoia when it was 20 feet tall in the early 1970s near a Macy's store at Fourth Avenue and Stewart Street. Officials fought to save it in 2010, when experts questioned whether it could survive in its city environment."

  • Tennessee Trees Moved to London Ontario? (news article) by Spencer Van Dyk, 23 December 2015, in The London Free Press (Canada), title: "London's urban foresters are laying the groundwork to test tree species now found in warmer climates". EXCERPTS:
       If rising global temperatures and Mother Nature have their way, pecan trees could be growing in London in 100 years or so. If urban foresters at city hall have their way, some trees indigenous to Tennessee, more than 1,000 kilometres to the south, will be rooted here a lot sooner than that. They want extra money in the 2016 budget from council for a project that would diversify the kinds of trees that grow in London, bringing in ones more suited to a warmer climate. It's a process called assisted migration.
         "Species that can survive in Tennessee today might be able to survive our future climate," said Sara Rowland, an urban forestry planner for the city. The first step would be more testing in 2016 by planting seeds in test plots from species that don't grow here now.
         . . . Assisted migration accomplishes what would otherwise take generations. If the city imports trees from 1,000 km south, London's trees could be moved north to somewhere like Thunder Bay, Rowland said.

  • "Species Migration Shaping Ecosystems of the Future" by Ruby Russell, 14 October 2014, Deutsche Welle
    KEY POINT: Those of us in the northern hemisphere may need to assist the poleward migration of today's even common species, but the biggest problem resides in the Southern Hemisphere — where terrestrial species may ultimately run out of southern latitude lands, owing to the shape and locations of the continents.

    CONCLUDING EXCERPT: "Looking at all life-forms, it is trees that move the slowest. The majority of trees cannot keep pace with climate change," Torreya Guardians' founder Connie Barlow says, adding that the Florida torreya's seeds are too large to be carried by the wind or most animals. Assisted migration is controversial, but Barlow and others argue that on a continental landmass like Europe or North America, terrestrial species have shifted back and forth with climatic change over the millennia, so that what seem like 'new' species combinations have actually existed in the past.
         What is unprecedented is the rate at which climate change is now happening. Chris Thomas says this means defending current species combinations may not always be the best approach. "If all our biological communities are going to change anyway, why should we not think about including within those biological communities — even if it requires us to intervene — some of those species which are truly endangered?" asks Thomas. He says some may not think this is very natural. But, then neither is current climate change, he points out.

  • "Assessing the potential for urban trees to facilitate forest tree migration in the eastern United States" by C.W. Woodall et al., 2010, Forestry Ecology and Management - helpful charts showing large urban areas of northeastern USA that have tree species in plentiful plantings north of their native range (e.g., Sweet Gum (Liquidambar) planted in New York City is 2 degrees latitude farther north; Southern Live Oak and Water Oak planted in Boston are 8 degrees and 5 degrees, respectively, farther north). Caveat: Ability of those individuals to actively move seed into surrounding wild forests is low; thus suburban plantings and outward plantings by landscapers will be more important to facilitate assisted migration in pace with climate change.

  • "As World Warms, How Do We Decide When a Plant is Native?" by Janet Marinelli, 2016, in Yale Environment 360. This excellent journalistic piece puts a recent botanical paper in the wider context of climate change and assisted migration. Lead author Jesse Bellemare is quoted in the article; his original paper (which features the USA understory tree Umbrella Magnolia), "Horticultural escape and naturalization of Magnolia tripetala in western Massachusetts: Biogeographic context and possible relationship to recent climate change", is excerpted in the Magnolia section of this webpage. Marinelli's article highlights the role of horticultural gardens in (inadvertently) facilitating long-distance assisted migration of otherwise slow-to-migrate native plant species. Her final paragraph:
    "While scientists grapple with the implications of escaped magnolias, there is poetic justice that a plant from the Dickinson homestead has sparked the discussion. Although the view of enduring wilderness championed by Thoreau and John Muir came to dominate conservation thinking, Emily Dickinson, who perceived the beauty and destructive capacity of nature all around her, may be the more appropriate literary icon for an age of climate disruption."


    2016

  • The broad footprint of climate change from genes to biomes to people, by Brett R. Scheffers, Science, 11 November 2016.
    EDITOR'S NOTE: Science is a top science journal in the world. In the excerpts below, it is now indisputable that climate is changing already far too fast for many species to keep pace with, absent human-assisted migration.
         EXCERPTS: In addition to reducing greenhouse gases, climate action and policy must therefore focus equally on strategies that safeguard biodiversity and ecosystems... Atmospheric concentrations of greenhouse gases from burning fossil fuels and de-forestation are approaching levels that have not been detected in the past 20 million years... We present examples of case studies of observed impacts across terrestrial and aquatic biomes and find evidence that climate change is now affecting most biological and ecological processes on Earth — spanning genetics, organismal physiology and life-history, population distributions and dynamics, community structure, and ecosystem functioning... Changes in species ranges have altered or created new hybridization zones across the planet. For example, in North America, hybrid zones between black-capped (Poecile atricapillus) and Carolina chickadees (P. carolinensis) are shifting in response to warmer winter temperatures, and because the southern flying squirrel (Glaucomys volans) has expanded its range northward in eastern North America, it is now hybridizing with the northern flying squirrel (G. sabrinus)... One of the most rapid responses observed for marine, freshwater, and terrestrial species is a shift in their distributions to track optimal habitat conditions. Across land and aquatic ecosystems, species have expanded their leading (cold limit) edge by 19.7 km per decade, with marine species expanding by 72 km per decade compared with 6 km per decade in terrestrial species... Several native insect species from North America, with no prior records of severe infestation, have recently emerged as severe pathogens of forest resources because of changes in population dynamics. These include the Aspen leaf miner (Phyllocnistis populiella), the leafblotch miner (Micrurapteryx salicifoliella), and the Janet's looper (Nepytia janetae), which have decimated millions of hectares of aspen, willows, and spruce-fir forests since the early 1990s. Known pests such as mountain and southern pine beetles (Dendroctonus frontalis and D. ponderosae, respectively) and spruce beetles (D. rufipennis) have recently expanded their distribution and infestation intensity on commercially important pine and spruce trees. These outbreaks may increase in the future because hundreds of plant pest and pathogen species have shifted their distributions 2 to 3.5 km year poleward since the 1960s.

  • Tree die-offs soaring, bringing fire danger and exacerbating water problems, news report, Orange County Register, 19 November 2016.
    EDITOR'S NOTE: Although this article makes no mention of assisted migration, the shocking escalation in tree deaths in California calls out for the need to normalize assisted migration as a first-order climate adaptation approach — now.

    EXCERPTS: Agriculture Secretary Tom Vilsack and Forest Service officials are seriously hampered not only by short-term budgets passed by Congress but also a broken budget for the Forest Service that sees an increasing amount of resources going to firefighting while less is invested in restoration and forest health, Vilsack said in a statement. Most of the 102 million dead trees are within 10 counties in the southern and central Sierra Nevada region. The Forest Service also identified increasing tree mortality in the northern part of the state, including Siskiyou, Modoc, Plumas and Lassen counties. This year, California had a record-setting wildfire season, with the Blue Cut fire alone scorching over 30,000 acres, mostly in the San Bernardino National Forest, and triggering the evacuation of 80,000 people, the statement said. As the state enters the sixth year of drought, water-starved trees have lost their ability to fight off bark beetles and disease, Cameron Barrows said. This is compounded by the rapid warming of winter temperatures, caused by global warming, which would turn the winter season into a continuation of their breeding season, he said. Cold winters would kill or at least slow the growth of tree enemies like the bark beetle and bacteria. Now their numbers can multiply significantly in their normally dormant season, Barrows said.

  • Climate Change Hits Turkey's Richest Highland, by Daniel J. Pierce, Daily Sabah, 9 November 2016.
    EXCERPTS: The people living in the highland villages of Kozak, located in the Aegean province of Izmir, enjoyed the highest per capita income in Turkey until eight years ago, when climate change hit their pine nut production. Nowadays, the villagers either make a meager living by working in stone quarries or mines. The villages are situated among dense pine forests, known by locals as the "green sea" and used to produce up to 2,000 tons of pine nuts, about 10 percent of global production... Many experts had investigated the reasons why the dramatic drop in pine nut production, Camgul said, adding, "At first everyone focused on bugs or fungus. At the end, the Izmir Forestry Department concluded that the cause was climate change."

  • Prehistoric Trees Could 'Future-Proof' Forests Against Climate Change, by Daniel J. Pierce, Motherboard, 24 October 2016.
    Explores the climate adaptation forestry work on British Columbia's Cortes Island by part-time resident (and "landscape artist") Oliver Kellhammer, who has been restoring a clearcut property he purchased with "formerly native trees", including Sequoia, Metasequoia, Redwood, and Cunninghamia.
         EXCERPTS: "We've been experimenting with growing trees [on Cortes] that have been extinct here for 50 million years and are still found in other parts of the world," Kellhammer told me. "It's an experiment to gauge whether the redwood, say, could be a replacement for the red cedar." Kellhammer had been planting Eocene trees in his garden on the island since 2002. In 2008, he got the chance to scale the project up when his friend, botanist Rupert Sheldrake, along with a co-operative of Cortesians, purchased a 60-acre clear-cut on the island. Kellhammer pitched the idea to Sheldrake, as he explained it to me: "Here we have an opportunity, Rupert, of a barren piece of land that's been terribly abused. Can we try to restore the land in a way that speaks to the future and to future climatic conditions?" Sheldrake was on board with the idea and agreed to bankroll the reforestation, according to Kellhammer. "Yes, we are playing God," he told me. "But we've already played God. The human species has changed the climate. I'm in the 'You broke it, you fix it' school, and we're trying to fix it." According to Kellhammer, the intention of this project was to start a conversation about how far we are willing to go to help forests adapt. "Do we let giant swaths of the landscape die [because of] things like the pine beetle? I thought that by starting this project, people would start asking what the appropriate response should be." While some people feel inclined to let the forests migrate on their own in response to the changing climate, we are on pace to see 50 million years' worth of planetary warming in about a century. Forests don't move that quickly. I mean the trees aren't just going to jump on people's cars and hitchhike up to B.C.," Kellhammer said. "It would take thousands of years." "We can't just sit back and hope it all works out. It's not working out," Kellhammer said. "I think we need to be moving species from more southerly latitudes to higher latitudes if we want them to survive." Seeing these strange trees grow on Cortes is a powerful reminder of just how much the climate has already changed. But it's also a reason to be hopeful. "The best candidates are the coast redwood and the giant sequoia. Those two are, hands down, very happy on Cortes Island," Kellhammer said.
         Note: See also Kellhammer's website for more detail on this paleoclimate restoration project. EXCERPT: Metasequoias in particular have done spectacularly well and a couple of my ten year-old specimens have reached over 8 metres in height. These are amazing trees — deciduous conifers long though to have been extinct and causing a sensation when they were found surviving in a remote part of China back in 1944. Yet their fossil remains are distributed throughout the Northern hemisphere, from mid latitudes right up to the high Arctic where their deciduous needles might have conferred them an advantage during the darkness of the polar winter. Work on this "Climate Change Forest" is ongoing and our hope is that the successes and failures in establishing the various tree species will yield some useful information on the future of forests under conditions of rapid global warming. Perhaps some of the trees might possess a kind of genetic memory and will once again flourish in BC's forests as they did so many aeons ago. If that is the case, the reintroduction of these Eocene survivors might prove part of a larger strategy to manage the climate cataclysm that has only just begun.

  • Planning for assisted colonization of plants in a warming world, by Alessandro Ferrarini et al., Nature, 27 June 2016.
    Excerpt: Results raise one main question: are assisted colonization activities worthwhile if they are only expected to be successful in the short or medium term? It is evident that a modelling approach like that proposed here can provide the basis to rigorously examine this question. It has been suggested that the success of assisted colonization activities also involves the population dispersing seeds into the surrounding countryside and producing satellite populations. Our results indicated that not only is C. foetida likely to disappear from the peripheral area in the future due to climate scenarios, but also that in the N-Apennines mountain system (Emilia-Romagna region) there will be no further suitable sites for this species. In other words, producing satellite populations in surrounding areas is unlikely for C. foetida even under current climate conditions, and it will become increasingly improbable as time goes by.

  • Ravaged Woodlands, by staff of The Economist, 9 July 2016.
    Editor's note: This lengthy article excels in presenting the scale and frightening implications of climate-induced bark beetle outbreaks and wildfires in wild forests of western North America, focusing on California. This is a superb introduction and/or review of the impact of climate change on forests and forestry for the public and experts alike. Although only a few paragraphs deals with assisted migration as a climate adaptation strategy, the article as a whole establishes the need and the difficulty in compelling terms.
        EXCERPT: Mitigating those effects would require a massive intervention to clear dead trees and plant new ones, which is currently unthinkable. Last year the U.S. Forest Service spent more than half its budget on firefighting, to the detriment of its ongoing effort to thin some 80 million acres of dangerously overgrown forest. By 2025, the service estimates that 67% of its budget will be consumed by fires. Even if the lost forest were replanted much of it would fail: because species distribution is changing as temperatures rise. Broadly speaking, a warmer, drier climate should force trees uphill and to higher latitudes; the Ponderosa pine will climb from the montane to the subalpine zones, displacing or finding refuge among white firs and lodgepole pines. Anticipating this, foresters are replanting trees at the highest elevations of their range. The effect of fire and bug-death has, in this way, created opportunity for a massive experiment in tree migration and regrowth. But it may not be a predictable, or happy, transition. Whether a species can migrate may depend as much on factors such as soil type, distance from a seed source, the pace at which it reaches reproductive maturity and the vulnerability of higher-elevation vegetation to infiltration as on temperature alone. The rate of warming will be even more important. It took the Ponderosa pine 11,000 years to migrate from New Mexico to Wyoming after the most recent Ice Age: it will not keep stride with rapid warming. A study of USFS data suggests nearly 60% of tree species are experiencing range contraction at both their northern and southern boundaries. Only 20% are making the predicted northward shift.

  • "Agency launches long-term spruce, aspen treatment plan by Dennis Webb, The Daily Sentinel (Grand Junction, Colorado), 6 August 2016.
    EXCERPTS: Responding to habitat shifts resulting from climate change will be one of the considerations for the Grand Mesa, Uncompahgre and Gunnison national forests as the Forest Service embarks on a new forest treatment project over the next eight to 12 years. Its new Spruce Beetle Epidemic and Aspen Decline Management Response project is a response to about 223,000 acres where spruce have died from beetle infestation on the forests, and 229,000 acres that have been affected by what's called Sudden Aspen Decline, over a decade.
         The Forest Service expects mortality in spruce stands "to continue at relatively high levels for several years to come," according to the final environmental impact statement for the project. In 2009 the detection of new areas of aspen decline dropped considerably, but stands already affected continue to decline, and the Forest Service expects the aspen and spruce problems to be exacerbated in the future by climate change.
         While the new forest treatment plan is intended to also address other goals like reducing safety hazards such as falling trees and increased wildfire danger, improving forest resiliency is a key goal. That includes trying to make the forest resilient in the face of a changing climate. "In the climate change world, that's called adaptation measures — basically trying to adapt the forest to a changing climate," said Jim Worrall, a Forest Service forest pathologist who helped do the climate modeling. He said quite a few outcomes of the management response project "could help adapt the forest to a warmer and potentially drier climate."
         Worrall said where logging of beetle-killed spruce occurs, that could provide an opportunity for regenerating those acres with more aspen, or other trees more tolerant of an expected hotter, drier climate, such as Douglas fir, ponderosa pine and blue spruce. "I think at first it's going to be baby steps because people are a little bit cautious, and reasonably so, about completely changing a (forest) cover type," he said. Where there's spruce-fir forest, it might be crazy to start planting pinon-juniper now, even if models say it would be good pinon-juniper habitat by the end of the century, he said.

  • Also by Dennis Webb, 6 August 2016, "Cycle of decline: Estimate portends big changes in makeup of forests".
         EXCERPTS: Lovers of the local high country could find a recent projection of a warming world's impacts on area forests to be chilling. By 2060, according to a U.S. Forest Service estimate, almost all of the Uncompahgre Plateau would no longer be able to sustain growth of new aspen and spruce, meaning that the plateau could be virtually aspen- and spruce-free by century's end after the remaining trees die. On the southern and eastern fringes of Grand Mesa, aspen also could see sizable losses of suitable habitat by 2060, with spruce habitat largely slipping into a threatened category across the mesa, meaning the future climate isn't favorable to sustaining it.
         The modeling used by the Forest Service found that 52 percent of current aspen distribution across the forests would be in the lost habitat category by 2060, and 42 percent in the threatened category, "meaning it is conceivable that 94 (percent) of current aspen distribution may not continue into the next century," the Forest Service says in its final environmental impact statement for the project, released earlier this year. Aspen habitat generally would be lost at low elevations, especially on south-facing slopes, with the western West Elks also sharing in that habitat loss. Some of that habitat loss could be offset by newly emerging habitat at higher elevations. But Samantha Staley, a Forest Service planner, says while the climate may shift to support the species at a higher elevation, that doesn't mean that other ecological components necessary to support the species will be present. Some higher elevations may not be suitable thanks to things such as poor soil conditions or rocky scree slopes. The model projects a 22 percent loss of current spruce distribution, and that 58 percent of distribution will become threatened, meaning that 80 percent of current distribution may not continue into the next century.
         The model is based on an assumption of a continuing warming trend on the forests. The statement says temperatures are expected to rise 5.4 to 7 degrees by 2040-60. Higher temperatures could foster more spruce beetle outbreaks, further stress trees because of increased drought and result in more damage from wildfire. "I think what those maps show is stunning,"Zukoski said. "I think those kind of maps are extremely helpful because they permit people to see in their areas, places that they care about in their backyards, what the world's going to be like for their kids and grandkids, and for themselves if they live long enough. I think giving people that picture over that longer term really helps them understand how dramatic the impacts of climate change could be if we don't work darn hard to get a handle on it."
         Meanwhile, a 2006 model created by researchers led by Gerald Rehfeldt, who worked at the Forest Service's Moscow Forestry Sciences Laboratory in Idaho before retiring, projected a 47 percent drop in suitable spruce habitat in the western United States in the decade around 2060, and a 72 percent loss by 2090. The Forest Service statement says that for the forests, that model was rebuilt using local data, more "topographical predictors," newer global climate models and carbon scenarios, and higher-resolution climate data. Its resulting projections are an average from three climate models and three greenhouse gas emission scenarios. "These are models, which necessarily include some amount of error," Staley said. She said it's based on the best available information today, and the Forest Service understands the science will be a lot better in a decade. "We have to look at it as it's not the gospel, but it's the best available scientific information that we have today about where vegetation may be headed in the future," Staley said.
         Jim Worrall, a forest pathologist with the Forest Service’s Rocky Mountain Region 2, which includes Colorado, said Rehfeldt worked with him and others to localize his methods, and they developed a model for 13 tree species in southwest Colorado, including spruce and aspen. Worrall said one of the biggest uncertainties pertains to the climate models, because there are so many models and carbon scenarios to choose from. He said the forest-habitat predictions the Forest Service came up with concern him and he hopes they're wrong, but they're the best idea researchers now have of what the future holds. "It's really a very objective process. There's really no subjectivity in the model development," he said. Interpreting the results to make them simple and easy to digest can be a little subjective, he said. "But we've been pretty conservative in that," he said, adding that the predictions are based on what the models are telling researchers, and those models are built on a lot of data.
         Staley said the agency is compelled to use that science in its planning and efforts to manage sustainably into the future, and current research acknowledges that warming will result in shifting of not just animals but trees in terms of habitat. "The environment is changing and that's why we're using as much information as we can to make the best decisions," she said. Forests are always changing, thanks to factors such as insect infestation and wildfire, and cycles such as aspen thriving first in disturbed areas and later being succeeded by other types of trees. But now the Forest Service is learning more about how that's happening in the context of "pretty rapid climate change," and what the forest may look like in that context, Staley said.
         While every generation sees a slightly different version of a forest, future forests may be ones that people have never seen locally, she said. Rather than a mid-elevation forest shifting back and forth from aspen to spruce, it may shift to oakbrush. "And that's a new shift," she said. Oakbrush and mixed-mountain shrubs cover about a quarter of the Uncompahgre Plateau now.
         [Jim Worrall] said of the modeling's findings, "I think we need to plan for the worst and hope for the best, is what I suggest. But most likely even if the models are a little off, we're going to be looking at very different conditions in the future for our children and our children's children than we have now."
  • "Relocating Australian tortoise sets controversial precedent" by Dyani Lewis, news report, Science, 11 August 2016.
    EXCERPTS: [final 3 paras] Even if the tortoises prove benign, as Mitchell and Kuchling anticipate, Ricciardi fears that such trials set an alarming precedent. "Other people are going to be looking at [this trial] and they're going to be saying, 'OK, what about my species?'" he says. "I wouldn't like to spin that roulette wheel very many times."
         Assisted colonization has already been used for plant species, such as Torreya taxifolia, an endangered conifer native to the Florida panhandle. Conservationists in New Zealand are also weighing the strategy to save the endangered hihi, or stitchbird (Notiomystis cincta), which faces an uncertain future if not moved to cooler climates farther south.
         But Possingham doubts the floodgates will open any time soon. "It's not open slather," he says, and scientists will judge each proposed colonization on its merits. For Possingham, who thinks assisted colonization will become a "pragmatic" conservation tool to prevent extinctions, results of the trial can't come soon enough. "Unless we try these things, we'll never learn how to do them, so the sooner the better."

  • "Uprooted: How climate change may kick off an artificial migration of trees" by Alessandra Potenza, news report, The Verge, 22 August 2016.
    EXCERPTS: "The problem with trees is they can migrate only very slowly," says Sally Aitken, the director of the Centre for Forest Conservation Genetics at the University of British Columbia. "They really can't move quickly enough to keep up on their own." Climate change has already altered how we approach forest management. . . Park managers will soon need to find new ways to protect trees, whether it's with assisted migration or some other solution. "A national park has generally been a system where we take a hands-off approach to management," Mark Schwartz says. "If anything, trying to restore ecosystems to some historic, pristine state." But now, park managers are struggling to find new ways to preserve the nation's forests.
         Some people are taking conservation in their own hands. Connie Barlow, a retired science writer and amateur ecologist, launched her own assisted migration program in the US. Her goal is to save Torreya trees, which only survive in northern Florida in their native range and are listed as endangered under the Endangered Species Act. In early 2000, Barlow acquired Torreya seeds and seedlings from botanical gardens and nurseries, and began planting them in private forests and yards in North Carolina. Since then, she's also planted Torreya trees in Virginia, Tennessee, Ohio, and New Hampshire, with the help of other volunteers. "Citizens need to step forward and we've shown we can do it," Barlow says. "What's undeniable now is that climate change is happening so rapidly ... that even common species are going to have to be moved by humans, intentionally."
         Some ecologists, however, are wary of her actions, and accuse her of acting too fast, without conducting the proper research. "I thought it was very premature," Schwartz says. "We have no indication yet that management will be able to save the species within its native range. It is declining toward extinction." Others support what Barlow's doing. Torreya trees are very "low risk" — their seeds don't disperse easily, so they're not likely to become invasive species, says Gray-Steinhauer at the University of Alberta. "As far as a conservation effort, it's appropriate," she says. "It's a good strategy."
         In the US, forest managers are considering a less controversial form of assisted migration that has to do with seed selection, according to Christopher Woodall, a research forester at the Forest Service. Instead of moving trees north, forest managers are selecting seeds of the same tree species that live in warmer climates and are therefore more resistant to droughts.
         Whatever strategy is used, most conservationists agree that something needs to be done. Saving trees means much more than just saving forests: it means saving the habitat where many other species live in, it means saving the roots that regulate water flow, and the mechanisms that take in carbon dioxide and create the oxygen we need to live. "Doing nothing, we lose the species," says Gray-Steinhauer. "Doing something, we take a risk but we don't know for sure. So you have to weigh out those pros and cons."

  • "How Climate Change Will Transform the National Parks' Iconic Animals and Plants", by Ker Than, Smithsonian Magazine, 8 August 2016.
    EXCERPTS: There was a time when the notion of letting prized native species die out seemed heretical. Now the agency is bracing for the possibility that some of the species under its care simply won't make it. It is also openly discussing the possibility of "assisted migration": manually relocating some animals and plants if it turns out they can't survive within the park's changing landscapes. These kinds of last-resort actions are controversial even amongst conservationists, but the NPS believes it is time to consider implementing them one day. "We don't rule out managed relocation in the future," says Patrick Gonzalez, the agency's principle climate change scientist. "But there are a lot less costly and less risky things we can try first."
         Faced with the possibility of losing one of its most iconic symbols, the park service must now consider what lengths it is willing to go to save the giant sequoias. One of its options is assisted migration, also known as managed relocation or climate translocation. Last year, NPS scientists used this technique to move bull trout in Montana's Glacier National Park. The researchers transferred trout from a lake where their numbers were dwindling—as a result of warming conditions and predation from another invasive trout species—to a higher-elevation lake that was cooler and free of predators.
         A sequoia relocation project in California would be even more ambitious. "We managed the giant sequoia forests now in such a manner that they can reproduce, but do we know whether or not that particular niche will allow those trees to mature in the future?" Jarvis says. "Is there a place in the Southern Cascades, as opposed to the Sierras, that we should be thinking about planting giant sequoias so that they'll still be around a thousand years from now? That's the way we've got to be thinking. We are in the perpetuity business here, so that's the space that we're beginning to explore."
         Christy Brigham, chief of resources management and science at Sequoia and Kings National Park, says the NPS's plans for assisted migration of giant sequoias are still purely speculative. "I would say we are at least five to ten years away from having to decide whether we need to take that step," Brigham says. "So far, a warming climate hasn't really been hurting the giant sequoias," adds Stephenson.
         Another drastic option is to transplant pikas into parks where the animals once existed but are not currently found. "Great Basin National Park is a place that looks like it could support pikas," says Tom Rodhouse, an NPS ecologist who headed the Pikas in Peril project. "But if we do that, it's controversial. These are really interesting conversations, and I think the park service is going to have many more like them in the coming decades."
         NPS director Jarvis says that if the parks are to survive another century, there is no question they will have to change. He gives the example of the iconic Joshua Tree National Park in California. "We may not be able to maintain Joshua trees in Joshua Tree National Park, but that doesn't mean that Joshua Tree National Park is somehow devalued," he says. "It will just become home to something new."

  • "Climbers Are Scaling The World's Tallest Trees In An Effort To Save Them", by Dominique Mosbergen, Huffington Post, 7 September 2016.
    EXCERPTS: Assisted migration, or the process of moving plants to new habitats, is a contentious topic among scientists. Some believe that "playing God" in this way could have negative consequences to fragile ecosystems. Others, however, are adamant that such efforts are necessary to save species at risk of extinction due to climate change and other human impacts. Archangel and the Eden Project both fall firmly in this second camp. The two groups are now working together to bring "living archives" of trees to other countries worldwide. They hope to bring their propagation efforts to all seven continents in the coming years. China, Canada and Australia are among the countries to be tackled next.




    PALEOECOLOGY and BIOGEOGRAPHY

  • Taking the Long View: Integrating Recorded, Archeological, Paleoecological, and Evolutionary Data into Ecological Restoration - by Rebecca S. Barak et al., 2015, International Journal of Plant Sciences
    EXCERPTS from the "Climate Change" section: Looking at the past is the best way to predict the effects of climate change on communities and ecosystems (Jackson 2007). Many North American plant species originated 20-40 million years ago and have thus been exposed to numerous periods of warming and cooling over that time period (Millar and Brubaker 2006). Understanding the trajectories of species and communities over past climate changes can help inform design and implementation of modern restorations. Paleoecological and evolutionary data—combined with modeling—allow for the reconstruction of past responses to climate change and can help contemporary restorationists plan for the future.
         Paleoclimate reconstructions paired with paleoecological data expand the range of conditions that supply perspective to restoration efforts. The paleoecological record contains examples of community stability over thousands of years, despite climate change (Brubaker 1975; Minckley et al. 2011), as well as sometimes dramatic and rapid community changes in response to climate change (Grimm 1983; Umbanhowar 2004). There are also no-analog pollen records from the past during the late glacial periods of the Quaternary, from 17,000 to 12,000 yr ago (Williams and Jackson 2007). These communities contained species that still exist today but are no longer found together in ecological communities (Williams and Jackson 2007). Such communities also existed much more distantly in the past, for example, during the Paleocene-Eocene Thermal Maximum (PETM), a period of intense climatic change ca. 55.8 million years ago that is used as an analog for today's anthropogenic climate change, since warming during the PETM was also caused by elevated carbon dioxide emissions (Dietl and Flessa 2011; McInerney and Wing 2011). Studying plant macrofossils from before, during, and after the PETM, Wing and Currano (2013) determined that plant community composition during the PETM is distinct from that before or after. This reflects migration rather than extinction, since missing species reappeared in the fossil record following the PETM. That there was little evidence of mass extinctions during the warming of the PETM may provide some comfort to restoration ecologists today. However, it is unclear to what extent current warming will mirror that of the PETM, especially as contemporary rises in carbon dioxide emissions are occurring at much faster rates than during the PETM (McInereny and Wing 2011).
         Paleoecological and phylogeographic data, along with species distribution modeling, are being used to determine the locations of past climate refugia—areas where species survived periods of intense climate change—and to predict the locations of future refugia (Gavin et al. 2014). Management can be prioritized to conserve and/or restore these areas in preparation for further change (Millar et al. 2007; Shoo et al. 2013). Similarly, phylogenetic data can be used to determine species that are likely to be vulnerable to climate change. Willis et al. (2008) studied the phylogenetic signal of changes in species' abundance and flowering time after 150 yr, using data initially collected by Henry David Thoreau in Concord, Massachusetts. They found that lineages with flowering times that did not track with climate change were declining and in danger of local extirpation. Thus, phylogeny, along with historical data, could be used to identify vulnerable species that would be unlikely to adapt (through evolution or plasticity) to changing climates and prioritize those species for interventions, such as assisted migration (Vitt et al. 2010).
         Historical and modeling data can also be used to identify locations for establishing neonative communities, defined as restoring species to an area where they were found in the past but do not currently occur (Millar et al. 2007). On a shorter timescale, dendrochronology in combination with climate projections can be used to identify the tree species and communities most vulnerable to changing climates (Williams et al. 2010). Fule (2008) recommends focusing management on forest habitats that are likely to persist through climate change—such as higher-latitude, higher-elevation sites—and using both historical and predicted climate data to engineer forests in areas where they are likely to persist in future climates.
         Several of these ideas, including climate refugia and corridors, are tied into the concept of conserving nature's stage. This strategy focuses on conserving geological diversity (geodiversity) as a surrogate for biological diversity (Beier et al. 2015). Geodiversity is strongly tied to biological diversity, and conservation of geodiversity may help to mitigate species losses due to climate change (Gill et al. 2015; Lawler et al. 2015). Ensuring that restoration areas include geomorphic heterogeneity may be one way to prepare for a changing climate. Appropriate species (the actors on the stage) may be added as climates change (Comer et al. 2015). Conserving the stage will create diverse habitats for evolution in future climate regimes (Lawler et al. 2015).

  • Projected distributions of novel and disappearing climates by 2100 AD - by John W. Williams et al., 2007, Proceedings of the National Academy of Sciences

       ABSTRACT: Key risks associated with projected climate trends for the 21st century include the prospects of future climate states with no current analog and the disappearance of some extant climates. Because climate is a primary control on species distributions and ecosystem processes, novel 21st-century climates may promote formation of novel species associations and other ecological surprises, whereas the disappearance of some extant climates increases risk of extinction for species with narrow geographic or climatic distributions and disruption of existing communities.

    Here we analyze multimodel ensembles for the A2 and B1 emission scenarios produced for the fourth assessment report of the Intergovernmental Panel on Climate Change, with the goal of identifying regions projected to experience (i) high magnitudes of local climate change, (ii) development of novel 21st-century climates, and/or (iii) the disappearance of extant climates. Novel climates are projected to develop primarily in the tropics and subtropics, whereas disappearing climates are concentrated in tropical montane regions and the poleward portions of continents. Under the high-end A2 scenario, 12-39% and 10-48% of the Earth's terrestrial surface may respectively experience novel and disappearing climates by 2100 AD. Corresponding projections for the low-end B1 scenario are 4-20% and 4-20%. Dispersal limitations increase the risk that species will experience the loss of extant climates or the occurrence of novel climates. There is a close correspondence between regions with globally disappearing climates and previously identified biodiversity hotspots; for these regions, standard conservation solutions (e.g., assisted migration and networked reserves) may be insufficient to preserve biodiversity.
         By the end of the 21st century, large portions of the Earth's surface may experience climates not found at present, and some 20th-century climates may disappear. The combination of high CO2 concentrations, still-extensive ice sheets in Greenland and Antarctica, and current orbital and land-ocean configurations are geologically unprecedented. Already, CO2 concentrations exceed any recorded for the last 650,000 years and, without a substantive intervention, are projected to increase to 540-970 ppm (140-263% relative to 2000 levels) by 2100 AD. Global mean temperatures are projected to increase by 1.4-5.8 degrees C by 2100 AD, with decreases in diurnal and seasonal temperature ranges and spatially variable changes in precipitation. It is increasingly likely that some end-21st-century climates will include conditions not experienced at present ('novel' climates) and that some present climates may disappear.
         This conceptual framework is reinforced by observed ecological responses to the last deglaciation, which were characterized by large changes in species ranges, and, in places where past climates apparently lacked modern analogs, the development of species associations and biomes with no modern counterpart. Metaanalyses indicate already detectable responses to 20th-century temperature rises, with range shifts averaging 6.1 km per decade toward the poles. Dispersal limitations may cause species responses to lag rapid climate change, promoting the formation of disequilibrial relationships between species distributions and climate. . . Rapid changes further enhance extinction risk by increasing the rate of climate change relative to the capacity of species to adjust by migration and colonization.
         Different ecological risks are associated with the prospect of novel versus disappearing climates. Novel temperature regimes, combined with changes in precipitation, may lead to novel species associations and other unexpected ecological responses, as has occurred in the past. Because the pre-Industrial Revolution climate system was already in a warm state, further increases in temperatures are likely to be novel not just relative to the 20th century but also to climates for at least the last million years. Tropical species may be particularly sensitive to 21st-century warming because (i) tropical temperatures vary less than high-latitude temperatures at daily, seasonal, orbital, and tectonic timescales, and (ii) range size tends to decrease toward the equator (Rapoport's Rule), so that tropical species are more narrowly endemic in both geographic and climatic space. Ecosystem models suggest that Amazonia is at particular risk for increased fire frequency and loss of forest cover. The potential for ecological surprises in the tropics adds urgency to current conservation efforts.
         Disappearing climates increase the likelihood of species extinctions and community disruption for species endemic to particular climatic regimes, with the largest impacts projected for poleward and tropical montane regions. Many have warned that climate change may drive certain species and ecosystems to extinction, e.g., in high latitudes, the South African Fynbos, and neotropical cloud montane forests. Our analysis places these regional alarms in a global context and goes further by showing that, in many cases, these climates may disappear entirely from the global set of end-21st-century climates. The areas of disappearing climates closely overlay regions identified as critical hotspots of biological diversity and endemism, including the Andes, Mesoamerica, southern and eastern Africa, Himalayas, Philippines, and Wallacea. In these areas, elevated risks of extinction are likely, as is the disruption and disaggregation of extant communities. Even with a conservative estimate of dispersal constraints, dispersal limitations greatly increase the risk that species will experience the loss of extant climates or the occurrence of novel climates. Efforts to conserve biological diversity in the face of climate change, e.g., by establishing dynamic networks of connected reserves that can facilitate species migrations or "rewilding" or otherwise assisting species migrations, may help overcome dispersal limitations. However, for those regions, communities, and species whose 20th-century climates lack 21st-century analogs anywhere globally, such approaches will be insufficient. Furthermore, because of the spatial segregation between novel and disappearing climates, species at risk of extinction due to disappearing climates are unlikely to be well positioned to take advantage of new climatic regimes.

  • The Influence of Paleoclimate on Present-Day Patterns in Biodiversity and Ecosystems - by Svenning et al., 2015, Annual Review of Ecology, Evolution, and Systematics
    P. 565 - Modeling studies suggest that we should expect disequilibria not just in assemblage composition (Dullinger et al. 2012a, Normand et al. 2013) but also in ecosystem structure, with tree line advances lagging behind climate for 100s to 1000s of years (Chapin & Starfield 1997, Normand et al. 2013). . . . The existence of paleoclimatic legacies also has important implications for conservation actions. These legacies indicate that species are often not able to track climate changes and point to the need for considering assisted migration as a tool to preserve biodiversity and sustain or restore ecosystem functioning under future climate change (Lunt et al. 2013). This will particularly be the case for the broader landscape and in particular in human-impacted and/or lowland areas where it will be most difficult for species to migrate fast enough to track climate change, as already seen (Bertrand et al. 2011). However, as active relocation will be unfeasible for much of biodiver- sity, there will be a strong need for protecting areas that offer good local possibilities for climate tracking or are likely to act as climatically stable refugia (Ackerly et al. 2010, Loarie et al. 2009).
         P. 566 - Importantly, the majority of studies of biodiversity and ecosystem patterns still do not consider the potential role of paleoclimate in codetermining the observed patterns, despite its potential importance in many cases. For example, this is true for many studies that rely on species distribution modeling to test ecological hypotheses or for conservation assessments (e.g., to assess risks from future climate change). The strong evidence for paleoclimatic legacies in species distributions have implications for how such modeling should be implemented. Notably, in forecasting studies it is important to avoid approaches that strongly rely on species ranges being in equilibrium with the current environment (e.g., De Marco et al. 2008); at the minimum, a critical assessment should be made of the extent to which such an assumption is valid in every given case and careful consideration given to the consequences of any violations.

  • Will Plant Movements Keep Up with Climate Change? - by Richard T. Cortlett and David A. Westcott, 2013, Trends in Ecology and Evolution.
    ABSTRACT: In the face of anthropogenic climate change, species must acclimate, adapt, move, or die. Although some species are moving already, their ability to keep up with the faster changes expected in the future is unclear. 'Migration lag' is a particular concern with plants, because it could threaten both biodiversity and carbon storage. Plant movements are not realistically represented in models currently used to predict future vegetation and carbon-cycle feedbacks, so there is an urgent need to understand how much of a problem failure to track climate change is likely to be. Therefore, in this review, we compare how fast plants need to move with how fast they can move; that is, the velocity of climate change with the velocity of plant movement.
        EXCERPTS: Paleoecological studies show that movement was a near universal response to past changes in climate and many species have moved in recent decades in response to rates of climate change that are apparently unprecedented in the Holocene. However, some plant species failed to keep up with the generally slower warming at the end of last glacial period and most plant populations have tracked recent warming only partly or not at all. Failure to track climate change is expected to have a large impact on growth and survival, leading to plant extinctions and a reduction in the strength of the terrestrial carbon sink.
         No plant extinctions have so far been attributed to recent climate change and only one species, the previously widespread Picea critchfieldii, is known to have become globally extinct during the Late Pleistocene from natural climate change. In vertebrates, however, the strong association between low rates of local endemism and high velocities of climate change since the last glacial maximum is most easily explained by increased extinctions when species fail to track climate change. Moreover, the association is strongest in amphibians, the most poorly dispersed group, and weakest in the relatively mobile birds. Although there has not yet been a similar study for plants, these results suggest that we are underestimating the number of species lost to natural climate change and, thus, the importance of movement velocity in buffering against extinction.

  • Paleoecology meets genetics: deciphering past vegetational dynamics - by Feng Sheng Hu, Arndt Hampe, and Remy J. Petit, 2009, Frontiers in Ecology Environ.
    EXCERPTS: Genetic data compensate for some of the shortcomings of the paleoecological approach. Recent surveys of DNA polymorphisms yield new insights into past vegetational dynamics and help address key paleoecological questions. However, studies that truly integrate genetics and paleoecology are rare. This paper highlights some of the recent developments in this field, rather than providing a comprehensive review of all the relevant literature. We focus on tree taxa with extensive fossil records that can be compared with marker-based genetic surveys (for a discussion focusing on adaptive traits, see Davis et al. 2005). We first briefly explain how ice-age refugial populations and their post-glacial recolonization left such durable genetic imprints on modern-day tree populations. We then review case studies that provide genetic insights into the locations of glacial refugia and the spatial patterns of postglacial recolonization. We discuss the consequences of past population dynamics on the genetic structure (eg variation in allelic frequency and genetic diversity) of extant trees, as well as the implications for conservation. During glacial episodes, temperate and boreal tree species were primarily restricted to areas far south of the continental ice sheets, although small populations of some species apparently also survived in periglacial (the outer perimeter of a glacier) environments and in high-latitude areas that were free of glaciers. At the end of each glacial episode, refuge populations responded to climatic amelioration and expanded their distributions to form interglacial plant communities, including those we see on the landscape today. . . Refugial tree populations that have persisted through multiple glacial cycles tend to have highly divergent gene pools. They are therefore potential priorities for the conservation of diversity and evolutionary heritage. . . Latitudinal patterns of genetic diversity and divergence should be taken into consideration in the current debate over the possible advantages of assisted migration in response to climate change. . . Some tree taxa, such as Picea glauca and Pinus banksiana (jack pine) in North America, went regionally extinct in the areas of their main glacial refugia during postglacial range shifts (Jackson et al. 1997). Massive diversity losses must have occurred at the trailing edges; today, therefore, their southern populations may not have a greater diversity than that of northern populations.

  • Conserving Biodiversity Under Climate Change: The Rear Edge Matters - by Arndt Hampe and Remy J. Petit, 2005, Ecology Letters.
    EXCERPTS: Here, we argue that rear edge populations, defined as those populations residing at the current low-latitude margins of species' distribution ranges, are disproportionately important for the long-term conservation of genetic diversity, phylogenetic history and evolutionary potential of species and that their investigation and conservation deserve high priority. . . The value of relict populations at the low-latitude margins of many species' distribution ranges has remained largely unperceived by conservation biologists. Some glacial relicts have been included in regional or national red lists, but neither research nor conservation programs seem to have been dedicated to rear edge populations per se (although Lesica & Allendorf (1995) have considered the conservation value of peripheral populations in general). Here, we outline three areas in which further development of research and conservation measures appears particularly necessary. Hence, specific conservation measures will have to be identified to effectively preserve these relict populations.

  • "Paleoecology and the Assisted Migration Debate: Why a Deep-Time Perspective Is Vital" - online essay by Torreya Guardian Connie Barlow, February 2011.
    Connie Barlow (with assistance from Russell Regnery) has posted a short, 11-point summary essay that aggregates the data and develops strong scientific reasoning in favor of assisted migration for Torreya taxifolia. The essay also advocates a shift in the foundational paradigm from assuming 1491 is the proper time-standard for assessing native range to a "deep-time" perspective grounded in a paleoecological understanding that native ranges for all plants in temperate latitudes of the Northern Hemisphere have undergone substantial altitudinal and/or latitudinal migrations that have tracked changes in climate during the past several million years of Pleistocene glacial and interglacial cycles.

  • "Deep-Time Lags: Lessons from Pleistocene Ecology" by Connie Barlow, in Gaia in Turmoil: Climate Change Biodepletion, and Earth Ethics in an Age of Crisis, edited by Eileen Crist and H. Bruce Rinker, 2009, MIT Press.
    Torreya Guardians founder Connie Barlow contributed a chapter on the importance of a "deep time" perspective for conservation biologists and biodiversity activists coming to grips with the extinction crisis in an age of rapid climate change. The plight of Torreya taxifolia and the work of Torreya Guardians are used as the key example of "Assisted Migration in a Time of Global Warming".

  • "The Torreya taxifolia USF&WS Recovery Plan Process: An Opportunity to Shift to a Deep-Time Perspective of Native Habitat" - comments and suggestions by Connie Barlow, 12 May 2010
    Submitted to the U.S. Fish & Wildlife Service officer in charge of updating the Endangered Species Recovery Plan for Torreya taxifolia. EXCERPT: "If one agrees with the widely held premise that the habitat along the Apalachicola River in northern Florida and southern Georgia served as a premier 'pocket refuge' for many temperate-zone species during the peak glacial episodes of the past several million years, then one is moved to revamp formal ecological definitions of 'native habitat' and 'native range' in ways that comport with a perspective that geographic range for temperate zone species of the eastern United States has always and must continue to shift in tandem with climate change. With respect to Torreya taxifolia, the premise is that this species is endangered today because it is a 'glacial relict.'"

  • "Climate Change and Forests of the Future: Managing in the Face of Uncertainty,", by Constance I. Millar et al., Ecological Adaptations, 2007.
    EXCERPT: Establish 'neo-native' forests. Information from historical species ranges and responses to climate change can provide unique insight about species responses, ecological tolerances, and potential new habitats. Areas that supported species in the past under similar conditions to those projected for the future might be considered sites for 'neo-native' stands of the species. These may even be outside the current species range, in locations where the species would otherwise be considered exotic. For instance, Monterey pine (Pinus radiata), endangered throughout its small native range, has naturalized along the north coast of California distant from its present native distribution. Much of this area was paleohistorical range for the pine, extant during climate conditions that have been interpreted to be similar to expected futures in California. Using these locations for 'neo-native' conservation stands, rather than removing trees as undesired invasives, is an example of how management could accommodate climate change. (p. 2148)
  • "Conservation Paleobiology: Leveraging Knowledge of the Past to Inform Conservation and Restoration", by Gregory P. Dietl et al., 2015, Annual Review of Earth and Planetary Sciences.
    EXCERPTS: Humans are now the principal architects of environmental and biotic change on planet Earth. In response, conservation paleobiology has emerged over the past decade as a powerful intellectual approach and effective tool for acquiring longer-term perspectives on changes in species, communities, and ecosystems, beyond the limited time frame of direct human observation, and applying this information to pressing conservation issues. The overarching goal of conservation paleobiology is to use geohistorical analysis to develop knowledge, principles, and tools for conserving and restoring biodiversity and ecosystem services in the face of climate change and other human impacts.
         Research in conservation paleobiology generally takes two approaches. A near-time approach uses the relatively young fossil record, primarily from the past 2 million years, to provide a context for present-day conditions, focusing largely on extant species. Such geohistorical records are used to (a) define baselines to compare conditions before and after disturbance, (b) examine the response of species and ecosystems to recent natural and anthropogenic perturbations, (c) develop a narrative of the historical range of variability, (d ) set realistic targets for restoration, (e) differentiate between anthropogenic and nonanthropogenic change, and (f) recognize ecological legacies that can be explained only by events or conditions that are not present in the system today. A deep-time approach uses the much older geologic record as an archive of repeated natural experiments. This approach permits analysis of biotic responses to system perturbations of diverse kinds and magnitudes, some of which approximate present-day disturbances or those predicted for the near future, such as substantial climate warming and ocean acidification. The deep-time approach also permits testing of biotic responses under a broader array of conditions than is available in the modern world or its recent past.
         Predicting changes in species' distributions under different scenarios of climate change is a major objective in conservation biology. Paleoecological data can be used to detect shifts in geographic distribution of species in response to recent climate change. For example, bones from now-abandoned breeding sites of Adelie penguins on Anvers Island, Antarctic Peninsula, show that these sites were occupied exclusively by that species back through the Little Ice Age (1400-1850 CE) and that the gentoo and chinstrap penguins now breeding there have expanded their ranges to this region only within the past 50 years, presumably in response to climate warming. The fossil record is also sometimes the sole means to indicate where species occurred in the past, beyond their present-day geographic range. For example, Greenstein & Pandolfi (2008) used fossil occurrences in seacliffs along the coast of Western Australia to document how reef-building coral species shifted their distribution in response to climate change since the Late Pleistocene. This understanding enabled them to forecast coral response to future climate warming. Tropical-adapted coral species are predicted to migrate south along the coast of Western Australia and persist in temperate refugia. Knowing where and which coral species might migrate is critical to developing effective management practices that enhance their chances of survival in an era of climate warming.
         Paleobiological studies are useful to (a) recognize that ecological conditions have in fact changed, (b) establish the timing of the change and thereby disentangle possible anthropogenic from natural drivers, and (c) in the best cases, establish "what was natural" or at least what biological conditions prevailed at some specified time in cultural history.
  • "Paleoecological Insights on Conservation of Biodiversity: A Focus on Species, Ecosystems, and Landscapes" by Paul A. Delcourt and Hazel R. Delcourt in Ecological Concepts in Conservation Biology 1998.
    EXCERPTS: "Regional projections of future greenhouse-gas induced climatic warming indicate that Picea rubens and Abies fraseri forests may become extinct in the southern Appalachians. . . Over glacial-interglacial cycles, climatic and environmental changes have restructured biological systems, resulting in disassembly and reassembly of communities, individualistic migrations of species, and changes in genetic diversity resulting from alternate restriction and release of refugial populations."
        "In this paper, we evaluate the applicability of two contrasting ecological approaches to conserving biodiversity in the Appalachian Mountains in light of past and possible future shifts in the ecotones between alpine tundra, boreal coniferous forest, and temperate deciduous forest. Toward this end, we summarize available plant-fossil data from late-Quaternary sites in order to evaluate a previously developed model of changing landscape states, and then we project future shifts in ecotones in a greenhouse world based on scenarios from two different atmospheric circulation models."     "Below the climatic Picea-Abies/deciduous forest ecotone, isolated montane populations of Picea and Abies persist in locales of suitable edaphic and microclimatic conditions, such as streamside ravines, topographic depressions with pockets of cold-air drainage, and wetlands and alluvial glades with impeded water flow or perched water tables. These edaphic outliers of Piecea-Abies forest extend below their climatic ecotone by as much as 400 m in the Great Smoky Mountains and by 500 m in the central Appalachians."
        CONCLUSIONS: "The strong focus of many conservation biologists on immediate recovery of small populations of rare and endangered species diverts attention from the probability that widespread environmental changes in the near future may compound other, more local threats to continued existence of species that are narrowly adapted to specific habitats. . . In many instances extinction of rare species is likely to result from loss of suitable habitat and inability of species to migrate rapidly. Even species that are now common may be vulnerable to local or global extinction if environmental changes cross physiological thresholds of tolerance."

  • "Paleoecology and 'inter-situ' restoration on Kauai, Hawaii" by David A. Burney and Lida Pigott Burney, in Front Ecol Environ 2007; 5(9): 483-490, doi 10.1890/070051.
    Review paper of ongoing work on Kauai that actively uses a pre-historic baseline (prior to first human arrival one- or two-thousand years ago) for developing standards for plant restoration ecology on the island. A great example that there is a continuum between "historic" and "Pleistocene" standards for "restoration" and "rewilding." A must-read for those who cling to "historic native range" standards for opposing on principle "assisted migration."

  • "Return of the Ericads: Students Dig and Reestablish a Prehistoric Species", by Michael Heim, Journal American Rhododendron Society, Winter 2010
    Michael Heim is a science teacher at Lac Courte Oreilles Ojibwe High School, Hawyard WI, whose students planted in May 2009 cloned cuttings from a very rare eastern native: the evergreen Box Huckleberry, Gaylussacia brachycera. The 2 page, photo-rich PDF of this article is a fascinating look at "rewilding" of an endangered species, based on a "deep-time" perspective in which "native" is regarded as including a plant's presumed preglacial regional distribution. In a March 5 comment posted on the Torreya Guardians site, Heim reports that he and his students have also planted cuttings from clones of Torreya taxifolia and Taxus floridana on the same tribal forest lands next to the school in northern Wisconsin, thus signifying another citizen-initiative of assisted migration, based on a deep-time understanding of native range.
    PALEOECOLOGY SPECIFIC TO FORESTRY (helpful for assisted migration)

  • "Forest Responses to Changing Climate: Lessons from the Past and Uncertainty for the Future", 2000, Donald H. DeHayes et al., book chapter in Responses of northern U.S. forests to environmental change.
    EXCERPT: Continent-wide changes in distribution and abundance of plant taxa are species-specific, consistent with Gleason's (1926) individualistic concept of plant-species responses (Davis, 1983; Jacobson et al., 1987). Contrary to popular belief, modern communities are not highly organized, finely tuned units representing long periods of co-evolution among species. Rather, present communities are merely transitory combinations of taxa that have been responding individualistically to continual and sometimes major climate changes (Hunter et al., 1988). [includes "Eastern White Pine Case Study"] Paleoecological evidence shows that eastern white pine made its first post-glacial appearance in Virginia (Craig, 1969), perhaps moving in from a full glacial location on the exposed continental shelf. It reached northern New England by 10,000 years ago (Davis and Jacobson, 1985), the central Great Lakes region by 9,000 years ago (Brubaker, 1975), and Minnesota and western Ontario by 7,000 years ago (Jacobson, 1979; Bjorck, 1985). Eastern white pine reached its northernmost extent about 4,000 years ago, with areas of high abundance shrinking substantially and shifting southward thereafter. This coincides with climate cooling that has allowed boreal taxa to move southward. Another factor in the late-Holocene decline in eastern white pine is the decrease in frequency of fire. Further details of these late-Holocene changes may be found in Jacobson and Dieffenbacher-Krall (1995). The western range limit of eastern white pine occurs today where precipitation equals evapotranspiration (Transeau, 1905). Unless its habitat is manipulated by human activity, white pine does not thrive when conditions become too cool or moist, for example, at the southern margins of the boreal forest in northern New England and adjacent Canada where disturbance by fire may be too infrequent for widespread establishment of seedlings. The current abundance of eastern white pine in the Northeast results largely from abandonment of farmland during the last 150 years.
         Paleoecological studies of the later Holocene show that the boreal forest of eastern Canada developed only in the past 6,000 years (Webb, 1987) and that hemlock has been abundant in the forests of the eastern Great Lakes-New England region for that same period of time (Fig. 14.4). Other data show that southern populations of spruce (Picea spp.) shifted from Canada into the northern tier of states from Maine to Minnesota in the past 1,000 to 1,500 years, accompanied by a general decrease in abundance of eastern white pine that has continued to the present (see Fig. 14.2). Small populations of balsam fir (Abies balsarnea [L.] Mill.) were scattered throughout the northeast during most of the Holocene, but they, too, expanded recently to form the spruce-fir forests of today. The spatial array of changes has been influenced by variations in importance of fire (Foster, 1983) and other disturbances.
        Northern populations of most temperate and boreal zone species have no difficulty tolerating climates more than 5°C warmer on an annual basis. The only exception may be with trees having substantial winter chilling requirements. For example, red maples from Massachusetts exhibit sporadic and delayed spring budbreak and have poor survival when grown in Florida (Perry and Wang, 1960). This possibility should be examined carefully because some climate models project that much of the future warming will be experienced in the winter (Woodward, 1992). Observations of horticultural plantings also suggest that species can be grown in climates far warmer than any place in their natural range. Coupled with the relatively rapid rate of predicted climate warming, these data and experiences highlight the possibility that many species distributions may not simply shift northward or upward, but may actually remain competitive in their current locations and actually expand their distributions.
         A greater concern is that a warmer and drier environment may reduce germination and seedling survival. The most sensitive stage of a tree's life is the beginning. Losses in this period are very high, owing mostly to conditions that are inhospitable at this vulnerable stage. On sites that are prone to drought or lethal temperatures, such as south-facing slopes, higher temperatures would exacerbate losses. The area affected by these lethal agents would increase to some degree. Furthermore, germination could be reduced or unfavorably delayed in species with unmet cold stratification requirements. These unknown factors related to seed germination and success of the seedling stage in forest trees all contribute to uncertainty in predicting future forest composition.
         Many species found a "glacial refugium" in the southern Appalachian region. If the Appala- chian Mountains were aligned east-west instead of north-south, perhaps many of these species would have been unable to migrate far enough southward to endure the climatic cooling experienced during glaciation.
         Uncertainty exists about the nature and extent of future climatic change and its effect on migration of forest tree species. Although it is tempting to speculate that climate change may be too rapid for forest tree species to successfully migrate or that large gaps may be created that can restrict species dispersal, historical evidence indicates that climate changes in the past have been more rapid than changes projected for the next few centuries without any great restriction to species movement.

  • PALEO DATA USED TO PREDICT SEVERE 21st CENTURY PROBLEMS FOR TREES SHIFTING RANGES: "Pushing the Pace of Tree Species Migration", by Eli Lazarus and Brian McGill, 27 August 2014, PLOS One. Editor's note: This paper deals exclusively with tree species whose seeds are wind-dispersed. The outlook for trees with animal-dispersed seeds is even gloomier. EXCERPT:
    Field measurements of typical seed dispersal distances would suggest that tree fronts migrate across a landscape by a process of local diffusion, at rates significantly slower than the velocities reflected in pollen data. But seeds are occasionally carried long distances from their source by wind or by animals. If those seeds mature into trees that in turn dispense seeds, the plant species may migrate at rates that far exceed diffusive propagation. Existing models of tree migration by long-distance dispersal produce migration rates between approximately 100 to 200 m yr-1. A global analysis of temperature-change rates across geographic gradients and biomes finds that temperate broad-leaf and mixed forests, which includes the North American taxa that spread by wind-blown dispersal, will need to shift at a mean velocity of 350 m yr-1. These required migration rates appear to exceed the fastest modeled rates, but may fall within the ranges empirically observed in the last deglaciation. Migration rates barely sufficient to track with climate, combined with the well-documented effect that landscape fragmentation further impedes migration, points to the apparently unequivocal conclusion that climatic change will outpace the migration of wind-dispersed tree species through human-dominated landscapes. One of the few known cases in which climate-driven species migration was impeded comes from Europe, where east-west mountain ranges and the Mediterranean Sea prevented trees and plants from advancing far enough south during Pleistocene glaciation, resulting in a high proportion of extinction. By extension, understanding how human fragmented landscapes interfere with migration rates might mean the difference between minimal extinction rates and massive extinction rates in next few hundred years.

  • PALEOECOLOGICAL DISTRIBUTION OF E. NORTH AMERICA TREES: "Molecular Indicators of Tree Migration Capacity Under Rapid Climate Change", by McLachlan et al., in Ecology, 2005. CONTENT: Excellent review of paleocological investigations using paleo-pollen, macrofossils, and genetic data to ascertain (a) locations of glacial refuges of N.A. temperate trees during the last glacial maximum, and (b) the northward path and speed of movement as the peak glacial episode began to wane some 18,000 years ago. EXCERPT: "Molecular evidence suggests that American beech (Fagus grandifolia) and red maple (Acer rubrum) persisted during the late glaciation as low-density populations, perhaps within 500 km of the Laurentide Ice Sheet. Because populations were closer to modern range limits than previously thought, postglacial migration rates may have been slower than those inferred from fossil pollen. Our estimated rates of <100 m/yr are consistent with model predictions based on life history and dispersal data, and suggest that past migration rates were substantially slower than the rates that will be needed to track 21st-century warming."

  • LATE-QUATERNARY VEGETATION DYNAMICS IN NORTH AMERICA: SCALING FROM TAXA TO BIOMES, by John W. Williams et al., 2004, Eccological Monographs.
    EXCERPTS: This paper integrates recent efforts to map the distribution of biomes for the late Quaternary with the detailed evidence that plant species have responded individualistically to climate change at millennial timescales. Using a fossil-pollen data set of over 700 sites, we review late-Quaternary vegetation history in northern and eastern North America across levels of ecological organization from individual taxa to biomes, and apply the insights gained from this review to critically examine the biome maps generated from the pollen data. Higher-order features of the vegetation (e.g., plant associations, physiognomy) emerge from individualistic responses of plant taxa to climate change, and different representations of vegetation history reveal different aspects of vegetation dynamics. Vegetation distribution and composition were relatively stable during full-glacial times (21,000 to 17,000 yr BP) [calendar years] and during the mid-to late Holocene (7,000 to 500 yr BP), but changed rapidly during the late-glacial period and early Holocene (16,000 to 8,000 yr BP) and after 500 yr BP. Shifts in plant taxon distributions were characterized by individualistic changes in population abundances and ranges and included large east-west shifts in distribution in addition to the northward redistribution of most taxa. Modern associations such as Fagus-Tsuga and Picea-Alnus-Betula date to the early Holocene, whereas other associations common to the late-glacial period (e.g., Picea-Cyperaceae-Fraxinus-Ostrya/Carpinus) no longer exist. Biomes are dynamic entities that have changed in distribution, composition, and structure over time. The late-Pleistocene suite of biomes is distinct from those that grew during the Holocene. The pollen-based biome reconstructions are able to capture the major features of late-Quaternary vegetation but downplay the magnitude and variety of vegetational responses to climate change by (1) limiting apparent land-cover change to ecotones, (2) masking internal variations in biome composition, and (3) obscuring the range shifts and changes in abundance among individual taxa.
         Plant taxa responded individualistically to past environmental change. This observation is a central feature of late-Quaternary vegetation history and fits well with Gleason's view of plant communities (Gleason 1917, 1926). In a classic example (Davis 1976, Davis 1981b), Fagus and Tsuga today have closely associated distributions yet their histories of range and abundance changes differ. Tsuga pollen percentages were below 1% in eastern North America until 14,000 yr BP in the central Appalachians, increased northward along the Appalachian corridor, and by 12,000 yr BP had begun to increase in southern New England. Fagus abundances were low until 14,000 yr BP, increased briefly in the southeast between 14,000 and 12,000 yr BP, but did not expand into New England until after 9,000 yr BP. The distributions of Fagus and Tsuga did not attain their modern overlap until the mid-Holocene. Many other taxa that co-occur today — e.g., Picea and Abies, Quercus and Castanea, and Fagus and Acer — have had similar types of differences in history. The temporal changes in taxon distribution and abundance illustrate how plant species respond individualistically to climate change at continental to regional scales, so that most plant associations have little or no permanence.

  • CLASSIC PALEOECOLOGY PAPER ON PAST FOREST RESPONSES TO CLIMATE CHANGE: "Range Shifts and Adaptive Responses to Quaternary Climate Change", by Margaret B. Davis and Ruth G. Shaw, 2001, Science. Excerpt: "Although all the tree species that remain in our flora shifted or contracted ranges, adapting to climate changes in the past, there are reasons to question whether these processes will occur as readily during the present period of climate change."

  • CLASSIC FORESTRY PAPER ON THE DIRE PROBLEM OF THIS CENTURY'S SPEED OF CLIMATE CHANGE: "Adaptation, Migration or Extirpation: Climate Change Outcomes for Tree Populations", by Sally N. Aitken et al., in Evolutionary Applications, 2008. EXCERPT: "Findings of relatively slow tree migration rates in response to historical changes in climate (potentially < 100 meters per year) are unfortunate in light of model predictions of how fast tree species will need to migrate to track current climates under climate change scenarios. Tests of 14 combinations of GCMs and global SDMs show up to 100% of the models predicting migration rates of 1000 meters per year or higher to be necessary to track habitat under 2x CO2 climate forcing."

  • HOW NORTH AMERICAN TREES SPECIES AND BIOMES SHIFTED FROM PEAK GLACIAL TO WARM TIMES: "Late-Quaternary Vegetation Dynamics in North America: Scaling from Taxa to Biomes" - John W. Williams et al., Ecological Monographs, 2004. Excerpts: "This paper integrates recent efforts to map the distribution of biomes for the late Quaternary with the detailed evidence that plant species have responded individualistically to climate change at millennial timescales. We show how the individualistic shifts in range and abundance for plant taxa scale upward to cause (1) compositional shifts within plant communities, (2) appearances and disappearances of novel plant associations, and (3) changes in the position, area, composition, and structure of biomes. Modern associations such as Fagus-Tsuga and Picea-Alnus-Betula date to the early Holocene, whereas other associations common to the late-glacial period (e.g., Picea-Cyperaceae-Fraxinus-Ostrya/Carpinus) no longer exist."

  • "RELICT" SPECIES RESTRICTED TO DISJUNCT AND SMALL RANGES BY PLEISTOCENE GLACIALS: In 2012 an exemplary paper was published by forest researchers that demonstrated how a paleoecological perspective is vital to understand the importance of "assisted colonization" as a management tool in this century's time of rapid climate shift: "Projections of suitable habitat under climate change scenarios: Implications for trans-boundary assisted colonization", by Ledig, Rehfeldt, and Jaquish, 2012, American Journal of Botany.
        Importantly, this paper also diminishes fears that such relicts might become invasive: "In part, objections to assisted colonization rest on the fear that exotic translocated species will become invasive and compete with native species or that they will carry new pests or on the esthetic argument that such movements result in a homogenization of the flora (Seddon et al., 2009; Ricciardi and Simberloff 2009a, , 2009b; McLachlan et al., 2007). With regard to the issue of native vs. exotic, spruces have moved north and south across North America over geological time (e.g., discussion in Ledig et al., 2004)."     The focal species of this paper is Brewer Spruce, Picea breweriana, which is limited today to the Klamath region of coastal Oregon/California. The paper finds that projected climate change will necessitate the assisted movement of this unique spruce to coastal British Columbia in 2030 to 2060 and finally to the Yakutat coastal region of Alaska by 2090. Here is how the paper begins (citations eliminated):
    "The western United States was warm, subtropical forest in the Eocene (40 million years ago [Ma]). Above 50 degrees N, about the latitude of Vancouver, British Columbia, Canada, was the Arcto-Tertiary Forest. A species like dawn redwood (Metasequoia) was a common element of the Arcto-Tertiary Forest. Genera like bald cypress (Taxodium) and blackgum (Nyssa), now found only in the southeastern United States, grew along the interface of the Arcto-Tertiary Forest and the subtropical forest. Along the streams in the Arcto-Tertiary Forest were species similar to Port-Orford-cedar [Chamaecyparis lawsoniana (A. Murr.) Parl.] and coast redwood [Sequoia sempervirens (D. Don) Endl.], and species of the genus zelkova (Zelkova). Spruce (Picea), fir (Abies), and maples (Acer) grew on the uplands. Cooling occurred at the end of the Eocene, and by the Oligocene (28 Ma), the Arcto-Tertiary Forest had moved south to occupy the western United States. Mountains, including the Coast Ranges of Oregon and California, the Cascades, Sierra Nevada, Olympic Mountains, and Klamath Mountains, began to form in the Miocene (23 Ma). These ranges created a rain shadow to their east, and the Arcto-Tertiary Forest began to shrink and fragment. New communities formed as old ones segregated along new habitat lines. By the Pliocene, 5 Ma, the rich mesophytic forest was gone and was replaced by woodland, grassland, and desert. Many species went extinct and the closest analogue to the Arcto-Tertiary Forest now exists only in the southeastern United States or eastern Asia. However, California and, to a lesser extent, Oregon became a refuge for some elements of this forest. . . Brewer spruce is a relict of past climate change. According to the fossil record, Brewer spruce had a wide distribution in the Miocene and Pliocene, at least as far east as Idaho and Nevada, north to central Oregon, and south to central California. The fossil species, Sonoma spruce (Picea sonomensis Axelrod), which is synonymous with Brewer spruce, occurred in the Creede Flora in the San Juan Mountains of southwestern Colorado in the Oligocene. As cool, moist forests shrank toward the coast and higher elevations, Brewer spruce became endemic to the Klamath Geomorphological Province, which in the West retains forests most nearly equivalent to the western North American Arcto-Tertiary forests.
        To facilitate the conservation of Brewer spruce and possibly prevent extinction, we have planned a program of assisted colonization through the establishment of carefully managed trial plantations on sites with suitable projected climates in northwestern British Columbia. Because such trans-boundary movements and intergovernmental collaboration may, indeed, be necessary to protect a multitude of species threatened and endangered by climate change, we examined the applicable restrictions and found few or no barriers to assisted colonization."
    VIDEO: Brewer spruce - Relict Conifer in the Klamath Mountains

  • The Influence of Paleoclimate on Present-Day Patterns in Biodiversity and Ecosystems - by Svenning et al., 2015, Annual Review of Ecology, Evolution, and Systematics
    P. 565 - Modeling studies suggest that we should expect disequilibria not just in assemblage composition (Dullinger et al. 2012a, Normand et al. 2013) but also in ecosystem structure, with tree line advances lagging behind climate for 100s – 1000s of years (Chapin & Starfield 1997, Normand et al. 2013). . . . The existence of paleoclimatic legacies also has important implications for conservation actions. These legacies indicate that species are often not able to track climate changes and point to the need for considering assisted migration as a tool to preserve biodiversity and sustain or restore ecosystem functioning under future climate change (Lunt et al. 2013). This will particularly be the case for the broader landscape and in particular in human-impacted and/or lowland areas where it will be most difficult for species to migrate fast enough to track climate change, as already seen (Bertrand et al. 2011). However, as active relocation will be unfeasible for much of biodiver- sity, there will be a strong need for protecting areas that offer good local possibilities for climate tracking or are likely to act as climatically stable refugia (Ackerly et al. 2010, Loarie et al. 2009).

    P. 566 - Importantly, the majority of studies of biodiversity and ecosystem patterns still do not consider the potential role of paleoclimate in codetermining the observed patterns, despite its potential importance in many cases. For example, this is true for many studies that rely on species distribution modeling to test ecological hypotheses or for conservation assessments (e.g., to assess risks from future climate change). The strong evidence for paleoclimatic legacies in species distributions have implications for how such modeling should be implemented. Notably, in forecasting studies it is important to avoid approaches that strongly rely on species ranges being in equilibrium with the current environment (e.g., De Marco et al. 2008); at the minimum, a critical assessment should be made of the extent to which such an assumption is valid in every given case and careful consideration given to the consequences of any violations.

  • "How Fast Can Trees Migrate?" a PALEOECOLOGICAL PERSPECTIVE by Jacquelyn Gill, (blogpost) 8 May 2013
    EXCERPT: "The simple story of the last 2.5 million years of vegetation response to climate change could be summed up like this: temperature goes up and down, plants go back and forth. We've had over a dozen ice ages and interglacials since the beginning of the Quaternary Period. In response, flora and fauna are repeatedly displaced by the expanding ice sheets and changing climates. As carbon dioxide concentrations approach 400 ppm (any day now) for the first time since the mid-Pliocene, ecologists and conservation biologists turn to the paleorecord to get a sense of how well plants can track their optimal climates."

  • "Vegetation Response to Early Holocene Warming as an Analog for Current and Future Changes" by Kenneth L. Cole, Conservation Biology, 2009. Although this paper does not address the issue of "assisted migration" as a management tool during this century of rapid climate change, it does scrutinize botanical shifts during late Pleistocene and early Holocene analogous episodes of rapid warming. Based on plant-species data collected from packrat middens that were active during those episodes, Cole concludes and forecasts that, while plant species extinctions may not be imminent in our time, nonetheless, slow-moving late-successional species are likely to be severely restricted in range by the last quarter of this century. The result: large swathes of the American Southwest that now support late-successional species (e.g., pinyon pine and Douglas Fir) may become home to only fast-arriving early successional species (grasses and weedy herbs) for centuries and millennia that follow. It will take that long for slow-dispersing, warm-adapted, late successional species (including trees) to migrate long distances from their at-present much more southerly ranges.
    "An encouraging result of my analyses is that most extant plant species have previously survived a sudden climate warming that was at least similar in magnitude to the changes starting now, albeit without the current anthropogenic alterations on the landscape. The slow-colonizing species abundant today probably experienced a population bottleneck at the time but have successfully re-expanded since. This is the case for the pinyon pines in western North America (Cole et al. 2008b) and the oak species in Europe (Dumolin-Lapegue et al. 1997). . . It seems unlikely that a continent-wide climate-driven disturbance would equilibrate even a century after the climate change reached a stable point, much less while it is still shifting. Both the paleoecological data presented here and the ecological evidence of small-scale historical disturbances imply that ecosystems could not adjust to such a climate perturbation for at least a millennium, or more likely, several millennia.
  • "Niche syndromes, species extinction risks, and management under climate change" by Dov Sax, Regan Early, and Jesse Bellemare in Trends in Ecology and Evolution 2013.
    Although this paper is not substantially paleoecological, it is grounded in the distinction between "fundamental niche" and "realized niche", and applies those concepts to ecological constraints (including seed dispersal limitations) that have resulted in the "realized niche" (known current range) of some species lagging substantially southward of where the climate envelopes of post-glacial "fundamental niches" have likely shifted to. The authors introduce a new concept of "tolerance niche", which could be well applied to "assisted migration" experiments and actions in behalf of tree species. A species living in its "tolerance niche" is not self-sustaining (e.g., it may be able to grow and thrive, but not reproduce). Conservationists acting in advance of climate change could thus aim to establish a species northward into a "tolerance niche" habitat, while expecting ongoing climate change to advance to the point that long-lived tree species eventually are able to reproduce (thus transforming the tolerance niche into both a fundamental and a realized niche for that particular species). Note: See also Bellemare and Moeller "Climate Change and Forest Herbs of Temperate Deciduous Forests (TDF)" for a superb paleoecological review, with implications for conservation when the climate is rapidly changing.




    CONSERVATION BIOLOGY ASSISTED COLONIZATION

  • "A Modern Ark: To save endangered species move them to more congenial places, December 2015, in the Special Issue on Climate in The Economist magazine.
    EXCERPTS: Conservation, as traditionally practised, is being overtaken by fast-moving reality. In future the question will no longer be how to preserve species in particular places but how to move them around to ensure their survival. Global warming has already set off mass migrations. Having crossed the Baltic Sea, purple emperor butterflies are fluttering northward through Scandinavia in search of cooler temperatures. Trees and animals are climbing mountains. The most spectacular migrations have taken place in the oceans, says Elvira Poloczanska of CSIRO, Australia's national science agency. Many sea creatures can move quickly, which is just as well: in the oceans it is generally necessary to travel farther than on land to find lower temperatures. Phytoplankton populations are moving by up to 400km a decade.
        Not all plants and animals can make it to new homes, though. Some will be hemmed in by farmland, cities or coasts. Animals that live in one mountain range might be unable to cross a hot plain to reach higher mountains. And many will find that the species they eat move at a different speed from their own: carnivorous mammals can migrate more quickly than rodents, which in turn migrate faster than trees. The creatures that already inhabit the poles and the highest mountains cannot move to cooler climes and might be done for.
        Editor's note: In this article, the assisted migration project of Torreya Guardians is featured, along with a butterfly assisted migration project in the U.K., as discussed by Professor Chris Thomas.


  • Botanic Gardens to participate in Assisted Migration:
    1. Botanic Gardens Conservation International (BGCI) climate change and assisted migration programs. Webpages include: "The assisted migration debate: botanic gardens to the rescue?" and "Chaperoned Managed Relocation. Access a white paper on chaperoned assisted migration written by the Missouri Botanical Garden in October 2013. EXCERPT: "In contrast to managed relocation where species would be transferred from one natural area to another, we propose a program of 'chaperoned' managed relocation in which species would be transferred from natural areas to botanical gardens. As climate continues to change, populations would be transferred serially from garden to garden. Chaperoned managed relocation should only occur within each species' 'potential dispersal envelope,' meaning the area into which the species could be expected to naturally migrate, were climate change slower and habitats less fragmented by roads, fields, and cities."
        Highly recommended: Box 1 of the Missouri Botanical Garden paper directly addresses the need to "bridge the two cultures" of botanical gardens and conservation biology.

    2. "Plan Seeks 'Chaperones' for Threatened Species" news report on a talk by Adam Smith (ecologist at Missouri Botanical Garden) presented at the Ecological Society of America meeting, August 2013. Report by Virginia Gewin, published in Nature 09 August 2013
         EXCERPT: "Critics claim that such 'assisted migration' could transform struggling species into destructive invaders, or inadvertently transmit disease, or that hybridization between species could occur that would lower the planet's overall genetic diversity. But without some form of assistance, many plants will face certain extinction as the planet warms. With that in mind, researchers are proposing a heavily supervised form of assisted migration — using a network of more than 3,100 botanical gardens to 'chaperone' plant relocations. . . The researchers recommend that endangered species collected in the wild should be relocated to botanical gardens in stages, moving between gardens following a dispersal path that would be considered an evolutionarily realistic response to climate change. . .  With few other options for preserving rare and threatened species in the face of global warming, [Adam] Smith and his colleagues are forging ahead with their plans. They aim to release a more detailed proposal in October at the 5th Global Botanic Gardens Congress in Dunedin, New Zealand, that is likely to include a list of candidate species. They also hope to start a pilot project soon to test the feasibility and cost of chaperoning. See also the detailed blog on this topic by Kate Whittington, "Plant Pioneers: Assisting The Migration Of Climate-Endangered Species".

        Secrest Arboretum in Wooster Ohio participates in Florida Torreya assisted migration. Fred Bess of Cleveland Ohio (left in photo) is the Torreya Guardians liaison collaborating with Ohio State University's Secrest Arboretum (Paul Snyder is at right in photo) to encourage and foster the planting of a Torreya taxifolia grove on their grounds. A 10-minute video, recorded by Connie Barlow during a site visit in September 2014, shows the early stages in that effort.

    Note: The photo at left shows the potted seedlings (grown from seeds harvested autumn 2011 by Torreya Guardians) that will eventually be planted out on the arboretum grounds.


  • Assisted Migration Debate Takes a Sharp Turn in May 2013 - On May 8, CO2 in the atmosphere reached 400 ppm for the first time in human history. On May 9, Science journal published a stunning analysis of Siberian lake-sediment data that offers irrefutable evidence that a 400 ppm atmosphere (when it equilibrates air and ocean conditions) will produce an ice-free Arctic. Henceforth, responsible discourse about assisted migration will no longer question should it be undertaken, but rather when, how, and by whom. Below are the key links to the May 9 paper, beginning with the paper's title and abstract page.
  • "Pliocene Warmth, Polar Amplification, and Stepped Pleistocene Cooling Recorded in NE Arctic Russia" by Julie Brigham-Grette and 15 international coauthors, in Science May 9, 2013.

  • "The Arctic was once warmer, covered by trees": Pliocene epoch featured greenhouse gas levels similar to today's but with higher average temperatures", reported by Erin Wayman in Science News, 9 May 2013.

  • "Climate Sensitivity Stunner: Last Time CO2 Levels Hit 400 Parts Per Million The Arctic Was 14°F Warmer!", blogpost by Joe Romm, 12 May 2013

  • IUCN updated in 2013 its "Guidelines for Reintroductions and Other Conservation Translocations" because, "while 'assisted colonisation' is controversial, it is expected to be increasingly used in future biodiversity conservation."
  • "Managed Relocation: Integrating the Scientific, Regulatory, and Ethical Challenges" by Mark W. Schwartz and 30 coauthors, BioScience August 2012 (12 pp in pdf)
    EXCERPT: "We report on the findings of the Managed Relocation Working Group (MRWG), an independent collection composed of over 30 scientists, scholars, and policymakers that met to discuss dimensions of managed relocation. Managed relocation raises a difficult suite of biological, legal, and ethical issues. Owing to the nature of this committee, most of the examples refer specifically to the United States, but the issues we treat are broadly applicable, including those related to policy. The MRWG represents an interdisciplinary group seeking a comprehensive consideration of managed relocation.
        "Conservation ecologists are beginning to call for adapting management strategies for climate change (e.g., increasing the connectivity, resistance, and resilience of natural protected areas; e.g., Heller and Zavaleta 2009). Others have suggested more radical approaches, such as embracing novel anthropogenic ecosystems as a management goal (Hobbs et al. 2006, Thomas 2011). The proponents of managed relocation contend that conventional conservation strategies will not provide sufficient protection from future environmental change (Vitt et al. 2010, Thomas 2011).
        "Our view is that the starting point for developing a decision framework for managed relocation should be an examination of the goals of conservation, values underlying those goals, and the possibility for conflict among both goals and underlying values. The next step is to examine the legal and institutional framework within which managed relocation decisions are made. Third, we must develop and agree on scientific standards of evidence to support managed relocation decisions. Finally, we must create tools for resolving goal or value conflicts. Toward this end, the MRWG identified a series of ethical, policy, ecological, and integrated questions that should be answered to support a socially and scientifically acceptable decision framework.
        "There are thorny ethical questions surrounding any shift to an adaptationist understanding of conservation ethics and policy that would sanction managed relocation. The conservation message for decades has stressed the importance of saving species within historical ranges. Managed relocation may create perverse opportunities for relaxing societal commitments to habitat protection (Camacho 2010). Perhaps an even more troubling question is whether the acceptance of adaptive and anticipatory strategies, such as managed relocation, will function as a moral hazard by undercutting society's resolve to pursue aggressive climate change mitigation policies. There is a danger that even a measured adoption of managed relocation will encourage ethically irresponsible behavior. Policies sanctioning managed relocation could therefore provide leverage to those who wish to dismantle legal and policy tools designed to protect species and their habitats. Policymakers will have to take great care in communicating the need for relocation proposals to a public with divided interests so that policy revisions do not confuse and weaken human ethical responsibilities toward conservation."
        Editor's note: This paper is an ideal place to learn about the full history of and key publications on this issue, as of mid 2012. The table below is reprinted from this paper.

  • COMMENTS (on the above 31-coauthor paper), along with RECOMMENDATIONS for further policy work, were posted by Connie Barlow, Torreya Guardian, December 2012.

  • A now-classic paper establishing "intervention ecology" in opposition to rigid adherence to historical baselines (applied within "restoration ecology") is important reading in this assisted migration debate. See "Intervention Ecology: Applying Ecological Science in the Twenty-first Century", 2011 BioScience, Richard J. Hobbs et al. (Paul Ehrlich is among the coauthors).

  • Lead author Mark W. Schwartz continues to advocate structured decision-making prior to "managed relocation" in a 2013 article, in which climate change as an impetus for such species relocations is added to the mix: "Translocation of Imperiled Species Under Changing Climates", Annals of the New York Academy of Sciences.

  • "An Assessment of Invasion Risk from Assisted Migration" by Jillian M. Mueller and Jessica J. Hellmann, Conservation Biology, 28 June 2007.
    Content: Distinguishes history of inter- v. intra-continental invasive species in assessing the risks. Concludes that fish and crustaceans may pose a high risk. "We conclude that the risk of AM to create novel invasive species is small, but assisted species that do become invasive could have large effects."

    Editor's note: In 2014, a team of authors proposed "A Unified Classification of Alien Species Based on the Magnitude of their Environmental Impacts", which is essential for distinguishing the vast gray zone of problems caused by non-natives (those worth fighting against v. those worth simply accepting as part of the new landscape).

  • "Translocation of Species, Climate Change, and the End of Trying to Recreate Past Ecological Communities" by Chris D. Thomas, Trends in Ecology and Evolution, May 2011.
    Abstract: Many of the species at greatest risk of extinction from anthropogenic climate change are narrow endemics that face insurmountable dispersal barriers. In this review, I argue that the only viable option to maintain populations of these species in the wild is to translocate them to other locations where the climate is suitable. Risks of extinction to native species in destination areas are small, provided that translocations take place within the same broad geographic region and that the destinations lack local endemics. Biological communities in these areas are in the process of receiving many hundreds of other immigrant species as a result of climate change; ensuring that some of the 'new' inhabitants are climate-endangered species could reduce the net rate of extinction.

    EDITOR'S NOTE: For suggested standards for translocations of aquatic species, see "Challenges and Opportunities in Implementing Managed Relocation for Conservation of Freshwater Species" by Julian D. Olden et al., Conservation Biology, February 2011. See also "Standards for Assisted Migration, which was posted on the Torreya Guardians website in 2004.

  • "Can "Assisted Migration" Save Species from Global Warming?" by David Appell (news report), March 2009, Scientific American
    EXCERPTS: One amateur group, the Torreya Guardians, are attempting to "rewild" the endangered Florida torreya, a conifer tree. Native only to a 65-kilometer length of the Apalachicola River, it began to decline in the 1950s, probably because of fungal pathogens, and is thought to be "left behind" in a habitat hole that has prevented its migration northward. A few dozen seedlings were planted on private land near Waynesville, N.C., last July, with more expected. Such assisted migration, Camille Parmesan acknowledges, horrifies some conservation biologists: "They spend a good bit of time working against invasive species, and one big cause of species being endangered is being outcompeted by invasive species." In the particular case of the Torreya Guardians, "many biologists are queasy about it because they feel they didn't do the groundwork to see how it would impact the [new] community," she says. So she advocates systematic studies of threatened species' habitats where they thrive and why and what might threaten them.

  • "Ecological Implications for Assisted Migration in Canadian Forests" by Richard Winder et al., 2011, The Forestry Chronicle
    EXCERPTS: This paper examines the ecological constraints and consequences of AM, and discusses options for their mitigation at three scales: translocation over long distances (assisted long-distance migration), translocation just beyond the range limit (assisted range expansion), and translocation of genotypes within the existing range (assisted population migration). From an ecological perspective, we find that AM is a feasible management option for tree species and that constraints and consequences can be minimized through careful application of available knowledge and tools. . . Humans have already translocated tree species for long distances in many parts of the world; although these translocations were not motivated by concerns about climate change, they nevertheless provide relevant experience in this mode of assisted migration and are discussed in greater detail later in this paper.
         Globally, issues concerning invasive tree species have focused on intercontinental movements, e.g., broad-leaved paperbark (Melaleuca quinquenervia) in the Florida Everglades (Turner et al. 1998); Pinus spp., Eucalyptus spp., and others in South Africa (Richardson 1998; Le Maitre et al. 2002); lodgepole pine in New Zealand (Ledgard 2001); and Scots pine in Nova Scotia and Ontario (Catling and Carbyn 2005). On the other hand, some intercontinental introductions have resulted in "naturalized" populations with less aggressive behavior, e.g. Norway spruce in the forests of eastern North America (e.g. Stover and Marks 1998; Hunter and Mattice 2002; Pennsylvania Department of Conservation and Natural Resources 2011); sycamore in England (Peterken 2001); or lodgepole pine in Scandinavia (Knight et al. 2001). In some cases, the "invasive" behaviour can be relatively subtle or localized, as in the tendency for Douglas-fir to occupy and shade-out previously unforested rocky slopes in Europe (Klingenstein and Diwani 2005), or in the potential for Siberian larch to dominate some Alaskan sites despite lower densities across the overall forest landscape (Alden 2006). In Patagonia, some introduced species initially thought to be invasive now appear to be less aggressive (Simberloff et al. 2002). A similar effect has been noted in Britain, where trees introduced over the last 400 years are changing genetically and assimilating into forest communities; the long-term ecological impacts of these species are not yet fully manifest (Peterken 2001).
         Regarding the intra-continental migration of tree species, it is difficult to find examples of assisted long-distance migration resulting in invasive behavior. There are some reports of "invasive" behavior in species native to North America, particularly in areas experiencing changes in land management. For example, Douglas-fir is reported to become invasive in oak savannas as a result of long-term fire suppression (Devine and Harrington 2007). Another example, resulting from anthropogenic and natural causes, would be the expansion of American beech vs. the decline of sugar maple in some hardwood forests of Quebec (Messier et al., 2011). In other cases, the "invasiveness" of native species within North America, for example eastern hemlock in sugar maple and basswood forests of upper Michigan, may relate to localized patterns of natural migration responding to changes in climatic conditions (Davis et al., 1998). Overall, very few species become invasive when introduced into a novel environment (Mueller and Hellman 2008); for forestry, the greater risk in assisted migration efforts may be the unintentional introduction or exacerbation of forest pests and pathogens, as discussed below.
         Subsection titles: Ecological Constraints of Assisted Migration; Genetic and physiological factors; Tree-associated species; Pests and pathogens; Competing vegetation; Interactions and surprises; The Canadian context; Mitigation of ecological constraints at different scales of assisted migration • Ecological Consequences of Assisted Migration; Invasion risk of introduced species; Invasion risks of pests and pathogens of introduced species; Invasion in a forestry context; Conclusions.


  • "Assisted Colonization: A Question of Focal Units and Recipient Localities" by Juergen Kreyling et al., Restoration Ecology 2011
    DEFINITIONS: We define assisted colonization as 'the intentional movement of focal units (ecotypes, species, taxa, functional types, life forms) to recipient localities, where these focal units are currently absent, and where they cannot be expected to colonize by natural means within a short time frame (i.e. years or decades).' We agree with Hunter (2007) that assisted colonization is a more appropriate term than assisted migration, because the final goal of this approach is not only to assist dispersal but rather the successful establishment of individuals and the subsequent development of self-sustaining populations, which is much more demanding. Managed relocation or 'managed translocation' are further used as synonyms for this approach. However, these terms are not necessarily confined to the context of adaptation against climate change (Ricciardi & Simberloff 2009).

    DIFFERENT PARADIGM IN FORESTRY: A different view prevails in forestry, where economic benefits (i.e. a high and stable productivity of ecosystems) are given top priority (Chapin et al. 2007; McKenney et al. 2009). This reasoning shifts the focus of attention from taxonomic units to the stability and productivity of a given geographic unit. The discussion about assisted colonization among conservationists might benefit from an acknowledgement of this view, as the creation of habitats adapted to climate change might meet several conservation goals.

    CONCLUSIONS: The debate about assisted colonization as a management tool to conserve biodiversity in the face of climate change is based largely on two opposing arguments. On the one hand, high extinction risks are projected due to the fact that focal units might not adapt fast enough to climate change through migration or genetic adaptation. Invasion biology, on the other hand, provides evidence that the intentional introduction of species may adversely affect recipient ecosystems. A more important consideration may be that assisted colonization will not be feasible for many endangered taxa due to their limited availability and due to a lack of recipient localities. We conclude that the assisted colonization of single endangered species is risky and not useful in many cases. Therefore, we propose that the structure and micro-climate of habitats containing rare and endangered species could be the focus for climate change adaptation (i.e. climate-safe habitats) via the establishment of pre-adapted ecotypes of the relevant foundation species. We suggest moving ecotypes of foundation species within the species' natural range in order to minimize possible adverse effects. The assisted colonization of foundation species ecotypes might provide a means for sustainable climate change adaptation in restoration efforts. The history of conservation biology informs us that the restoration or conservation of suitable habitat including its dynamic processes (e.g. disturbance regimes) is the only sustainable option to manage endangered species. Building climate-safe habitats by the use of pre-adapted ecotypes of foundation species may therefore be a better investment toward the conservation of biodiversity than aiming at single endangered species.


  • "The precautionary principle in managed relocation is misguided advice" by Mark W. Schwartz, Jessica J. Hellmann, and Jason S. McLachlan, Trends in Ecology and Evolution 2009
    EXCERPT: "The precautionary principle has been historically useful in guiding conservation management, but global environmental change presents a different sort of problem. There are real risks of harm to biodiversity through inaction as well as action. The only way forward to confront unprecedented problems such as global anthropogenic climate change is careful risk analysis, including an honest evaluation of uncertainty and potential harm, along with broad public debate beyond the technical expertise of scientists and managers. We must engage in careful study of ethical, legal and biological issues surrounding the idea of managed relocation even if the ultimate conclusion is that it is the wrong approach to managing a difficult problem."
    NOTE: The September 2009 issue of Trends in Ecology and Evolution contains a total of 6 short papers or opinion pieces on the issue of assisted migration.


  • "The success of assisted colonization and assisted gene flow depends on phenology" by SM Wadgymar et al., Global Change Biology 21 October 2015.
    ABSTRACT EXCERPT: Assisted colonization, or the movement of species beyond their current range boundary, is a conservation strategy proposed for species with limited dispersal abilities or adaptive potential. However, species that rely on photoperiodic and thermal cues for development may experience conflicting signals if transported across latitudes. Relocating multiple, distinct populations may remedy this quandary by expanding genetic variation and promoting evolutionary responses in the receiving habitat — a strategy known as assisted gene flow. photoperiodic constraints will likely necessitate evolutionary responses for long-term persistence, especially when involving populations from disparate latitudes. With strategic planning, our results suggest that assisted colonization and assisted gene flow may be feasible options for preservation.

  • "Endangered Species: Will it be extinction or translocation as impacts of climate change increase?" by Nina Heikkinen, Climate Wire 15 August 2014
    SUMMARY: Short investigative article on shifting views in whether 'translocation' (assisted migration) of endangered species should be normalized as non-controversial, given the inexorable trends in climate change. Lee Barnes of Torreya Guardians was interviewed for this piece. Key statements by Chris Thomas, professor of biology at University of York (U.K.): "Many of the threatened species are just the kind of spices that can't move on their own." In Thomas's opinion, criticism of translocation is "driven by nostalgia, or a feeling that there was a romanticized period in the past when somehow humanity and nature were in balance." As to the potential danger that a translocated species might become invasive in the recipient ecosystem, Thomas counters that endangered species should be regarded as "innocent until proven guilty."

  • "Using assisted colonisation to conserve biodiversity and restore ecosystem function under climate change" by Ian D. Lunt et al, Biological Conservation, Vol 157, 2013
    EXCERPT: "To date, the assisted colonisation literature has focused primarily on a single rationale: to enhance the survival prospects of the taxon being moved, or small numbers of interdependent taxa, such as butterflies and host plants (Hellmann, 2002). However, here we suggest that assisted colonisation could also be undertaken to achieve a very different conservation goal — to maintain declining ecosystem processes. Adopting the terminology of Seddon (2010), this type of assisted colonisation would be classified as ecological replacement — the release of "a species outside its historic range in order to fill an ecological niche left vacant by the extirpation of a native species", and is akin to the "anticipatory restoration" activities proposed by Manning et al. (2009). This goal may become prominent in future climate change adaptation programs as the impacts of climate change become more severe, but the juxtaposition of goals has not been considered in the assisted colonisation literature and demands benefit-risk evaluation.
        "For simplicity, we characterize these two contrasting rationales for assisted colonisation as 'push' and 'pull' strategies. Push strategies that focus on conserving individual taxa or small groups of inter-dependent taxa are already widely discussed in the assisted colonisation literature. In these cases, issues such as rarity and threat guide the selection of target taxa, and populations are 'pushed' into one or more localities where it is expected that they will maintain viable populations for an extended period under climate change (e.g. Willis et al., 2009). Risk assessments are required to ensure that informed decisions are made to relocate taxa such that there is minimal impact on other species where they are introduced (Burbidge et al., 2011). In contrast, assisted colonisation that is also motivated by a desire to restore ecosystem function should expect to have an appreciable impact at the recipient site. In such 'pull' scenarios, desired ecosystem functions and potential recipient sites would first be identified, and appropriate candidate species would then be 'pulled' into recipient sites to maintain or restore the specified function. Relocation of taxa may be undertaken to deliver ecological functions that are directly affected by climate change, or where climate change exacerbates other causes of decline."

  • "Restoration Ecology" blogpost by Julissa Roncal, 7 July 2012
    EXCERPT: As a plant ecologist at Fairchild Tropical Botanic Garden I was part of a team led by Dr. Joyce Maschinski working on the conservation and restoration of endangered species in South Florida. We addressed questions like: Can endangered species be translocated outside their historic distribution range? Have the fundamental and realized niches changed due to anthropogenic influence? Does the new suitable habitat support favorable biotic interactions? What should be the genetic source to establish new populations? Do seeds, seedlings, cuttings, or adults are better transplant material? We conducted experimental introductions of several endangered species to answer these questions, and to reduce extinction risk, learn more about the biology of rare species, and advance restoration ecology theory. Our experimental results indicated that the species Amorpha herbacea (Fabaceae) can be translocated outside its known historic range, however, highest growth was attained on a different microhabitat than was historically known, reflecting the influence of anthropogenic disturbance on native plants' future optimal habitat.

  • "Climate Change: Killing Cloud-Side Forests" - 2015 popular Australian article, based on technical paper. EXCERPT: "There are many unique, high-altitude forests found on mountains that rely on the moisture and cover of passing clouds to survive. Now, with climate change altering atmospheric currents throughout the world, experts have estimated that many of these forests are in trouble. That's at least according to a study recently published in the journal Biological Conservation, which details how many key plant species endemic to high-altitude forest will likely not be able to survive in their current locations past the year 2080."

  • "Can Vulnerable Species Outrun Climate Change?" by Emma Marris, Environment 360 3 November 2011
    EXCERPT: "Reagan Early says that before she completed her research [on the California Newt], she believed that physically moving species to help them reach suitable habitat — a strategy called 'managed relocation' or 'assisted migration' — was a bad idea. But the maps she made [of regional speeds of climate change during the past glacial], with those yawning gaps between the amphibians and the places where they could live happily in the future, changed her mind."

  • "Assisted Migration may save some species from climate change doom" by Thomas B. Smith, Los Angeles Times (op-ed) 21 September 2014

  • "The Debate about Assisted Migration" by Extension: America's Research-based Learning Network, 2012
    EXCERPT: This so-called assisted migration of species remains controversial among forest managers, with most favoring one of three distinct policy options: (1) Support aggressive assisted migration; (2) Oppose assisted migration; (3) Support exploring assisted migration.

  • "8 Wild Proposals to Relocate Endangered Species" by Brandon Keim, Wired Science 1 February 2012
    The 8 proposals are for "assisted migration" and/or "rewilding" of: (1) Komodo Dragons and elephants to Australia (the former to predate on alien herbivores; the latter to graze down the fire-prone overgrowth of alien grasses). (2) Rewilding America's Great Plains with proxy herbivores and carnivores from Africa that are close kin of America's own beasts that went extinct at the end of the Pleistocene. A specific example would be (3) Bring Back the Cheetah to America's plains, where a larger cheetah (that went extinct 13,000 years ago) had co-evolved with America's unique pronghorn — the fastest hoofed mammal on Earth. (4) Saving Torreya taxifolia conifer trees, which are too sickly to reproduce in their historic range in northern Florida, by planting seedlings in the mountains of North Carolina (an action already undertaken and apparently succeeding). (5) Antarctic Polar Bears? is the least serious of any proposal, as it would have dire consequences for land-breeding penguins. (6) Whitebark Pine in the western USA, dying in part owing to rapid climate change. (7) Madagascan lemurs to a Caribbean island, to be financed by billiionaire Richard Branson. (8) Aldabran Tortoises to islands in the Indian Ocean a project advocated in 1874 by Charles Darwin and continuing with fresh impetus today — especially to islands in which closely related giant tortoises were hunted to extinction by humans.

  • "Multidimensional Evaluation of Managed Relocation" 22-author paper by David M. Richardson et al, Proceedings National Academy of Sciences, May 2009.
    ABSTRACT: Managed relocation (MR) has rapidly emerged as a potential intervention strategy in the toolbox of biodiversity management under climate change. Previous authors have suggested that MR (also referred to as assisted colonization, assisted migration, or assisted translocation) could be a last-alternative option after interrogating a linear decision tree. We argue that numerous interacting and value-laden considerations demand a more inclusive strategy for evaluating MR. The pace of modern climate change demands decision making with imperfect information, and tools that elucidate this uncertainty and integrate scientific information and social values are urgently needed. We present a heuristic tool that incorporates both ecological and social criteria in a multidimensional decision-making framework. For visualization purposes, we collapse these criteria into 4 classes that can be depicted in graphical 2-D space. This framework offers a pragmatic approach for summarizing key dimensions of MR: capturing uncertainty in the evaluation criteria, creating transparency in the evaluation process, and recognizing the inherent tradeoffs that different stakeholders bring to evaluation of MR and its alternatives. [Ed. note: This paper is the product of the Managed Relocation Working Group project. Details of three species-specific case studies, including pro and con managed relocation of Florida Torreya, are described in a supplementary pdf. Click the url at the bottom right of page 1 of the pdf of the main paper.

    Read the National Science Foundation press release of the above article, where you can also access short VIDEOS of Jessica Hellmann talking about the importance of managed relocation.

  • "Assisted Colonization: Moving Species for Conservation Purposes" undated website announcement of Conservation Breeding Specialist Group (CBSG), affiliated with the IUCN
    "IUCN has requested a review and update of its policies on this topic, with the aim of having a comprehensive IUCN position for submission at the 2012 World Conservation Congress. Accordingly the SSC has established the RSG-ISSG Task Force on Moving Species for Conservation Purposes. The lead person in this task force is Mark Stanley Price. Mark will convene a working group to discuss that scale, scope and terminology around this initiative and to gather answers to the questions: (1) How, where and for what do the benefits and risks of assisted colonization or conservation introduction compare favorably to doing nothing to assist species vulnerable to extinction? (2) What taxa of plants and animals do participants feel are the best bet for assisted colonization? and (3) What should be done to test some hypotheses?

  • Rare S. Appalachian plant being tested for assisted migration Smith College News, 26 July 2010.
    Excerpts: Last fall, Kaila Matatt '10 joined Jesse Bellemare, assistant professor of biological sciences, on a five-year investigation into the success of relocating one plant, the Umbrella Leaf, to cooler climes. The native of southern Appalachia met the typical criteria of plants that are most in danger of extinction — those with small geographic ranges and limited ability to disperse, she said. When Bellemare began the investigation in 2008, he sought and received approval to temporarily transplant the Umbrella Leaf to areas within state forests in Virginia, Maryland, Pennsylvania, New York and Massachusetts. He also identified three control sites within the native range to provide a comparison. Until the end of the project in 2013, the plants will continue to be monitored for germination and growth, as well as monitored for flowers and seeds, she said. After that, all of the transplants will be removed.

  • "Deciding when to move plants and animals to save them from global warming" journalist report by Cassandra Brooks, Stanford Report, 5 June 2009.
    Report of 25 May 2009 multi-author paper in Proceedings of the National Academy of Sciences, which proposes a new management tool for choosing which species are most viable for relocation based on a series of social and ecological criteria—for example, how much is known about the biology, geographical distribution and the ecological uniqueness of the species, as well as how easy they are to catch and move. Social factors, such as cultural importance, financial impact and even the laws and regulations regarding the species, also are considered. Partially funded by the National Science Foundation (NSF), the working group is co-led by Jessica Hellmann and Jason McLachlan of the University of Notre Dame, Dov Sax of Brown University, and Mark Schwartz of the University of California at Davis. David Richardson of Stellenbosch University in South Africa led the writing of the paper. See also this Press Release on the paper.

  • "Between the Devil and the Deep Blue Sea" science journalist article by Jim Robbins, Conservation, Apr-Jun 2009.
    Arresting article on the extent and speed of the paradigm shift in conservation away from traditional "preservation" modes of intervention in behalf of biodiversity to "adaptationist" modes, including the growing acceptance of "assisted migration" as a management tool to cope with globally and regionally shifting climates. Superb coverage of the wrenching change of heart (and financial focus) for conservation programs rooted in "restoration" to practically address the irreversible shifts in climate now inarguably underway. "Managed retreat" (term used by conservation biologist Reed Noss, who argues for an overhaul of Everglades restoration policy) now joins "assisted migration" in the growing panoply of conservation terms and tools.

  • "Anachronistic Fruits and the Ghosts Who Haunt Them", by Connie Barlow, 2001, in Arnoldia Magazine.
    Note: This article may be the first published advocacy of translocation (assisted migration) of Torreya taxifolia. The last section of the article is titled, "Is the Endangered Torreya Tree Anachronistic?". Barlow concludes, "Transplantation across great distances is an uncommon and controversial technique for biodiversity conservation today. But as the greenhouse effect ratchets up temperatures and reroutes rainfall, and as botanical preserves become even more isolated islands in a sea of human development, long-distance transplantation will become the norm. If gardening a few local patches of endangered plants is tough today, it's going to get a lot tougher when, like it or not, we become gardeners of the planet. Helping plants track climate change from one patch of habitat to another will be a routine tactic for conserving biodiversity decades hence. Is it too early to begin now with florida torreya?"

    VIDEO: Assisted migration for Florida Torreya

       Connie Barlow presents the rationale for advocating "assisted migration" northward to help an endangered conifer tree, Florida Torreya (Torreya taxifolia), recover from otherwise certain extinction. Barlow's talk was filmed in 2004 — the same year that she and Paul S. Martin co-authored an advocacy piece, "Bring Torreya Taxifolia North Now," published in Wild Earth magazine. 2004 was also the year that Connie coordinated the formation of and created a website for Torreya Guardians, torreyaguardians.org

    Four years after this talk was filmed, Barlow and other Torreya Guardians" legally planted 31 nursery-grown seedlings of Torreya taxifolia in two forested plots of private land in the mountains of North Carolina. This action is recognized as the first intentional "assisted migration" for a plant species in the USA in direct response to climate change.

    PROGRESS REPORT VIDEOS of Torreya Guardians actions here.

  • "Bring Torreya Taxifolia North — Now", by Connie Barlow and Paul S. Martin, 2004, in Wild Earth Magazine.
    Note: This paper is the first full advocacy of assisted migration for Torreya taxifolia. The authors conclude, "'Left behind in near time' may thus be a syndrome that applies to a number of extinct, imperiled, and soon-to-be imperiled plants, and perhaps to small, isolated populations of species that are not themselves in danger of extinction. How might this awareness alter our conservation options as climate shifts? By assisting the migration of Torreya taxifolia now, we can help to shape a better next chapter for this beleaguered tree and, perhaps, many other plants." A first-cut set of 8 "Standards for Assisted Migration of Plants" (by Barlow and Martin) was also posted online in 2004 here.


       Download in PDF two CLASSIC ARTICLES, for and against assisted
       migration of Torreya taxifolia, published as the featured
       Forum in the Winter 2005 issue of Wild Earth. Download
       the pro and con articles separately for printing on standard   
       size paper. Or, for viewing the 2-article Forum as it
       appeared in publication (wide-screen, with all illustrations),
       download the "Forum."
       


      FOR assisted migration, by Connie Barlow & Paul Martin  
     

      ANTI assisted migration by Mark Schwartz
     

      FORUM (both articles for wide screen)
     

      STANDARDS for assisted migration by Barlow and Martin
     

  • "Deep-Time Lags: Lessons from Pleistocene Ecology" by Connie Barlow, in Gaia in Turmoil: Climate Change Biodepletion, and Earth Ethics in an Age of Crisis, edited by Eileen Crist and H. Bruce Rinker, 2009, MIT Press.
    Torreya Guardians founder Connie Barlow contributed a chapter on the importance of a "deep time" perspective for conservation biologists and biodiversity activists coming to grips with the extinction crisis in an age of rapid climate change. The plight of Torreya taxifolia and the work of Torreya Guardians are used as the key example of "Assisted Migration in a Time of Global Warming".

  • "Guardian Angels" article by Janet Marinelli, Audubon Magazine, May/June 2010.
    In-depth exploration of "the biggest controversy in contemporary conservation science." Engagingly written for both a popular and professional audience, journalist Marinelli draws from her interviews with leading scientists, horticulturalists, and activists to present the core arguments for and against assisted migration. A site visit to an endangered plant breeding facility (the Atlanta Botanical Garden) is paired in the article with Marinelli's eye-witness description of "eco-vigilante" action, when the loose-knit citizens group Torreya Guardians intentionally planted into forested landscapes of mountainous North Carolina 31 seedlings of the highly endangered Florida Torreya — an assisted migration of some 400 miles northward of historically known native habitat.

  • "NASA: Climate Change May Bring Big Ecosystem Changes", press release, December 2011, Jet Propulsion Laboratory.
    Excerpts: By 2100, global climate change will modify plant communities covering almost half of Earth's land surface and will drive the conversion of nearly 40 percent of land-based ecosystems from one major ecological community type . . . Most of Earth's land that is not covered by ice or desert is projected to undergo at least a 30 percent change in plant cover - changes that will require humans and animals to adapt and often relocate. . . While Earth's plants and animals have evolved to migrate in response to seasonal environmental changes and to even larger transitions, such as the end of the last ice age, they often are not equipped to keep up with the rapidity of modern climate changes that are currently taking place. Human activities, such as agriculture and urbanization, are increasingly destroying Earth's natural habitats, and frequently block plants and animals from successfully migrating.

  • "The Hidden Battle Behind Formal Gardens", report by Paddy Woodworth, 10 July 2010, in Irish Tmes
    Excerpt: Perhaps the most radical update on the table now is the concept of 'assisted migration', a benign phrase that just might be the key to keeping many trees, shrubs and flowers in the landscape — and out of the chilled filing cabinets. But it is a concept that also raises as many problems as it proposes to lay to rest. As with animals, plants migrate to find the best living conditions, but plants do it slowly, over generations. Trees, with their very long life spans, are especially slow. Earthworms are sprinters by comparison. Ten thousand years ago, as the ice sheets retreated from the North American Midwest, trees migrated up the continent at the rate of about 100km per century, until the global climate settled into relative stability — the condition we thought of as normal until very recently. Global change models suggest that climate 'envelopes' will soon be moving north at speeds of 1,000km per century. So, if the models are right, this is a race that trees are certain to lose. . . Donnelly knows that the best outcome of assisted migration will involve the disintegration of cherished and valuable communities of plants and animals. Whatever novel communities will emerge may be poorer, or even richer, in biodiversity than what we know today, but they will certainly be different. However, he argues soberly that assisted migration must be among our options for "managing long-lived trees for an uncertain future". Restoration used to be about attempting to return ecosystems to a past (and more biodiverse) state, but the wild card of climate-change is pushing restoration science towards the creation of new systems, with the proviso that maintaining biodiversity is still the target. EDITOR'S NOTE: A 2011 survey of the actual movement poleward or altitudinally by 1,376 species found that the average rate was 10 miles per decade poleward and 40 feet per decade upslope, but the individual variation was quite wide. See "Climate Change: Species Climbing Higher and Migrating North, Study Says".

  • "A Home from Home: Saving Species from Climate Change" news story by Suzanne Goldenberg in Guardian.co.uk, (12 February 2010):

    Click above for Parmeson talking about
    the need for assisted migration in U.K. 2014
       Conservation biologist Camille Parmeson is profiled in her advocacy for translocation of species threatened by climate change. She is quoted, "It doesn't make any sense to say it's OK for the shipping industry and the transport industry to accidentally move stuff around, for the aquarium trade to move stuff around, for the garden trade to move stuff all over the place, but that it's not OK for a conservation biologist who is desperately trying to save a species from extinction to move it 100 miles. Come on, we have mucked around with Earth to such a degree that I think it's a ridiculous argument.''

    2014 UPDATE: Parmesan's focal butterfly species along s. coastal California (Quino Checkerspot) defied the climate-caused extirpation of its caterpillar host plant by shifting larval diet to an entirely different plant species at a higher altitude eastward of its historically tiny native range: "Endangered butterfly defies climate change with new diet and habitat"

  • "Taking Stock of the Assisted Migration Debate" by Nina Hewitt et al, Biological Conservation (volume 144, pages 2560-72), 2011.
    Lead author Dr. Nina Hewitt (a biogeographer and IRIS Senior Fellow) and her coauthors conducted a bibliometric study of the existing academic literature on assisted migration, classifying it in terms of study methods, geographic and taxonomic (species) focus, and degree of knowledge transfer from the natural sciences to other academic disciplines and non-academic sectors. They show that the volume of scholarly writing on assisted migration has exploded in the past three years, addressing a wide range of regions and species. The article's main contribution is to analyze the scholarly debate about the desirability and feasibility of assisted migration as a response to climate change. At a general level, a majority of the papers reviewed were generally supportive of using or at least considering assisted migration, but a closer examination shows that the debate is intensifying. NOTE: A news article on this report quotes Hewitt as saying, "With this paper, we were hoping to highlight the different sides of the debate so that scientists and policymakers can evaluate the risks and benefits and together make some progress so we don't get stuck in that paralysis. . . What I found was that the debate seemed to be stuck around what we call 'other issues' — neither direct risks nor benefits to implementing a particular assisted migration, but rather, counter arguments to the opposite side of the debate. These counter arguments need to be distinguished from direct risks and benefits because they can't provide justification for scrapping or adopting the policy."

  • "Big Moving Day for Biodiversity: A macroecological assessment of the scope for assisted colonization as a conservation strategy under global warming" by Jens-Christian Svenning, IOP Conf. Series: Earth and Environmental Science 8 (2009). 12-page report in PDF.

  • "Wildlife Service Plans for a Warmer World" news report by Janet Fang, NatureNews Published online 17 March 2010 | Nature 464, 332-333 (2010) | doi:10.1038/464332a
    The report, a collaboration between the USFWS, the US Geological Survey, academics and a collection of environmental and wildlife groups, quantified the vulnerability of each species on the basis of its breeding behaviour, habitat, migratory pattern and ecological niche. George Wallace, vice-president for oceans and islands at the American Bird Conservancy in The Plains, Virginia, says the report shows that "we need to consider climate change as we continue conservation work into the future".

  • "The Velocity of Climate Change" by Scott R. Loarie et al. Nature, 462, 1052-1055 (24 December 2009)
    Important scholarly/scientific work that results in an estimate of 1/3 mile per year on average of latitudinal shift in climate and only 8% of protected lands being large enough to include today's climate within its bounds in a century. The abstract only is available for free online, at the url above, but you can read a news report of it at Discovery News.

  • "From Reintroduction to Assisted Colonization: Moving along the Conservation Translocation Spectrum" by Philip J. Seddon, opinion article in Restoration Ecology 2010
    "Historic distribution records will always provide a good starting point for identifying translocation release sites, but global climate change and the dynamic nature of ecosystems mean that historical species ranges have only limited use. Other, even pre-historic reference points, and species-specific habitat suitability assessments should be considered.
        "Single-species conservation actions in the core of historic range will remain the backbone of many conservation efforts, but increasingly we need to adopt an ecosystem focus and consider the translocation of suites of species to restore key ecological functions. Ecological functions once performed by now-extinct taxa can be restored through the introduction of ecological replacements, which may themselves be threatened in their native range."

  • "Big Moving Day for Biodiversity? A macroecological assessment of the scope for assisted colonization as a conservation strategy under global warming" by Jens-Christian Svenning et al. IOP Conf. Series: Earth and Environmental Science, 8 (2009) 012017
    clip from ABSTRACT: "Our results suggest that there is substantial room for additional plant species across most areas of Europe, indicating that there is considerable scope for implementing assisted colonization as a proactive conservation strategy under global warming without necessarily implicating negative effects on the native flora in the areas targeted for establishment of translocated populations. Notably, our results suggest that 50% of the cells in Northern Europe, the likely target area for many translocations, could harbor at least 1/3 as many additional species as they have native species."

  • "Assisted Colonization: Integrating Conservation Strategies in the Face of Climate Change", by Scott R. Loss et al., Biological Conservation, December 2010
    A 3-page comprehensive review of the major papers and arguments, primarily useful for all the linked references. It is too compressed to be useful for fully understanding the major implications. As with virtually all the published papers through 2010, the major argument against assisted migration is risk of invasiveness in its targeted new range. And as with all its predecessor papers cited, it fails to put this issue in the context of deep time: that is, it fails to recognize that species that may be considered for assisted migration are millions (even tens of millions) of years old, and have been moving vast distances independently of one another north and south and also up and down mountains throughout the significant climate shifts of the Pleistocene epoch, and before. This point is brought out in one key paper cited in this review article. It is the paper by Mueller and Hellman, 2008: "An Assessment of Invasion Risk from Assisted Migration", which concludes that N-S translocations of land species on the same continent pose relatively little risk, while moving crustaceans and fish between aquatic watersheds evidences a history of problems. The strongest advocacy of a deep-time perspective is by Connie Barlow of Torreya Guardians, in her 2005 paper (co-authored with Paul S. Martin): "Bring Torreya taxifolia North Now" and her 2011 onine piece: "Assisted Migration (Not Assisted Colonization) for Endangered Torreya".

  • "A Hunt for Seeds to Save Species, Perhaps by Helping Them Move" science journalist article by Ann Raver, New York Times, 9 November 2009.
    "Scientists from the [Chicago Botanic Garden] are sending teams out across the Midwest and West to the Rocky Mountains and Great Basin to collect seeds from different populations of 1,500 prairie species by 2010, and from 3,000 species by 2020. The goal is to preserve the species and, depending on changes in climate, perhaps even help species that generally grow near one another to migrate to a new range." "'We recognize that climate change is likely to be very rapid and that seeds only disperse a few hundred yards, half a mile at most, naturally,' said Kayri Havens, the botanic garden's director of plant science and conservation. 'They'll need our help if we want to keep those species alive.'"

  • "Assisted Migration of Plants: Changes in Latitudes, Changes in Attitudes" by Pati Vitt et al., Biological Conservation, 23 September 2009.
    Excerpt: "Intra-continental translocation has also proven an important conservation tool to help species escape diseases driving them to extinction in their native range. This includes numerous Australian species like Lambertia orbifolia (roundleaf honeysuckle), declining due to the devastating effects of Phytophthora cinnamomi (root rot fungus disease). For these species, translocation has been employed as a conservation measure since the mid-1990s (Cochrane, 2004), and in the United States, the formerly abundant Florida Torreya (Torreya taxifolia) has lost at least 98.5% of its former population size since the 1900s due largely to disease (Schwarz et al., 2000). Since 1989, ex situ collection and propagation, as well as translocation, have become key modes of conservation for the species. The Torreya Guardians, a group of citizens undertaking the translocation of the Florida torreya, now cite climate change as an additional rationale for movement of the species outside its historic range (Barlow and Martin, 2005), though the practice is not universally accepted (Schwartz, 2005; Ricciardi and Simberloff, in press).
        "Translocating plants is not without risk, the most problematic is the potential for a species to become invasive in its introduced range. Intercontinental movement of species has indeed resulted in problems with invasive species, but the vast majority of introduced species do not become invasive. It is estimated that less than 1% of species become invasive when imported to a new range (Williamson and Fitter, 1996), and only a small percentage of those (7.5% of invasives in the US) are a result of intra-continental introductions (Mueller and Hellmann, 2008). Most discussions of assisted migration in the context of climate change involve moving species relatively short distances poleward or higher in elevation within a continent, and many focus on species with limited dispersal ability which are less likely to become weedy (Rejmanek and Richardson, 1996). In many anthropogenically fragmented habitats, migration assistance in the form of short distance jump dispersal or corridor creation may be necessary for species to survive. These types of dispersal pathways are less likely to result in enemy release and biological invasion than are long distance and mass dispersal (Wilson et al., 2009).
        "Ultimately, implementation of assisted migration, or other large scale conservation mechanisms, will require reconciliation between the hubris of being able to control nature, with the hubris that humans are somehow not a part of nature. Incorporating the newly emerging science of restoration genetics, and the lessons learned from both rare plant translocation experiments and the practice of restoration ecology will provide a road map for how to design assisted migration events. While natural communities of the future may not have current day analogs, our job is to ensure that they are as species-rich and genetically-diverse as possible."
        "We envision a future where well-conceived translocations of species may reduce the risk of extinction, as well as increase the number of potential taxa creating new assemblages in a fluid landscape responding to broad scale changes.
      
        "While we debate about whether and how to implement assisted migration strategies, species already at risk are being further stressed by the unpredictability of the environmental changes they are experiencing. For plants, at any rate, the solution seems clear: collect and bank them now, and then plan the implementation stage when it is appropriate. As Hunter (2007) points out: implementation of an ex situ conservation strategy is far less problematic for plants, and a great deal less expensive, than for other taxa of conservation interest."

    Editor's norte: Figure left is a map of no-analog ("extra-mural") bio-climatic envelopes forecast to arise during the 21st century of climate change, by Rehfeldt et al. 2006, "Empirical Analyses of Plant-Climate Relationships for the Western United States". "Fig. 16 Shading marks pixels predicted to be extramural to the contemporary climate profiles of 25 biotic communities of the western United States for the contemporary climate (upper left) and the climates of the decades beginning in 2030 (upper right), 2060 (lower left), and 2090 (lower right)."

  • "Science Journal Podcast" AAAS transcript. 24 September 2009
    One of the topics covered is the scientific controversy over the pros and cons of assisted migration. The work of citizen group Torreya Guardians is mentioned. (In PDF, so do internal Find search for "assisted migration".)

  • "Garden Plants Get a Head Start on Climate Change" by Sebastiaan Van der Veken et al, May 2008, Frontiers in Ecology and the Environment
    "We compared the natural ranges of 357 native European plant species with their commercial ranges, based on 246 plant nurseries throughout Europe. In 73% of native species, commercial northern range limits exceeded natural northern range limits, with a mean difference of ~ 1000 km. With migration rates of ~ 0.1 - 5 km per year required for geographic ranges to track climate change over the next century, we expect nurseries and gardens to provide a substantial head start on such migration for many native plants. While conservation biologists actively debate whether we should intentionally provide "assisted migration", it is clear that we have already done so for a large number of species." (excerpt from Abstract)

  • "Mapping California's Shifting Climate" KQED Climate Watch blog. 26 February 2010
    Cross-institutional report, with maps, on possible occurrence and velocity of climate change in California, along with response alternatives.

  • "Butterflies Reeling from Impacts of Climate and Development" Proceedings National Academy of Sciences January 2010.
    Their most significant findings: 1. Butterfly diversity (the number of different species present) is falling fast at all the sites near sea level. It is declining more slowly or holding roughly constant in the mountains, except at tree line. 2. At tree line, butterfly diversity is actually going up, as lower-elevation species react to the warming climate by moving upslope to higher, cooler elevations. 3. Diversity among high-elevation butterflies is beginning to fall as temperatures become uncomfortably warm for them and, Shapiro says, "There is nowhere to go except heaven."

  • "Some California Amphibians May Need a Lift to Survive Climate Change" Scientific American online, by Brendan Borrell, 7 August 2009.
    "As temperatures rise over the next century, three California amphibian species could be pushed to the cusp of extinction because the warming climate will effectively block their migration to more suitable habitats. Interventions by humans who physically relocate the animals may be the only way to help them survive. . . The Torreya Guardians, a self-organized group of naturalists, botanists, ecologists and others, are the most well-known proponents of assisted migration. Last July, the group planted endangered Torreya taxifolia seedlings in new habitat patches north of their customary domain in Florida, where it is becoming too hot for the conifers to survive." (and more)

  • "Are Butterflies the Silent Harbinger of Global Warming?" report by journalist Seth Shulman, Grist, 17 June 2010.
    Excellent summary of Camille Parmesan's early and continuing leadership in pointing out the shift poleward and upslope in native range of butterfly and other species, including her landmark 1996 and 2003 papers in the journal Nature. Parmesan is the lead scientist on the United Nation's Intergovernmental Panel on Climate Change (IPCC).

  • "Driving Mr. Lynx" Ideas page article by journalist Chris Berdik, Boston Globe, 12 October 2008.
    Lengthy news article that surveys the assisted migration debate, from its roots in a 2004 article in Wild Earth journal to citizen-activism, scientific backlash, and the beginnings of a worldview shift. The work of Torreya Guardians is highlighted, along with the August 2008 official filing, under the Endangered Species Act, of a request (by scientist Camille Parmesan) to undertake the first intentional movement of an animal species (an endangered butterfly) in response to shifting climate.

  • "Rules of the Wild", sidebar to above article in Boston Globe, 12 October 2008.

  • "Moving on Assisted Migration" news report by Emma Marris, Nature, online 28 August 2008.
    One of the top journals in science reports on the article (immediately below) that had been published in the other top science journal, plus coverage of the special session on assisted migration at the Ecological Society of America meeting in August 2008. Torreya Guardians is presented as taking the action lead in pressing for a rethinking of how biodiversity is best protected.

  • POLICY FORUM: ECOLOGY: "Assisted Colonization and Rapid Climate Change" by O. Hoegh-Guldberg, L. Hughes, S. McIntyre, D. B. Lindenmayer, C. Parmesan, H. P. Possingham, and C. D. Thomas, in Science 18 July 2008: 345-346. PDF of original article
    This 2-page article in America's top science journal has spurred enormous coverage and debate over the topic of what was once known as "assisted migration". Click here for news reports of the article:

  • Earth News online (posts full report of journalist Lauren Morello, who interviewed Connie Barlow of Torreya Guardians to demonstrate the citizen-action side of the issue)
  • climateshifts.org (a spin-off report that mentions the work of Torreya Guardians)
  • Scientific American online (a spin-off report that mentions Torreya Guardians)
  • in Wired News
  • Wired Magazine commentary by Brandon Keim
  • CNN.com
  • Science Daily (online)
  • Official website "Managed Relocation" posted by the "Working Group" that formed at the Ecological Society of America meeting, August 2008.
    Content: Right now this is just a skeleton website, as the group goes about its work. But after it achieves a product, estimated for autumn 2009, this will be a key site to watch. Right now, you can find a list of group leaders and members on that site. Check out their LIST OF PUBLICATIONS AND MEDIA REPORTS on this topic.

  • University of Queensland interview with first author of the Science forum above.
    Hoegh-Guldberg says, "If we are to take the latest climate science seriously, then our current conservation strategies will not work for the majority of the species. To be blunt, they need to change. Even under the mildest rates of climate change, the habitat of many species will contract. Consequently, the future for many species and ecosystems is so bleak that assisted colonisation might be their only chance of survival."

  • "Can Assisted Migration Save Species from Global Warming?" Scientific American, March 2009
    A lengthy article featuring Camille Parmesan, first advocate for assisted migration among professional conservation biologists. Lots of excellent details on butterflies and other species threatened by climate change. Mentions work of Torreya Guardians in assisting Torreya taxifolia tree seedlings to venture northward in July 2008.

  • "Should Species Be Relocated to Prevent Extinction", by Devin Powell, Inside Science News Service, 24 August 2009
    EXCERPT: The most recognized assisted migration project to date may be the Torreya Guardians. This network of conservationists, which includes botanists and ecologists, is trying to save the Torreya taxifolia, an endangered evergreen that grows to 60 feet in height. The group has transplanted dozens of trees from the Florida panhandle, where it is rapidly disappearing, to sites in North Carolina that are thought to have a suitable climate. "Plants are so much easier to replicate than pandas," said Rob Nicholson of the Botanic Garden at Smith College in Northampton, MA. "Torreya roots easily ... and you could start knocking them out by the tens of thousands if you wanted to."

  • Science Writer Carl Zimmer surveys the assisted migration controversy, as of 6 May 2006 in "As climate warms, species may need to migrate or perish", published online in ONLINE OPINION: Australia's e-journal of social and political debate.
    Zimmer's survey includes the context of the Ricciardi and Simberloff paper (directly above), and Jessica Hellman's comment on that paper, where she says, "Is the alternative just to forsake a species?" she asks. "I just don't want to sit back and say, 'Oh the world is going to hell'."

  • "Bugs: The Forgotten Victims of Climate Change", 3 July 2009 news article online in Live Science.
    Surveys managed relocations controversy as it pertains to insects; mention of need to assess insect tolerance of climate change in all their life stages; quotes Jessica Hellman.

  • "Big Plans for a Little Butterfly", 6 July 2009 news article online Mercury News.
    Project proposed to re-introduce extinct populations of Bay Checkerspot at the famous site where Paul Ehrlich and students studied them for 5 decades: "'We may end up having to try to readjust natural communities all over the planet,' Ehrlich warned. 'Reintroduction is a dice game,' said Carol Boggs, a Stanford biologist who would direct the experiment. 'What we'd like to understand is how to load the dice in our favor. And this is the perfect place to try it.' Researchers will spend the next year designing the experiment, which must be approved by both Stanford officials and the U.S. Fish and Wildlife Service. Stanford spokesman Larry Horton cautions that the university has not yet taken a position. The U.S. Fish and Wildlife Service, which protects endangered species, said it would support the effort, if done correctly. The Stanford scientists would use contrasting strategies — perhaps introducing insects at different phases in the life cycle, into different plots, at different seasons, Boggs said. Mowing, grazing or other human interventions would be needed to sustain it. By managing the introduction, Stanford scientists would build, in essence, a butterfly lab."

  • "Rewilding Torreya taxifolia to Waynesville, North Carolina, July 2008" Torreya Guardians webpage posted by Connie Barlow, August 2, 2008.
    A richly illustrated PHOTO-ESSAY, with links to a complete chronology, of the REWILDING ACTION that Torreya Guardians undertook for 31 potted seedlings. A writer and a photographer commissioned by Audubon magazine documented the action, which was published in a 2010 issue: "Guardian Angels".

  • "Terrestrial Orchid Conservation in the Age of Extinction", Annals of Botany 2009 104(3):543-556.
    Excerpt: "Assisted translocation/migration represent new challenges in the face of climate change; species, particularly orchids, will need artificial assistance to migrate from hostile environments, across ecological barriers (alienated lands such as farmlands and built infrastructure) to new climatically buffered sites. It is likely that orchids, more than any other plant family, will be in the front-line of species to suffer large-scale extinction events as a result of climate change."
        See also an online biogeographic article that reports on the existing use of assisted migration for Australian orchids.

  • "Orchids Flourish with Assisted Migration", Yale Environment Review (of June 2012 paper in Biological Conservation by Hon Liu et al).
    Excerpt: A recent study in Biological Conservation announced success with the migration of one of the world’s most beloved and charismatic plants: orchids. Chinese researchers examined the effects of assisted migration during a massive orchid rescue effort in 2006 that relocated 1000 endangered plants of 29 rare and endangered species from a lowland area that would be flooded by a hydropower project in the Longtan reservoir in Guangxi, southwestern China. Individual plants were moved 30 kilometers southeast to an altitude of 1000 meters above sea level, 600 meters higher than their original setting. Researchers labeled and mapped 462 individual plants from 20 species and tracked their flowering and survival six times over a 5-year period following the migration. The relocation area was situated outside the native elevation range of 70 percent of the species, offering the opportunity to compare responses between individuals within and outside of their native range. The researchers found that nearly all orchids were remarkably resistant to the climatic and grazing pressures, and that all species flowered in the new conditions.

  • "Species on the Move" June 8, 2009 May 28, 2009 ABC Science (online) report by Dani Cooper
    Lots of excellent details on the AUSTRALIAN species for whom assisted migration is being assessed, plus scientists quoted pro and con.

  • "University of Otago Rock Wren Project", 6 July 2009 online New Zealand abstract of new research project.
    Project abstract discusses methods to help ailing New Zealand bird, including assessment of assisted migration.

  • "Why Saving a Species is a Mathematical Matter", 26 July 2011 news article online in Brisbane Times.
    Interview with lead author, Eve McDonald-Madden, of July 2011 paper in Nature Climate Change, "Optimal timing for managed relocation of species faced with climate change", with example of Australia's Golden Bowerbird. See also article in Live Science.

  • "Climate Change and Translocations: The Potential to Re-establish Two Regionally Extinct Butterfly Species in Britain", Biological Conservation, Matthew J. Carroll et al.
    ABSTRACT: Climate change is causing many organisms to migrate to track climatically-suitable habitat. In many cases, this will happen naturally, but in others, human intervention may be necessary in the form of "assisted colonisation." Species re-establishments in suitable parts of their historic ranges provide an opportunity to conserve some species and to test ideas about assisted colonisation. Here, bioclimatic models of the distributions of two extinct British butterflies, Aporia crataegi and Polyommatus semiargus, were used to investigate the potential for re-establishment in Britain. . .

  • "Assisted Colonization Key to Species' Survival in Changing Climate" Feb 19, 2009 Innovations Report.
    Detailed news report of "the first successful test case of assisted colonization". In 1999 and 2000, scientists introduced populations of two species of butterfly miles north of their then-current range in England. A just-published paper reports the results:
    Source: Willis, S.G. et al. 2009. Assisted colonization in a changing climate: a test-study using two U.K. butterflies. Conservation Letters DOI: 10.1111/j.1755-263X.2008.00043.x. Their abstracts concludes, "We suggest that assisted colonization may be a feasible and cost-effective means of enabling certain species to track climatic change."

  • "Assisted Migration" chapter of 2007 PhD thesis by the scientist who coined the term: Brian Keel.
    The full title of Keel's thesis is "Assisted Migration as a Conservation Strategy for Rapid Climate Change: Investigating Extended Photoperiod and Mycobiont Distributions for Habenaria repens Nuttall (Orchidaceae) as a Case Study". The link above connects to a PDF of his chapter 3. Note: His PhD thesis abstract is available online and in book format: Assisted Migration as a Conservation Strategy for Rapid Climate Change: Investigating Extended Photoperiod and Mycobiont Distributions of Habenaria Repens Nuttall (Orchidaceae) as a Case Study. Keel is also coauthor of a chapter on Managed Relocation in a 2012 edited volume, Plant Reintroduction in a Changing Climate: Promises and Perils.

  • "When Worlds Collide" by Douglas Fox, Conservation Magazine, Jan-March 2007 (cover story).
    Subtitle: "Climate change will shuffle the deck of plants, animals, and ecosystems in ways we've only begun to imagine."
    Content: Surveys beginnings of debate about whether to actively assist species in shifting their geographic ranges. The work of Torreya Guardians is mentioned.

  • "A Framework for Debate of Assisted Migration in an Era of Climate Change" by Jason S. McLachlan, Jessica J. Hellman, and Mark W. Schwartz, Conservation Biology, April 2007, Vol 21: 297-302.
    Content: The paper begins, "The Torreya Guardians are trying to save the Florida torreya from extinction. . . The focus of Torreya Guardians is an 'assisted migration' program that would introduce seedlings to forests across the Southern Appalachians and Cumberland Plateau. Their intent is to avert extinction by deliberately expanding the range of this endangered plant over 500 km northward. . . If circumventing climate-driven extinction is a conservation priority, then assisted migration must be considered a management option. . . Assisted migration is a contentious issue that places different conservation objectives at odds with one another. This element of debate, together with the growing risk of biodiversity loss under climate change, means that now is the time for the conservation community to consider assisted migration. Our intent here is to highlight the problem caused by a lack of a scientifically based policy on assisted migration, suggest a spectrum of policy options, and outline a framework for moving toward a consensus on this emerging conservation dilemma."

  • "Assisted Migration: Helping Nature to Relocate" by Bob Holmes, New Scientist, 3 October 2007.
    Content: Superb and lengthy science reporting on the above paper that appeared in Conservation Biology, with much additional information, insights, and arguments culled from the authors and other scientists and conservation managers. Highlights issues related to speed of migration (past evidence as well as estimates of future needs) and regional changes in climate. An article referenced within the report by Jason McLachlan et al., is also important to read: "Molecular Indicators of Tree Migration Capacity Under Rapid Climate Change" in Ecology, 2005, Vol 86, pp. 2088-98.

  • "A Radical Step to Preserve Species: Assisted Migration" by Carl Zimmer, New York Times (Science Times), 23 January 2007 (lead story).
    Zimmer's next NYT story is 18 Sept 2014: "For Trees Under Threat, Flight May Be Best Response". EXCERPT: "Traditionally, conservation biologists have sought to protect endangered plants and animals where they live, creating refuges where species can be shielded from threats like hunting and pollution. But a refuge won't help the whitebark pine, and so now scientists are pondering a simple but radical new idea: moving the trees to where they will be more comfortable in the future. It's called assisted migration, and the debate over its feasibility comes as biologists everywhere begin to reassess their tactics and the impact of climate change on endangered species."

  • "Threatened Species 'Need Help' Finding Cooler Homes" news report by Catherine Brahic New Scientist Environment (online), 18 July 2008.
    News report on the 18 July 2008 paper in Science by Hoegh-Guldberg et. al (above).

  • "What Another Century of Global Warming Could Do to Our Wilderness" by Bert Gildart in Wilderness Magazine, September 2008.
    Great overview of looming problems for ecosystems (such as the Everglades) and species (such as Mountain Pica), some of which are already happening. No mention of assisted migration, of course, as this degree of human intervention would be a very delicate issue for the "wildest" of landscapes, especially for formally designated wilderness areas.

  • "Plants at Thoreau's Walden Pond Affected by Climate Change in the Area", Assoc. Press News Story, 27 October 2008.
    A 4.3 degree F. area-specific rise in temperature over the past century has affected plants in this sacred spot of environmentalism in Massachusetts. Notably, the plants hardest hit are those that did not alter their spring flowering time in tandem with the shift in earlier seasonal warming.

  • "Pre-emptive Strike: Outwitting Extinction", by Emma Marris, Nature Reports Climate Change (Online) 23 October 2008.
    The IUCN has issued a report on "climate change susceptible" species. "Assisted migration" is mentioned as one of the possible management responses, as well as enlarged biological preserves and focussing on entire ecosystems, not merely individual species.

  • "Coevolution of Cycads and Dinosaurs" paper by George E. Mustoe, The Cycad newsletter, March 2007.
    Barlow and Martin 2004 proposed that Torreya taxifolia might have gotten trapped in its peak-glacial pocket reserve (in northern Florida) for lack of its coevolved seed disperser, and thus was unable to geographically respond to the warming interglacial climate. The above paper suggests that another taxon of gymnosperm that thrived (along with genus Torreya) in the Jurassic period might have suffered from an inability to easily track climate change when the seed-dispersing dinosaurs died out.

  • "Biologists Debate Relocating Imperiled Species" by Philip Bethge Spiegel Online International (English edition) 23 November 2007. Content: News report on how climate change will threaten animal and plant species; includes coverage of Torreya taxifolia and mentions Torreya Guardians.

  • Discussion on a Blog Devoted to Snails and Slugs editorial, December 2008. Content: Blogs and comments debate "assisted migration/colonization" with respect to snails; includes some case history of attempt to relocated endangered snails from New Zealand mainland to an island off NZ.

  • "Some Endangered Species May Be Shifted to More Congenial Habitats" editorial, in The Times of India 3 February 2007. Content: Editorial in favor of assisted migration for endangered species.

  • "Climate Change and Assisted Migration of At-Risk Orchids" by Brian G. Keel, p. 9 of Orchid Conservation News (Woodland, CA), March 2005.

  • "Climate Change and Moving Species: Furthering the Debate on Assisted Colonization" by Malcolm L. Hunter, 2007, Conservation Biology Vol 21: 1356-58. Content: Makes case for using the term "assisted colonization" rather than "assisted migration"; proposes three features for testing advisability of any particular species for such intervention: (1) their probability of extinction due to climate change, (2) their vagility, (3) and their ecological roles.

  • "Assisted Colonisation" blog by Andrew Guerin, 18 July 2007. Content: Marine biologist highly skeptical of the merits of considering assisted colonisation for marine species.

  • "Macquarie Biologist's Grave Warning on Species Survival", news report. Content: Professor Lesley Hughes, co-author of the 18 July 2008 paper in the journal Science (O. Hoegh-Guldberg et. al), is interviewed by the web news of her university. Also click on an AUDIO INTERVIEW with Professor Hughes (scroll down to 30 June 2008, "Climate Change Peril").



    VERTEBRATE ASSISTED MIGRATION

  • "University of Arizona Study: Evolution Too Slow to Keep Up with Climate Change" press release of "Rates of projected climate change dramatically exceed past rates of climatic niche evolution among vertebrate species" by Ignacio Quintero and John J. Wiens, Ecological Letters August 2013 (abstract)
    EXCERPT (from press release): "Many vertebrate species would have to evolve about 10,000 times faster than they have in the past to adapt to the rapid climate change expected in the next 100 years, a study led by a University of Arizona ecologist has found. . .  terrestrial vertebrate species appear to evolve too slowly to be able to adapt to the dramatically warmer climate expected by 2100. The researchers suggested that many species may face extinction if they are unable to move or acclimate. . . The sampling covered 17 families representing the major living groups of terrestrial vertebrates, including frogs, salamanders, lizards, snakes, crocodilians, birds and mammals.

  • "Projected Climate-Driven Faunal Movement Routes" by J. J. Lawler et al., Ecology Letters 2013
    ABSTRACT: Historically, many species moved great distances as climates changed. However, modern movements will be limited by the patterns of human-dominated landscapes. Here, we use a combination of projected climate-driven shifts in the distributions of 2903 vertebrate species, estimated current human impacts on the landscape, and movement models, to determine through which areas in the western hemisphere species will likely need to move to track suitable climates. Our results reveal areas with projected high densities of climate-driven movements — including, the Amazon Basin, the southeastern United States and southeastern Brazil. Some of these regions, such as southern Bolivia and northern Paraguay, contain relatively intact landscapes, whereas others such as the southeastern United States and Brazil are heavily impacted by human activities. Thus, these results highlight both critical areas for protecting lands that will foster movement, and barriers where human land-use activities will likely impede climate-driven shifts in species distributions.
         EDITOR'S NOTE: The 2,903 vertebrate species modeled do not include any species for which bioclimatic projections indicate that discontinuities in livable landscapes will block easy species movements to respond to climate change. Hence, those vertebrate species that may require human-assisted migration were excluded from the study results.
         EXCERPTS: "The southern Appalachian Mountains in the southeastern United States and the Atlantic Forest in Brazil were two prominent areas highlighted by our models as likely to have high concentrations of species movements. Both of these areas are suspected to have served as climate refugia in the past." . . . "Our models do not account for dispersal distances and thus some of the movements included in our results may be unrealistic as they may be in areas that a given species will not be able to reach in a 100-year period. Many moles, shrews and primates, for example, may not be able to disperse fast enough to keep pace with climate change in the Western Hemisphere (Schloss et al. 2012)."

  • Biotic and Climatic Velocity Identify Contrasting Areas of Vulnerability to Climate Change" by Joshua Lawler et al., 2015, PLOS One.
    EXCERPTS: Metrics that synthesize the complex effects of climate change are essential tools for mapping future threats to biodiversity and predicting which species are likely to adapt in place to new climatic conditions, disperse and establish in areas with newly suitable climate, or face the prospect of extirpation. The most commonly used of such metrics is the velocity of climate change, which estimates the speed at which species must migrate over the earth's surface to maintain constant climatic conditions. However, "analog-based" velocities, which represent the actual distance to where analogous climates will be found in the future, may provide contrasting results to the more common form of velocity based on local climate gradients. Additionally, whereas climatic velocity reflects the exposure of organisms to climate change, resultant biotic effects are dependent on the sensitivity of individual species as reflected in part by their climatic niche width. This has motivated development of biotic velocity, a metric which uses data on projected species range shifts to estimate the velocity at which species must move to track their climatic niche.
         We calculated climatic and biotic velocity for the Western Hemisphere for 1961 - 2100, and applied the results to example ecological and conservation planning questions, to demonstrate the potential of such analog-based metrics to provide information on broad-scale patterns of exposure and sensitivity. Geographic patterns of biotic velocity for 2954 species of birds, mammals, and amphibians differed from climatic velocity in north temperate and boreal regions. However, both biotic and climatic velocities were greatest at low latitudes, implying that threats to equatorial species arise from both the future magnitude of climatic velocities and the narrow climatic tolerances of species in these regions, which currently experience low seasonal and interannual climatic variability.
         Biotic and climatic velocity, by approximating lower and upper bounds on migration rates, can inform conservation of species and locally-adapted populations, respectively, and in combination with backward velocity, a function of distance to a source of colonizers adapted to a site's future climate, can facilitate conservation of diversity at multiple scales in the face of climate change.
         Our results suggest that geographic patterns of vulnerability to climate change differ depending on whether conservation of locally-adapted populations, species, or sites is of primary interest. This contrast should be considered when identifying areas which may function as refugia or conversely are likely to be at high risk of biodiversity loss under climate change.
         Recent reviews have advocated consideration of multiple metrics of exposure to climate change. One widely-adopted approach integrates representation of coarse-filter or non-species-specific information with fine-filter information on individual species. Consideration of both climatic and biotic velocity allows such a coarse-filter/fine-filter approach to be extended to address the novel context of conservation under climate change.

  • "Scientists Try Radical Move To Save Bull Trout From A Warming Climate" by Christopher Joyce, NPR 8 October 2015.
    SUMMARY: Biologists are moving juvenile Bull Trout (a native species) in Glacier National Park upstream, beyond the blockages of waterfalls, to higher elevations as climate warms: "A team in Montana has undertaken one of the boldest translocations yet — moving an iconic Western fish, the bull trout, to protect it from climate change. . . The team's first translocation of bull trout was last year. They captured 125 fish and moved them to the upper lake. They know some survived — the fish were electronically tagged — but overall, it's still an experiment. This year, they don't know how many they'll catch. Already, these lakes and streams are getting warmer. 'I mean the time to act is now,' Chris Downs says, noting that it's the Park Service's mission to protect life in the nation's parks. 'We don't want to be looking back on this in 25 or 50 years and saying once again, we wished we'd done something when we had a chance.'"

  • "Relocating Australian tortoise sets controversial precedent" by Dyani Lewis in Science, (11 August 2016)
    "As long as it has been known to science, the diminutive western swamp tortoise has been in peril. By the time it was formally named in 1901—using a decades-old museum specimen—Pseudemydura umbrina was presumed extinct. And since it was rediscovered in the 1950s, biologists have struggled to protect it from the twin threats of habitat loss and introduced predators, which drove its numbers to bottom out at just 30 individuals in the 1980s. Now that climate change poses an even more urgent threat to the endangered tortoise, biologists have a controversial plan to safeguard its future—by moving it to new sites outside of its known historical range. The translocation, which took place today, makes the tortoise the first vertebrate to be deliberately relocated because of climate change.

  • "Location, Location, Location: Assisted Migration May Be Coming Closer to a Reality as a Response to Climate Change" by Yee Huang in CPR Blog, (01 February 2011)
    "In the UK, the Environment Agency is "exploring" moving thousands of vendace and schelly, both freshwater whitefish, from the northern Lake District in England to cooler waters in Scotland. While still in the planning stages, this strategy represents a remarkably specific and dramatic response to climate change." Includes link to the UK study mentioned.

  • "Britain Should Welcome Climate Refugee Species" by Chris Thomas, New Scientist 2 November 2011
    Popular adaptation of "Translocation of species, climate change, and the end of trying to recreate past ecological communities", an opinion piece in Trends in Ecology and Evolution, 15 March 2011. EXCERPT: "Britain is already home to around 2000 introduced species which have increased biodiversity while causing few, if any, major problems. True, there have been ecological changes, and we spend a lot of money trying to get rid of aliens, but Britain appears virtually immune to extinctions from introduced species. It therefore represents an ideal destination for endangered species from elsewhere in Europe. One is the Iberian lynx, the most endangered cat in the world. Establishing it in Britain would represent a great contribution to global conservation. Another is the Spanish imperial eagle; a third possibility is the Pyrenean desman, a semi-aquatic mammal restricted to streams in north-west Iberia. Various butterflies and water beetles might also find a suitable home in Britain. In fact, the vast majority of species endangered by climate change are likely to be plants and insects that would be relatively easy to accommodate. . . Conservation is now about managing change. Retaining or restoring the past is no longer feasible. We should avoid the unproductive question 'how can we keep things as they are?' and instead ask 'how can we maximise our contributions to global conservation?' One way will be to open our doors to endangered aliens."
        NOTE: See also, "Experts strive to re-introduce Norfolk's lost species" (reintroduction from Sweden of the pool frog that went extinct in the UK in 1993).


  • "U.S. Agrees to Consider Protection for Pikas" report by Jane Kay in San Francisco Chronicle, 13 February 2009.
    Endangered Species Act invoked by Center for Biological Diversity to protect pikas threatened by global warming in the alpine peaks home in mainland U.S. No mention yet of assisted migration for the subspecies of pika trapped on warming mountain tops.

  • "Testing alternative models of climate-mediated extirpations?"(American Pika) by Erik A. Beever et. al, Ecological Applications January 2010
    EXCERPT: "Research on American pikas (Ochotona princeps) in montane areas of the Great Basin during 1994-1999 suggested that 20th-century population extirpations were predicted by a combination of biogeographic, anthropogenic, and especially climatic factors. Surveys during 2005-2007 documented additional extirpations and within-site shifts of pika distributions at remaining sites."
        Editor's Note: See also the 2012, "Not-so-splendid isolation: modeling climate-mediated range collapse of a montane mammal Ochotona princeps [American pica] across numerous ecoregions", which includes "Nineteen of the 31 traditional US pika subspecies were predicted to lose > 98% of their suitable habitat under a 7 degree C increase in the mean temperature of the warmest quarter of the year, and lineages were predicted to lose 88 95% of suitable habitat. Under a 4 degree C increase, traditional subspecies averaged a predicted 73% (range = 44-99%) reduction." SEE ALSO 2012 book chapter by Chris Ray et. al, "Retreat of the Amerian Pika: Up the Mountain or into the Void?", which includes: "The majority of evidence for effects of climate on O. princeps derives from studies within the Great Basin . . . In this region, the species has been losing ground for at least 10,000 years: the minimum elevation of the pika's distribution has retracted upslope by nearly 800 meters once the last glacial maximum, eliminating some populations and isolating others."

  • "Alpine biodiversity and assisted migration: the case of the American pika", 2015, Biodiversity by Jennifer L. Wilkening et al. Note: This paper is quoted at length because (a) the American Pika is the "poster animal" for assisted migration climate action in the continental USA, and (b) it may historically be deemed one of the first detailed justifications and prescriptions for how to carry out a species-specific assisted migration project in the USA.
    EXCERPTS: "Assisted migration can be defined as the intentional movement of a species outside of its current range to areas predicted to be favourable under future climate projections. Related terminology is still under debate, and this process is also currently known as assisted colonisation (Hunter 2007), facilitated migration (Hoegh-Guldberg et al. 2008), managed relocation (Richardson et al. 2009), assisted range expansion (Hayward 2009) and species translocation (Heller and Zavaleta 2009). As a conservation strategy, assisted migration can be used to prevent populations of some species from becoming functionally extinct and/or to mitigate expected biodiversity losses resulting from climate change or other anthropogenic disturbance. Within the conservation community however, assisted migration remains a controversial topic due to its highly manipulative nature and the potential social and ecological consequences. Additionally, this is not a viable conservation strategy for some species affected by climate change (e.g. cold-adapted large mammal species such as polar bears), and therefore selection of appropriate candidate species is also important.
         "Central to the arguments against assisted migration are concerns related to the ability of a translocated species to become invasive. Past research has attempted to identify which characteristics predispose a species towards invasiveness, but determining potential unintended ecological consequences remains challenging (Kolar and Lodge 2001; Ricciardi and Simberloff 2009). Typically species in need of assisted migration tend to be characterised by low dispersal ability and slow population growth rates, traits not commonly associated with invasive species. This may not always hold true though, and it could become more difficult to predict the risk of a species' invasiveness when faced with continued climate change and altered resilience of ecological communities.
         As ecosystem community composition changes in response to altered climate regimes, uncertainty surrounding future species assemblages complicates questions related to moving species around. Time frames used traditionally in conservation planning may no longer apply, as managers will likely be faced with novel ecosystems requiring new strategies and iterative processes such as adaptive management. Finally, the efficacy of assisted migration as a long term mitigation strategy for climate change remains questionable, since at some point suitable habitat for certain species may no longer be available under future climate scenarios.
         "Although there are numerous caveats associated with assisted migration, it may represent the only option to prevent extinctions of species that cannot adapt to rapid climate change. Massive extinction events have occurred as a result of global climate change in the past, but these were not driven by human activities (Raup 1992). Given that the rate of species extinctions continues to accelerate due to anthropogenic degradation or destruction of natural habitats (Ceballos et al. 2015), many scientists could argue that intervention is warranted (Travis 2003). Arguments in favour of halting species extinctions include those recognising the various medicinal, agricultural and recreational values of species diversity. Added to this is the concept of intrinsic value, or the idea that each species has value regardless of services provided for humans or other species. Finally, species that occupy a dominant or keystone role in an ecosystem deserve special consideration, since continued existence of other species and maintenance of ecological integrity may depend upon them (Kreyling et al. 2011).
         "The debate about when and where to undertake assisted migrations is furthered by practical and economic concerns, and various decision-making frameworks have emerged to address these as well as those mentioned above (Germano et al. 2015; Hunter 2007; Hewitt et al. 2011; Hoegh-Guldberg et al. 2008; Kreyling et al. 2011; Loss, Terwilliger, and Peterson 2011; Mclachlan, Hellmann, and Schwartz 2007; Richardson et al. 2009). Criteria incorporated into these frameworks include the technical feasibility of translocation and establishment of the considered species, the potential impacts to a source population and the recipient ecosystem and whether or not the overall benefits outweigh the biological and socioeconomic costs and constraints. Non-mobile species isolated in disparate habitats, where effects of climate change are more pronounced (such as mammals on mountaintops), remain as some of the best candidates (Popescu and Hunter 2012). Many of these occupy specialised or dominant roles in the ecosystem, strengthening the claim to focus on these species as ideal choices for assisted migration (Thomas 2011).
         "One such species is the American pika (Ochotona princeps), a habitat specialist which occurs in rocky or mountainous areas throughout the western United States. American pikas (hereafter pikas) are lagomorphs with a narrow thermal tolerance (MacArthur and Wang 1973) that only inhabit areas that provide access to cooler microclimates for behavioural thermoregulation (Figure 1). Subsequently, many populations are isolated on mountaintops or within other rocky features surrounded by a sea of unsuitable habitat, making dispersal difficult. Climate has been identified as a driver of recent popula- tion declines (Beever et al. 2010, 2011) and pikas are considered a sentinel species for detecting ecological effects of climate change (Beever, Berger, and Brussard 2003; Grayson 2005; Hafner 1993, 1994; Krajick 2004; Lawlor 1998; McDonald and Brown 1992; Morrison and Hik 2007; Smith, Li, and Hik 2004). In the US, pikas are of conservation concern and the species has been considered for listing as threatened or endangered at the state and federal level (USFWS 2010; Osborn and Applebee 2011). Additionally, they may serve as a key species in alpine ecosystems, since they cache vegetation for a winter food source, which influences local vegetation communities (Aho et al. 1998). These factors combined make pikas a good candidate species for consideration of assisted migration. Here we summarise information related to the known habitat requirements and physiological constraints of this species, to be considered for selection of source populations and candidate relocation sites. We also include disease and genetic considerations appropriate when moving individuals into areas not currently occupied. Finally, we present conclusions about the efficacy of assisted migration in mitigating climate change impacts on this species and preserving alpine biodiversity overall.
         The genetic consequences of assisted migrations can be difficult to predict (Weeks et al. 2011). When selecting source populations, genetic matching of source and recipient populations may be important both for the inherent value of maintaining the full range of genetic variation present across the species range but also for adaptive potential with regard to local conditions. In contrast, for small, isolated populations threatened by low levels of genetic variation, it may be beneficial to combine source populations in order to avoid the continuing loss of genetic variation despite the risk of outbreeding depression (Weeks et al. 2011).
         "Assisted migrations can be differentiated genetically by the specific objective triggering the perceived need to move individuals from a source population to another location. For the American pika, the first assisted migrations will likely involve the movement of individuals into a local population of conspecifics, a process also known as augmentation (Weeks et al. 2011). To prevent the random loss of small populations, augmentation can be a tool to ease the maladaptive genetic effects that often occur in fragmented populations (e.g. inbreeding depression, diminished genetic variation) by increasing reproductive fitness through genetic rescue or genetic restoration (Weeks et al. 2011). The continued loss of previously occupied pika populations in the Great Basin (and therefore the reduction of gene flow among fragmented populations; Beever et al. 2010, 2011) may eventually lead to the need for genetic rescue, or the introduction of new alleles into an isolated population experiencing the detrimental effects of genetic load.
         "Additionally for pikas, a species that is predicted to be severely impacted by the effects of global climate change (Beever et al. 2011; Popescu and Hunter 2012), it may become important in the near future to consider a specific type of assisted migration known as genetic adaptation. The goal of this genetic-based assisted migration is to enable climate change-threatened species to persist by moving individuals outside of their current range to areas deemed suitable according to future climate scenarios (Weeks et al. 2011). Similar to restoration-based efforts, it may be important to genetically evaluate source populations in order to confirm that locally adapted alleles 'match' the local environment at the new site. In fact, the ability of source populations to respond to future environmental change will depend upon this evolutionary genetic potential which requires the maintenance of large population sizes and perhaps, repeated introductions of source individuals into a recipient site. Furthermore, if assisted migration is aimed at improving the adaptability of a population threatened by climate change, it will require the identification of putatively adaptive genetic loci, in conjunction with analysis of neutral genetic differentiation that reflect demographic processes and patterns of movement (Weeks et al. 2011).
         EXCERPTS FROM CONCLUSIONS SECTION: "The ability for pikas to respond through adaptation (rather than plasticity or dispersal) is an important mechanism to maintain in the face of climate change (Weeks et al. 2011). Therefore, preserving locally-adapted genetic variation present within pika populations, as well as upholding population adaptability and fitness, will be critical for their persistence. Initially, assisted migration efforts should emphasise the importance of evolutionary potential by sustaining or establishing relatively high levels of genetic diversity (Weeks et al. 2011).
         "Pikas could be trapped from at least four populations, consisting of a minimum population size of 30 individuals, distributed across the geographic range of Ochotona princeps in the western US. Care should be taken to ensure that individuals of both sexes are equally selected for translocation, and this will require the assistance of an expert pika biologist since sex determination is difficult. Juvenile pikas typically disperse away from natal territories, suggesting that juveniles are most likely to thrive when attempting assisted migrations for this species (Smith and Weston 1990). Multiple translocation sites should be considered, since the success of the assisted migration overall could depend on the number of founding populations (Griffith et al. 1989). Translocation sites could be selected within the historic range of American pikas, and also the predicted range under future climate scenarios, that fulfil criteria known to support a pika community. Such habitat criteria should include talus slope terrain, adjacent meadows rich in mixed grasses and forbs, sufficient precipitation and at an elevation that provides a suitable temperature range for pika occupation (Beever et al. 2010; Erb, Ray, and Guralnick 2011; Hafner 1993, 1994; Huntly, Smith, and Ivins 1986; Smith and Weston 1990; Varner and Dearing 2014).
         "GIS spatial analysis could be utilised to assist in the selection of potential translocation sites by querying for appropriate land cover/plant type, slope, ambient temperature, soil type and satellite imagery. In addition, interviews could be conducted with local field biologists to refine possible locations, and final selection should be made following site visits. During these site visitations, the presence of pika vocalisations, hay piles, or fresh scat should be assessed to determine whether or not pikas already occupy the potential study sites." Editor's note: The conclusions section contains details for carrying out assisted migration projects for the American pika, including specific guidelines for source and recipient sites, for trapping and moving individuals, and for monitoring.

  • "Analysis of climate paths reveals potential limitations on species range shifts" by Regan Early and Dov Sax, Ecology Letters (29 September 2011)
    From press release: In a new study based on simulations examining species and their projected range, researchers at Brown University argue that whether an animal can make it to a final, climate-friendly destination isn't a simple matter of being able to travel a long way. It's the extent to which the creatures can withstand rapid fluctuations in climate along the way that will determine whether they complete the journey. Regan Early and Dov Sax examined the projected "climate paths" of 15 amphibians in the western United States to the year 2100. Using well-known climate forecasting models to extrapolate decades-long changes for specific locations, the researchers determined that more than half of the species would become extinct or endangered. The reason, they find, is that the climate undergoes swings in temperature that can trap species at different points in their travels.
        Confronted with these realities, Early and Sax say wildlife managers may need to entertain the idea of relocating species, an approach that is being hotly debated in conservation circles. "This study suggests that there are a lot of species that won't be able to take care of themselves," Sax said. "Ultimately, this work suggests that habitat corridors will be ineffective for many species and that we may instead need to consider using managed relocation more frequently than has been previously considered." news report on; illustrated report on.

  • "Snakes Struggle to Keep Pace with Climate" news story in Futurity, (13 December 2011)
    Summary of PLoSOne paper, "Pleistocene Climate, Phylogeny, and Climate Envelope Models: An Integrative Approach to Better Understand Species' Response to Climate Change", by A. Michelle Lawing and P. David Polly, 12/2/11. Quotes from the news summary: "We find that, over the next 90 years, at best these species' ranges will change more than 100 times faster than they have during the past 320,000 years," says lead author Michelle Lawing, a doctoral candidate in geological sciences and biology at Indiana University. "This rate of change is unlike anything these species have experienced, probably since their formation." . . . Snakes won't be able to move fast enough to keep up with the change in suitable habitat, the study suggests. Creation of habitat corridors and managed relocation may be needed to preserve some species.

  • "Temperature-Dependent Sex Determination and Contemporary Climate Change" by N.J. Mitchella, F.J. Janzen. Journal: Sexual Development, published online, only abstract freely available (9 February 2010)
    Whether species that have persisted throughout historic climatic upheavals will survive contemporary climate change will depend on their ecological and physiological traits, their evolutionary potential, and potentially upon the resources that humans commit to prevent their extinction. For those species where temperatures influence sex determination, rapid global warming poses a unique risk of skewed sex ratios and demographic collapse. Here we review the specific mechanisms by which reptiles with temperature-dependent sex determination (TSD) may be imperilled at current rates of warming, and discuss the evidence for and against adaptation via behavioural or physiological means. We propose a scheme for ranking reptiles with TSD according to their vulnerability to rapid global warming, but note that critical data on the lability of the sex determining mechanism and on the heritability of behavioural and threshold traits are unavailable for most species. Nevertheless, we recommend a precautionary approach to management of reptiles identified as being at relatively high risk. In such cases, management should aim to neutralise directional sex ratio biases (e.g. by manipulating incubation temperatures or assisted migration) and promote adaptive processes, possibly by genetic supplementation of populations.

  • "Climate Change Risks and Conservation Implications for a Threatened Small-Range Mammal Species" by Morueta-Holme et al., PLOS One29 April 2010
    "Here, we provide a detailed assessment of the climate sensitivity and potential distributional impacts of 21st century climate change for an illustrative endemic species limited to a restricted part of the Mediterranean region. This region is rich in endemic species and is expected to experience particularly severe global-change-driven biodiversity losses over the 21st century. The study species is the Iberian desman Galemys pyrenaicus (E. Geoffroy Saint Hilaire, 1811), a small semi-aquatic mammal endemic to the Iberian Peninsula.

  • "Relocating Animals to Safer Climes" journalist report by Reena Amos Syes, Emirates Business, 6 June 2010.
    Focal species is the reintroduction of extirpated Oryx to its homeland in Oman and how that will be affected soon by the scheduled release in 2012 of international guidelines for translocation of species in response to climate change by the "Species Survival Commission." Quotes fr Dr Mark Stanley Price, incl: "That is why chosen scientists from all over the world have been asked by the International Union for the Conservation of Nature and Natural Resources (IUCN), to set up a group to look at assisted colonisation globally. It wants us to set up guidelines for assisted animal colonisation and release new guidelines at the World Conservation Congress in 2012 in South Korea."



    ASSISTED MIGRATION FOR FORESTS OF NORTH AMERICA

    "The true meaning of life is to plant trees,
    under whose shade you do not expect to sit."
    — Nelson Henderson


       "Foundational Literature for Moving Native Plant Materials in Changing Climates

    U.S. Forest Service 2015 document, by Mary I. Williams, R. Kasten Dumroese, Jeremiah R. Pinto, and Martin F. Jurgensen. 303 pages in PDF.

    Annotated bibliography grouped into four topics:

    • Climate Change   • Conservation and Restoration
    • Migration   • Seed Transfer Guidelines and Zones


    Best Review Articles:

    "Assisted Migration of Forest Populations for Adapting Trees to Climate Change", by Cuauhtemoc Saenz-Romero et. al, in Revista Chapingo Serie Ciencias Forestales y del Ambiente, Autumn 2016, (Spanish and English).

    EDITOR'S SUMMARY: As of 2016, this is the best (and most up-to-date) review article of assisted migration as a tool for helping tree populations and species pace climate change, from both a commercial forestry and a conservation perspective:
    "We address the following questions: In order to accommodate climate change, what forest management options do we have? What would be the consequences of inaction, i.e., continuing as if climate change does not exist? We aim to provide foresters with a framework of basic knowledge regarding the magnitude and speed of climate change and its current and potential effects on forest resources, as well as suggesting some options for active management aimed at maintaining healthy tree ecosystems in the future... As a management option, we suggest assisted migration, which is the realignment of natural populations to the climate for which they are adapted, through reforestation in sites where their suitable climate is predicted to occur in the future. This represents an active management option that aims to provide healthy tree ecosystems in the future. "
    EXCERPTS: Actions must be taken to ensure that the forests harvested today are re-planted with genetic resources that are adapted for the temperatures predicted for the period centered around 2030 or at most 2060, in order to avoid the excessive forfeiture of growth that will occur if these trees are planted on a site where suitable climate will not occur until too far ahead into the future... There is a common belief among the general public that nature allows species to evolve and populations to adapt to environmental changes (such as the glaciations) and that therefore this should occur once again in response to climatic change. This belief is mostly wrong, at least for tree populations. The problem is the speed of the current, human-induced climate change... in order to successfully track these climates, geographic shifts of tree populations will have to be 10 to 100 times faster than they have been in the past or are at present.
         Selection of species to be moved by assisted migration is complicated in countries of extensive biodiversity, such as Mexico or Colombia. Which species should be chosen for relocation? It is clear that not all species can be moved. One option would be to give priority to those that are already on the brink of extinction; such is the case in three rare, endemic and endangered Mexican spruces: Picea chihuahuana, Picea mexicana, and Picea martinezii Patterson, which present relictual, fragmented, inbred populations in northern Mexico. . . . It has also been proposed that the species of greatest economic interest and/or those that constitute keystone species that provide the structure of a plant community (generally tree species) should have priority for assisted migration. It can thus be expected that when populations of such keystone species are established, they will provide suitable habitat for several other species, including fauna.
         There is concern that assisted migration would be designed based on possibly erroneous predictions of climatic change, given the inadequacies of modeling or uncertainty regarding the quantity of greenhouse gases that will be released in the future. While valid, these concerns have led to inaction and it is therefore pertinent to ask the question: is inaction a better option? There are no reasons to believe that inaction would keep current tree populations intact. The massive and sudden decline of forest tree populations that has occurred with the mean annual temperature increase of around 1 degree C as a result of the climate change already in place, seems to us a strong indication that the predicted temperature increases of 2, 3, 4 or 5 degrees C will cause a disastrous disruption to plant communities. There is a point where assisted migration would no longer be an option: if forest trees in the future become dead or too weak to produce healthy seeds, then it might be impossible or unaffordable to assist their migration in the future.

    ♦ SOCIETY OF AMERICAN FORESTERS REVIEW ARTICLE (2013): "Preparing for Climate Change: Forestry and Assisted Migration", by Mary I Williams and R. Kasten Dumroese, in Journal of Forestry, July 2013.

    SUMMARY QUOTE: "Climate is changing at a faster pace than natural plant migration, which poses a major challenge to forest management and conservation. We can draw from a century of forest research and management to curtail losses in forest growth, productivity, and conservation by implementing strategies, such as assisted migration. Even though we have seed transfer guidelines and seed zones for many commercial tree species, we lack clear, standard operating procedures to determine how, when, and where to implement movement. Movements outside current guidelines and zones may run afoul of legal restrictions and state and federal directives, but facilitating climatic adaptation through assisted migration has the potential to preserve forest health and productivity, subsequently maintaining ecosystem services, such as carbon sequestration, soil and water conservation, timber, and wildlife habitat. Our review and presentation of current information for researchers, foresters, landowners, and nurseries provides components to consider in their climate change adaptation plans." EXAMPLE: "Alberta is considering ponderosa pine (Pinus ponderosa) and Douglas-fir, now absent in the province, as replacements for lodgepole pine (Pinus contorta) because it is predicted to decline in productivity or suffer from extinction under climate change."

    Editor's Note: The above article is ideal for learning the historical and policy reasons why commercial and public foresters are generally accepting of and at ease with "assisted migration" strategies for coping with anticipated climate change, as applied to populous (and also commercial) tree species. In contrast, resource managers responsible for endangered species and restoration of botanically targeted conservation lands are far more cautious about adopting (even considering) assisted migration as a management tool.

    See also Williams and Dumroese 2013, "Climatic Change and Assisted Migration: Strategic Options for Forest and Conservation Nurseries". A very readable version by the same authors, but intended for land managers and the nurseries that supply seedlings was published in 2014: "Planning the Future's Forests with Assisted Migration". Also, this internal USFS document by same authors, which specifies suggested standards and actions: Williams and Dumroese, 2013, "Growing Assisted Migration: Synthesis of a Climate Change Adaptation Strategy", USDA Forest Service Proceedings, RMRS-P-69. VIDEO by Mary I. Williams, 2013: "Charting Assisted Migration as a Climate Change Adaptation Strategy" (37 min.) Note: Call up two windows on your browser; watch/listen to the embedded youtube video on one window while you click on the "Presentation slides" in a separate window. Also, there is a direct youtube link to video (no slides).

    Also, "Placing Forestry in the Assisted Migration Debate", by John H. Pedlar et al, 2012, Bioscience, which distinguishes "Forestry Assisted Migration" (movement of population genetics to track climate change during post-harvest replantings) v. "Species Rescue Assisted Migration" (e.g., the action of Torreya Guardians). Conclusion: "Much of the recent debate around assisted migration (AM) has been implicitly focused on the species rescue form, which we suggest has relatively limited spatial scope, low feasibility for near-term science-based implementation, and arguably higher levels of risk. Alternatively, forestry AM is a highly feasible adaptation approach that is already being implemented in some jurisdictions and that could help to maintain forest productivity and certain ecosystem services across large areas in the face of rapid climate change."

    Also: "An Overview of Some Concepts, Potentials, Issues, and Realities of Assisted Migration for Climate Change Adaptation in Forests", by Louis R. Iverson et al., 2013. This latter document distinguishes between two forms of assisted migration: Species Rescue AM v. Ecosystem Services AM; it concludes that the latter is less problematic and has "been underway for centuries" by foresters. (Example of black oak AM into northern Wisconsin under consideration to cope with expected climate change.) For a review of how well U.S. Forest Service policy statements prepare that institution to engage in "assisted migration" rapidly and extensively enough to track expected climate change, see "Policy and Strategy Considerations for Assisted Migration on USDA Forest Service Lands", 2013, Randy Johnson et al. One conclusion is that existing policy "statements imply that the only instance one should engage in assisted migration on an operational basis is when past scientific research supports success. In addition, untested assisted migration can take place if it is part of a research or administrative study. In all cases, monitoring is required. Presently, this limits operational assisted migration to only the handful of species that have provenance trial data available from longer-term field trials and those species where seed sources have been moved previously."

    ♦ REVIEW ARTICLE in The Forestry Chronicle" of Canada (2011) by Catherine Ste-Marie et al., "Assisted migration: Introduction to a multifaceted concept".

    EDITOR'S SUMMARY: Although this paper has an applications focus on Canadian forestry, it surveys the broad scope of the issue as widely published. Superb details are included in this review paper. (Only intro and conclusion excerpts are in the blockquote below.) More excerpts focus on the issue of naming this climate adaptation tool; although "assisted migration" is the most frequently used, a literature search of the range of terminology used is also excerpted within the 2011 list of "Assisted Migration or Assisted Colonization: What's in a Name?".
    This introductory paper for the special issue of The Forestry Chronicle on the subject of assisted migration describes increasing interest in the subject and its complexity. It also provides an overview of the potential scale of assisted migration, proposes a terminology, and briefly introduces the following papers. Overall, the five papers aim to present a comprehensive state of the scientific and operational knowledge and the debate on assisted migration in the context of Canada's forests.
         The immobility of individual plants makes them especially vulnerable to climate maladaptation, and this is often more pronounced for tree species because their long generation time may limit rapid adaptation (Vitt et al. 2010). Based on atmosphere–ocean GCMs, McKenney et al. (2007) estimated that climatic envelopes for major North American tree species could shift 330 to 700 km northward over the next half-century (6,600 to 14,000 metres per year). Rates of northward tree migration after the last glacial maximum in Europe and North America, estimated from fossil pollen data, range between 100 and 2,000 metres per year (Davis 1981, Huntley and Birks 1983, Pakeman 2001). In the eastern United States, the migration potential of five tree species, persimmon (Diospyros virginiana), sweetgum (Liquidambar styraciflua), sourwood (Oxydendrum arboreum), loblolly pine (Pinus taeda) and southern red oak (Quercus falcata), is predicted by models not to exceed 100 to 200 metres per year (Iverson et al. 2004). Other factors add challenge to migration. Landscape fragmentation presents significant, and in some cases insurmountable, barriers to northward migration (Fazey and Fischer 2009, Vitt et al. 2010). Competition with existing vegetation for light, nutrients and space can limit the establishment of seedlings in a new environment; intact ecosystems are often resistant to introduced plant species, and are less likely to readily support self-sustaining populations of new species (Hunter 2007).
         Assisted migration is multifaceted. It poses new and complex questions. It requires new knowledge to be generated, and management practices, paradigms and policies to be revisited, and it questions our fundamental values concerning the relationship of humans with nature. Because of the interest in assisted migration as a potential adaptation option and because of the complexity of the issue, the need to develop a comprehensive review of assisted migration as a forest management option to adapt to climate change in Canada is addressed in this special issue of The Forestry Chronicle. Assisted migration is an emerging concept with many unknowns. To move forward on this issue requires the best scientific and technical knowledge available, an informed and open discussion among all potentially affected parties and a framework for the decision-making process. The goal of this special issue is to present a comprehensive yet accessible review of the state of the scientific and operational knowledge and the debate on assisted migration. To facilitate the reading of our series, a glossary of technical terms that re-occur throughout the articles is included in the present special issue for easy reference to their definitions. The authors hope that these five papers will contribute to inform future decisions related to assisted migration in Canada's forests.

    "Considerations for restoring temperate forests of tomorrow: forest restoration, assisted migration, and bioengineering" by R. Kasten Dumroese et al., 2015, New Forests. Introduces some leading-edge considerations and tactics, including "no regrets" decision-making and "functional restoration" — both of which could utilize "assisted migration" (introduction of southerly genotypes of existing tree species or introduction of southerly species, both for the overriding goal of maintain forest canopy/function in a rapidly warming time).

    As discussed earlier, native populations adapted to sites under current climate may become maladapted as changes in climate occur. Assisted migration may be used to ensure adapted populations by countering two limitations of tree migration: long generation cycles and reduced dispersal ability (Potter and Hargrove 2012). Assisted migration can be applied at different scales, including moving populations within a species' current range, beyond a species' range proximate a current distribution, or long distances outside its current range (Fig. 3) (Ste-Marie et al. 2011; Winder et al. 2011; Williams and Dumroese 2013). In addition, movements can be geographic (e.g., distance along an elevation gradient), climatic (e.g., change in number of frost-free days along an elevation gradient), and/or temporal (e.g., date when the current climate of the migrated population equals the future climate of the outplanting site). By introducing adapted plant materials, assisted migration has potential to promote resilience to change and/or ease habitat transitions already occurring and realigning systems where resources are severely degraded or fragmented (Millar 2014). Assisted migration is beginning to find its way into climate change adaptation plans (e.g., IPCC 2014) although consensus about its implementation is hampered by research and conservation challenges, existing management policies, uncertainty about future conditions, and non-standardized terminology (Hewitt et al. 2011). Assisted migration terminology, like that of restoration (see Stanturf et al. 2014a) becomes unwieldy because universalism in definitions is trumped by historical use within various disciplines and creation of context-base descriptions (Fig. 2). Although no explicit solution exists for this, remaining mindful to discuss assisted migration within the context of the restoration goal should support better communication among scientists and among scientists, land managers, and the public.

        Eventually, shifting climates may render current species or populations maladapted, as predicted, for example, for Picea abies in the southwestern portion of its current European range (Sykes and Prentice 1996) and for broadleaved species moving northward from temperate European forests to the current boreal forests (Thuiller et al. 2006). This may force managers to plant to increase genetic diversity and the adaptive potential of existing forests (St. Clair and Howe 2011). These interplantings within the landscape matrix of existing forest may be most efficiently established after management or natural stochastic events. Depending on the level of maladaptation, outplanted seedlings could include a mixture of local seed sources and non-local seed sources identified to be better adapted under future climates (on-set of maladaptation) or entirely distant seed sources (well-manifested maladaptation). Given the uncertainty of future climates, combinations of current and future seed sources would provide a "no-regrets" approach (sensu Kates et al. 2012) for land managers; poor performers would be lost through natural selection or silvicultural activities such as thinning. The challenge will be monitoring for maladaptation, defining a threshold for action, identifying the source of new materials, and obtaining appropriate balance in deployed genetic resources. The approval for testing and conducting assisted migration is likely to be case and region specific. In Canada, assisted migration is being tested and considered for Abies albicaulis (McLane and Aitken 2012) and Larix occidentalis (NRC 2013), both foundation species of commercial importance and hosts to many other plants and animals. In southern Mexico, it has been suggested that seed sources of Abies religiosa be moved 275 m upwards in altitude in order that populations growing 15 years from now would still experience today's climate (Fig. 4) (Sa'enz-Romero et al. 2012) and continue to provide essential overwintering habitat for the charismatic, threatened, international migrant Danaus plexippus (Lepidoptera: Nymphalidae). Similar recommendations are being made for Pinus oocarpa (Sa'enz-Romero et al. 2006) and Pinus hartwegii (Viveros-Viveros et al. 2009) in Mexico and Central America. In the U.S., a citizen-driven initiative to save Torreya taxifolia, a southeastern evergreen conifer, from extinction is by planting it well north of its current and historic range (McLachlan et al. 2007; Barlow 2011).

        Assisted migration undoubtedly disrupts established understandings of natural resource management and long-held views in conservation biology, therefore it must be implemented in a framework that assesses species and population vulnerability to climate change, sets priorities, selects options and management targets, emphasizes long-term monitoring, and adjusts as needed. Adoption requires land managers to balance species conservation against risks posed by introduced species (Schwartz 1994), although this risk may be overstated as few forestry tree species have become invasive (see Koskela et al. 2014). Assisted population migration and assisted range expansion are more likely scenarios than assisted species movement, and the risk of spreading pathogens from transferring seeds is relatively low compared to moving live plants (Pedlar et al. 2012; Santini et al. 2013). Assisted migration should consider the critical, in situ preservation of adapted species and populations at the trailing edges of changing ranges because, compared to leading edge populations, they have unique features that were important for maintenance of biodiversity during previous shifts in climate (Hampe and Petit 2005). Indeed, refugia (i.e., phylogeographical hotspots), areas of "significant reservoirs of unique genetic diversity favorable to the evolutionary process," have already persisted through repeated episodes of rapid and major environmental change (Me'dail and Diadema 2009). Although not all current refugia remaining from the Last Glacial Maximum may serve as refugia under contemporary climate change, their persistence on the landscape due to unique circumstances and characteristics of past warming and cooling events makes their identification valuable (Keppel et al. 2012). Indeed, understanding the process likely to produce refugia to contemporary climate change would be a powerful tool in preserving genetic diversity (Keppel et al. 2012).

    "Can Boreal and Temperate Forest Management be Adapted to the Uncertainties of 21st Century Climate Change?" by Andrew Park et al., 2014, Critical Reviews in Plant Science. This 35-page pdf by professional foresters from Canada, the UK, and USA is a stunning review of how the profession must evolve given rapid ongoing climate change. It is highly technical and covers concerns and practices far broader than assisted migration — including epigenetic effects of the climates where seed embryos develop and a survey of the pros and cons of various bioclimatic envelope modeling for predicting future preferred habitats on a species-by-species basis. But here are some of the assisted migration excerpts:

    "'Options Forestry' implies that we should simultaneously explore acclimation to higher temperatures among trees already in place, and the possibility that assisted migration (AM) of species to areas where they are not endemic will be needed to adapt to extreme warming. The AMAT experiment is aimed at establishing whether such transfers are possible across a wide temperature range and latitudinal gradient. The southernmost provenances in this experiment will be shifted by as much as 9.1 degrees C and over 2500 mm of precipitation relative to their native climates, and seed will be shifted up to 10 degrees of latitude from their origin (O'Neill et al., 2011). Both climatic and phenological limits will therefore be probed in this experiment.
         Assisted migration is controversial in North America (McLachlan et al., 2007; Minteer and Collins, 2010; Aubin et al., 2011), but in fact has been widely practiced in forestry for at least two centuries. In the UK, exotics such as Sitka spruce and Corsican pine (Pinus contorta var. maritima) comprise 66% of planted forests. These species are now essentially naturalized and are an important component of UK conservation strategies (Humphrey et al., 2003). In GERMANY, trials dating from 1880 show that red oak, Douglas fir, western red cedar, grand fir, and black locust [all North American trees] perform well under local climates. Currently, other non-endemic species are being assessed for their suitability for use in experimental silviculture (Bolte et al., 2006). In CANADA, European and non-endemic native conifers, including lodgepole pine, red, Scots, and ponderosa pines, Siberian larch, and blue spruce have been planted in upland forest "islands" in Canadian prairies since the 1920s. Some of these have grown to considerable size; for example, a 75-year-old red pine plantation was measured at 40 cm average dbh and 26 m in height (Bendzsak, 2006).
         Trees shifted latitudinally by 5 degrees C or more may be vulnerable to both weather extremes and normal weather variations in their new environment, especially during the seedling stage. These extremes can be buffered by establishing new species in shade of existing canopies, which can also mitigate competition from non-target species (Cameron and Watson, 1999). Underplanted species generally require more light as they grow (Messier et al., 1999), but tolerate a broader range of climate extremes as they mature (Jackson et al., 2009). Eventually partial or complete removal of the original overstory could be required to allow underplanted species to mature successfully. The timing, volume, and spatial pattern of overstory release will vary according to the desired balance between buffering weather extremes, maintaining soil water supplies, understory light levels and other site characteristics.
         No-analogue climates may demand development of no-analogue, designer, or "neonative" plantations in which trees are selected for their potential to combine compatible functional effect and response traits (SchererLorenzen et al., 2007). For example, because down-regulation of photosynthesis in elevated CO2 could be induced by nitrogen limitations (Franklin, 2007), intimate mixtures that include nitrogen-fixing trees and shrubs provide a potential means to leverage carbon fertilization effects. Nitrogen-fixing (e.g., alder species) and non-nitrogen fixing trees could and are already combined in mixed stands (e.g., Parrotta, 1999; Binkley et al., 2003; Maas-Hebner et al., 2005). For example, common (European) walnut (Juglans regia L.) has 22% to 80% better height growth when planted in intimate mixtures with nurse trees (e.g. western red cedar) and a nitrogen-fixing shrub (autumn olive), relative to walnut planted alone or with only a nurse tree (Clark et al., 2008).
    "Exploring tree species colonization potentials using a spatially explicit simulation model: Implications for four oaks under climate change", by Anantha M. Prasad et al., 2013, Global Change Biology.
    EXCERPTS: Even under optimistic scenarios, we conclude that only a small fraction of the suitable habitats of oaks predicted by DISTRIB is likely to be occupied within 100 years, and this will be concentrated in the first 10-20 km from the current boundary. We also show how DISTRIB and SHIFT [models] can be used to evaluate the potential for assisted migration of vulnerable tree species, and discuss the dynamics of colonization at range limits.
         Rapid climate change is forecast by the Intergovernmental Panel on Climate Change (IPCC, 2007) for all major biomes on earth. The estimates vary from 2C by the year 2100 under a conservative carbon emission scenario (B1) up to 4C under our current fossil fuel intensive pathway (A1FI). The implications of such a rapid change for the earth's biota can be staggering. A reassortment of suitable habitats and creation of novel ones are expected for various plant and animal species (Williams & Jackson, 2007). However, species range limits are dynamic and subject to local, regional and global processes that show complex interplay between ecological and evolutionary processes. The crucial question for tree species, the subject of our study, is whether they adapt, migrate, or go extinct under rapid climate change (Aitken et al., 2008). Historically, tree species niches have remained relatively constant in the face of historical climatic change (niche conservatism), causing them to migrate in line with their native climatic-niches, although adaptive changes have co-occurred as evidenced by changes in population's fitness optimum throughout the species' range (Jackson & Overpeck, 2000; Davis & Shaw, 2001; Wiens & Graham, 2005). Evidences of local adaptations, however, do not point to change in the absolute climate tolerances of species (Parmesan, 2006).
         Trees are capable of a wide range of local adaptation via phenotypic plasticity despite low evolutionary rates and are sufficiently long lived to have survived rare and extreme events at various points throughout their evolutionary history; these characteristics partly explain their ecological success. Their high genetic variability and abundant fecundity enable extensive gene flow and are therefore capable of rapid microevolution — but low levels of mutation, nucleotide substitution, and speciation rates allow only slow rates of macroevolution (Petit et al., 2004; Petit & Hampe, 2006). Genetic constraints on adaptation and impediment to both gene flow and dispersal by current landscape fragmentation could pose a twin threat to some tree species in the era of rapid climate change. Also, because tree species are subject to differential (perhaps novel) environments and interspecific interactions, the adaptive expression of phenotypic plasticity can be curtailed via ecological constraints (Valladares et al., 2007).
         Reid's paradox (Clark et al., 1998; Phillips et al., 2008), which noted the apparent disparity between the relatively slow dispersal capacity of trees and their rapid spread in the early Holocene era, has been a challenge for several generations of climate change and vegetation ecologists. Recently, there have been revisions in the dispersal estimates due to the role of ice-free mirorefugias (retention of low-density founder populations) during the Holocene. These refugias appear to have played a larger role in tree species advancing without the need for rapid migration speeds that are needed to reconcile pollen data with actual distributions (McLachlan & Clark, 2004, McLachlan et al., 2005; Anderson et al., 2006; Parducci et al., 2012). McLachlan et al., (2005) explain the discrepancy between the pollen record and current boundaries as a result of local dispersal by isolated persisting populations (refugia) during the early Holocene and migration rates may not have exceeded 10 km/century for many species (Pearson, 2006; Loarie et al., 2009), although other species could have far exceeded this rate in certain periods due to favorable conditions (Davis & Shaw, 2001; Cole, 2010).
         For the purposes of this article and brevity, we will focus on four oak tree species — black oak (Quercus velutina), post oak (Quercus stellata), chestnut oak (Quercus prinus), and white oak (Quercus alba). We chose these four oak species because they are strongly climate driven and future warmer climates will have substantial impact on their habitat distribution. We illustrate the utility of our approach in producing various outputs to help understand species dispersal response, evaluate migration corridors for managed relocation, and lay the groundwork for further analysis, and modelling strategies.
         The rate of 50 km/century is at the middle of the range suggested by the literature: 10km/century (McLachlan et al., 2005), 30km/century (Yansa, 2006), 50 km/century (Davis, 1989), and 100 km/century (Woodall et al., 2009; Chen et al., 2011). Recent molecular analyses show that because of glacial refugia effects, the range is likely to be at the lower end (10-25 km/century for most species) (Petit et al., 2003; McLachlan et al., 2005; Svenning & Skov, 2007; Dobrowski, 2011).
         Managed Relocation: Tree longevity, gene flow from distant populations and phenotypic plasticity will facilitate the process of local adaptation once a small founder population is established (Petit et al., 2003; Aitken et al., 2008). Therefore, predicted habitat openings and colonization potential indicated by the DISTRIB and SHIFT models can be opportunistically used to initiate new populations to facilitate migration and these populations need not be very large (McLachlan et al., 2007; Richardson et al., 2009). This strategy is especially useful for specialist species with narrow habitat requirements as they are far more likely to face extinction threat as compared to more generalist species (Trakhtenbrot et al., 2005). When this SHIFT model is combined with the DISTRIB model, which predicts 'potential suitable' hab- itats, they yield 'potential colonizable' habitats by the year 2100 (Iverson et al., 2011; Engler & Guisan, 2009; Midgley et al., 2010; Mustin et al., 2009). . . Despite all these deliberately optimistic assumptions, the rate of decline with distance is remarkable and casts doubt whether the dispersal ability of specialized species can compensate under current fragmented landscapes. . . This problem is exacerbated for narrowly endemic species, which may face an extinction crisis due to their inability to keep pace with climate forcing. . . In our simulations, we do not distinguish between animal and wind-dispersed species, because there is not enough empirical evidence suggesting that these two forms of dispersal created significant differences in seed dispersal (Higgins et al., 2003).

    "North American vegetation model for land-use planning in a changing climate: a solution to large classification problems", by Gerald E. Rehfeldt et al., 2012, Ecological Applications.

    TOP: current  •  BOTTOM: 2060

      ABSTRACT: Data points intensively sampling 46 North American biomes were used to predict the geographic distribution of biomes from climate variables using the Random Forests classification tree. Biome climates were projected into the future according to low and high greenhouse gas emission scenarios of three General Circulation Models for three periods, the

    (1) expansion of climates suitable for the tropical dry deciduous forests of Mexico

    (2) expansion of climates typifying desertscrub biomes of western USA and northern Mexico

    (3) stability of climates typifying the evergreen-deciduous forests of eastern USA

    (4) northward expansion of climates suited to temperate forests, Great Plains grasslands, and montane forests to the detriment of taiga and tundra climates.

    Our analysis uses the biotic communities of Brown (1994), mapped and digitized by Brown et al. (1998). This classification system meshes well with our goals: It is based on distributions of flora and fauna without reliance on physiography, the coverage includes all of North America, and altitudinal zonation of vegetation is an integral part of the system.

    Maps indicating either poor agreement among projections or climates without contemporary analogs identify geographic areas where land management programs would be most equivocal. Concentrating efforts and resources where projections are more certain can assure land managers a greater likelihood of success.

    EXCERPTS: Land managers require decision-support tools suitable for dealing with oncoming climate-mediated ecosystem changes. Progress has been made in convertng climatically static vegetation simulators to climatically dynamic models (see Crookston et al. 2010), and guidelines are in use for managing future generations of the broadly dispersed Larix occidentalis of western North America and the narrow endemics, Picea chihuahuensis, P. mexicana, and P. martinezii of Mexico. Yet, for much of North America, comprehensive management guidelines do not exist. Our goal was to develop a statistically valid, climate-driven vegetation model suitable for land-use planning during a changing climate.

    The maps convey a high likelihood that no-analog climates should arise early and increase in concentration throughout the century particularly along the Gulf of Mexico, but also in the interior Northwest of the United States and adjacent Canada, through much of California on the west coast, and sporadically through the Arctic. Despite disagreement among projections and an expectation for patches of novel climates along Alaska's (USA) south shore, future climates presage an influx of Rocky Mountain conifers and Canadian Taiga at the expense of the alpine tundra and subarctic conifers that occur there today. [Marked changes in a dozen additional regions are also narrated in detail.]


    ♦ 2012 ARTICLE ON EVEN COMMON TREES IN AMERICA'S FORESTS ARE LAGGING BEHIND THE PACE OF CLIMATE CHANGE: "Tracking suitable habitat for tree populations under climate change in western North America" - by Laura K. Gray and Andreas Hamann, 2012, Climatic Change. EXCERPTS:

       We find that, on average, populations already lag behind their optimal climate niche by approximately 130 km in latitude, or 60 m in elevation. For the 2020s we expect an average lag of approximately 310 km in latitude or 140 m in elevation, with the most pronounced geographic lags in the Rocky Mountains and the boreal forest. We show that our results could in principle be applied to guide assisted migration of planting stock in reforestation programs using a general formula where 100 km north shift is equivalent to approximately 44 m upward shift in elevation. However, additional non-climatic factors should be considered when matching reforestation stock to suitable planting environments.
        . . . In widespread tree species, genetically differentiated populations are uniquely and often narrowly adapted to their local environments. Hence, climate change impacts will not be limited to the trailing edge of a species range, but instead may apply to populations throughout the species range. . . For species and population level analysis we selected 15 major forest tree species of commercial importance in western North America.

  • "Failure to migrate: lack of tree range expansion in response to climate change", by Kai Zhu, C W Woodall, and J S Clark, in Global Change Biology, 2012.

    EXCERPTS: Anticipating whether or not species range limits can track climate change is a goal of global change research (Clark et al., 2001; Davis & Shaw, 2001; Jackson et al., 2009; Loarie et al., 2009; Dawson et al., 2011). Across the globe, mounting evidence confirms widespread temperature increases, particularly at high northern latitudes (IPCC, 2007). In the eastern United States, mean annual temperatures increased during the 20th century in the Midwest and Northeast, but not in the Southeast, where warming summers were balanced by cooling winters (Fig. 1a). When viewed in terms of a velocity, as has been advocated recently (Loarie et al., 2009), regions in the Northeast and Upper Midwest have seen climate shifts of more than 100 km during the 20th century (Fig. 1b). As the climate warms, new regions that become available for occupation may be colonized as those no longer suitable are abandoned. Inevitable time lags involved in plant dispersal, colonization, establishment, and maturation threaten not only rare species but also many that are abundant and provide vital ecosystem functions and services. Numerous datasets and models suggest a variety of species’ responses to changing climate, but robust empirical evaluation remains challenging. . .
        In this study, we develop a novel technique for examining the latitudinal difference between offspring and adults of trees at both northern and southern range limits across the eastern United States, and we evaluate the number of species showing evidence for range expansion or contraction. We then compare these patterns with changes in 20th century temperature and precipitation, as well as functional traits expected to influence migration potential, specifically, seed size and dispersal properties. We test the widely held hypothesis that trees could track climate change by migration, showing differences between offspring and adult range limits (Neubert & Caswell, 2000; Lewis et al., 2006), with the largest differences between offspring and adult extent being in areas where climate change has been most pronounced. There has been substantial effort in recent years to determine whether small-seeded species have greater migration potential than large-seeded species (reviewed by Angert et al., 2011). Four mutually exclu- sive and all-inclusive hypotheses are summarized by a four-quadrant diagram of range shifts at northern and southern frontiers (Fig. 2) . . .
        When compared with the 20th century climate changes that have occurred at the range boundaries themselves, there is no consistent evidence that population spread is greatest in areas where climate has changed most; nor are patterns related to seed size or dispersal characteristics. The fact that the majority of seedling extreme latitudes are less than those for adult trees may emphasize the lack of evidence for climate-mediated migration, and should increase concerns for the risks posed by climate change. . .
         Climate change has already been large (Fig. 1) — we do not have to wait decades to evaluate whether or not climate change is affecting migration. Our finding that the majority of species may experience range contraction at both northern and southern limits does not square with the expectation that species will migrate rapidly north in response to climate change. Many models predict rapid tree migration (Clark, 1998; McKenney et al., 2007), but some do not (Clark et al., 2001, 2003; Nathan et al., 2011). Iverson et al.'s (2008) habitat distribution model predicts that 61 to 68 of 134 species will increase at least 10%, and 50 to 58 species will lose at least 10% of their area-weighted importance value. Some of these predictions are consistent with our comparisons of offspring and adults (e.g. Acer nigrum and Juglans cinerea). On the other hand, Iverson et al. (2004) predicted that migration potential at northern range limit for Diospyros virginiana, Liquidambar styraciflua, Oxydendrum arboreum, Pinus taeda, and Quercus falcata would be limited to within 20 km of the area currently occupied. Our analysis of these species all show contraction at northern limits, in general agreement with Iverson et al.'s (2004) expectation that migration potential is limited. . .
         Many variables affecting these boundaries could preclude the large geographic shifts needed to track climate. For example, adults might be controlled by annual mean temperature and precipitation, but offspring might be driven by temperature variabilities and extremes, growing season temperature or drought, spring precipitation, first-last day of frost, and so forth. Soils, disturbance, and land use change could provide a backdrop for species interactions, including competition, herbivore, and disease. If habitat destruction, degradation, and fragmentation resulted from land use change are proximate factors limiting response to climate (Hof et al., 2011), vulnerability could shift from human effects in the near term to climate change in the near future.

  • "Adaptation, Migration or Extirpation: Climate Change Outcomes for Tree Populations", by Sally N. Aitken et al., in Evolutionary Applications, 2008.

    EXCERPT ON NEED FOR FACILITATED MIGRATION: Findings of relatively slow tree migration rates in response to historical changes in climate (potentially < 100 meters per year) are unfortunate in light of model predictions of how fast tree species will need to migrate to track current climates under climate change scenarios. Tests of 14 combinations of GCMs and global SDMs show up to 100% of the models predicting migration rates of 1000 meters per year or higher to be necessary to track habitat under 2x CO2 climate forcing. High-latitude biomes in particular are projected to necessitate unprecedented rapidity of migration for trees due to the more extreme warming that is occurring towards the poles (IPCC 2001). "

    EXCERPTS ON UTILIZING PROVENANCE TRIALS: It may be worthwhile to initiate new populations through facilitated migration as new habitat becomes available (McLachlan et al. 2007), and that these populations do not necessarily need to be large. . . The ability of trees to persist well outside their realized niche under reduced competition is evidenced by many trees in arboreta and botanical gardens. . . While long-term field provenance trials provide a tremendous resource for evolutionary ecology and climate change studies, there are limitations to inferences about natural populations from these trials. These experiments are typically established through growth of seedlings under optimal nursery conditions with abundant water and nutrients, then field planted after 1 or 2 years. Extrapolations to natural populations should be made cautiously as considerable opportunities for natural selection occur during seed germination, establishment, and early growth are largely circumvented. Competing vegetation is often controlled, trees are planted at a wide spacing, and trials are often fenced against large herbivores, potentially widening the apparent realized niche of a population and flattening response and transfer functions. Older provenance trials were typically only planted on productive sites and usually did not include sites at the edges of the species realized niche, and these data require extrapolation to predict responses to much warmer climates (Wang et al. 2006b). Spatial climatic variation is being substituted for temporal changes in climate, and we do not have a good idea of how the effects of climate differ with tree age and stand development. Finally, for both seedling and field common gardens, seeds are usually collected from natural populations experiencing different climatic conditions, and conditions during seed development can have epigenetic effects on seedling growth, phenology and cold hardiness that will inflate estimates of population differentiation (described below). . . Recent studies in Norway spruce (Picea abies) show that the temperature during both zygotic and somatic embryo development can dramatically affect cold hardiness and bud phenology in the offspring (Johnsen et al. 2005a,b; Kvaalsen and Johnsen 2007). In some cases, the offspring's phenotype varied the equivalent of 6 degrees of latitude from what was expected given the geographic origin of the parents. A crucial question that remains outstanding in this area is the extent to which these traits are persistent, both within an individual's lifetime and in its offspring and subsequent generations. . . New field common-garden experiments should sample as wide a range of populations as possible, attempt to include disjunct and peripheral populations from both leading and rear edges of migration, and select field sites based on predictions from SDMs. The development of more complex and more realistic SDMs that better incorporate factors such as age to sexual maturity, fecundity, dispersal ability, and competition effects is needed to move from predicting where habitat will be to where species will likely be without intervention. Estimation of parameters for such models will require field-based studies of reproduction and dispersal. Older field common-garden sites should be used to study variation in fecundity with transfer distances. They should also be used to conduct controlled crosses and provide seed from different populations that develops in the same environments, reducing epigenetic effects of maternal environments, and allowing the study of these effects in a greater number of taxa.

  • "Observed forest sensitivity to climate implies large changes in 21st century North American forest growth", by Noah Charney et al., in Ecoogy Letters, 2016. (press release)

    EXCERPT from press release: Forests take up 25-30 percent of human-caused emissions of carbon dioxide and are therefore considered to play a crucial role in mitigating the speed and magnitude of climate change. However, a new study that combines future climate model projections, historic tree-ring records across the entire continent of North America, and how the growth rates of trees may respond to a higher concentration of carbon dioxide in the atmosphere has shown that the mitigation effect of forests will likely be much smaller in the future than previously suggested. The study is the first to reveal the possible impact of a changing climate on the growth rate of trees across all of North America. The results are detailed forecast maps for the entire North American continent that reveal how forest growth will be impacted by climate change. The research team, led by scientists at the University of Arizona in Tucson, combined climate projections for North America developed by the IPCC with historic tree-ring records based on samples covering the period 1900 to 1950 at 1,457 sampling sites across the continent.
        "Many previous climate modeling studies counted on the boreal forests to save us from the climatic disaster by offsetting our emissions, but we don't see any greening in our results," said Valerie Trouet, an associate professor in the LTRR. "Instead, we see browning. The positive influence warmer temperatures are believed to have on boreal forests — we don't see that at all." The most dramatic changes in projected forest growth rates were found in the interior West of the North American continent, with up to 75 percent slower growth projected for trees in the southwestern U.S., along the Rockies, through interior Canada and Alaska. Increases in growth were seen only along certain coastal areas, mostly in the Pacific Northwest, Northeastern Quebec and the Maritime Provinces and the Florida panhandle.
    EARLY FORESTRY PAPER LEADING CLIMATE CHANGE PREPARATION, 1992

    Prior to the terms "assisted migration" and "facilitated migration" coming into use early in the 21st century, forest researchers were already planning for the climate change decades ahead, simply by extending their standard practice of finding best genetics (or best genetic diversity) to safely insure high timber productivity over the harvest life cycle for new plantings within each seed zone (elevation, latitude, etc.) This 1992 paper by USFS forest researchers F. Thomas Ledig and J.H. Kitzmiller is a must-read, especially for conservation biologists unaware of the long history of forest research and preparation re climate adaptation:

  • "Genetic strategies for reforestation in the face of global climate change", by F. Thomas Ledig and J.H. Kitzmiller, 1992, Forest Ecology and Management50:153-69.
    ABSTRACT: If global warming materializes as projected, natural or artificial regeneration of forests with local seed sources will become increasingly difficult. However, global warming is far from a certainty and predictions of its magnitude and timing vary at least twofold. In the face of such uncertainty, reforestation strategies should emphasize conservation, diversification, and broader deployment of species, seed sources, and families. Planting programs may have to deploy non-local seed sources, imported from further south or from lower elevations, which necessitates a system for conserving native gene pools in seed banks or clone banks. Planting a diverse array of species or seed sources is a hedge against the uncertainty inherent in current projections of warming. Most tree improvement programs already stress genetic diversity and deployment of multi-progeny mixes, but may better prepare for climate change by testing selections in an even wider set of environments than is now the case.

    EXCERPTS: "We do not wish to argue the merits of the various projections of global warming, but instead ask what forestry's response should be, assuming rapid climate change. Uncertainty must be the guiding factor for planning reforestation efforts over the next several decades [this paper was published in 1992]. The discussion is organized around three levels of forest management: (1) native, naturally regenerated forest; (2) plantation forestry where the seed source is controlled; (3) highly intensive forestry in which plantations are established from seeds produced on superior selections grown in seed orchards. Throughout, we refer to three tactics — conservation, diversification, and deployment.
         "Native forest may change in composition and some species may be entirely eliminated over large areas of the US as a result of climatic change. In the eastern half of the country, major components of the forest, such as paper birch, sugar maple, beech, and eastern hemlock may virtually disappear. Some species displacement may occur in as little time as 30 years. In the West, steep elevational gradients provide an escape route up which tree species can migrate for refuge. Nevertheless, many western species will suffer major reductions in range. Douglas-fir will be largely eliminated from California and coastal Oregon where it is now the most important timber species.
         The reductions in range are predicted as a direct effect of higher temperatures and drought stress on growth, and perhaps as the result of failure to meet winter chilling requirements. However, higher temperatures may also affect flowering and seed formation, reducing the ability of some species to regenerate at their southern margin and at low elevations, even though vegetative growth is not reduced. In addition to direct effects of global warming, higher temperatures will favor insect pests because they will suffer less overwinter mortality and may be able to complete more genertions during the longer growing seasons that result from global warming. High temperature and drought stress will weaken trees and make them more vulnerable to insect attacks, as evidenced by the increased mortality from bark beetles during the recent drought years in California [published in 1992].
         "Faced with global warming, they can either move seed northward from warmer climates or upward from lower elevations. Using seed from a seed zone lower in elevation should be safest. The seasonal change in photoperiod will be identical to the one in which the seed parents evolved and, if temperature changes are predicted correctly, the thermoperiod will match as well. According to Hopkins' Law, temperature decreases 1.4 degrees C for each 1,000 ft (305 m) increase in elevation in the US. Therefore, under projections of a 2.5 degree C change in temperature by 2050, seed should be imported from 1,800 ft (about 550 m) lower in elevations."
         "Since meteorologists are uncertain about the actual warming, foresters should employ the diversity principle. The best way to use diversity might be to mix seed sources. Forest managers could at least mix the local seed source and one they expect to be adapted under a worst-case scenario. The relative amounts of each would depend on how confident they felt about projected changes." Caveat: "Photoperiods during the growing season are longer in northern latitudes than in southern. Seed sources moved north are often 'tricked' into remaining active too late in the autumn and, therefore, suffer frost damage. Moving seed great distances northward is an uncertain solution. One- or two-hundred miles, however is not unreasonable.
        "Maximizing diversity is absolutely essential because climatic change will not stabilize for a long time. Most projections use 2050 only for convenience; 2050 is the year when atmospheric carbon dioxide will have doubled. Climatic change would continue on after 2050 even if society were to entirely halt the production of greenhouse gases right now because it will be some time before the oceans and the atmosphere equilibrate. And nothing suggests that the production of greenhouse gases will be halted anytime soon, so atmospheric conditions will continue to change. Therefore, neither diversity nor deployment can completely cope with rapid warming; the trees that survived the establishment phase might no longer be adapted in the second half of the rotation.
        "Although it is nice to close on a positive note, it would be even better if we could say that global change posed no threat. That depends less on forest practices than it does on social and policy changes that affect consumption and procreation. To prevent major global destruction, society must curb the wasteful use of resources and control population growth." [Editor's note: This paper was published in 1992.]


    MAPS OF USA FOREST TREE SPECIES FUTURE RANGES:

    Note: The "current" ranges of each species used in the following USDA climate model maps are drawn from the classic USDA species range maps prepared by Elbert Little from 1971-77. You can access those original maps here: ""Atlas of United States Trees" by Elbert L. Little, Jr".

  • WESTERN USA: "Plant Species and Climate Profile Predictions".


       Highly detailed online maps to compare current, 2030, 2060, and 2090 range predictions for 76 species of western USA trees. (Always click on the .png versions to see the maps.) For example, Alligator Juniper, now absent from Colorado, is expected to have ideal range open up west of Denver in 2030, while southerly populations become stressed. (How are they going to get there, as the closest current population is near Santa Fe NM?) Note: A superb paper that details the data-source and modeling used to generate these range maps is "North American Vegetation Model for Land-Use Planning in a Changing Climate", 2012, G.E. Rehfeldt et al. Note: Professionals should read the 2006 explanatory paper of how these modeled map projections were generated, "Empirical Analyses of Plant-Climate Relationships for the Western United States", G.E. Rehfeldt et al., International Journal of Plant Sciences.

  • EASTERN USA: Easy-to-use USFS webpage of maps imaging current and climate-shifted ranges of 134 tree species in eastern North America: Climate Change Tree Atlas interactive site (also, a combined Tree and Bird Atlas eastern USA). See also a multi-agency generated Forecasts Maps Projects for the Eastern USA. A 2008 paper by USDA forest researchers (Iverson et al.), published in Forest Ecology and Management, introduces the 134-species online range-map projection tool (professionals must read): "Estimating potential habitat for 134 eastern US tree species under six climate scenarios".

       EXCERPT: "Of the 134 species, approximately 66 species would gain and 54 species would lose at least 10% of their suitable habitat under climate change. A lower emission pathway would result in lower numbers of both losers and gainers. When the mean centers, i.e. center of gravity, of current and potential future habitat are evaluated, most of the species habitat moves generally northeast, up to 800 km in the hottest scenario and highest emissions trajectory. The models suggest a retreat of the spruce-fir zone and an advance of the southern oaks and pines. In any case, our results show that species will have a lot less pressure to move their suitable habitats if we follow the path of lower emissions of greenhouse gases. . . . . . Our predictions of increase in range (potential future suitable habitat) are very likely to be overestimates of the actual ranges that would be achieved by the end of this century, as migration of most species will not keep up with relatively abrupt changes in climate, unless humans get seriously involved in moving species."

    CLICK IMAGE ABOVE for 18-minute VIDEO TUTORIAL by lead author, Louis Iverson. For depth treatment of the modeling strengths and weaknesses, see Iverson et al., 2010, "Potential changes in habitat suitability under climate change: Lessons learned from 15 years of species modelling". Also, Iverson et al. 2014, chapter 2 "Climate as an agent of change in forest landscapes", within Forest Landscapes and Global Change: 29 Challenges for Research and Management. The chapter also recommends, "Tests of assisted migration will also be necessary to begin the process of understanding how we can help forests adapt to the new conditions created by climate change. . . Humans are largely responsible for modern climate change and must therefore decide whether and how to reduce carbon emissions to mitigate the coming changes. Humans must also decide to improve our understanding of forests and other ecosystems, including human-dominated ecosystems, and, where practical and scientifically prudent, help them adapt to the changing conditions. Part of this effort can be to simply promote healthy ecosystems via sound management. Artificially moving species also may become more and more part of the equation." See also Iverson et al. 2011, "Lessons Learned While Integrating Habitat, Dispersal, Disturbance, and Life-History Traits into Species Habitat Models Under Climate Change", Ecosystems. For details on how dispersal rate and potential colonization were built into this "Climate Change Tree Atlas" model, click here.

  • WHOLE USA: This forest tree website builds on the previous (above) two, while adding a new feature of color-coded images that show relative difficulties in moving/adapting of different geographic populations of each species. Access here: The ForeCASTS Project, subtitle: Forecasts of Climate-Associated Shifts in Tree Species.
  • UNDERSTANDING THE FORESTRY-CLIMATE RANGE PROJECTION MAPS:

  • A quick history of the modeling efforts - "Shifts in geographic distribution have been modeled for many tree species, mostly those of the eastern United States (e.g., Iverson et al., 2005). Approaches to modeling originally used climate envelopes, multivariate limits of the climate conditions in which a species now finds itself (see Box et al., 1993, 1999) and projected the distribution of those conditions into the future using general circulation models (GCMs). Envelope analyses evolved into empirically based bioclimatic models with the incorporation of statistical procedures (Iverson and Prasad, 1998; Elith et al., 2006), of which Random Forests (Breiman, 2001) has proven to be robust for predicting the realized climate niche (Iverson et al., 2005; Rehfeldt et al., 2006). . . The distribution of suitable habitats, either contemporaneous or under global warming scenarios, can be predicted for forest tree species based on detailed climatic models, such as spline climatic models (Rehfeldt, 2006; Rehfeldt et al., 2006, 2008) and climate envelope modeling (van Zonneveld et al., 2009)." Excerpted from F. Thomas Ledig et al., 2010, "Projections of Suitable Habitat for Rare Species under Global Warming Scenarios" in American Journal of Botany. Note: The materials and methods section offers details on how the modeling was done.

  • Modeling species-specific shifts in geographic ranges in parallel with various climate models has a number of complications one should be aware of. Here is an excellent review paper of these issues: "Adaptation, migration or extirpation: climate change outcomes for tree populations", by Sally N. Aitken et al., 2008, Evolutionary Applications. Excerpt re assisted migration: "Reproduction and regeneration should be monitored in protected areas to determine if facilitated migration of populations is necessary among protected areas or to extend species ranges. Translocations of populations for reforestation from milder to colder environments may eventually provide a source of pre-adapted alleles into conservation populations through gene flow, once planted areas reach reproductive maturity. Population response curves should be used to predict the maximum extent to which seed can be moved from milder to colder climates for reforestation in the short term and tree growth in the longer term, and seed transfer guidelines should be changed accordingly. To end on a cautionary note: the above predictions all suggest that lodgepole pine should be one of the species least affected by climate change. However, the recent climate-associated population explosion of the mountain pine beetle and the resulting decimation of vast tracts of lodgepole pine forest in western North America underscore the difficulty of predicting complex ecological interactions and the limitations of the models described herein."

  • A highly detailed analysis of the pros and cons of the several approaches to modeling and mapping how "bioclimatic envelopes" for trees will shift under various climate scenarios is "Can Boreal and Temperate Forest Management be Adapted to the Uncertainties of 21st Century Climate Change?" by Andrew Park et al. (the six authors are Canadian, USA, and UK). This 35-page review and analysis was published in 2014 in Critical Reviews in Plant Sciences.

  • A much shorter and less detailed overview of the pros and cons of several types of species-specific climatic range shift models is "Tree-species range shifts in a changing climate: detecting, modeling, assisting", 2013, by Iverson and McKenzie in Landscape Ecology. (Nonprofessionals will want to read this article first before tackling the Park et al. treatise.) Final paragraph:
    We encourage continued research to move the science forward on detecting, modeling, and the potential assisting of actual and potential tree range shifts in a changing climate. Many additional advances will be possible by making continued improvements in the integration among the avenues reviewed here. For example,the merger of process models, demography models, and species distribution models allows for some of the best attributes of each, in working with suitable habitats into which multiple species must migrate, colonize, compete, and successfully reproduce, all at fine temporal and spatial scales. It is an exciting time for research as the computer-based tools, available data, and methods are simultaneously advancing at a remarkable rate. Meanwhile, we must be diligent to continue to provide the natural history and demography studies (=field work!) to provide the fuel for the modeling and interpretation of model outputs. Many species are poorly known as to their reproductive, competitive, ecological, and adaptability capacities, and how these vary under changing climates, including climates novel to their evolutionary history. There will always be plenty of uncertainty, but we cannot let that stifle our endeavors to bring the best science possible to decision-makers and managers to mitigate and adapt to the coming impacts from climate change.
  • "Tracking suitable habitat for tree populations under climate change in western North America", by Laura K. Gray and Andreas Hamann, 2013, Climatic Change.
    In widespread tree species, genetically differentiated populations are uniquely and often narrowly adapted to their local environments. Hence, climate change impacts will not be limited to the trailing edge of a species range, but instead may apply to populations throughout the species range. Under climate change, all populations may occupy environments at or beyond the margins of their individual climate niches. This is also supported by empirical evidence suggesting that genetic population structure in widespread forest trees should not be ignored. For example, O'Neill et al. (2008) and Wang et al. (2006b, 2010) found that when genetic structure was considered, the predicted growth and survival of locally adapted lodgepole pine (Pinus contorta) populations was reduced. Chen et al. (2010) found that northern and high elevation Douglas-fir (Pseudotsuga meniesii) populations are more vulnerable to climate change than the populations from the southern end of the species range, presumably due to narrow genetic adaptation of local populations.
         In this study we illustrate how genetic population structure can be integrated in bioclimate envelope modeling by using ecosystem delineations as modeling units, which serve as proxy for locally adapted species populations. For practical applications of seed movement, we can then identify the geographic origin of locally adapted populations that best match the anticipated future climate. In this study we project suitable habitat for populations of 15 wide-ranging tree species in western North America under observed and projected climate change. Our objective is to determine how far populations already lag behind their assumed optimal climate habitat, and how these adaptational lags of populations are predicted to change in the future. An ensemble classifier modeling approach (RandomForest) was used to spatially project the climate space of tree populations under observed climate trends (1970s to 2000s) and multi-model projections for the 2020s, 2050s and 2080s. We find that, on average, populations already lag behind their optimal climate niche by approximately 130 km in latitude, or 60 m in elevation. For the 2020s we expect an average lag of approximately 310 km in latitude or 140 m in elevation, with the most pronounced geographic lags in the Rocky Mountains and the boreal forest. We show that our results could in principle be applied to guide assisted migration of planting stock in reforestation programs using a general formula where 100 km north shift is equivalent to approximately 44 m upward shift in elevation. However, additional non-climatic factors should be considered when matching reforestation stock to suitable planting environments.
         For species and population level analysis we selected 15 major forest tree species of commercial importance in western North America: pacific silver fir (Abies amabilis Douglas ex J. Forbes), Alaska yellow-cedar (Chamaecyparis nootkatensis (D. Don) Sudworth), tamarack (Larix laricina (Du Roi) K. Koch), western larch (Larix occidentalis Nuttall), Engelmann spruce (Picea engelmannii var. engelmannii Parry ex Engelmann), white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Miller) Britton), Sitka spruce (Picea sitchensis (Bongard) CarriŹre), lodgepole pine (Pinus contorta Douglas ex Loudon), western white pine (Pinus monticola Douglas ex D. Don in Lambert), ponderosa pine (Pinus ponderosa Douglas ex Lawson & C. Lawson), Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco), western red-cedar (Thuja plicata Donn ex D. Don in Lambert), western hemlock (Tsuga heterophylla (Rafinesque) Sargent), and trembling aspen (Populus tremuloides Michaux).
         Even though the life span of most tree species included in this study exceeds the 2080s, we think that forest resource managers need to focus on the immediate future when developing seed transfer prescriptions for a number of reasons. First, uncertainty in habitat projections for the 2020s are moderate, but they dramatically increase towards the 2080s. Secondly, since trees are most vulnerable to climatic factors at the seedling stage, we could not currently plant genotypes that would be optimally adapted to 2080s climate. Third, long-distance transfers far outside the current species range implied by 2080s projections may lead to issues not considered by the model (e.g. required mycorrhizal associations, or changes to day length regimes that control the species' phenology). Therefore, seed transfers according to the 1997-2006 and 2020s projections will have the best chance of success. Although we realize that this will mean that tree populations will continue to lag behind their optimal climate, targeting current and 2020s climate conditions is still a low-risk improvement over status-quo management practices that essentially target climate conditions of the past century.
  • Though focused on British Columbia tree species, this paper explains why maps derived from bioclimatic envelope modeling of future ranges are an excellent starting point for forestry adaptive management, with supplemental interpretations suggested: Projecting future distributions of ecosystem climate niches: uncertainties and management applications, by Tongli Wang et al, 2012, Forest Ecology and Management
    EXCERPT: Projections of future ecosystem change can be achieved with either niche-based climate envelope models or process-based mechanistic models. Mechanistic models simulate an array of ecological processes and they have been used forecast changes in ecosystem biomass and productivity as well as changes in geographic distribution of vegetation types, species, or ecological zones (e.g., Peng, 2000; Coops et al., 2009; Morin and Thuiller, 2009; Coops and Waring, 2011). The computational complexity and the large data requirements needed to parameterize these models can present challenges for generating accurate forecasts about ecosystem change across vast, mountainous regions (Mohren and Burkhart, 1994; Porte and Bartelink, 2002). Because of this, climate envelope models — also called bioclimate envelope models, or more generally, ecological niche models — have been used more widely to date. They correlate readily available occurrence data with climate variables to model the geographic distribution of realized climate niches for any biological entity (e.g., allele, population, species, ecosystem, vegetation community, natural disturbance, or biome). Climate envelope models of ecosystem change have been criticized for their failure to account for species migration capacity, changes in species interactions, and alterations to biogeochemical cycles, including increased atmospheric CO2 concentrations (Pearson and Dawson, 2003; Araujo and Guisan, 2006; Austin, 2007; Botkin et al., 2007; Thuiller et al., 2008). While species dispersal considerations are important when the goal is to project actual geographic distributions, climate envelope models do not project actual future ecosystem or species distribution, per se, but rather the distribution of climatically suitable habitats, or 'climate niches', which are the target of many ecosystem management activities. As Rehfeldt et al. (2012) recently suggest, the assumption of stable species interactions in ecosystem climate envelope models is only invalidated under novel future climates and robust methods for incorporating biogeochemical processes are not yet well-developed for either climate envelope or mechanistic modeling approaches. We believe that when the results of climate envelope model projections are appropriately conveyed and used with their limitations in mind, they can provide a powerful framework for evaluating and illustrating potential climate change impacts and guiding land-use planning.
    Editor's note: See caveat for absence of within-species / between-populations nuances typical of bioclimatic envelopes in Integrating environmental and genetic effects to predict responses of tree populations to climate, (same 3 coauthors as T. Wang, above), 2010, Ecological Applications
    EXCERPTS: We present a novel approach that integrates both genetic and environmental effects into a single 'universal response function' (URF) to better predict the influence of climate on phenotypes. As the URF is mechanistically based on observations of growth responses and accounts for among-population variation, it may produce more accurate predictions of future species distributions than the climatic envelope approach (Hamann and Wang 2006, Rehfeldt et al. 2006), which utilizes the climatic breadth of niches from natural species ranges and does not consider population-specific niches or the climatic niches of planted (rather than naturally regenerated) trees. The URF predictions for species range shifts may therefore overcome a critical shortfall of commonly used species range prediction models (reviewed by Aitken et al. 2008).
  • Because only fine-grid bioclimatic mapping can accurately assess species vulnerability (and the availability of refugia) in topographically complex landscapes, Gerald.E. Rehfeldt collaborated with James J. Worrall and colleagues to produce a mapping at the scale of 90 meter grid cells for habitat shifts in ASPEN and ENGELMANN SPRUCE within three USA national forests in Colorado. This paper is excerpted at length because it serves as a model of the leading-edge, proactive tools for moving ahead with climate adaptation projects in forestry, including assisted migration:

    "Adapting forest management to climate change using bioclimate models with topographic drivers" by G.E Rehfeldt et al., 2015, Forestry.

    EXCERPTS: Predictions made for future climates described by three General Circulation Models and three emissions scenarios were used to map on 90-m grids the habitat expected to be lost, threatened, persistent or emergent. The habitat categories are used to identify those areas where treatments should have highest likelihood of success.
         Rates of climate change are projected to be much faster than natural systems can respond such that a quasi-equilibrium is maintained between plant distributions and climate. Adjustment to change, therefore, will be governed by the time lags imbedded in ecological processes: lags between cause and effect occurring at the trailing edge as the changing climate exceeds the physiologic plasticity of individuals; migration lags on the leading edge developing from the contingencies of seed dispersal and colonization; and adaptation lags arising between the edges as microevolution restores fitness of species becoming less well attuned physiologically to the climate they inhabit. Considered together, these effects portend widespread disruption to the vegetation, a conclusion inferred unanimously by numerous researchers (e.g. Rehfeldt et al., 2006). Dependence on natural processes, therefore, seems destined for negative long-term effects on the amenities and services that humans expect from native ecosystems, particularly those dominated by long-lived, sessile forest trees (see Joyce and Rehfeldt, 2013; Rehfeldt et al., 2014c).
         Once potential impacts are understood, managers can focus limited resources where they can be the most effective, that is, implement resilience and recovery tactics where threats are greatest, assist migration where new habitat is emerging or conduct traditional management where species should persist. By defining ecologic optima climatically and designing plans to exploit these optima, this approach relies less on risk assessment and more on identifying where projected impacts are most likely to occur.
         We chose 8-variable models as being reasonably parsimonious while providing a measure of assurance that projections would not be dependent on single variables (Rehfeldt et al., 2006). Out-of-bag errors were 16 and 17 percent for the ASPEN and SPRUCE models, respectively. Of them, errors of commission were slightly higher than errors of omission. The most important predictor of ASPEN's distribution was the mean maximum temperature in the warmest month, followed sequentially by the summer-winter temperature differential and the topographic vectors. Of the latter two, the east-west vector was of slightly greater importance than the north-south vector. The other variables were the length of the frost-free period, a winter temperature sum based on the monthly minimum, winter temperatures weighted by an annual dryness index and an interaction of annual precipitation with growing season degree-days. For SPRUCE, greatest importance was shared by the length of frost-free period and the east-west topographic vector. Third in importance were winter temperatures weighted by an annual dryness index followed by the summer-winter temperature differential, the north-south topographic vector, two variables describing winter cold and winter precipitation.

      

    With an ability to represent the contemporary distribution of suitable habitat for ASPEN and SPRUCE, the models display an accuracy that makes them useful tools for managers. . . Our category of persistent habitat does not necessarily imply that the genotypes currently inhabiting these areas will continue to be optimal genetically in future climates.
         Encouraging ASPEN migration has the potential of addressing dual goals, as 43 percent of the land in ASPEN's emergent category is SPRUCE habitats classified as lost or threatened. As spruce succumbs to spruce beetle, fire or drought in these habitats, an appropriate management action would be to facilitate aspen migration. However, procedures appropriate for securing either natural or artificial regeneration are not yet established. Although the efficacy of reproduction via seeds in Rocky Mountain aspen forests has long been questioned, fecund females tend to produce lightweight, wind-dispersed seeds with high germination rates. Seedlings, moreover, have been found up to 18 km from mature trees. With sexual reproduction more widespread than formerly thought and suckering after seedling establishment not at issue, stimulating migration via natural reproduction would seem to be a viable option.
         SPRUCE: In spruce habitat classified as threatened or persistent, enhancing resilience to both drought and the spruce beetle is urgently needed. Resilience of established stands can be augmented by reductions in basal area, thereby alleviating drought stress to residual trees. . . Because the climate to which contemporary populations are adapted is warming, maintaining health of planted trees requires moving contemporary sources of seeds upwards into climates projected to be suitable in the near future, that is, assisting their migration. New seed transfer guidelines are needed that will maximize the genetic flexibility of transferred populations for coping with uncertainties of the future.
         Much of the SPRUCE habitat classified as emergent currently is inhabited by ALPINE vegetation. These lands, however, should continue to be unsuitable for spruce because factors other than climate (e.g. unstable slopes and absence of soil) are limiting. Where site conditions are suitable, natural reproduction should gradually become established and, therefore, where soils exist, planting programs also can be considered. However, until seed transfer protocols are established, migration should be limited to 100 m or so in elevation, within which natural dispersal is common.
         Visualizing the vegetation destined to replace SPRUCE, however, is not necessarily straightforward. While ASPEN will be suited to a portion, some also should become suited for species such as Juniperus spp., Pinus contorta, Picea pungens and Pseudotsuga menziesii, although the outlook for the latter species is not necessarily promising.
         Contemporary decline of ASPEN forests is combined with SPRUCE beetle outbreaks to produce conditions on the GMUG requiring the immediate attention of land managers. Because these events are coupled with large projected impacts from the changing climate, conditions on the GMUG are opportune for adapting forest management to climate change. Widespread mortality is occurring and is expected to continue in forest types likely to become unsuitable for future climates. Extensive landscapes, therefore, will be available for programs designed to renew forests such that health, growth and productivity are maintained. Yet, the GMUG contains extensive lands designated as WILDERNESS or roadless within which adjustment to change will proceed naturally.
         Our proposals for adapting management to climate change are 'no-regrets' strategies (Vose et al., 2012). Such strategies incorporate programs designed for low risk in the event of an undesirable outcome despite the uncertainties surrounding the future. Beneficial outcomes, therefore, are expected from such programs regardless of the uncertainties. Our strategy for the GMUG is comprised of such actions. If, on the one hand, rates of climate change are less than projected by most GCMs, the actions we advocate nonetheless will provide for the perpetuation of forests with enhanced resiliency. If, on the other hand, rates of change are more extreme than projected, the actions we propose would foster forest health, but for shorter time intervals than planned.
         The uncertainties surrounding GCM output are not only well documented but also are frequently used as an excuse to stymie proaction. Yet, whether any one GCM or scenario will turn out to have been accurate is not the question that should control decision-making. The many GCMs and scenarios describe similar impacts to the vegetation that vary primarily in timing. By (a) recognizing that GCM output for the decade surrounding 2060 translates into impacts expected sometime for mid-century or beyond and (b) focusing on agreement among projections rather than their variation, managers can evade the inertia bred by uncertainty.
  • "Multi-model comparison on the effects of climate change on tree species in the eastern U.S.: results from an enhanced niche model and process-based ecosystem and landscape models", 2016, by Louis R. Iverson et al, Landscape Ecology.
       EXCERPT: This comparative study, a first of its kind as far as we know, standardizes outputs from three unique forest landscape models across spatial (four regions) and temporal (2000, 2100, 2300) scales, a range of climate scenarios (PCM B1 and GFDL A1fi), species (30 total, most common species; region totals varied from 15 to 24), and evaluation metric (future:current ratios). Standardizing in this manner enables an increased understanding of underlying drivers of differences across models that use diverse approaches and assumptions.

  • "Integrating mechanistic and empirical model projections to assess climate impacts on tree species distributions in northwestern North America", 2016, by Michael J. Case and Joshua J. Lawler, Global Change Biology. Editor's note: This is a crucial paper because it concludes that if the empirical models (such as those developed by USFS researchers above) will overstate future habit suitability for tree species unless key ecological factors (notably, competitive exclusion and forest fire impacts) supplement the model outputs. Because this paper is behind a paywall, I am excerpting extensively from it.
    ABSTRACT: Empirical and mechanistic models have both been used to assess the potential impacts of climate change on species distributions and each modeling approach has its strengths and weaknesses. Here, we demonstrate an approach to projecting climate-driven changes in species distributions that draws on both empirical and mechanistic models. We combined projections from a dynamic global vegetation model (DGVM) that simulates the distributions of biomes based on basic plant functional types with projections from empirical climatic niche models for six tree species in northwestern North America. These integrated model outputs incorporate important biological processes, such as competition, physiological responses of plants to changes in atmospheric CO2 concentrations, and fire, as well as what are likely to be species-specific climatic constraints. We compared the integrated projections to projections from the empirical climatic niche models alone. Overall, our integrated model outputs projected a greater climate-driven loss of potentially suitable environmental space than did the empirical climatic niche model outputs alone for the majority of modeled species. Our results also show that refining species distributions with DGVM outputs had large effects on the geographic locations of suitable habitat. We demonstrate one approach to integrating the outputs of mechanistic and empirical niche models to produce bioclimatic projections. But perhaps more importantly, our study reveals the potential for empirical climatic niche models to over predict suitable environmental space under future climatic conditions.

    EXCERPTS: Empirical climatic niche models are one of the most commonly used tools for assessing the potential impacts of climate change on tree species distributions. However, empirical niche models do not directly incorporate biotic factors, such as competition, establishment, dispersal, migration, growth, mortality, and evolutionary change (Pearson & Dawson, 2003; Pearson, 2006; Davis et al., 1998; Hampe, 2004). Although climate has been shown to control range limits at upper treeline, recent research suggests that local drivers, such as competition, influence tree growth in closed-canopy forests (Ettinger et al., 2011). Thus, climate-induced range shifts in closed-canopy forests will likely be difficult to accurately predict with conventional empirical niche models.
        ... For example, tree species distributions in the Pacific Northwest were projected to contract and shift northward by roughly 330 km under a no-dispersal scenario and by approximately 700 km under a full-dispersal scenario (McKenney et al., 2007, 2011). However, these regional modeling approaches do not address the dynamic processes such as competition among species or the direct and indirect effects of CO2 enrichment. Here, we combine the strengths of both empirical climatic niche models and mechanistic models by integrating projections from a DGVM that simulates the distribution of biomes based on plant physiology, interactions between plant functional types, the effects of CO2 enrichment, and fire, with empirical niche models for six tree species in northwestern North America... The six species included, Pacific silver fir (Abies amabilis), grand fir (Abies grandis), subalpine larch (Larix lyallii), western larch (Larix occidentalis), Pacific yew (Taxus brevifolia), and western redcedar (Thuja plicata).

       Hereafter, we refer to the two sets of model projections as "unrefined" and "refined" niche model projections. The unrefined projections define the future locations of the climatic conditions in which the species is found today (and thus areas that are likely to be climatically suitable), whereas the refined projections define the areas that are likely to be climatically suitable in the future and, given the effects of soils, interactions between plant functional types, the effects of CO2 enrichment, and fire, will likely support the plant functional type to which the species belongs.

        ... METHODS ... We identified models with the fewest number of predictor variables that still successfully predicted at least 70% of the presences and 90% of the absences in the evaluation dataset. We used the mean decrease in the Gini index to identify the most important variables and of these, selected the least correlated. We then rebuilt the models using these reduced sets of predictors. Most models had two to three predictor variables. Having fewer climate variables in these final models provided more parsimonious models and simplified our inferences as to the climatic controls for each species. We then used the final models to predict potential climatic suitability for each species.
        ... Niche model projections refined by mechanistic DGVM projections resulted in smaller future distributions than our unrefined projections for five of the six species, including Pacific silver fir, grand fir, Pacific yew, western larch, and western redcedar (Fig. 2). Neither of our modeling approaches predicted any environmentally suitable areas for subalpine larch in the future. Refined future projections were also considerably different from unrefined projections for three species — Pacific silver fir, Pacific yew, and western redcedar (Fig. 3). For these species, the refined future projections contained fewer areas that were projected to be stable or newly suitable in the future (i.e., expand) as well as more areas of likely contraction. Although also smaller in extent, the refined projections for western larch and grand fir are somewhat similar in appearance to the unrefined projections (Fig. 3).
        ... Refining the projections of the niche models with the outputs of the DGVM had the greatest impact on the projected areas of suitability for Pacific silver fir, Pacific yew, and western redcedar (Fig. 3). For these species, the area of projected expansion in suitability was substantially smaller and the area of projected contraction was larger after the projected future biomes were integrated. By contrast, modifying the outputs of the niche models with the DGVM outputs did little to change projected potential future distributions for western larch and grand fir. These two species also had similar projected changes in their distributions (with respect to areas of potential expansion and contraction of suitability) as forecasted by the refined and unrefined model projections. Our results also show that refining species distributions with DGVM outputs had large effects on the geographic locations of suitable habitat. These differences are most evident when examining future areas of expansion for Pacific silver fir in southwestern British Columbia, Canada and northwestern Washington State, USA (Fig. 4)...These results lend credence to the concern that empirical climatic niche models that are based solely on correlations, and hence may not fully reflect the actual processes controlling a species' distribution (Guisan & Zimmermann, 2000), potentially over-predict future areas of suitability (Araújo et al., 2005).
        ... [NO PROJECTIONS OF DISPERSAL were attempted in the models.] Although we did not assess dispersal, western larch seeds are small and lightweight and can disperse greater distances than the heavier seeds of some of its competitors, such as Douglas-fir (Pseudotsuga menziesii) and subalpine fir (Abies lasiocarpa) (Shearer, 1959). Nevertheless, it is potentially unlikely that even tree species with greater dispersal abilities will be able to track their suitable habitat (McKenney et al., 2011). Furthermore, it is likely that changes in disturbances, such as fire, will play an increasing role in determining which tree species persist. Large fires are projected to become more frequent and intense in western North America (Littell et al., 2010; Rogers et al., 2011; Westerling et al., 2011) and many of these events may be too severe for western larch establishment.
        ... The lack of suitable habitat for subalpine larch in the future corresponds with other studies (e.g., Hamann & Wang, 2006; Crookston et al., 2010) and is supported by ecological information about the species. For instance, subalpine larch has been found to be relatively sensitive to changes in climate and occupies some of the coldest high-elevation sites on which trees grow (Case et al., 2015). Therefore, a change in snowfall or the seasonal duration of snowpack, will likely influence the ability of this species to persist in some areas. Subalpine larch also has a disjunct distribution, with a portion in the Rocky Mountains and another portion in the Cascade Range (Arno & Habeck, 1972), providing a barrier to gene flow.
        ... Our two modeling approaches indicate areas of expansion for grand fir and Pacific yew to the north of their current distributions, largely driven by warming temperatures and an increasingly moist climate. Also, grand fir’s very small net decrease in suitable habitat as projected by the refined model is attributed to the projected increase in precipitation and moisture throughout the region. Moreover, both the refined and unrefined projections for grand fir were largely driven by spring precipitation, which is projected to increase in western Washington, western British Columbia, and the Canadian Rockies (Fig. S3). LPJ, the mechanistic model used, also indicates that the extent of cool forests and coastal cool forests are projected to expand and therefore, we have more confidence that there will be suitable habitat for grand fir to the north.
        ... We have presented one approach for integrating empirical climatic niche and mechanistic model projections, however, other studies have explored alternative modeling techniques and methods (e.g., Iverson & McKenzie, 2013 for a review). Some of these other approaches have incorporated dispersal (Iverson et al., 2004), competition (Meier et al., 2012), and the effects of disturbance regimes (Iverson et al., 2011; Lawson et al., 2012), however, none, to our knowledge, have explicitly incorporated the effects of CO2 enrichment and the subsequent species responses. For instance, higher concentrations of CO2 are likely to have profound effects on the growth of plants by increasing the rate of photosynthetic carbon fixation by leaves as shown by a range of Free-Air Carbon dioxide Enrichment (FACE) experiments (Ainsworth & Rogers, 2007).
        ... Finally, it is possible that our analyses underestimate the potential for a species to move into areas that are outside of its current climatic envelope. Because we modeled suitability as a subset of a species' climate envelope, we were unable to capture potential fundamental niche shifts resulting from processes such as increased water-use efficiency or changes in the factors that determine the realized niche (e.g., reduced competition). There is ample evidence of species being able to live outside of their current climate envelopes (e.g., eucalypts, Booth et al., 2015; 2016). Thus, it is possible that these types of fundamental and realized ecological niche expansions could offset the projected contractions as forecasted by our refined versus unrefined model projections.


    SUPERB OVERVIEWS FOR STUDENTS, ACTIVISTS, JOURNALISTS, AND FORESTERS:

        A September 2014 4-page article, "Have Tree, Will Travel" is a superb way to grasp the paleoecological foundation that undergirds projects for which poleward "assisted migration" on the continent of origin is becoming standard practice in this century of rapid climate change. The author, park planner Kevan Williams, weaves the science and policy viewpoints into three sequential narratives:
        (1) a futile recent Nature Conservancy project of attempting to "rewild" a native camellia, Franklinia alatamaha, southward to its "native" (actually, peak-glacial) habitat in southern Georgia from its cultivated (rescue) domain near Philadelphia.
        (2) the ongoing (and thus far successful) attempt by citizen naturalists to work around the Endangered Species Act and thus on their own initiative move a critically endangered Florida conifer, Torreya taxifolia (photo left), from its peak glacial refuge in northern Florida into the southern Appalachians and points farther north.
        (3) the disaster looming large for even common forest trees, as climate shifts rapidly, along with the role that massive projects of assisted migration, on the one hand, and urban forest landscaping, on the other, could play in helping species move north.

    Other articles on URBAN FORESTRY:

  • "Climate change to Philly trees: It's not 1910 anymore" (news article) by Carolyn Beeler, 23 January 2015.
  • Tennessee Trees Moved to London Ontario? (news article) by Spencer Van Dyk, 23 December 2015

  •     "Assisted Migration: What It Means to Nursery Managers and Tree Planters" is an excellent short introduction intended for landscapers and their clients, urging that planting for climate change become integral to the profession.

    LEFT: The authors (Williams and Dumroese) distinguish 3 types of assisted migration: (1) Assisted population migration, (2) Assisted range expansion, and (3) Assisted species migration. (Florida Torreya is the illustrated example of type 3.)

  • "How Megafires Are Remaking American Forests" by Laura Parker, 2015. Excellent 2015 National Geographic article conveys that there can be no denial of climate change among foresters in the western USA. EXCERPT: Southern Idaho, where much of the forest has burned in the last quarter-century, has seen a dramatic transformation from forest to open range. "We're seeing the migration of the Great Plains ecosystems northward into Idaho now," says Dick Bahr, deputy director of the Interior Department's wildlands fire office. "People are going, 'whoa, what happened?'"

  • "Wilderness Conservation in an Era of Global Warming and Invasive Species: a Case Study from Minnesota's Boundary Waters Canoe Area Wilderness" by Lee Frelich and Peter Reich, 2009, in Natural Areas Journal. The concepts in this 9-page pdf are wide-ranging and perhaps alarming to those new to the literature on climate change consequences for American forests. The quality of prose and flow of ideas enable this densely packed paper to be understood even by nonprofessionals. HIGHLY RECOMMENDED! Readily understood terminology is also introduced, as in the distinction between "Local assisted migration" (moving genotypes of tree species to north-facing slopes or other cooler or moister microclimates within its existing range to serve as micro-refugia as climate warms) and "long-distance assisted migration" (the latter broadly encompasses what Williams and Dumroese label in the above figure as "assisted range expansion" and "species assisted migration").
        Wilderness advocates and proponents will want to pay special attention to the subsection, "Wilderness Law and Management Issues. All readers will benefit from contemplating forestry-climate management issues within the rich details of a single case study.

  • VIDEO: Greg Aplet "Managing for resilience through a portfolio approach to reducing climate risk" (47 min video) of talk by Greg Aplet from a 2013 "Restoring the West" Conference at Utah State University Extension Forestry.

         

    Greg Aplet is an ecologist with The Wilderness Society. Key points of his talk: "We are moving from a production paradigm to a risk management paradigm" in our forests. TWS is broadening its focus from exclusive attention to designated wilderness areas to influencing the management of broader "wildlands ecosystems" in ways that will "sustain a network of wildlands into the future." Owing to the impending power of climate change, it is now best to regard wildlands management as "needing all three strategies": (1) Observation only; (2) Restoration; (3) Innovation and Experimentation. THIS VIDEO IS HIGHLY RECOMMENDED!

    Editor's Note: On the question of climate adaptation in designated wilderness areas, see "Climate Change: Wilderness's Greatest Challenge", 2014, by Nathan L. Stephenson and Constance I. Millar, in USDA Forest Service RMRS-P-71 (8 pages in pdf).



    PALEOECOLOGICAL PERSPECTIVES ON ASSISTED MIGRATION FOR FOREST MANAGEMENT

  • "Forest Responses to Changing Climate: Lessons from the Past and Uncertainty for the Future", 2000, Donald H. DeHayes et al., book chapter in Responses of northern U.S. forests to environmental change.
    EXCERPT: Continent-wide changes in distribution and abundance of plant taxa are species-specific, consistent with Gleason's (1926) individualistic concept of plant-species responses (Davis, 1983; Jacobson et al., 1987). Contrary to popular belief, modern communities are not highly organized, finely tuned units representing long periods of co-evolution among species. Rather, present communities are merely transitory combinations of taxa that have been responding individualistically to continual and sometimes major climate changes (Hunter et al., 1988). [includes "Eastern White Pine Case Study"] Paleoecological evidence shows that eastern white pine made its first post-glacial appearance in Virginia (Craig, 1969), perhaps moving in from a full glacial location on the exposed continental shelf. It reached northern New England by 10,000 years ago (Davis and Jacobson, 1985), the central Great Lakes region by 9,000 years ago (Brubaker, 1975), and Minnesota and western Ontario by 7,000 years ago (Jacobson, 1979; Bjorck, 1985). Eastern white pine reached its northernmost extent about 4,000 years ago, with areas of high abundance shrinking substantially and shifting southward thereafter. This coincides with climate cooling that has allowed boreal taxa to move southward. Another factor in the late-Holocene decline in eastern white pine is the decrease in frequency of fire. Further details of these late-Holocene changes may be found in Jacobson and Dieffenbacher-Krall (1995). The western range limit of eastern white pine occurs today where precipitation equals evapotranspiration (Transeau, 1905). Unless its habitat is manipulated by human activity, white pine does not thrive when conditions become too cool or moist, for example, at the southern margins of the boreal forest in northern New England and adjacent Canada where disturbance by fire may be too infrequent for widespread establishment of seedlings. The current abundance of eastern white pine in the Northeast results largely from abandonment of farmland during the last 150 years.
         Paleoecological studies of the later Holocene show that the boreal forest of eastern Canada developed only in the past 6,000 years (Webb, 1987) and that hemlock has been abundant in the forests of the eastern Great Lakes-New England region for that same period of time (Fig. 14.4). Other data show that southern populations of spruce (Picea spp.) shifted from Canada into the northern tier of states from Maine to Minnesota in the past 1,000 to 1,500 years, accompanied by a general decrease in abundance of eastern white pine that has continued to the present (see Fig. 14.2). Small populations of balsam fir (Abies balsarnea [L.] Mill.) were scattered throughout the northeast during most of the Holocene, but they, too, expanded recently to form the spruce-fir forests of today. The spatial array of changes has been influenced by variations in importance of fire (Foster, 1983) and other disturbances.
        Northern populations of most temperate and boreal zone species have no difficulty tolerating climates more than 5°C warmer on an annual basis. The only exception may be with trees having substantial winter chilling requirements. For example, red maples from Massachusetts exhibit sporadic and delayed spring budbreak and have poor survival when grown in Florida (Perry and Wang, 1960). This possibility should be examined carefully because some climate models project that much of the future warming will be experienced in the winter (Woodward, 1992). Observations of horticultural plantings also suggest that species can be grown in climates far warmer than any place in their natural range. Coupled with the relatively rapid rate of predicted climate warming, these data and experiences highlight the possibility that many species distributions may not simply shift northward or upward, but may actually remain competitive in their current locations and actually expand their distributions.
         A greater concern is that a warmer and drier environment may reduce germination and seedling survival. The most sensitive stage of a tree's life is the beginning. Losses in this period are very high, owing mostly to conditions that are inhospitable at this vulnerable stage. On sites that are prone to drought or lethal temperatures, such as south-facing slopes, higher temperatures would exacerbate losses. The area affected by these lethal agents would increase to some degree. Furthermore, germination could be reduced or unfavorably delayed in species with unmet cold stratification requirements. These unknown factors related to seed germination and success of the seedling stage in forest trees all contribute to uncertainty in predicting future forest composition.
         Many species found a "glacial refugium" in the southern Appalachian region. If the Appala- chian Mountains were aligned east-west instead of north-south, perhaps many of these species would have been unable to migrate far enough southward to endure the climatic cooling experienced during glaciation.
         Uncertainty exists about the nature and extent of future climatic change and its effect on migration of forest tree species. Although it is tempting to speculate that climate change may be too rapid for forest tree species to successfully migrate or that large gaps may be created that can restrict species dispersal, historical evidence indicates that climate changes in the past have been more rapid than changes projected for the next few centuries without any great restriction to species movement.

  • PALEO DATA USED TO PREDICT SEVERE 21st CENTURY PROBLEMS FOR TREES SHIFTING RANGES: "Pushing the Pace of Tree Species Migration", by Eli Lazarus and Brian McGill, 27 August 2014, PLOS One. Editor's note: This paper deals exclusively with tree species whose seeds are wind-dispersed. The outlook for trees with animal-dispersed seeds is even gloomier. EXCERPT:
    Field measurements of typical seed dispersal distances would suggest that tree fronts migrate across a landscape by a process of local diffusion, at rates significantly slower than the velocities reflected in pollen data. But seeds are occasionally carried long distances from their source by wind or by animals. If those seeds mature into trees that in turn dispense seeds, the plant species may migrate at rates that far exceed diffusive propagation. Existing models of tree migration by long-distance dispersal produce migration rates between approximately 100 to 200 m yr-1. A global analysis of temperature-change rates across geographic gradients and biomes finds that temperate broad-leaf and mixed forests, which includes the North American taxa that spread by wind-blown dispersal, will need to shift at a mean velocity of 350 m yr-1. These required migration rates appear to exceed the fastest modeled rates, but may fall within the ranges empirically observed in the last deglaciation. Migration rates barely sufficient to track with climate, combined with the well-documented effect that landscape fragmentation further impedes migration, points to the apparently unequivocal conclusion that climatic change will outpace the migration of wind-dispersed tree species through human-dominated landscapes. One of the few known cases in which climate-driven species migration was impeded comes from Europe, where east-west mountain ranges and the Mediterranean Sea prevented trees and plants from advancing far enough south during Pleistocene glaciation, resulting in a high proportion of extinction. By extension, understanding how human fragmented landscapes interfere with migration rates might mean the difference between minimal extinction rates and massive extinction rates in next few hundred years.

  • PALEOECOLOGICAL DISTRIBUTION OF E. NORTH AMERICA TREES: "Molecular Indicators of Tree Migration Capacity Under Rapid Climate Change", by McLachlan et al., in Ecology, 2005. CONTENT: Excellent review of paleocological investigations using paleo-pollen, macrofossils, and genetic data to ascertain (a) locations of glacial refuges of N.A. temperate trees during the last glacial maximum, and (b) the northward path and speed of movement as the peak glacial episode began to wane some 18,000 years ago. EXCERPT: "Molecular evidence suggests that American beech (Fagus grandifolia) and red maple (Acer rubrum) persisted during the late glaciation as low-density populations, perhaps within 500 km of the Laurentide Ice Sheet. Because populations were closer to modern range limits than previously thought, postglacial migration rates may have been slower than those inferred from fossil pollen. Our estimated rates of <100 m/yr are consistent with model predictions based on life history and dispersal data, and suggest that past migration rates were substantially slower than the rates that will be needed to track 21st-century warming."

  • LATE-QUATERNARY VEGETATION DYNAMICS IN NORTH AMERICA: SCALING FROM TAXA TO BIOMES, by John W. Williams et al., 2004, Eccological Monographs.
    EXCERPTS: This paper integrates recent efforts to map the distribution of biomes for the late Quaternary with the detailed evidence that plant species have responded individualistically to climate change at millennial timescales. Using a fossil-pollen data set of over 700 sites, we review late-Quaternary vegetation history in northern and eastern North America across levels of ecological organization from individual taxa to biomes, and apply the insights gained from this review to critically examine the biome maps generated from the pollen data. Higher-order features of the vegetation (e.g., plant associations, physiognomy) emerge from individualistic responses of plant taxa to climate change, and different representations of vegetation history reveal different aspects of vegetation dynamics. Vegetation distribution and composition were relatively stable during full-glacial times (21,000 to 17,000 yr BP) [calendar years] and during the mid-to late Holocene (7,000 to 500 yr BP), but changed rapidly during the late-glacial period and early Holocene (16,000 to 8,000 yr BP) and after 500 yr BP. Shifts in plant taxon distributions were characterized by individualistic changes in population abundances and ranges and included large east-west shifts in distribution in addition to the northward redistribution of most taxa. Modern associations such as Fagus-Tsuga and Picea-Alnus-Betula date to the early Holocene, whereas other associations common to the late-glacial period (e.g., Picea-Cyperaceae-Fraxinus-Ostrya/Carpinus) no longer exist. Biomes are dynamic entities that have changed in distribution, composition, and structure over time. The late-Pleistocene suite of biomes is distinct from those that grew during the Holocene. The pollen-based biome reconstructions are able to capture the major features of late-Quaternary vegetation but downplay the magnitude and variety of vegetational responses to climate change by (1) limiting apparent land-cover change to ecotones, (2) masking internal variations in biome composition, and (3) obscuring the range shifts and changes in abundance among individual taxa.
         Plant taxa responded individualistically to past environmental change. This observation is a central feature of late-Quaternary vegetation history and fits well with Gleason's view of plant communities (Gleason 1917, 1926). In a classic example (Davis 1976, Davis 1981b), Fagus and Tsuga today have closely associated distributions yet their histories of range and abundance changes differ. Tsuga pollen percentages were below 1% in eastern North America until 14,000 yr BP in the central Appalachians, increased northward along the Appalachian corridor, and by 12,000 yr BP had begun to increase in southern New England. Fagus abundances were low until 14,000 yr BP, increased briefly in the southeast between 14,000 and 12,000 yr BP, but did not expand into New England until after 9,000 yr BP. The distributions of Fagus and Tsuga did not attain their modern overlap until the mid-Holocene. Many other taxa that co-occur today — e.g., Picea and Abies, Quercus and Castanea, and Fagus and Acer — have had similar types of differences in history. The temporal changes in taxon distribution and abundance illustrate how plant species respond individualistically to climate change at continental to regional scales, so that most plant associations have little or no permanence.

  • CLASSIC PALEOECOLOGY PAPER ON PAST FOREST RESPONSES TO CLIMATE CHANGE: "Range Shifts and Adaptive Responses to Quaternary Climate Change", by Margaret B. Davis and Ruth G. Shaw, 2001, Science. Excerpt: "Although all the tree species that remain in our flora shifted or contracted ranges, adapting to climate changes in the past, there are reasons to question whether these processes will occur as readily during the present period of climate change."

  • CLASSIC FORESTRY PAPER ON THE DIRE PROBLEM OF THIS CENTURY'S SPEED OF CLIMATE CHANGE: "Adaptation, Migration or Extirpation: Climate Change Outcomes for Tree Populations", by Sally N. Aitken et al., in Evolutionary Applications, 2008. EXCERPT: "Findings of relatively slow tree migration rates in response to historical changes in climate (potentially < 100 meters per year) are unfortunate in light of model predictions of how fast tree species will need to migrate to track current climates under climate change scenarios. Tests of 14 combinations of GCMs and global SDMs show up to 100% of the models predicting migration rates of 1000 meters per year or higher to be necessary to track habitat under 2x CO2 climate forcing."

  • HOW NORTH AMERICAN TREES SPECIES AND BIOMES SHIFTED FROM PEAK GLACIAL TO WARM TIMES: "Late-Quaternary Vegetation Dynamics in North America: Scaling from Taxa to Biomes" - John W. Williams et al., Ecological Monographs, 2004. Excerpts: "This paper integrates recent efforts to map the distribution of biomes for the late Quaternary with the detailed evidence that plant species have responded individualistically to climate change at millennial timescales. We show how the individualistic shifts in range and abundance for plant taxa scale upward to cause (1) compositional shifts within plant communities, (2) appearances and disappearances of novel plant associations, and (3) changes in the position, area, composition, and structure of biomes. Modern associations such as Fagus-Tsuga and Picea-Alnus-Betula date to the early Holocene, whereas other associations common to the late-glacial period (e.g., Picea-Cyperaceae-Fraxinus-Ostrya/Carpinus) no longer exist."

  • "RELICT" SPECIES RESTRICTED TO DISJUNCT AND SMALL RANGES BY PLEISTOCENE GLACIALS: In 2012 an exemplary paper was published by forest researchers that demonstrated how a paleoecological perspective is vital to understand the importance of "assisted colonization" as a management tool in this century's time of rapid climate shift: "Projections of suitable habitat under climate change scenarios: Implications for trans-boundary assisted colonization", by Ledig, Rehfeldt, and Jaquish, 2012, American Journal of Botany.
        Importantly, this paper also diminishes fears that such relicts might become invasive: "In part, objections to assisted colonization rest on the fear that exotic translocated species will become invasive and compete with native species or that they will carry new pests or on the esthetic argument that such movements result in a homogenization of the flora (Seddon et al., 2009; Ricciardi and Simberloff 2009a, , 2009b; McLachlan et al., 2007). With regard to the issue of native vs. exotic, spruces have moved north and south across North America over geological time (e.g., discussion in Ledig et al., 2004)."     The focal species of this paper is Brewer Spruce, Picea breweriana, which is limited today to the Klamath region of coastal Oregon/California. The paper finds that projected climate change will necessitate the assisted movement of this unique spruce to coastal British Columbia in 2030 to 2060 and finally to the Yakutat coastal region of Alaska by 2090. Here is how the paper begins (citations eliminated):
    "The western United States was warm, subtropical forest in the Eocene (40 million years ago [Ma]). Above 50 degrees N, about the latitude of Vancouver, British Columbia, Canada, was the Arcto-Tertiary Forest. A species like dawn redwood (Metasequoia) was a common element of the Arcto-Tertiary Forest. Genera like bald cypress (Taxodium) and blackgum (Nyssa), now found only in the southeastern United States, grew along the interface of the Arcto-Tertiary Forest and the subtropical forest. Along the streams in the Arcto-Tertiary Forest were species similar to Port-Orford-cedar [Chamaecyparis lawsoniana (A. Murr.) Parl.] and coast redwood [Sequoia sempervirens (D. Don) Endl.], and species of the genus zelkova (Zelkova). Spruce (Picea), fir (Abies), and maples (Acer) grew on the uplands. Cooling occurred at the end of the Eocene, and by the Oligocene (28 Ma), the Arcto-Tertiary Forest had moved south to occupy the western United States. Mountains, including the Coast Ranges of Oregon and California, the Cascades, Sierra Nevada, Olympic Mountains, and Klamath Mountains, began to form in the Miocene (23 Ma). These ranges created a rain shadow to their east, and the Arcto-Tertiary Forest began to shrink and fragment. New communities formed as old ones segregated along new habitat lines. By the Pliocene, 5 Ma, the rich mesophytic forest was gone and was replaced by woodland, grassland, and desert. Many species went extinct and the closest analogue to the Arcto-Tertiary Forest now exists only in the southeastern United States or eastern Asia. However, California and, to a lesser extent, Oregon became a refuge for some elements of this forest. . . Brewer spruce is a relict of past climate change. According to the fossil record, Brewer spruce had a wide distribution in the Miocene and Pliocene, at least as far east as Idaho and Nevada, north to central Oregon, and south to central California. The fossil species, Sonoma spruce (Picea sonomensis Axelrod), which is synonymous with Brewer spruce, occurred in the Creede Flora in the San Juan Mountains of southwestern Colorado in the Oligocene. As cool, moist forests shrank toward the coast and higher elevations, Brewer spruce became endemic to the Klamath Geomorphological Province, which in the West retains forests most nearly equivalent to the western North American Arcto-Tertiary forests.
        To facilitate the conservation of Brewer spruce and possibly prevent extinction, we have planned a program of assisted colonization through the establishment of carefully managed trial plantations on sites with suitable projected climates in northwestern British Columbia. Because such trans-boundary movements and intergovernmental collaboration may, indeed, be necessary to protect a multitude of species threatened and endangered by climate change, we examined the applicable restrictions and found few or no barriers to assisted colonization."
    VIDEO: Brewer spruce - Relict Conifer in the Klamath Mountains

  • The Influence of Paleoclimate on Present-Day Patterns in Biodiversity and Ecosystems - by Svenning et al., 2015, Annual Review of Ecology, Evolution, and Systematics
    P. 565 - Modeling studies suggest that we should expect disequilibria not just in assemblage composition (Dullinger et al. 2012a, Normand et al. 2013) but also in ecosystem structure, with tree line advances lagging behind climate for 100s – 1000s of years (Chapin & Starfield 1997, Normand et al. 2013). . . . The existence of paleoclimatic legacies also has important implications for conservation actions. These legacies indicate that species are often not able to track climate changes and point to the need for considering assisted migration as a tool to preserve biodiversity and sustain or restore ecosystem functioning under future climate change (Lunt et al. 2013). This will particularly be the case for the broader landscape and in particular in human-impacted and/or lowland areas where it will be most difficult for species to migrate fast enough to track climate change, as already seen (Bertrand et al. 2011). However, as active relocation will be unfeasible for much of biodiver- sity, there will be a strong need for protecting areas that offer good local possibilities for climate tracking or are likely to act as climatically stable refugia (Ackerly et al. 2010, Loarie et al. 2009).

    P. 566 - Importantly, the majority of studies of biodiversity and ecosystem patterns still do not consider the potential role of paleoclimate in codetermining the observed patterns, despite its potential importance in many cases. For example, this is true for many studies that rely on species distribution modeling to test ecological hypotheses or for conservation assessments (e.g., to assess risks from future climate change). The strong evidence for paleoclimatic legacies in species distributions have implications for how such modeling should be implemented. Notably, in forecasting studies it is important to avoid approaches that strongly rely on species ranges being in equilibrium with the current environment (e.g., De Marco et al. 2008); at the minimum, a critical assessment should be made of the extent to which such an assumption is valid in every given case and careful consideration given to the consequences of any violations.

  • "Paleoecology and the Assisted Migration Debate: Why a Deep-Time Perspective Is Vital" online essay by Torreya Guardian Connie Barlow, February 2011,
    an 11-point summary essay that aggregates the paleoecological data and develops strong scientific reasoning in favor of assisted migration for Torreya taxifolia. The essay also advocates a shift in the foundational paradigm from assuming 1491 is the proper time-standard for assessing native range to a "deep-time" perspective grounded in a paleoecological understanding that native ranges for all plants in temperate latitudes of the Northern Hemisphere have undergone substantial altitudinal and/or latitudinal migrations that have tracked changes in climate during the past several million years of Pleistocene glacial and interglacial cycles.
  • "How Fast Can Trees Migrate?" a PALEOECOLOGICAL PERSPECTIVE by Jacquelyn Gill, (blogpost) 8 May 2013
    EXCERPT: "The simple story of the last 2.5 million years of vegetation response to climate change could be summed up like this: temperature goes up and down, plants go back and forth. We've had over a dozen ice ages and interglacials since the beginning of the Quaternary Period. In response, flora and fauna are repeatedly displaced by the expanding ice sheets and changing climates. As carbon dioxide concentrations approach 400 ppm (any day now) for the first time since the mid-Pliocene, ecologists and conservation biologists turn to the paleorecord to get a sense of how well plants can track their optimal climates."

  • "Vegetation Response to Early Holocene Warming as an Analog for Current and Future Changes" by Kenneth L. Cole, Conservation Biology, 2009. Although this paper does not address the issue of "assisted migration" as a management tool during this century of rapid climate change, it does scrutinize botanical shifts during late Pleistocene and early Holocene analogous episodes of rapid warming. Based on plant-species data collected from packrat middens that were active during those episodes, Cole concludes and forecasts that, while plant species extinctions may not be imminent in our time, nonetheless, slow-moving late-successional species are likely to be severely restricted in range by the last quarter of this century. The result: large swathes of the American Southwest that now support late-successional species (e.g., pinyon pine and Douglas Fir) may become home to only fast-arriving early successional species (grasses and weedy herbs) for centuries and millennia that follow. It will take that long for slow-dispersing, warm-adapted, late successional species (including trees) to migrate long distances from their at-present much more southerly ranges.
    "An encouraging result of my analyses is that most extant plant species have previously survived a sudden climate warming that was at least similar in magnitude to the changes starting now, albeit without the current anthropogenic alterations on the landscape. The slow-colonizing species abundant today probably experienced a population bottleneck at the time but have successfully re-expanded since. This is the case for the pinyon pines in western North America (Cole et al. 2008b) and the oak species in Europe (Dumolin-Lapegue et al. 1997). . . It seems unlikely that a continent-wide climate-driven disturbance would equilibrate even a century after the climate change reached a stable point, much less while it is still shifting. Both the paleoecological data presented here and the ecological evidence of small-scale historical disturbances imply that ecosystems could not adjust to such a climate perturbation for at least a millennium, or more likely, several millennia.
  • "Niche syndromes, species extinction risks, and management under climate change" by Dov Sax, Regan Early, and Jesse Bellemare in Trends in Ecology and Evolution 2013.
    Although this paper is not substantially paleoecological, it is grounded in the distinction between "fundamental niche" and "realized niche", and applies those concepts to ecological constraints (including seed dispersal limitations) that have resulted in the "realized niche" (known current range) of some species lagging substantially southward of where the climate envelopes of post-glacial "fundamental niches" have likely shifted to. The authors introduce a new concept of "tolerance niche", which could be well applied to "assisted migration" experiments and actions in behalf of tree species. A species living in its "tolerance niche" is not self-sustaining (e.g., it may be able to grow and thrive, but not reproduce). Conservationists acting in advance of climate change could thus aim to establish a species northward into a "tolerance niche" habitat, while expecting ongoing climate change to advance to the point that long-lived tree species eventually are able to reproduce (thus transforming the tolerance niche into both a fundamental and a realized niche for that particular species). Note: See also Bellemare and Moeller "Climate Change and Forest Herbs of Temperate Deciduous Forests (TDF)" for a superb paleoecological review, with implications for conservation when the climate is rapidly changing.
  • Forests in Peril: Tracking Deciduous Trees from Ice-Age Refuges into the Greenhouse World, by Hazel R. Delcourt, 2002. Editor's note: This is the book that convince Connie Barlow to launch the Torreya Guardians assisted migration project.

  • "Paleoecological Insights on Conservation of Biodiversity: A Focus on Species, Ecosystems, and Landscapes" by Paul A. Delcourt and Hazel R. Delcourt in Ecological Concepts in Conservation Biology 1998.
    EXCERPTS: "Regional projections of future greenhouse-gas induced climatic warming indicate that Picea rubens and Abies fraseri forests may become extinct in the southern Appalachians. . . Over glacial-interglacial cycles, climatic and environmental changes have restructured biological systems, resulting in disassembly and reassembly of communities, individualistic migrations of species, and changes in genetic diversity resulting from alternate restriction and release of refugial populations."
        "In this paper, we evaluate the applicability of two contrasting ecological approaches to conserving biodiversity in the Appalachian Mountains in light of past and possible future shifts in the ecotones between alpine tundra, boreal coniferous forest, and temperate deciduous forest. Toward this end, we summarize available plant-fossil data from late-Quaternary sites in order to evaluate a previously developed model of changing landscape states, and then we project future shifts in ecotones in a greenhouse world based on scenarios from two different atmospheric circulation models."     "Below the climatic Picea-Abies/deciduous forest ecotone, isolated montane populations of Picea and Abies persist in locales of suitable edaphic and microclimatic conditions, such as streamside ravines, topographic depressions with pockets of cold-air drainage, and wetlands and alluvial glades with impeded water flow or perched water tables. These edaphic outliers of Piecea-Abies forest extend below their climatic ecotone by as much as 400 m in the Great Smoky Mountains and by 500 m in the central Appalachians."
        CONCLUSIONS: "The strong focus of many conservation biologists on immediate recovery of small populations of rare and endangered species diverts attention from the probability that widespread environmental changes in the near future may compound other, more local threats to continued existence of species that are narrowly adapted to specific habitats. . . In many instances extinction of rare species is likely to result from loss of suitable habitat and inability of species to migrate rapidly. Even species that are now common may be vulnerable to local or global extinction if environmental changes cross physiological thresholds of tolerance."

  • "The importance of biological inertia in plant community resistance to invasion" by Betsy Von Holle et al. in Journal of Vegetation Science 2003. "Early use of 'inertia' was usually to describe the persistence of individuals after the environmental conditions for their establishment had disappeared. The notion evolved towards the usage of inertia as a community property, but it is in fact a property of certain species."

  • "Late Quaternary Vegetation History of the Eastern Highland Rim and Adjacent Cumberland Plateau of Tennessee" by Hazel Delcourt in Ecological Monographs 1979.


    2014 PAPER ANALYZES PARADIGM SHIFT IN FORESTRY THAT DEFUSES ASSISTED MIGRATION CONTROVERSY:

  • "The assisted migration of western larch in British Columbia: A signal of institutional change in forestry in Canada? by Nicole L. Klenk and Brendon M.H. Larson, Global Environmental Change 2014.
    EXCERPTS: Based on 46 interviews with policy actors across Canada, our results suggest that the deployment of the first assisted migration policy in Canada successfully avoided the controversy surrounding the idea in the scientific community by changing the scientific discourse associated with best forest management practices. The shift from an ecological discourse to a genetics discourse over forest policy in British Columbia signals what we might expect in future forest adaptation policy development in Canada.
        Clearly, a genetics characterization of forests looks back to the distant past for guidance in future 'climate change fitness of species'. This represents a major conceptual shift, which significantly affects the temporal and spatial scales on which forest management planning occurs. This shift can be characterized, furthermore, by the deployment of new normative goals for forest management: rather than trying to recreate current forest composition and functions, the values and norms guiding forest management from a genetics perspective seek to accelerate forest transition to the future, to a 'climate resilient' state. This normative shift has real material consequences, such as enabling the movement of western larch 1000 km north of its current distribution, sidestepping the issue of its ecological appropriateness in the recipient ecological community, because from a 'climate fitness' perspective, western larch may eventually migrate to northern BC.
        Thus given the genetical frame structuring the AM policy coordinative discourse, we argue that there is a major shift in the cognitive and normative content of ideas at the program level. However, when we analyzed the communicative discourse on western larch AM policy, we found that concerted efforts were taken by policy developers to downplay the significance of this program change in their communication to the public. To begin, educational and training outreach activities stressed the low risk associated with population range expansion, as the following interviewee explains: "We are very open and inclusive in talking about AM. I talk about the risk of action and inaction and more importantly the difference between the various forms of AM. We are very clear that we are not testing or interested in exotic translocations."
        To sum up, our analysis suggests that policy analysts, forest geneticists and policy implementers in the BC Tree Improvement Branch characterized forests so as to highlight and diffuse an evolutionary theory of forest ecosystems that is tied to a new set of norms and values associated with a humanistic philosophy that are highly controversial in the conservation community—yet which, in turn, are signals of major institutional change in forest policy in BC. . .  Our results suggest that the deployment of the first AM policy in Canada has successfully avoided the philosophical debates on AM in the conservation scientific community by changing the scientific discourse associated with best forest management practices (i.e., from an ecological point of view to a genetics point of view) and this discursive shift may signal what we might expect in future forest adaptation policy development in Canada.

    Editor's note: For a superb example of Canadian foresters utilizing the best communication skills in reported news stories, see the 14 June 2015 "Canadian scientists help trees adapt to changing climate". Here is the lead quote by researcher Sally Aitken, "Trees are adapted to historical climate and the climate's moving out from under them. We're using genomics to generate answers more quickly than they can." Here is her closing quote: "We have changed things to the point where we really have to foster the future of the environment and the forest. I think it would be very foolish and irresponsible to say, 'Let nature take care of itself.'" As well, see Aitken quoted in 29 January 2014 news story: "New genes for old forests as Canada warms": "So my research is focused on the best way to better match trees with new and future climates, to assist the movement of that genetic material through reforestation." Aitken is also quoted here (for Whitebark Pine, 18 September 2014, NYT): "For Trees Under Threat, Flight May Be Best Response".

    See also; "Opinions on strategies for forest adaptation to future climate conditions in western Canada: Surveys of the general public and leaders of forest-dependent communities", 2014, Reem Hajjar et al., Canadian Journal of Forest Research.



    FORESTS OF CANADA: The government of Canada (Natural Resources Canada) and the Canadian Forest Service each are moving forward with strategies for adapting forests and forest resources to anticipated climate change. Natural Resources Canada maintains
    a webpage on "Assisted Migration", which as of mid 2013 includes these excerpts: "Forests are climate sensitive, and a range of climate change impacts are already evident across Canada. Trees appear to be responding to warming temperatures by dispersing into more climatically suitable habitats. However, some populations will be unable to keep up with the rapid rate of environmental change. Numerous adaptation options are being considered as ways to maintain the biodiversity, health and productivity of Canada's forests under continued climate change. One option that is of increasing interest is 'assisted migration,' the human-assisted movement of plants or animals to more climatically suitable habitats. . . British Columbia has extended seed transfer zones 200 metres higher in elevation for most species, and introduced new policy to allow the planting of western larch outside of its previous range. Alberta has extended seed transfer zones 200 metres higher in elevation and 2 degrees of latitude northward for most species. And Quebec has incorporated the risk of climate change maladaptation into seed transfer functions, planting seed mixtures composed of local and more southern seed sources in some regions.2016 UPDATE: a revised Natural Resources Canada webpage is now titled: "Spotlight: Assisted migration as a climate change adaptation tool. Key extract: "Climatic ranges for many tree species in Canada are expected to shift northward by roughly 300 kilometres (km) over the next 50 years. Given that tree species have an average migration rate of about 5 km per 50 years, it is unlikely that they will be able to keep up with these projected shifts."

    THREE CATEGORIES OF ASSISTED MIGRATION are identified:

  • Assisted population migration: The human-assisted movement of populations within a species' established range. (lower risk)
  • Assisted range expansion: The human-assisted movement of species to areas just outside their established range, facilitating or mimicking natural range expansion (intermediate risk)
  • Assisted long-distance migration: The human-assisted movement of species to areas far outside their established range, beyond areas accessible through natural dispersal. (higher risk)
  • Canadian Forest Service Publications:
  • Placing forestry in the assisted migration debate 2012
  • Why we disagree about assisted migration: ethical implications and the future of Canada's forest 2011
  • Assisted migration: Introduction to a multifaceted concept 2011
  • Assisted Migration to Address Climate Change in British Columbia: Recommendations for Interim Seed Transfer Standards" 2008
  • The implementation of assisted migration in Canadian forests 2011
  • Review of science-based assessments of species vulnerability: contributions to decision-making for assisted migration 2011.
    EXCERPT: "Recently, many tools have been developed for assessing species-specific vulnerability to climate change. These tools are question-based assessments that consider multiple criteria for individual species; the criteria are related to exposure and sensitivity to climate change. The following tools are discussed in relation to their use in Canada: (1) the NatureServe Climate Change Vulnerability Index; (2) the System for Assessing Vulnerability of Species to Climate Change (SAVS); (3) the Forest Tree Genetic Risk Assessment; (4) the Index for Predicting Tree Species Vulnerability; (5) ecological standards developed for the assisted migration for Torreya taxifolia; and (6) the Seeds of Success Program. These tools can all be applied to different forest species and they vary in such areas as their species-specific evaluation criteria, means for addressing uncertainty, and the integration of climate change models."

  • "Climate Change Impacts and Adaptation: A Canadian Perspective" Natural Resources of Canada.
    Content: Governmental publication in favor of assisted migration of tree species in anticipation of climate change.


    BEST OVERVIEW (with Canadian emphasis):

      

    This 2011 paper by Susan March Leech et al. is still (as of 2015) the best place to begin learning about assisted migration in Canadian forestry practices.

    It was published 2 years after field experiments began for British Columbia's Assisted Migration Adaptation Trial, and is a superb overview of that effort. The forestry researchers cooperating in the AMAT project are centered in British Columbia academia and timber companies, but also have collaborators in the USA Pacific NW and Alaska.

    Crucially, it sets the Canadian practices within the context of global climate initiatives in forestry. It also includes the citizen-initiated assisted migration action of Torreya Guardians in the USA.

  • "Ecological Implications for Assisted Migration in Canadian Forests" by Richard Winder et al., 2011, The Forestry Chronicle
    EXCERPTS: This paper examines the ecological constraints and consequences of AM, and discusses options for their mitigation at three scales: translocation over long distances (assisted long- distance migration), translocation just beyond the range limit (assisted range expansion), and translocation of genotypes within the existing range (assisted population migration). From an ecological perspective, we find that AM is a feasible management option for tree species and that constraints and consequences can be minimized through careful application of available knowledge and tools. . . Humans have already translocated tree species for long distances in many parts of the world; although these translocations were not motivated by concerns about climate change, they nevertheless provide relevant experience in this mode of assisted migration and are discussed in greater detail later in this paper.
         Globally, issues concerning invasive tree species have focused on intercontinental movements, e.g., broad-leaved paperbark (Melaleuca quinquenervia) in the Florida Everglades (Turner et al. 1998); Pinus spp., Eucalyptus spp., and others in South Africa (Richardson 1998; Le Maitre et al. 2002); lodgepole pine in New Zealand (Ledgard 2001); and Scots pine in Nova Scotia and Ontario (Catling and Carbyn 2005). On the other hand, some intercontinental introductions have resulted in "naturalized" populations with less aggressive behavior, e.g. Norway spruce in the forests of eastern North America (e.g. Stover and Marks 1998; Hunter and Mattice 2002; Pennsylvania Department of Conservation and Natural Resources 2011); sycamore in England (Peterken 2001); or lodgepole pine in Scandinavia (Knight et al. 2001). In some cases, the "invasive" behaviour can be relatively subtle or localized, as in the tendency for Douglas-fir to occupy and shade-out previously unforested rocky slopes in Europe (Klingenstein and Diwani 2005), or in the potential for Siberian larch to dominate some Alaskan sites despite lower densities across the overall forest landscape (Alden 2006). In Patagonia, some introduced species initially thought to be invasive now appear to be less aggressive (Simberloff et al. 2002). A similar effect has been noted in Britain, where trees introduced over the last 400 years are changing genetically and assimilating into forest communities; the long-term ecological impacts of these species are not yet fully manifest (Peterken 2001).
         Regarding the intra-continental migration of tree species, it is difficult to find examples of assisted long-distance migration resulting in invasive behavior. There are some reports of "invasive" behavior in species native to North America, particularly in areas experiencing changes in land management. For example, Douglas-fir is reported to become invasive in oak savannas as a result of long-term fire suppression (Devine and Harrington 2007). Another example, resulting from anthropogenic and natural causes, would be the expansion of American beech vs. the decline of sugar maple in some hardwood forests of Quebec (Messier et al., 2011). In other cases, the "invasiveness" of native species within North America, for example eastern hemlock in sugar maple and basswood forests of upper Michigan, may relate to localized patterns of natural migration responding to changes in climatic conditions (Davis et al., 1998). Overall, very few species become invasive when introduced into a novel environment (Mueller and Hellman 2008); for forestry, the greater risk in assisted migration efforts may be the unintentional introduction or exacerbation of forest pests and pathogens, as discussed below.
         Subsection titles: Ecological Constraints of Assisted Migration; Genetic and physiological factors; Tree-associated species; Pests and pathogens; Competing vegetation; Interactions and surprises; The Canadian context; Mitigation of ecological constraints at different scales of assisted migration • Ecological Consequences of Assisted Migration; Invasion risk of introduced species; Invasion risks of pests and pathogens of introduced species; Invasion in a forestry context; Conclusions.

  • "Hot Issue: Should We Deliberately Move Species?" Assoc. Press, 19 July 2009. Reports on the work of Greg O'Neill, a geneticist with the British Columbia Ministry of Forests and Range, who is already working with logging companies to replant logged forests in British Columbia not with the species that were logged, but with seeds of species currently native to much lower elevations or latitudes. [Same story also online at: http://www.cbsnews.com/stories/2009/07/20/tech/main5174392.shtml.]
  • Potential Impacts of Climate Change on the Distribution of North American Trees - Daniel W. McKenney et al., BioScience, December 2007. Excerpt: "The mean centers of future climate envelopes are predicted to shift northward by 6.4 and 3.0 degrees latitude (i.e., roughly 700 km and 330 km) on average under the full-dispersal and no-dispersal scenarios, respectively (figure 2). The smaller northward shift shown by the no-dispersal scenario is not surprising given that, for this scenario, northward shifts are constrained by the northern edge of the current CE. However, the shifts predicted under the full-dispersal scenario are indeed drastic. The 25 tree species showing the greatest latitudinal shifts are listed in table 2. With the exception of white alder (Alnus rhombifolia), a western species, all of these species exhibit an extensive distribution in the southeastern quadrant of the continent, generally ranging north to the Great Lakes region. By the end of this century, the CE for most of these species is predicted to shift into northern Ontario and Quebec — in many cases to Hudson Bay. Results for the entire 130 tree species (and others) can be viewed at http://planthardiness.gc.ca/."

    BRITISH COLUMBIA : Re: "Assisted Migration Adaptation Trial (AMAT)" in British Columbia Content: "Can a tree native to coastal British Columbia, given climate change, flourish in Fort Nelson? Can a tree native to the Interior live prosperously on Vancouver Island? Those are questions Greg O'Neill hopes to find answers for. O'Neill is a geneticist with Vernon's Kalamalka Forestry Centre, and is overseeing forestry's biggest climate change research trial in North America." Note: O'Neill and other foresters in British Columbia may be the furthest along of anyone in terms of already doing assisted migration of plants and on a massive scale, though it is mostly at the level of reseeding logged lands with seedstock drawn from populations of the same species lower in altitude or latitude.
       What O'Neill and colleagues are doing in British Columbia can be learned in the most detail in this article published in the scientific journal Nature on 18 June 2009. You can access the PDF here: "Forestry: Planting the Forest of the Future". See also a transcript of a Canadian television documentary on O'Neil's work with assisted migration for British Columbia forest tree species. Also, O'Neill is a coauthor of the 2011 paper by Leech et al.: "Assisted Migration: Adapting Forest Management to a Changing Climate". See also the 2013 AMAT bulletin. Superb 2013 VIDEO on the AMAT Trial and introduction to seed transfer guidelines by Greg O'Neil.
       Meanwhile, in the USA, a US Forest Service report, 2009 Science Accomplishments of the Pacific Northwest Research Station includes this: "To test the viability of assisted migration, researchers planted seedlings from locations throughout western Oregon and Washington and northern California at nine sites in western Oregon and Washington. Responses of the different seed sources will be evaluated relative to test site environments and the environments of the seed sources." Page 49 of Part 2 PDF
       Also see a cautionary comment published in BC Forest Professonal, which includes "Growing taller and being more resistant to two diseases in three years does not mean that one population is better adapted to an environment than another. What will happen during the rest of the cottonwood clones' lifetimes? There could be an unseasonal frost or a pathogen that is adapted to attacking mature black cottonwood, killing a large proportion of the assisted southern population, while these trees focus their energy budget on growth at the cost of decreased defenses." Also see 2009 "Climate change and Canada's forests: from impacts to adaptation".
       Also see, "Climate Change to Drive Lodgepole Pine Trees from British Columbia", 1 March 2011 Vancouver Sun; "Whitebark Pine (Pinus albicaulis) Assisted Migration Trial"; "Whitebark Pine Assisted Migration Trial at Blackcomb site in B.C."; "Assisted Migration for Larch" (see also a 2011 Discovery Magazine article on the larch project: "The Transplanted Forest: A Bold Experiment in Preemptive Climate Adaptation"; "Moving Trees Helps Prepare for Climate Change", Scientific American 24 August 2011; "Assisted Migration Vital, Researcher Says" (Sally Aitkin), 7 November 2012; "Assisted migration to address climate change: recommendations for aspen reforestation in western Canada" (L.K. Gray et al, in Ecological Applications, 2011).

    NOTE: A key, lengthy "discussion paper" was published in 2011 in the BC Journal of Ecosystems and Management: "Assisted Migration: Adapting forest management to a changing climate" by Leech, Almuedo, and O'Neill.

    BRITISH COLUMBIA 2016 UPDATE: "How British Columbia Is Moving its Trees", by Stephen Buranyi. EXCERPTS: "The Western Larch can live for hundreds of years and grow to over 200 feet, but the oldest Larch trees in northern British Columbia's Bulkley Valley are only about four feet tall. In fact, the nearest full grown Western Larch is nearly 900 kilometers south by the US border, which has been the Larch's natural range for thousands of years. These are the first trees of their kind to be planted so far north. But for the past seven years the province of BC has allowed millions of trees to be planted toward the northernmost reaches of their natural range and beyond. The government is working with scientists who predict that our climate is changing so quickly that, 50 years from now, when the trees are fully grown, the conditions in the trees' new homes will actually be more like their old ones. . . Meanwhile in BC, where 200 million trees are planted in the province every year, the upper range limit has already been extended by up to 400 km in some cases to allow the steady northward march of large populations — and in the case of the larch, an unprecedented thousand kilometer leap."

  • AdapTree program at University of British Columbia (website). "Genetic conservation in the Anthropocene: The case for assisted gene flow in forest trees", by S.N. Aitken and M.C Whitlock:
    EXCERPT: Assisted migration is being evaluated and in some cases already being used as a tool for maintaining resource production or conserving species as climates change. However, there is a lack of scientific consensus on this subject. Much of the debate arises from a lack of a common definition for assisted migration. To some, it primarily refers to the human movement of seed or individuals within existing species ranges, which we define here as assisted gene flow (AGF). To others, assisted migration primarily refers to species introductions outside of their historical range. In order to evaluate the risks and benefits of assisted migration, it is necessary to consider AGF and assisted migration outside of native ranges separately. AGF has greater genetic implications for existing native populations than assisted migration outside of native ranges as existing recipient populations will be altered, while assisted migration into novel areas has greater ecological implications than AGF as species will be introduced to ecosystems. Here we focus on the genetic effects of AGF.

    ONTARIO: In May 2011, the Canadian province of Ontario published a detailed scholarly bibliography of papers pertaining to climatic needs and adaptability of FOREST TREES IN ONTARIO, CANADA. Downloadable in PDF, the title is: "Assessing assisted migration as a climate change adaptation strategy for Ontario's forests: Project overview and bibliography"; same reported updated in 2014. Note: In 2015 the owner of Haliburton Forest (a vast private forest in Ontario) announced of the native, more southerly species, black walnut "We think that might be one of the trees of the future," said Schleifenbaum. "The scientific term for what we are doing is called assisted migration."
        In 2016 the Muskoka Watershed Council (north of Toronto) issued a report: Planning for Climate Change in Muskoka. Dorthea Hangaard, an environmental writer in the region, wrote a summary of the report, which included the frightening outlook for several native tree species. EXCERPTS:

    Considering the rapid pace of climate change, trees are going to have great difficulty adapting quickly enough because they are long-lived and can't just get up and walk north. The white spruce will have the hardest time: By 2041, it won't be able to survive anywhere south of Sault Ste. Marie. It looks like the sugar maple will be able to hang on in our area into 2071, but the eastern white pines will be a thing of the past, only able to survive north of Lake Couchiching. The authors of "Planning for Climate Change" suggest we consider "assisted migration" — the planting of trees commonly found to the south of us today — in the hopes they will be able to thrive here in the not-too-distant future. Maybe you still plant that sugar maple or white pine, but consider also planting a Carolinian species such as a sycamore, tulip tree, or witch hazel shrub.

    QUEBEC: "Dominant forest tree species are potentially vulnerable to climate change over large portions of their range even at high latitudes", by Catherine Perie and Sylvie de Blois, 2016.

    Excerpt: "Here we assess habitat suitability with climate change for five dominant tree species of eastern North American forests, focusing on areas of greatest vulnerability (loss of suitability in the baseline range) in Quebec (Canada) rather than opportunities (increase in suitability). Results show that these species are at risk of maladaptation over a remarkably large proportion of their baseline range. Depending on species, 5-21% of currently climatically suitable habitats are projected to be at risk of becoming unsuitable. This suggests that species that have traditionally defined whole regional vegetation assemblages could become less adapted to these regions, with significant impact on ecosystems and forest economy. In spite of their well-recognised limitations and the uncertainty that remains, regionally-explicit risk assessment approaches remain one of the best options to convey that message and the need for climate policies and forest management adaptation strategies. . . . . . Based on the proportion of their baseline range that is projected to become unsuitable, our target species rank as follows, in decreasing order of vulnerability: balsam fir (21%), black spruce (18%), white birch (14%), sugar maple (8%), and yellow birch (5%)."


    FORESTS OF EUROPE

  • "Assisted Migration of Forests as a climate change economic mitigation strategy: Marie Curie Actions Final Report" by Minh Ha-Duong and Marta Benito-Garzon", 2015, Research Report CIRED. 2015
    ABSTRACT: The main purpose of this proposal was to provide the necessary tools to address a particular case of adaptation and mitigation of forests to climate change in Western Europe: the translocation of tree populations to compensate for climate change (Assisted Migration; AM). Tree populations have been moved with different purposes before, and we started analyzing these particular cases in Europe. In particular, we analyzed a well-documented failed case of population translocation of Pinus pinaster from the Iberian peninsula to southern France, which entailed an enormous economic loss that led to the only case where the use of foreign tree populations was prohibited by the European Union, which otherwise promotes the free exchange of seeds between ecologically matched sites (EU Council Directive 1999/105/EC of 22 December 1999). An opinion paper (Restoration Ecology 2013) and a reply letter (Bioscience 2013) are related to these experiences analyzing translocations in the past.
         A second step was devoted to propose new scenarios for translocations in the future based on climate data and the fitness (measured as the volume/year as recorded in NFI). To do that, we produced scenarios (theoretical representation) of assisted migration actions for two important candidates for AM in Europe: Pinus pinaster and Pinus halepensis. We harmonized the Spanish and French National Forest Inventories for standing volume and mortality, which allowed us to run models covering Western Europe. Target zones were selected from provenances with high sensitivity and seed zones from provenances with low sensitivity to climate change; the latter can be considered "seed refugia" as the climate changes.
        Three plausible scenarios for translocation to the target zone were developed on the basis of volume simulations calibrated with different planting Abies alba strategies: 1) seeds only from foreign provenances; 2) foreign provenances plus local seeds; and 3) only local seeds. Our results suggested that volume and mortality trends were not always correlated with seed sources and targets, that projected provenances mortality do not follow always a southern-northern pattern and that seed refugia, if any, may be useful for compensating for the effects of climate change only in a subset of provenances (this approximation has been published in the journal New Forests 2015).
        To evaluate which native forests are likely candidates for AM we estimated the vulnerability of the native species in Western Europe including the sensitivity, the exposure and the adaptive capacity of the major tree species in ecological models for creating scenarios for current climatic conditions and future ones. The results of these simulations are considering for publication in the journal Ecological Applications.
        Our results suggest that management programs should be different for mountain conifers populations occurring at the rear-edge of their distribution that need to be sampled more intensively to preserve their genetic resources compared to lowland widespread temperate species where vulnerabilities seem lower and populations more homogeneous. Likewise, for rear-edge populations, ex-situ programs considering some compensation for climate change may be essential to preserve the populations for which conditions become too harsh but that may have a better chance in higher latitudes and altitudes.
        The adaptation of socio-ecological systems to climate change depends not only on the evolutionary potential of natural populations but on the decisions taken by social actors that mediate natural processes. To succeed in moving trees to compensate for climate change the development of a decision framework based on variations in tree fitness in relation with climate is a priority.
        In trees, provenance trials provide new insights to understand the future of populations under climate change. We use data from a European network of 33 provenance tests of Abies alba planted in 5 sites in France to predict spatial variation in tree height at 9 years old in the present and in the near future. We integrated the outputs of the height tree model in combination with the ones of habitat suitability for each of the climate scenarios in a decision framework to guide assisted colonization to compensate for climate change. We apply three decision rules to cope with the uncertain states of the world represented by four climate change scenarios showing that there is no unique 'best decision' and that the general recommendation of mixtures of populations, although probably not the most productive, can reduce uncertainty in the long term by allowing natural forests to evolve.


    FORESTS OF USA

  • Foundational Literature for Moving Native Plant Materials in Changing Climates (by U.S. Forest Service, 2015)

  • 2016 Research Summary (Technical Report) of U.S. Forest Service (289 pages in pdf): Effects of Drought on Forests and Rangelands in the United States: A Comprehensive Science Synthesis, James Vose et al., editors (collaborative effort of 77 scientists).
    Editor's note: Although this document pertains to projecting and managing for drought the forests of the USA, it necessarily deals with the whole of climate change. This document is HIGHLY RECOMMENDED as an overview of the current research and for its superb lists of key references by chapter. Excerpts pertaining directly or indirectly to ASSISTED MIGRATION as a management tool are below.

    p. ii (from the ABSTRACT:) ". . . establishes the scientific foundation needed to manage for drought resilience and adaptation. Large, stand-level impacts of drought are already underway in the West, but all U.S. forests are vulnerable to drought. Drought-associated forest disturbances are expected to increase with climatic change. Management actions can either mitigate or exacerbate the effects of drought. A first principal for increasing resilience and adaptation is to avoid management actions that exacerbate the effects of current or future drought. Options to mitigate drought include altering structural or functional components of vegetation, minimizing drought-mediated disturbance such as wildfire or insect outbreaks, and managing for reliable flow of water."

    p.1 "The assessment is a collaborative effort authored by 77 scientists from the Forest Service and other Federal agencies, research institutions, and various universities across the United States. The authors identified key issues from a series of virtual workshops involving scientists and stakeholders. Focal areas in the assessment include drought characterization, drought impacts on forest processes and disturbances such as insect outbreaks and wildfire, and the consequences on forest and rangeland values. The assessment closely follows the Intergovernmental Panel on Climate Change (IPCC) process, which is organized with convening authors, lead chapter authors, and contributing authors. The convening authors for the assessment had the chapters individually peer reviewed, and the lead and contributing authors revised the text in response to reviewer comments."

    p. 70 "Drought-Mediated Biogeographic and Biome Shifts in U.S. Forests" (subsection) Editor's note: This section is excellent background on slow tree migration rates and difficulties in paleo-pollen interpretation.

    p. 72 "Although researchers could argue that migrations are simply undetected, it appears clear that waves of rapid spread exceeding 103 meters per year that would be required to match the pace of shifting habitats are not occurring."

    p. 76 -78 Editor's note: Summary and links to the variety of modelling techniques used for projecting climate impacts on tree species ranges and abundance. For the eastern USA: "By 2100, mean latitudes are predicted to move northeastward from 400 km (kilometers) for a less CO2-sensitive model (PCM) with high energy-resource efficiency (B1) to 800 km for a more sensitive model (HadleyCM3) with a 'business as usual' scenario (A1F1) (Iverson and others 2008b)."

    p. 80 "Managers can also encourage the natural regeneration of more drought-tolerant trees by exploiting their propensity to resprout, a characteristic of some species with extensive root systems [for example, post oak (Quercus stellata), Gambel oak (Quercus gambelii), or alligator juniper] (Larsen and Johnson 1998, Savage and others 2013). Indeed, such targeted treatments to favor sprouters can be most effective during droughts, as their extensive established root systems give them an advantage to those species that can only establish via seed."

    p. 81 Assisted Migration [subsection title] p. 81 "SDMs suggest that shifts in potential distributions may occur faster than many tree populations can accommodate through migration. While there is substantial evidence that more mobile terrestrial and aquatic invertebrates, birds, and herbaceous plants are changing their distributions sufficiently to keep pace with rapid warming (Chen and others 2011, Parmesan and Yohe 2003), many tree populations are moving northward (Zhu and others 2012) and upward (Gehrig-Fasel and others 2007) much slower than changes in climate. Fearful of local extinctions, some have proposed that managers engage in 'assisted migration' or 'managed relocation' to establish species outside their historic distributions as a biological diversity conservation measure (Schwartz and others 2012). Assisted migration is a deliberate effort to establish populations in areas that are expected to have a suitable climate in the future, including populations sensitive to drought, to at least partially offset losses on sites no longer suitable. However, the effectiveness of widespread assisted migration is not yet known (Williams and Dumroese 2013), and some have expressed concerns about the risk of introducing invasive species (Mueller and Hellman 2008)."

    p. 81 "Centuries of horticultural and decades of silvicultural practices show that growth and establishment (reproductive success) of many tree species is possible well outside of their native ranges. Many commercial (e.g., loblolly pine) and ornamental species have had their ranges greatly expanded across the Southeastern United States. The widespread plantings of the southern magnolia in the southeastern Piedmont (Gruhn and White 2011) and upper Coastal Plain, and bois d'arc (Maclura pomifera) across the Eastern United States (Burton 1990) are examples of such facilitated migrations, helping to establish these species well beyond their native ranges. While these cultivated successes could be viewed as examples of the potential conservation value of assisted migration, far less is known about the likelihood of success of this management practice for the species most directly threatened by climate-induced environmental change. Efforts are currently underway to see if assisted migration can help with the federally endangered Florida torreya (Torreya taxifolia) as well as a number of other tree species imperiled by the anticipated impacts of increased drought and higher temperatures on their limited native distributions (McLachlan and others 2007, Williams and Dumroese 2013).

    p. 82 As suggested earlier, some managers are moving ahead with assisted migration even though success is far from assured, and science has not comprehensively studied the ecological and socioeconomic implications of this practice. For example, the scarcity of information on tree regeneration in rare species constrains our ability to determine if assisted migration will prove to be a cost-effective option for biological conservation (Williams and Dumroese 2013).

    p. 83 Limited evidence of migration during the 21st century, a time when scientists have verified that climate change has been substantial in the Northern United States (Zhu and others 2012), diverges from predictions of rapid spread — and we need to understand why.

    p. 84 There is broad consensus from modeling studies, increasingly supported by observations, that combinations of heat and moisture limitation, and their corresponding indirect effects, will change the health, dynamics, abundance, and distribution of tree species — changes that may accelerate in coming decades. This provides a sense of urgency for many forest managers who would like to proactively treat their forests. After all, management decisions regarding the size, age, and compositional conditions of any given stand have important implications for the degree of functional resistance and resilience to future drought (e.g., Guldin 2014). Although drought-based advice is context-dependent, in general management strategies expecting increasing drought should benefit from developing more resilient forests by promoting tree (genotypic) diversity (especially drought-tolerant species or families) in lower density stands. Assisted migration, or drawing on species or genotypes outside their current geographic ranges, remains an option but needs to be better understood before it is widely implemented.

    182. Assisted migration, a management strategy where organisms are translocated from sites with suboptimal environmental conditions to sites with more optimal conditions, may become integral to conservation strategies as the rate of climate change increases (Peters and Darling 1985). Assisted migration can encompass a broad range of goals, from minimizing loss of biodiversity to preventing extinction, and operate at a range of spatial scales, from local to continental (Williams and Dumroese 2013). Seed transfer guidelines, because they determine transfer distances that avoid maladaptation (Johnson and others 2004) and can be re-projected using models of expected future environmental conditions (Thomson and others 2010), will play an integral role in the planning of assisted migration efforts under global change.

  • MAPS OF USA FOREST TREE SPECIES FUTURE RANGES:

        WESTERN USA: "Plant Species and Climate Profile Predictions". Highly detailed online maps to compare current, 2030, 2060, and 2090 range predictions for 76 species of western USA trees. (Always click on the .png versions to see the maps.) For example, Alligator Juniper, now absent from Colorado, is expected to have ideal range open up west of Denver in 2030, while southerly populations become stressed. (How are they going to get there, as the closest current population is near Santa Fe NM?) Note: A superb paper that details the data-source and modeling used to generate these range maps is "North American Vegetation Model for Land-Use Planning in a Changing Climate", 2012, G.E. Rehfeldt et al. Note: Professionals should read the 2006 explanatory paper of how these modeled map projections were generated, "Empirical Analyses of Plant-Climate Relationships for the Western United States", G.E. Rehfeldt et al., International Journal of Plant Sciences.

        EASTERN USA: Easy-to-use USFS webpage of maps imaging current and climate-shifted ranges of 134 tree species in eastern North America: Climate Change Tree Atlas interactive site. See also a multi-agency generated Forecasts Maps Projects for the Eastern USA. A 2008 paper by USDA forest researchers (Iverson et al.), published in Forest Ecology and Management, introduces the 134-species online range-map projection tool (professionals must read): "Estimating potential habitat for 134 eastern US tree species under six climate scenarios". Note a terrific review chapter ("Climate Change and Forest Herbs of Temperate Deciduous Forests (TDF)" (USA) by Jesse Bellemare and David Moeller offers a cautionary perspective that the baseline presence/absence data used to construct climate envelopes and apply those to future climate predictions geographically may be flawed in that species with seed dispersal constraints may already be lagging in post-glacial habitat recovery, and thus "because hotspots of endemism and diversity tend to be localized to southern states where TDF species survived climatic cooling in the past, their range may now be poorly positioned to withstand future climatic warming. . . Large-scale dispersal limitation may be a relatively common phenomenon among small-ranged TDF plants and, as a result, assisted colonization could be both a necessary and effective conservation strategy for some species."

        WHOLE USA: This forest tree website builds on the previous (above) two, while adding a new feature of color-coded images that show relative difficulties in moving/adapting of different geographic populations of each species. Access here: The ForeCASTS Project, subtitle: Forecasts of Climate-Associated Shifts in Tree Species.

       Climate Change Response Framework

    The Framework is a collaborative, cross-boundary approach among scientists, managers, and landowners to incorporate climate change considerations into natural resource management. It provides an integrated set of tools, partnerships, and actions to support climate-informed conservation and forest management.

    Six Framework projects (see map left) encompass 19 states in the eastern USA, including 14 National Forests and millions of acres of forestland. Each regional project interweaves four components: science and management partnerships, vulnerability assessments, adaptation resources, and demonstration projects. Learn more about how the components interact to build a flexible, scalable, and effective strategy.

  • U.S. FOREST SERVICE: (December 2012) "Effects of Climatic Variability and Change on Forest Ecosystems: A Comprehensive Science Synthesis for the U.S. Forest Sector" - Document prepared for the National Climate Assessment. Page 57 has a section on Assisted Migration:
    Many species will be unable to migrate to suitable habitat within 100 years (Iverson et al. 2004a, 2004b) and may face serious consequences if they cannot adapt to new climatic conditions. Assisted migration may help mitigate climate change by intentionally moving species to climatically suitable locations outside their natural range (Hoegh-Guldberg et al. 2008, McLachlan et al. 2007). Assisted migration has been controversial, with some advocating for it (Minteer and Collins 2010, Vitt et al. 2010) and some against (Ricciardi and Simberloff 2009). Proponents state that these drastic measures are needed to save certain species that cannot adapt or disperse fast enough in an era of unprecedented global change. The main concern of opponents is that the placement of species outside their range may disturb native species and ecosystems when these "climate refugees" establish themselves in new environments. The uncertainty of climate in the future and the complexity and contingency associated with ecosystem response also argue against assisted migration.
        One way to resolve the debate is to subdivide assisted migration into "rescue assisted migration" and "forestry assisted migration." As the names imply, rescue assisted migration moves species to rescue them from extinction in the face of climate change, and this type is the source of most of the controversy. Forestry assisted migration is aimed more at maintaining high levels of productivity and diversity in widespread tree species that are commercially, socially, culturally, or ecologically valuable (Gray et al. 2011, Kreyling et al. 2011). With forestry assisted migration, maintaining forest productivity and ecosystem services are the most obvious desired outcomes.

  • U.S. FOREST SERVICE: A 2009 article, "Genetic Options for Adapting Forests to Climate Change", by Brad St. Clare and Glenn Howe (USFS), published in the Jan/Feb 2009 issue of Western Forester. Michelle Nijhuis posted a review article in Nature (Sept 19, 2012) about southwestern USA massive forest fires leading toward replacement of conifer trees by more drought-adapted shrubs and scrub oak — and how some forest managers already are replanting with lower-elevation and warm-adapted species as a "bridge to the future.": "Forest Fires: Burn Out". NOTE: 21 February 2013 the "Western Forestry and Conservation Association" held a conference entirely on "Assisted Migration: A Primer for Reforestation and Restoration Decision Makers". Also see 2012 "Determining suitable locations for seed transfer under climate change: a global quantitative method" - (excerpt) "Changing climate conditions will complicate efforts to match seed sources with the environments to which they are best adapted. Tree species distributions may have to shift to match new environmental conditions, potentially requiring the establishment of some species entirely outside of their current distributions to thrive. Even within the portions of tree species ranges that remain generally suitable for the species, local populations may not be well-adapted to altered local conditions." USFS OVERVIEW DOCUMENT 2013: "POLICY AND STRATEGY CONSIDERATIONS FOR ASSISTED MIGRATION ON USDA FOREST SERVICE LANDS".

      
  • U.S. FOREST SERVICE: A 2014 article, "A Practical Approach for Translating Climate Change Adaptation Principles into Forest Management Actions", by Maria K. Janowiak et al., published in Practice of Forestry.
    EXCERPTS: Beginning as a pilot program in northern Wisconsin, this highly collaborative effort expanded to several ecoregional projects across the midwest and northeast United States. It builds off of two fundamental ideas. First, because climate change inherently adds complexity and un- certainty to the process of making forest management decisions, there is no single "answer" for how managers should address climate change in management. Additionally, differences in existing management goals and values will naturally result in a diversity of adaptation actions. Rather than providing recommendations or prescriptive actions, we designed a flexible approach that accommodates a diversity of management goals, forest ecosystems, ownership types, and spatial scales (Swanston and Janowiak 2012). . . Given the need to consider incomplete information and to "learn by doing," adaptive management principles are well-suited for incorporating climate change considerations into management. . . . Although no active management is currently planned in these stands, swamp white oak (Quercus bicolor) and bur oak (Quercus macrocarpa) were identified as two potential species that could be planted in lowland hardwood forests to maintain forest cover if intervention was deemed necessary. These species are not currently present on the property but can be found in localized areas in northern Wisconsin, which would represent a small degree of assisted migration.
  • ROCKY MOUNTAINS USA: 2014 has a trilogy of papers published in Forest Ecology and Management, Rehfeldt et al., "Comparative genetic responses to climate in the varieties of Pinus ponderosa and Pseudotsuga menziesii" (Ponderosa Pine and Douglas Fir). Part III, Reforestation of Ponderosa Pine and Douglas Fir in the Rocky Mountain States (owing to the anticipated climate-induced vast die-off) is a detailed assessment of how anticipated climate change will necessitate not only the expansion of the ranges of both species northward but, owing to existing physiological distinctions within populations of these wide-ranging species, forest managers will need to assist northward movement of seeds in all parts of the range in order to ensure adequate genetics of physiology to meet the shifted climate zones. Note: Ponderosa Pine and Douglas Fir are dominant trees in Rocky Mountain forests; their anticipated weakening or outright extirpation owing to climate change by 2060 will be catastrophic both for ecosystem services and timber resources. In the authors' own words,
    "The potential impacts of Table 1 range from pronounced to dire. . . The conclusion seems inescapable that strategic adjustments of forest management and conservation practices are both urgent and inevitable. We advocate a robust artificial regeneration program as the single most important management tool for mitigating ecological impacts from climate change. This makes us ripe for criticism from those who object to 'assisted migration' largely because of the demonstrated abilities of humans to create ecological havoc, centered primarily on the concept of invasiveness (see Mueller and Hellman 2008). Yet careful analyses repeatedly have led to the conclusion that projected rates of climate change are faster than rates of response in natural systems. As a result, adaptation and migration lags are to be expected, leading, in turn, to the impoverished flora and loss of biodiversity evidenced in the climate change impacts recorded in packrat middens. . . For humans, the choice between action and inaction becomes an exercise in risk assessment. In our view, management objectives solely dependent on natural processes will be hopelessly ineffectual for supplying the amenities that humans expect from natural ecosystems within acceptable time frames. As indicated clearly by this series, perceived risks of inaction greatly outweigh the risks of action." (page 9)
  • "Ectomycorrhizal fungal maladaptation and growth reductions associated with assisted migration of Douglas-fir", by JM Kranabetter et al., 2015, New Phytologist, is a very technical publication that reports field data on the importance of nitrogen soil fertility plus suitable mycorrhizae in the recipient sites for assisted population migration. Less suitable N and mycorrhizae are important factors to consider for optimal timber value, but arguably hold little importance for judging success (basic thrival) for assisted species migration (a.k.a. species rescue).

       "Rocky Mountain Forests at Risk"

    September 2014

    by the Union of Concerned Scientists and the Rocky Mountain Climate Organization

    Although "assisted migration" is never mentioned in this 54-page report (freely available online in pdf), this is the ideal background document for the interested public (as well as forestry professionals) to read in order to grasp the extent and degree of dire climatic dieback of dominant species of Rocky Mountain trees — already underway.

  • MINNESOTA: Begin with these three online resources:
    2015: "A forest dilemma: What will grow in a changing climate?" - a brief news article that shows the agency controversies within Minnesota between those now experimenting on a large-scale with long-distant assisted migration and those who disapprove of planting more southerly species in Minnesota's northern forests.

    2010: "Trees Fit for the Future" by Gustave Axelson, in Minnesota Conservation Volunteer. Excerpt: "In Minnesota Frelich says forest managers should consider assisted migration of eastern hemlock trees from an isolated remnant stand near Duluth to areas along the North Shore. He says hemlocks could replace boreal conifers lost in a warmer climate."

    2009: "Wilderness Conservation in an Era of Global Warming and Invasive Species: a Case Study from Minnesota's Boundary Waters Canoe Area Wilderness" by Lee Frelich and Peter Reich, in Natural Areas Journal. This paper superbly explains a wide range of factors in the controversy over assisted migration (a.k.a. "facilitated migration" or "facilitation forestry"), including a distinction between "local assisted migration" (moving genotypes of local trees to north slopes and moister habitats to serve as micro-refugia) and "long-distance assisted migration", such as the eastern hemlock approach suggested in the Axelson article above.

  • "The Nature Conservancy: Adaptation Forestry in Minnesota's Northwoods" July 2013 status report by The Nature Conservancy.
    EXCERPTS: "In June 2013, over 33,000 seedlings from a combination of species and seed zones were planted at several project sites in northeastern Minnesota. Further planting will occur in 2014.

    "The Nature Conservancy is coordinating this project, in collaboration with the Northern Institute of Applied Climate Science (NIACS), University of Minnesota-Duluth, and other organizations. The project is being implemented on approximately 2,000 acres of forestland in northeastern Minnesota, on a mix of federal, state, and county land.

    "Much of current forest management in northeastern Minnesota focuses on maintaing and restoring native boreal species, such as aspen and white spruce. At the same time, forest composition in northeastern Minnesota is projected to change as the climate changes, and recent research suggests that these same species are at greater risk in a changed climate. These anticipated changes suggest that, in the long term, climate change may be working in direct opposition to some current restoration management actions.

    Modeling studies project changes in forest composition in northeastern Minnesota under future climate scenarios, including a shift towards more maple and a less diverse forest composition across the northern forested landscape. This suggests that many of the tree species that are currently a focus of restoration efforts, with the exception of white pine, may be unsuited to future conditions compared to more southerly distributed species, such as maples and oaks. More details are available in the TNC Background Study Summary."

    Note: See a superb, long popular article on this assisted migration action in a 2013 issue of the Minneapolis Star Tribune: "Saving the Great North Woods". Excerpt: "Driven by a warming climate, scientists predict, the [boreal forest in NE Minnesota] will soon follow the glaciers and retreat north by as much as 300 miles in the next century. Much of northern Minnesota, they say, will become open savannas like those in Nebraska and eastern Kansas — with grasses and brush, a few scattered trees, and domes of bare rock rising from the ground." Note: The article contains 2 excellent VIDEOS to watch. See also a 3 September 2014 news report on this project: "Moving a Forest: as climate changes, ecosystems will need to shift". Below is an excerpt from an October 2014 article in The Guardian, "If You Plant Different Trees in the Forest, Is It Still the Same Forest?".

    The Nature Conservancy will plant seeds for 100,000 red oak, bur oak and white pine trees on 2,000 acres of federal, state and local forests in Minnesota's Iron Range. Seeds from each species will come from two zones: one from within the test range, and another from distant parts of the species' historic range (mostly from southern Minnesota, and, in some cases, a portion of Michigan where the trees exist). Researchers from the University of Minnesota Duluth will then manage these test forests in different ways to find out whether varying how the trees are planted and managed affect how each species fares; how different climate conditions affect their viability; and whether seeds originating from other parts of the forest — where different conditions exist — impact how two seemingly identical trees withstand the same conditions. . . The term "assisted migration" was coined after proposals to transplant Torreya [trees] from Florida to North Carolina in 2007 sparked heated debate. But Julie Etterson, the University of Minnesota biologist conducting the study with the Nature Conservancy, says the definition of the practice isn't completely clear. Critics often seem to judge assisted migration projects using a double standard: traditional forestry practices are far more disruptive than the movement of small samples of distant genotypes that are part of the same species, she claims. While some ecologists believe that humans have meddled enough with the wilderness, others take a more pragmatic perspective. Meredith Cornett (of the Nature Conservancy) argues that there is an urgent need to do something to help Minnesota's forests survive. "We could argue that we should just let nature take its course, but nature has never really faced this situation before," she says. "We've just never seen things changing at this pace."

    Then consult: THE NATURE CONSERVANCY "Climate Change Adaptation Case Study: Updating Northeast Minnesota's Forest Management Strategies" (2011) Excerpt: "Recent research findings from The Nature Conservancy in Minnesota and University of Wisconsin- Madison (Ravenscroft et al. 2010) show that forest composition in Northeast Minnesota is projected to change in the next 200 years. Loss in overall forest complexity and an increase in maple species are dominant characteristics of this projected change. Findings also show that over the long term, climate change may be working in direct opposition to current ('climate-uninformed') restoration management actions. Forest management in Minnesota has been focused on restoring boreal species. Recent research suggests that these same species are also unlikely to survive in a changed climate. A new, 'climate smart' strategy will manage for a larger diversity of tree species, allowing opportunity for the best-suited species to thrive under changed climate conditions and thus sustain an adapted future forest. . . . As noted by Miller and Woolfenden (1999) over a decade ago, the work in Ravenscroft et al. (2010) demonstrates that rapid climate change poses serious questions to the practice of using historical data to develop management plans when we know that future climates will significantly differ from past climates. These results suggest that new approaches to forest management, that facilitate adaptation to new climates, may be needed to maintain functional forest ecosystems."
         Note: See a superb, long popular article on this assisted migration action in a 2013 issue of the Minneapolis Star Tribune: "Saving the Great North Woods". Excerpt: "Driven by a warming climate, scientists predict, the [boreal forest in NE Minnesota] will soon follow the glaciers and retreat north by as much as 300 miles in the next century. Much of northern Minnesota, they say, will become open savannas like those in Nebraska and eastern Kansas — with grasses and brush, a few scattered trees, and domes of bare rock rising from the ground.
         The Nature Conservancy is a participant in The Great North Woods climate adaptation work: "Adaptation Forestry in Minnesota's North Woods". Excerpt: "In the Great Lakes region, conventional forestry practices currently emphasize the regeneration of aspen-birch forests. Today's forestry techniques, such as clear-cutting and planting white spruce or red pine, are likely to become commercially and ecologically unviable as many northern tree species decline under anticipated warmer, drier conditions. . . Our suite of climate-adapted tree species includes bur oak, red oak, white pine, and basswood. We chose these species because ecological modeling suggests they are likely to thrive under warmer, drier conditions. All four species are native to the region, but uncommon due to a legacy of past harvesting practices, a climate that historically favored boreal species and dispersal limitations." See also a 3 September 2014 news report on this project: "Moving a Forest: as climate changes, ecosystems will need to shift".

       "Minnesota Forest Ecosystem Vulnerability Assessment and Synthesis: A Report from the Northwoods Climate Change Response Framework Project"

    May 2014 by U.S. Forest Service

    Although "assisted migration" is rarely mentioned in this report, the need for it is evident, particularly in the description of how the species mix is expected to shift:

  • Boreal species such as quaking aspen, paper birch, tamarack, and black spruce are projected to decrease in suitable habitat and biomass across the assessment area.

  • Species with ranges that extend to the south such as American basswood, black cherry, northern red oak, and eastern white pine may increase in suitable habitat and biomass across the assessment area.
  • "Potential Species Replacements for Black Ash (Fraxinus nigra) at the Confluence of Two Threats: Emerald Ash Borer and a Changing Climate", by Louis Iverson et al, 2015, Ecosystems . This paper is a leading edge example of how forest researchers and managers can use a 4-group analysis to determine suitable replacement tree species for those expected to lose current geographic range.

    CONCLUSIONS: The convergence of multiple global change pressures on forests and the individual stressors on species that inhabit them requires us to consider these stressors in concert. This study illustrates the intersection of the two pervasive challenges of climate change and insect pest invasion facing black ash in the Northwoods of Minnesota, Wisconsin, and Michigan (USA), and southern Ontario (Canada). Emerald ash borer continues to spread in North America and the climate continues to warm and become more variable. We have modeled the near-term risk of EAB and the long-term risk of climate change on the forests of northern Minnesota. Projected effects of both threats do not bode well for the continued existence of black ash in the Northwoods. Hence, it makes practical sense to evaluate tree species that may be suitable replacements for black ash in these habitats, either through natural regeneration and migration, or via planting. Though this process is demonstrated to simultaneously address the dual threats facing black ash in Minnesota, the elements to be considered and modeled would be similar for any other location and species which carries a serious pest or pathogen threat. It is our hope that the work presented here can serve as a mechanism and inspiration for further research aimed at addressing multiple global change issues, and most importantly, as guidance for managers in planning for these forests 'in peril.'

  • N WISCONSIN: A multi-author paper published 2014 in the Journal of Forestry is "A Practical Approach for Translating Climate Change Adaptation Principles into Management Actions". One of the case studies is a Nature Conservancy project in northern Wisconsin. Assisted migration is mentioned in this way:
    ". . . Swamp white oak (Quercus bicolor) and bur oak (Quercus macrocarpa) were identified as two potential species that could be planted in lowland hardwood forests to maintain forest cover if intervention was deemed necessary. These species are not currently present on the property but can be found in localized areas in northern Wisconsin, which would represent a small degree of assisted migration."
    Table 3 in that paper lists tree species expected to experience a large decrease, those expected to increase, and those not currently in northern Wisconsin but expect to be newly capable of thriving there. A partial list is:
    LARGE DECREASE expected: Balsam fir, Black and White Spruces, Eastern hemlock, Northern White Cedar, several species of birch, Quaking aspen. LARGE INCREASE expected: American Beech, Black Oak, Black Walnut, Black Willow, Bur Oak, Eastern Cottonwood, Eastern Red Cedar, Hackberry, Osage Orange, 4 species of Hickory, Silver Maple, Swamp White Oak, White Oak. NEW ENTRY opens up (the implication being that assisted migration will be necessary to bring the trees north): Chestnut and Chinkapin and Shingle oaks, Persimmon, Redbud, Dogwood, Honey locust, Ohio Buckeye, Pecan, Pin and Post and Scarlet oak, Red mulberry, Sassafras, River birch, Sycamore, Wild plum, Tuliptree.
    The paper concludes, in part:
    "Although adaptation inherently spans the boundary between the research and management communities, the current conversation within the forestry community is still largely centered on understanding the potential impacts of climate change on forests. In our opinion, this limited view is inadequate, as the complexity and increasing urgency of the issue as well as the need for place-based decisions require active engagement from forest managers and other natural resource professionals."

  • N WISCONSIN & MICHIGAN: A 249-page 2014 USDA report (freely available in pdf) is a must-read for all those interested in adapting Great Lakes area northern forests (zone marked above blue line, below left) in this century of rapid climate change:
       "Forest Ecosystem Vulnerability Assessment and Synthesis for Northern Wisconsin and Western Upper Michigan: A Report from the Northwoods Climate Change Response Framework Project". Although "assisted migration" is only slighted mentioned in this report, it will be apparent to all knowledgeable readers that such assistance will be vital in this region. Notably, the boreal tree species with their southern-most current ranges in this region will greatly diminish or entirely wink out, so more southerly species will need to be introduced to ensure multi-layer forest health. EXCERPT:
        "Many of the species projected to decline are boreal or northern species that are currently near the southern limit of their range in the assessment area, including black spruce, balsam fir, quaking aspen, paper birch, and white spruce. These species are currently very common across the landscape and play a dominant role in many forests, and the reduction of suitable habitat for these species may affect a large portion of northern Wisconsin and the western Upper Peninsula." (p.92)

    EXCERPT (of above report): "Suitable habitat will be available in the future under at least one of the climate scenarios for 26 species that are not currently present in the assessment area. This projection does not necessarily mean that a given species will be able to migrate to newly available habitat and colonize successfully, but rather that conditions may be suitable for a species to occupy the site if it is established. Many species that are not currently present in the assessment area would require long-distance migration, whether intentional or unintentional, in order to establish and occupy suitable habitat in the assessment area. Habitat fragmentation and the limited dispersal ability of seeds could also hinder the northward movement of the more southerly species, despite the increase in habitat suitability (Ibanez et al. 200). Further, species are generally expected to migrate more slowly than their habitats will shift (Iverson et al. 2004a, 2004b). Of course, human-assisted migration is a possibility for some species and may be tested and used over the coming decades (Pedlar et al. 2012)." (p. 93)

    A similar report to the above, also published by the USDA (USFS) in 2014, focuses exclusively on the "Mixed Laurentian Forest of MICHIGAN" (pictured in green in the image left). The 230-page report is freely available in pdf: "Michigan Forest Ecosystem Vulnerability Assessment and Synthesis: A Report from the Northwoods Climate Change Response Framework Project"

    Report excerpt at right:

       "Black spruce and white spruce are projected to have the most dramatic reductions in suitable habitat. Balsam fir, black ash, paper birch, and tamarack also have low modifying factor scores, suggesting that there are life-history traits or biological stressors that may cause these species to lose even more suitable habitat than the model results indicate." (p. 89)

    "17 species not already present will gain new suitable habitat within the assessment area by the end of the 1st century. A given species will not necessarily be able to migrate to newly available habitat and colonize successfully, however. Species not currently present in the assessment area would require long-distance migration, whether intentional or unintentional, to occupy suitable habitat in the assessment area. Because the Great Lakes and the Straits of Mackinac present substantial barriers to migration, southern species may be even less able to occupy suitable habitat in the eastern Upper Peninsula. Habitat fragmentation and the limited dispersal ability of seeds could also hinder the northward movement of the more southerly species, despite the increase in habitat suitability. Most species can be expected to migrate more slowly than their habitats will shift. Of course, human-assisted migration is a possibility for some species and is expected to become tested and used during the next decades."(p. 90)

       Click left chart for a short pdf by the forestry extension service, Michigan State University.

  • SOUTHWESTERN USA: "Massive Tree Die-off a Threat in Southwest" (New study shows climate change could devastate pinyons, junipers), by Chris Mooney, originally published in the Washington Post, 23 December 2015.
    In a troubling new study just out in Nature Climate Change, a group of researchers says that a warming climate could trigger a "massive" die-off of coniferous trees, such as junipers and pinyon pines, in the Southwest sometime this century. . . The study examined both an extreme warming scenario — which recent climate policies suggest we may be able to avert — and also a more modest scenario that would likely bring temperatures 2 degrees Celsius above pre-industrial levels by the year 2100, but not necessarily by that much. The more extreme scenario was certainly worse for these trees, but even under the moderate scenario, the negative results were merely "delayed by approximately one decade," the study found.
    Here is the actual study: "Multi-scale predictions of massive conifer mortality due to chronic temperature rise", McDowell et al. (19 coauthors), 21 December 2015, Nature Climate Change. Note: The sentence is red directly applies these disturbing results to the need for assisted migration.
    EXTRACTS: We first combined observational and experimental dat a sets with models (using both published and unpublished data and simulations to examine the likelihood of future mortality and survival for pinyon pine and juniper trees (Pinus edulis and Juniperus monosperma) in Southwest USA. In a field experiment, we removed 48% of ambient rainfall from three 1,600 m plots for five years in a pinyon-juniper woodland in central New Mexico, USA. . .

    The simulations suggest that even the particularly drought-tolerant pinyon pine and juniper trees, are likely to experience widespread mortality before 2100. Substantial documented pinyon mortality in the early 2000s and widespread observations of recent juniper mortality in Southwest USA are consistent with this result, despite juniper's reputation as being this region's most drought-tolerant conifer. . .

    Results suggest that temperature is the primary driver of mortality through increasing D [the atmospheric driving force for transpiration]. Given the importance of temperature to tree survival, future forest management may take advantage of potential refugia in cooler landscape locations and planting of warm-adapted genotypes. . .

    The eight simulations agreed that at least 50% of the NET [needleleaf evergreen trees] plant functional type could be lost within the Northern Hemisphere by 2100. . .

    [A CAUTIONARY NOTE ABOUT "DYNAMIC GLOBAL VEGETATION MODELS, DGVMs] - Global DGVM predictions have never been validated, so although their predictions represent the state of the art in global simulations, we cannot absolutely trust their outcomes to be realistic. Second, there are multiple processes not included in the models that could cause overestimates of future mortality, for example, by not accounting for acclimation, adaptation, and islands of refugia (such as those associated with beneficial topographic settings); or conversely underestimate future mortality by not including processes such as acceleration of insect population dynamics, increases in frequency and severity of wildfires, or failure of seedling recruitment. . .

    The rise in juniper mortality likelihood has alarming implications for conifers in general because juniper historically experienced far less mortality than other conifers during droughts. The consequences of such broad-scale change in forest cover are substantial, including massive transfer of carbon to a decomposable pool and changes in the surface energy budget. . .

    These simulations of climate-induced vegetation change are among the most rigorously tested by both experimental and observational data sets of physiological conditions associated with tree mortality. The ensemble analyses in this study consistently highlight vulnerability to collapse of the NET [needleleaf evergreen trees] biome across many parts of the globe in coming decades, driven by warming temperatures and associated drought stress.

    An earlier paper on climate stress on Southwestern forests is "A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests", by Craig D. Allen and 19 other coauthors, 5 February 2010, in Forest Ecology and Management 259(4): 660-84. EXCERPT from abstract: "Here we present the first global assessment of recent tree mortality attributed to drought and heat stress. Although episodic mortality occurs in the absence of climate change, studies compiled here suggest that at least some of the world's forested ecosystems already may be responding to climate change and raise concern that forests may become increasingly vulnerable to higher background tree mortality rates and die-off in response to future warming and drought, even in environments that are not normally considered water-limited. This further suggests risks to ecosystem services, including the loss of sequestered forest carbon and associated atmospheric feedbacks."

    For superb popular coverage of this article and the underlying forest-dieoff phenomenon, read the online report by Jim Robbins dated 15 March 2010: "What's Killing the Great Forests of the American West?".

  • PENNSYLVANIA: "Climate change to Philly trees: It's not 1910 anymore" (news article) by Carolyn Beeler, 23 January 2015. Surveys Philadelphia and Chicago urban trees and parks managers who have already begun planting more southerly tree species on municipal lands. Joan Blaustein, head of urban forestry and ecosystem management at the Philadelphia Parks Department, is quoted: "We need to anticipate what the conditions are going to be 100 years from now, rather than trying to restore to 100 years ago." Beeler writes, "In the fall, the city will plant non-native trees suited to warmer climates, including the Southern chestnut oak and bald cypress, and plant some species native to Pennsylvania that are currently at the northern end of their range, such as the Southern red oak and red mulberry. . . In five years, Blaustein hopes the early results of her experimental test plots will give her an idea of which new trees to plant city-wide."
        "Climate Change Threatens Forests" - 8 November 2015 news report by Robert Swift:
    The majestic forests that Pennsylvanians are familiar with today won't be the forests that future generations know because of global climate change, says John Quigley, secretary of the Department of Environmental Protection. While outlining his agency's agenda on a number of fronts last week, Mr. Quigley mentioned that several species of trees will disappear from the forests in the next 50 years as the Earth's temperatures warm: Sugar maple trees, the source for Pennsylvania's maple syrup crop, will be gone. Black cherry, the biggest cash crop for the forest products industry, won't survive. The eastern hemlock, the official state tree, will suffer additional threats from invasive species. . . Mr. Quigley made his comments when two important documents addressing the future of Pennsylvania's forests are in the public eye. The public comment period ended last week for the Pennsylvania Climate Impacts Assessment report released in August. This assessment was done by Pennsylvania State University for DEP to fulfill a 2008 state law.

  • NEBRASKA: Nebraska Forest Service Promotes Planting Trees for Future Climate, 2015, by Justin Evertson.
    With disease, insect and climate threats mounting against our trees, the Nebraska Forest Service has partnered with the Kansas Forest Service on an initiative called "Environmentally Adapted Trees" (EAT). The primary goal of EAT is to expand the species diversity of community forests and other planted landscapes across the region, thereby making them more resilient to natural threats. One objective toward achieving this goal is to work with nursery professionals, foresters and other tree experts to identify and prioritize the best of the proven but underutilized tree species in the region and then actively promote the greater planting of those species. A second objective of EAT is to identify new or rarely seen species that hold potential for survivability in the region. Because our climate is generally warming, we are acting on the hypothesis that some species to our south may hold promise for greater use further north. We've already figured this out with some things like the Caddo sugar maple from western Oklahoma, Frio River bald cypress, soapberry, post oak and persimmon to name a few.
         Another group of trees we have our eyes on are the very rare but long-lived trees found growing in just about any community and which cause a tree aficionado to exclaim "wow!" when they happen upon them. These are the true surprise trees that are often far out of their native or adaptive range, and which obviously haven't read the books that said they likely won't grow where they're now growing. Trees can be quite fascinating in this regard, with many of them holding genetic potential for wider adaptability than we often give them credit for. A few examples in Nebraska include large tuliptrees in Madison, horsechestnuts in Broken Bow, huge pecans in Kearney, redbuds in Chadron and bur oaks in Kimball. The initiative will collect seeds or cuttings of many of these surprise trees and propagate them for greater testing. A key activity of the initiative will be to plant at least 15 demonstration plantings throughout the region where promising but rare trees are trialed to determine their adaptability to a given area. An important part of evaluation will be the potential for invasiveness. We don't want to unleash the next Siberian elm, mulberry or Tree-of-heaven on the environment.
  • OREGON: Climate Change and the Future of Oregon Forests, 2016, by Robert Scheller, in blog of Union of Concerned Scientists.
    EXCERPTS: My research on forests and climate change over the past 20+ years has suggested that forests are not monolithically at risk due to climate change. There is a huge variation in potential responses to climate change, not all of it bad. When considering future investments in maintaining forest health, we may need to consider a broad 'landscape triage,' whereby we intentionally choose which landscapes to save, which to leave to natural processes, and in which to invest immediate care. . . . Between these two extremes are forests that can be maintained in a healthy condition despite climate change. These are forests where, 'managed resilience' can make all the difference: careful intervention can prevent the worst outcomes. In these areas, management actions can help 'bend the climate curve' away from negative outcomes. These actions will vary widely by location but may include fuel treatments to prevent crown fires, thinning to reduce insect mortality, planting a broad species mix when planting is required, even potentially including facilitated migration in anticipation of an altered climate. These are areas where our scarce resource management dollars can make the greatest difference.

  • CALIFORNIA BLUE OAKS: "A Landscape in Transit" by Betsy Mason, Contra Costa Times (Woodland, CA), 24 January 2007. Also for CALIFORNIA WALNUT AND OAKS: "Threats of future climate change and land use to vulnerable tree species native to southern California by Erin C. Riordan et al., June 2015, Environmental Conservation. Excerpt: "This paper compares the relative future impacts of land use and climate change on two vulnerable tree species native to Southern California (Juglans californica and Quercus engelmannii) using species distribution models. Under the Intergovernmental Panel for Climate Change's A1B future scenario, high levels of both projected land use and climate change could drive considerable habitat losses on these two already heavily-impacted tree species. Under scenarios of no dispersal, projected climate change poses a greater habitat loss threat relative to projected land use for both species."

  • MAPLE TREES: March 2012 news article: "Climate change could wreak havoc on maple syrup industry". Excerpt: "According to The Maple Daily, a news site dedicated to maple syrup, sugar maple trees now release their sap about 8.2 days earlier in the year and stop producing it 11.4 days earlier, resulting in a total of about 10 per cent loss in the duration of the maple production season . . . There is currently a debate as to whether forestry experts should be stepping in and taking action in the form of something like an assisted migration, moving trees to a more northern climate to protect them in a careful and controlled way, but like many other aspects of the industry, there is a lot of uncertainty."

  • SUGAR MAPLE in Great Lakes states: 2014 USDA report: "Forest Ecosystem Vulnerability Assessment and Synthesis for Northern Wisconsin and Western Upper Michigan: A Report from the Northwoods Climate Change Response Framework Project". EXCERPT:
    Box 11 (p. 115): Hardwood Decline in the Upper Great Lakes Region: Northern hardwood stands with sugar maple crown dieback have recently been reported in the upper Great Lakes region. Permanent plots have been established on industrial, Federal, and State land in the Upper Peninsula of Michigan, northern Wisconsin, and eastern Minnesota in order to investigate the cause of this dieback. Mean sugar maple crown dieback percentage of live trees at all plots varied from 15 percent in 2009 to approximately 7 percent in 2012. Healthy sugar maple stands typically have less than 10-percent dieback. Analysis has indicated that sugar maple dieback is related to many factors, including exotic earthworms, climate, and soil nutrient variability.
        Out of all plot variables measured, the forest floor condition was the significant factor related to mean sugar maple crown dieback (2009-12). The removal of the duff layer by high densities of European earthworms exposes roots, disturbs biogeochemical cycling, reduces soil moisture, increases soil temperature, affects mycorrhizal communities, and generally exacerbates further stresses on trees. Evaluation of basal area growth indicates a significant positive relationship with total winter snowfall, number of days with snowcover on the ground, and number of days below freezing temperatures across the region, all of which have been decreasing in recent decades. Tree roots of sugar maple and other northern hardwoods are generally frost intolerant, and lack of adequate snowcover exposes these shallow roots to freezing conditions. Moderate drought conditions in recent years, especially in the Upper Peninsula of Michigan, have likely further contributed to maple dieback (Bal 2013). The presence of earthworms and poor soil fertility are also likely contributing to poor crown conditions and decline in many areas.


       USDA regional report 2014:

  • "Central Hardwoods Ecosystem Vulnerability Assessment and Synthesis: A Report from the Central Hardwoods Climate Change Response Framework Project"

    This assessment evaluates the vulnerability of terrestrial ecosystems in the Central Hardwoods Region of Illinois, Indiana, and Missouri to a range of future climates.

    Species predicted to DECREASE: Sugar maple, American beech, White Ash, Shortleaf Pine, Post Oak, Blackjack Oak.

    INCREASE: "Habitat will become more suitable for southern species. . . A major transition in forest composition is not expected to occur in the coming decades." Editor's note: Global warming is expected to occur with strong latitudinal differences: more southerly latitudes will experience the least warming; more northerly, the greatest.

  • "Potential colonization of newly available tree-species habitat under climate change: an analysis for five eastern US species", 2004, Iverson et al. Note: the 5 species are: persimmon, sourwood, sweet gum, loblolly pine, and southern red oak. EXCERPT: "By evaluating the probability of colonization within the potential 'new' suitable habitat, we can estimate the proportion of new habitat that might be colonized within a century. This proportion is low (<15%) for all five species, suggesting that there is a serious lag between the potential movement of suitable habitat and the potential for the species to migrate into the new habitat. However, humans could hasten the migration of certain species by physically moving the propagulesbeech, that have lost many of their animal dispersers."


  • WESTERN LARCH: "Ecological Impacts and Management Strategies for Western Larch in the Face of Climate-Change" by Gerald E. Rehfeldt and Barry C. Jaquish, 2010, Mitig Adapt Strateg Glob Change.
    OVERALL EXCERPTS: "much of the future distribution of climates suitable for western larch would be on lands currently not inhabited by the species today. . . Because western larch rotations usually are longer than 50 years, these maps suggest that the speed of climate-change may force managers to compromise growth and adaptedness in the short term in order to secure survival over the long term. . . Climate change will disrupt the adaptedness of populations and ultimately force the realignment of species distributions. . . . Bioclimate models for western larch can be used in conjunction with modeled geographic patterns of genetic variation to develop and map for the contemporary climate the seed zones and seed transfer guidelines needed for reforestation. . . Our figures demonstrate unequivocally that climatic ecotypes transcend political boundaries. Consequently, programs involving seed procurement and deployment, tree breeding and maintenance of breeding populations, and accrual of genetic gains in commercially important traits will be most efficient through transboundary cooperation. Threatened populations in particular may require conservation plantings in ex situ reserves outside political jurisdictions where future climates are amenable to the species."

    EXCERPTS FROM INTRODUCTION: Over the last decade, the recognition of anthropogenic induced changes in climate has resulted in a dramatic increase in research focused on documenting and describing biotic responses to a rapidly warming climate (Parmesan 2006). Statistical and mechanistic models have been utilized to describe species' bioclimate relationships and model responses to climate-change in biomes (Prentice et al. 1992; Monserud et al. 1993; Rehfeldt et al. 2008) and ecosystems (Nitschke and Innis 2008), species (e.g. Rehfeldt 2006; McKenney et al. 2007; Tchebakova et al. 2005, 2010; Gomez-Mendoza and Arriaga 2007; and Iverson et al. 2008), and populations (Rehfeldt 2004; Tchebakova et al. 2005; Wang et al. 2006; St Clair and Howe 2007). These models have proven to be effective in describing contemporary distributions and predicting future distributions from climate-change scenarios. Their projections suggest in general that a wholesale geographic redistribution of the vegetation will be required to reestablish a semblance of equilibrium between the vegetation and climate by the end of the century. Yet, one of the weaknesses in much of this work centers on their inability to account effectively for species' intrinsic abilities to respond to climate change (Thuiller et al. 2008); life history characteristics, adaptive strategies, population genetic structure, and patterns of genetic variation are commonly ignored.
         Climate is generally recognized as the primary factor controlling plant distributions (e.g., Woodward 1987), largely through edaphoclimatic interactions that function as selection agents to mold systems of genetic variability (White et al. 2007, p. 207). Responses to selection thus determine the adaptive strategy, genetic architecture, and dispersal and establishment rates that interact to control the adjustment and adaptation to a changing climate (Ackerly 2003; Davis and Shaw 2001; Davis et al. 2005; Savolainen et al. 2007; Aitken et al. 2008). Consequently, without basic genetic knowledge, land managers lack science-based information fundamental to making informed decisions. In forestry, for instance, biologically sound conservation programs require an assessment of adaptedness of populations to a changing climate. Managers must also adjust seed transfer guidelines and seed zone boundaries to assure that planting stock remains physiologically suited to the climate of planting sites.
        In western larch, genetic variation in quantitative traits involving growth (e.g., tree height, annual height increments), phenology (e.g., timing of bud burst and bud set) and adaptation (e.g., tolerance to cold, disease resistance) is abundant among populations, among families within populations, and within families (e.g. Joyce 1985; Rehfeldt 1982, 1992; Zhang and Fins 1993; Zhang et al. 1994; Zhang and Marshall 1994). Populations tend to be differentiated according to the relative mildness of the climate; those native to warm and moist climates tend to have the highest growth potential, highest tolerance to needle diseases, and lowest tolerances to winter cold.
         The availability of comprehensive data sets, superb statistical software, and modern computers now makes possible analyses of scope not addressable until recently. Our analyses concern ecologic and genetic responses to climate of western larch, taking into consideration output from General Circulation Models (GCM) in order to develop management strategies applicable to the species' entire botanical distribution. Our specific objectives are to: (1) define the climate profile (sensu Rehfeldt et al. 2006) with a bioclimatic model that predicts presence or absence from climate variables, (2) develop models of genetic variation that predict genetic differences among populations from the inhabited climate, (3) develop and map seed zones within the climate profile for present climates and project their future distributions, (4) identify populations that are likely to become threatened and identify appropriate conservation strategies, and (5) develop management strategies for the transfer of the seeds from their source to the future location of suitable climates, taking into consideration future distributions, adaptation of populations, and variability in the output of disparate GCM.

    EXCERPT from RESULTS AND DISCUSSION: As demonstrated with analyses of aspen (Populus tremuloides) (Rehfeldt et al. 2009), bioclimate models using inventory data and the Random Forests algorithm provide a more accurate portrayal of the species' distribution than range maps, can reflect abundance where range maps cannot, and can pinpoint areas where the climate should be suitable but where the species is absent. In the remainder of this paper, the bioclimate model is used in place of the range map to represent contemporary distributions.

    LARCH 2016 news report: "How British Columbia Is Moving its Trees", by Stephen Buranyi. EXCERPTS: "The Western Larch can live for hundreds of years and grow to over 200 feet, but the oldest Larch trees in northern British Columbia's Bulkley Valley are only about four feet tall. In fact, the nearest full grown Western Larch is nearly 900 kilometers south by the US border, which has been the Larch's natural range for thousands of years. These are the first trees of their kind to be planted so far north. But for the past seven years the province of BC has allowed millions of trees to be planted toward the northernmost reaches of their natural range and beyond. The government is working with scientists who predict that our climate is changing so quickly that, 50 years from now, when the trees are fully grown, the conditions in the trees' new homes will actually be more like their old ones. . . Meanwhile in BC, where 200 million trees are planted in the province every year, the upper range limit has already been extended by up to 400 km in some cases to allow the steady northward march of large populations — and in the case of the larch, an unprecedented thousand kilometer leap."


  • DOUGLAS FIR AND PONDEROSA PINE: "Comparative genetic responses to climate in the varieties of Pinus ponderosa and Pseudotsuga menziesii: Reforestation", by Gerald E. Rehfeldt et al., 2014, Forest Ecology and Management. EDITOR'S NOTE: This paper is the third part in a trilogy of papers (same title, same authors). They characterized the preceding papers this way: "The intent of our modeling (PARTS 1 and 2) was to provide managers avenues for informed actions on two fronts. The first concerns the conservation of genetic diversity of species and climatypes before impending crises make action problematic, that is, while enough healthy trees exist for producing a sufficient number of outcrossed seeds for stocking seed banks. The second concerns the reforestation guidelines needed to accommodate the changing climate such that ecosystem resilience and productivity can be maintained. . ."The philosophy driving the approach we outline has been guiding reforestation for decades, if not centuries: regenerate with the proper species, using a climatype genetically suited to the environment of the planting site. Our approach is consistent with the 'assisted gene flow' of Aitken and Whitlock (2013) and the 'assisted range expansion' and 'assisted population migration' of Winder et al. (2011)." . . The conclusion seems inescapable that strategic adjustments of forest management and conservation practices are both urgent and inevitable.

    DOUGLAS FIR
      
    PONDEROSA PINE
    ABSTRACT: Impacts of climate change on the climatic niche of the sub-specific varieties of Pinus ponderosa and Pseudotsuga menziesii and on the adaptedness of their populations are considered from the viewpoint of reforestation. In using climate projections from an ensemble of 17 general circulation models targeting the decade surrounding 2060, our analyses suggest that a portion of the lands occupied today primarily by coastal varieties of each species contain genotypes that should remain suitable for the future climate. A much larger portion, particularly for varieties occupying inland sites, should require either introduction of better suited species or conversion to better adapted genotypes. Regeneration strategies are considered with the goal of matching growth potential of contemporary populations to the future climate where that potential can be realized. For some lands, natural reproduction should be suitable, but most lands will require forest renewal to maintain forest health, growth, and productivity. Projected impacts also illustrate the urgent need for conservation programs for P. menziesii in Mexico.

    EXCERPTS: In this paper, we synthesize the results of PART 1 and PART 2 to illustrate approaches for identifying contemporary sources of seeds having reasonable chances of being suited to forest landscapes of the future. While management strategies and options become more complex in a changing climate (see Millar et al., 2007), the underlying goal of reforestation should remain the same, that is, to optimize forest health, growth, and productivity by assuring that new generations are genetically suited to their environment. This goal is imbedded in the seed deployment strategies that are in use today. . . Responses to a changing climate can be viewed as (a) short-term plastic responses that accrue in endemic populations as physiological systems adjust to change, and (b) as long-term evolutionary responses that realign genetic variation with environmental diversity (see Rehfeldt et al., 2004). Both responses are unquestionably occurring today (Franks et al., 2013). Immediate short-term responses draw on the innate plasticity that allows forest trees to endure temporal environmental variation during their long lives. Yet, as unequivocally demonstrated by provenance testing (see PART 2), plastic responses are limited to a finite range of environmental variability; exposure to climates beyond these limits will produce maladaptive effects, commonly involving dieback and mortality. Provenance tests also have demonstrated for numerous species in North America and Eurasia that populations tend to occur in climates that are cooler than where they exhibit optimal growth, but that the degree of suboptimality is greater toward the leading edge than at the trailing edge. Consequently, plasticity should be less capable of accommodating change on the trailing edge; impacts should occur first and be the strongest at the trailing edge and rates of forest demise should be greatest at the trailing edge. Nonetheless, continued directional changes eventually will result in maladaptation everywhere; phenotypic plasticity can only delay its expression. . . As presented and discussed in PART 2, clines tend to be steeper, that is, evidence of stronger local adaptation, in the varieties of P. menziesii than those in P. ponderosa and in inland varieties rather than coastal varieties.
         By 2060, the area climatically suited to P. p var. ponderosa is projected to be 14% smaller than it is today. At the trailing edge, nearly 45% of the contemporary niche is projected to be climates in which this taxon does not occur today. This means that 55% of the area now inhabited should continue to be suitable for this taxon through 2060. While severe, these impacts on P. p var. ponderosa are considerably less than those for P. p. var. scopulorum. For the latter, suitable climate space in 2060 should be only one-half that of today, with 77% of the contemporary niche space being lost at the trailing edge. In neither variety would gains at the leading edge offset the losses at the trailing edge, but this is especially so in var. scopulorum. Projected impacts for the varieties of P. menziesii are moderate in var. menziesii, severe in var. glauca, and dire in Mexico’s un- named southernmost variety (Table 1). For var. menziesii, 82% of the current niche should remain suitable through 2060. Losses at the trailing edge should be offset by gains at the leading edge such that the climatically suitable area in 2060 should be about the same as today. For var. glauca, niche area of the future should be only slightly smaller than that of today, but only because large gains at the leading edge would tend to offset the 35% loss at the trailing edge. This would mean that 65% of the contemporary niche should remain climatically suitable through 2060. For the variety of southern Mexico, however, 98% of the contemporary climate niche is projected to be lost, but little new niche space would be added. Area of the climatic niche would be reduced by 94%.
         In the interior West potential impacts are astounding; few contemporary populations would be suited genetically for the future climates at sites where they occur today; nearly all of the persistent niche space would require climatype conversion for adaptedness to be maintained. To us, the future area projected to have either maladapted genotypes or inappropriate species is staggering. The magnitude of climate change impacts portends catastrophic ecological disruption on range-wide scales.
         The need for comprehensive artificial reforestation programs seems unequivocal. At the trailing edge, conversion of species should be the management objective; at the leading edge, rapid colonization of emergent habitat. Fostering adaptation within the climate niche with shortened intervals of forest renewal can be accomplished only with iterative shifts in seed transfer guidelines as a foundation for widespread artificial reforestation. Yet, programs of extraordinary scope would be needed to rehabilitate all those lands Table 1 would suggest as being in need. Managers obviously will be faced with difficult decisions in setting priorities regarding goals and species. Yet, as advocated by McLachlan et al. (2007), the time is ripe for policies to be established and implemented.
         We advocate a robust artificial regeneration program as the single most important management tool for mitigating ecological impacts from climate change. This makes us ripe for criticism from those who object to 'assisted migration' largely because of the demonstrated abilities of humans to create ecological havoc, centered primarily on the concept of invasiveness (see Mueller and Hellmann, 2008). Yet, careful analyses (e.g., Davis, 1989; Davis and Shaw, 2001; Davis et al., 2005) repeatedly have led to the conclusion that projected rates of climate change are faster than rates of response in natural systems (although see Kremer et al., 2012). As a result, adaptation and migration lags are to be expected, leading, in turn, to the impoverished flora and loss of biodiversity evidenced in the climate change impacts recorded in packrat middens (Betancourt, 1990). Impacts summarized in Table 1, moreover, can, themselves, be viewed as fostering ecological havoc. For humans, the choice between action and inaction becomes an exercise in risk assessment (McLachlan et al., 2007). In our view, management objectives solely dependent on natural processes will be hopelessly ineffectual for supplying the amenities that humans expect from natural ecosystems within acceptable time frames. As indicated clearly by this series, perceived risks of inaction greatly outweigh the risks of action.
         Developing the framework on which comprehensive planting programs depend undoubtedly will take time and resources, particularly in regions lacking adequate reforestation experience and forest nursery infrastructure. Nevertheless, the extent of projected impacts suggests urgency, particularly for developing and maintaining seed banks sufficient for supporting robust planting programs. As the climate changes, reliance on seed collections from natural stands will become problematic. This, coupled with the magnitude of geographic shifts in climate suitable to individual climatypes, suggests that interagency, interregional, and even international cooperation on a range-wide scale will be an essential attribute of effective seed bank management. . . Maladaptations to interim climates undoubtedly will constrain transfer distances. The managerial solution to this dilemma would be a staged program of shifting seed transfer rules, aimed at optimizing climatype adaptedness over the anticipated life of a stand. . . Abbreviated cycles of forest renewal undoubtedly will become the future norm. Silviculturists, therefore, will be facing 30- to 40-yr rotations in commercial forests regardless of the amount of wood that can be produced during that time. With managers reconciled to shortened rotations, proactive programs can be devised such that optimal sources transferred today can survive to reach the targeted future climate.

    EDITOR'S NOTE: A previous paper, "Projected future suitable habitat and productivity of Douglas-fir in western north America" (Weiskittel et al.), cautioned that "When compared to other species, Douglas-fir is considered a genetic specialist (Rehfeldt 1994). This means that Douglas-fir growth and mortality at any given site is highly dependent on its seed source, as the local population is often highly attuned to their growing environment. This is well illustrated in the work of Leites et al (in press) who showed that Douglas-fir seed sources had relatively narrow ranges in climate where potential height growth were achieved. As suggested by Crookston et al. (2010), this indicates that potential habitat should be considered at the population rather than species level

    EDITOR'S NOTE: The drought- and extreme-temperature adaptations in the interior populations of Douglas Fir (v. coastal populations) offer survival advantages in assisted migration projects, as shown in this study: Douglas-fir plantations in Europe: A retrospective test of assisted migration to address climate change, by Miriam G. Isaac-Renton et al., 2014, Global Change Biology.


  • ENGELMANN SPRUCE: "Interspecific and Intraspecific Variation in Picea engelmannii and its Congeneric Cohorts: Biosystematics, Genecology, and Climate Change" by G. E. Rehfeldt, 2004, USDA Report RMRS-GTR-134. EXCERPT from the "Global Warming" section on p. 16: "Immigration opportunities for taxa of the P. engelmannii complex are limited largely because taxa of the complex currently inhabit the high elevations. In the north, moreover, the distribution of the complex abuts and intermixes with that of P. glauca. While the P. engelmannii complex is montane, P. glauca is a component of the boreal forests distributed across the continental climates of the northern latitudes. These continental climates are warmer in the summer than the montane climates inhabited by taxa of the P. engelmannii complex. Climate data, for instance, show that habitats occupied by P. glauca range up to 2,100 degree-days greater than 5 degrees C and 21 degrees C for mean temperature in the warmest month, while maximums for the same variables in the P. engelmannii complex are 1,700 degree-days and 18 degrees C, respectively. A warming climate in the north, therefore, should further increase the inhospitality of the contemporary boreal forests to taxa of the P. engelmannii complex."
        "Extirpation and immigration notwithstanding, a portion of the region currently inhabited by taxa of the P. engelmannii complex should remain suitable for taxa of the complex throughout the century. Table 6 shows clearly, however, that those genotypes expected to be the best suited for the novel climates may today exist at large distances from the site of their future climatic optima. This means that accommodation of a warming climate by taxa of the P. engelmannii complex will not only involve extirpation and immigration, but also should result in a complete redistribution of genotypes across the landscape."
        Editor's note: In 2014 I created a 4-minute video of the devastation of Engelmann Spruce on Wolf Creek Pass (Colorado), set to music; watch it and weep. Go to the last four minutes of this hour-long video: "Climate, Trees, and Legacy 05 - Rocky Mountain Trees in Climate Peril". As well, Engelmann Spruce in AZ and NM are included in the Mexican Spruce paper, directly below.

  • Engelmann Spruce used as focal species for technical paper on climate-adapting the seed transfer guidelines in British Columbia: Comparison of fixed and focal point seed transfer systems for reforestation and assisted migration: a case study for interior spruce in British Columbia, by NK Ukrainetz, GA O'Neill, and B Jaquish, 2011, Canadian Journal of Forest Research
    EXCERPT: Using interior spruce (Picea glauca (Moench) Voss, Picea engelmannii Parry ex Engelm., and their hybrids) from British Columbia as a model species, the objectives of this study were to (i) create focal point and fixed seed zone systems, (ii) determine contour intervals (critical seed transfer distances) for the focal point seed transfer system based on forfeiture of growth, (iii) compare the area of seed use (number of square kilometres to which seed can be used) and risk of maladaptation for the two systems, and (iv) apply assisted migration to a focal point seed transfer system.
  • THREE RARE, ENDEMIC SPRUCE IN MEXICO: The 3 spruce are Picea martinezii, Picea mexicana, Picea chihuahuana (along with Picea engelmannii in AZ and NM for comparison). "Projections of Suitable Habitat for Rare Species Under Global Warming Scenarios", by F. Thomas Ledig et al., 2010, American Journal of Botany. Note: Excerpts from this paper are included in the Mexico section of this webpage.

  • NON-NATIVE LODGEPOLE PINE PLANTED ON KENAI PENINSULA (ALASKA) TO REPLACE NATIVE SPRUCE DEVASTATION BY CLIMATE-CAUSED SPRUCE BEETLE ERUPTION: Although not called "assisted migration", this intentional use of a more warm-adapted tree species (native to the dry northern Rocky Mountains, occurring naturally at lower elevations to the spruce zones on mountain slopes) is a clear example of foresters drawing upon a more southerly species native to the continent to replace forest dominants that are no longer viable, given the climate shifts already impacting Alaska. See: "Alaska: Across the Wildest State, Climate Change Threatens Many Species and Habitats", USF&WS June 2011.

  • WHITE SPRUCE (Alberta, Canada): "Climate change risk management in tree improvement programs: Selection and movement of genotypes", by Laura K. Gray et al., 2016, Tree Genetics & Genomes ADD LINK.
    EDITOR'S NOTE: This article comes from a reforestation and commercial perspective, assuming X year rotation periods for harvest of white spruce. In contrast, from a conservation / wildlands perspective, "assisted migration" of white spruce into wild areas decimated by forest fires (and not intended for rotational commercial harvest) would likely aim to find the tolerance range of warmer and/or drier adapted genotypes in anticipation of significant long-term continuation of greenhouse-gas-induced global warming. Thus, the aim would be more toward near-term survival in northward test plantings, rather than thrival. For example, with respect to Florida Torreya (a slow-growing relict yew-conifer, nearly extinct in its peak-glacial range in northern FL), the Torreya Guardians activist group is planting this species both in its currently ideal range (western North Carolina) while testing for its farthest current northward tolerance ranges (OH, MI, WI, NH?) in anticipation of possibly severe global warming this century and beyond.

    EXCERPTS: Reciprocal transfer of seed sources among breeding regions provides an opportunity to investigate how differently adapted populations respond in growth and survival when exposed to different climate conditions, and by implication, to climate change. Previous studies of one of these trial series (G103) have demonstrated genetic differentiation into three regions: northern, central, and high elevation (Rweyongeza et al. 2007b). Those differentiations primarily reflect adaptations to climate (Rweyongeza 2011), although some populations appear to inhabit suboptimal climate conditions with respect to growth potential (Rweyongeza et al. 2010). Climate-based seed transfer guidelines for observed and projected climate change have also been developed for WHITE SPRUCE in Alberta (Gray and Hamann 2012). However, they are based on the assumption that populations are currently optimally adapted to local climate conditions, and the recommendations did not consider actual growth response of different populations to climate change.
         In the present study, we contribute a comprehensive evaluation of long-term genetic testing efforts of both government and industry programs in Alberta. We analyzed growth of 1,170 white spruce families planted in 44 genetic tests both within and outside their native breeding regions. The primary objective of this study is to quantify growth of improved planting stock when transferred among breeding regions. The results are interpreted in the context of the climatic differences between the source and target environments to infer how populations are adapted to climate, and which transfers may be safe under current climate conditions and anticipated climate change. Additionally, we aim to infer how different populations (represented by breeding regions) might in general respond to anticipated climate change. As a potential mitigation strategy, we investigate if we can minimize the risk of planting maladapted trees, eliminating from breeding and deployment populations those genotypes that appear less tolerant to anticipated trends to warmer and drier conditions. The results can be applied in tree improvement programs through roguing of seed orchards and exclusion of vulnerable genotypes from breeding populations.
         . . . These provenance trial series test progeny from a total of 267 different populations planted across 20 trials at 14 sites (Table 1, Fig. 1). In total, approximately 25,000 trees in provenance trials were evaluated in this second analysis. We evaluated the latest available height measurements taken on all progeny and these varied between 7 and 32 years (Table 1). While these results suggest that in general, seed transfer guidelines should continue to limit the deployment of seed material to within local breeding regions, our results only reflect performance over each trial's respective evaluation period which ranges between 7 and 32 years (Table 1). Over the last 25 years, Alberta has experienced an approximate 0.8 degrees C annual temperature increase coupled with a 10% reduction in annual precipitation (Mbogga et al. 2009); thus, the magnitude of climate change experienced among trials during the evaluation period varied. Furthermore, a comparison of bioclimate envelope model outputs over a recent 25 year period (1961-1990 compared to 1997-2006) estimates that climatically optimal white spruce populations have already shifted approximately 207 km north and 91 m in elevation within the boreal ecosystem in western North America (Gray and Hamann 2013). While this difference in optimal and realized climate currently experienced by white spruce provenances and families may be contained within the majority of breeding regions, the magnitude of shift projected to occur for these populations in boreal ecosystems under future climate conditions is expected to drastically increase to approximately 419 km north and 184 m in elevation by the 2050s, and 817 km north and 359 m in elevation by the 2080s (Gray and Hamann 2013), in most cases likely spanning beyond breeding region borders.
         . . . We have shown that north and north-west transfers to colder climate conditions can be beneficial, as also observed for white spruce populations in Ontario and Quebec (Li et al. 1997). However, the apparent prevalence of population adaptation to cold temperatures should serve as a note of caution for assisted migration prescriptions that may move planting stock northward too fast or too far in case climate change does not materialize as rapidly as predicted.

       Movement of genotypes to much colder climates may result in poor seedling survival and suboptimal growth due to frost damage. Rather, we recommend moderate scale transfers among breeding regions that are supported by both appropriate climate differences and population performance from field trials. For example, a transfer from central breeding region D1 northwest into region G2 represents a 1.5 degree C difference in mean coldest month temperature (Table 2, MCMT). This transfer also results in slightly better performance of introduced D1 material compared to the local G2 sources (Table 3, 1.9 % above local sources). Genotypes adapted to warmer region D1 temperatures would be safe to transfer under current climates and additionally be suitable under warming of mean annual temperature by 0.8 °C over the rotation period of the stand.

    Given the uncertainty of future climate projections, methodological limitations inherent to provenance and progeny testing, and the need for planting stock to survive current climate conditions, assisted migration prescriptions should likely avoid very large transfer distances. While results from experimental seed transfers in provenance and progeny trials may be among the most valuable information to develop climate change adaptation strategies, the data is not without problems. Genotypes tested in field trials may not have experienced rare climate events such as unseasonal or extreme cold temperatures in the boreal north. Thus, good growth observed in populations transferred to colder climates may not necessarily reflect their long-term fitness. Another technical limitation of genetic field test is that competition in older trials may exaggerate genetic differentiation of genotypes. We therefore recommend that transfers should generally be moderate (approx. 300 km north) and should be restricted to geographically adjacent breeding regions, even if growth data seem to support long-distance transfers. Such restrictions could gradually be relaxed to allow for longer distance transfers as the climate continues to warm.
         . . . Only the top-performing families should be chosen for assisted migration prescriptions. As an alternative climate adaptation strategy to seed transfer among breeding regions, Table S1 may also be used to remove genotypes from local breeding populations, if their climate sensitivity is indicated by performing poorly when transferred to warmer breeding regions.


  • YELLOW CEDARS IN COASTAL ALASKA: USFS Assisted migration underway! February 2012 news article: "Death of Yellow Cedars Linked to Climate Change". Excerpt: "For more than a century, yellow cedars in Alaska and British Columbia have been dying, yet it was recently confirmed by U.S. Forest Service researchers that the cause was due to climate change. With climate change, there has been less snow on the ground to insulate the shallow roots from extreme temperatures. And with less snow on the ground, frozen roots have led to the decline of 60 to 70 percent of trees covering 600,000 acres in Alaska and British Columbia. Researchers also believe that yellow cedars may thrive in areas outside of where it has already migrated, leading to the hope that assisted migration may restore the dwindling population of these trees. However, there is also concern that assisted migration may cause yellow cedars to become an invasive species. Nevertheless, a trial planting of yellow cedars in Yakutat has been successful with a first-year survival rate of more than 90 percent." The US Forest Service reports a, 2009 "facilitated migration" of Yellow Cedar to Yakutat (where it does not exist in the wild) from native range in Hoonah.
        2012 USFS report identifies paleo-refugia of Alaska Yellow Cedar, in "Shifting Climate, Altered Niche, and a Dynamic Conservation Strategy for Yellow-Cedar in the North Pacific Coastal Rainforest", by Paul E. Hennon et al.
    EXCERPT: What change in the environment triggered tree death in previously healthy forests? A chronology of the natural his- tory of yellow-cedar helps put forest decline into temporal context. The location of Pleistocene refugia (Carrara et al. 2007) aligns with the current distribution of yellow-cedar in Alaska in a manner that indicates that existing yellow-cedar populations may have origins in these refugia. An ongoing population-genetics study will address this hypothesis for yellow-cedar. Climate reconstruction through pollen analysis suggests that only in the late Holocene has coastal Alaska experienced the cool, wet climate that led to the extensive peatland vegetation (Heusser 1960) favorable for yellow-cedar expansion — the same soil conditions that subsequently became a long-term predisposing factor in forest decline (figure 3). At one location near Petersburg, Alaska, cedar pollen became abundant about 2200 years ago (Ager et al. 2010). The Little Ice Age (c. 1200-1900 CE) was a period when the majority of the glaciers in coastal Alaska reached their maximum extensions since the end of the Pleistocene (Calkin et al. 2000), but it is not known whether these glacier advances were driven by colder temperatures or by more snowfall. The ages of mature yellow-cedar trees, whether they are dead or still living, indicate that most of them regenerated and grew to their canopy status in existing forests during the Little Ice Age (Hennon and Shaw 1994, Beier et al. 2008). We hypothesize that this favorable climate allowed yellow-cedar to regenerate prolifically — in part, because snow keeps populations of Sitka black-tailed deer (Odocoileus hemionus sitkensis) in check (White et al. 2009) and because deer are major herbivores of cedar seedlings. It was during the Little Ice Age that yellow-cedar became more abundant at lower elevations, where it would later be most vulnerable to decline. The onset of yellow-cedar decline coincided with the end of the Little Ice Age (Hennon et al. 1990c), which would be consistent with reduced snow's being the environmental change that triggered widespread yellow-cedar tree death. A large pulse of yellow-cedar mortality occurred in the 1970s and 1980s (Hennon and Shaw 1994) during a notably warm period of the Pacific Decadal Oscillation (Mantua 2011).
        A conservation strategy for a climate-sensitive species needs to consider the manner in which past, current, and future climates affect the various ecological traits and life stages of that species. Because climate changes through time, the adaptive range of species becomes a moving target, and a conservation strategy must be dynamic. Climate is expected to impact each tree species in a unique manner; therefore, there is a need to model each species individually (Iverson et al. 2008).
        Our conceptual approach is to integrate snow cover and drainage in order to identify unsuitable, suitable, and potential new habitats for yellow-cedar. Specifically, we nested soil drainage within favorable climate envelopes, with an emphasis on adequate snow-cover levels, to define habitat suitability as the foundation for a conservation and management strategy for yellow-cedar (figure 7).
        One species that might substitute for yellow-cedar in the maladapted zone is western red-cedar (Thuja plicata [Donn ex D. Don]), which grows in some of the declining yellow-cedar forests at lower elevations in Alaska and British Columbia, south of latitude 57 degrees N. Western redcedar is a calcium-accumulating, decay-resistant, long-lived tree of commercial value that is prized by the local indigenous people. Its bark and wood properties, including wood chemistry, differ from yellow-cedar's, but the two trees have some ecological redundancy and offer similar ecosystem services. The northern range extent and elevational limit of western redcedar suggest that future warmer climate conditions will favor this tree in Alaska, which also appears to be the case in coastal British Columbia (Hamann and Wang 2006). More knowledge is needed on redcedar's adaptation to the same freezing injury that afflicts yellow-cedar before intensive efforts of promoting redcedar in declining forests would be justified (Schaberg et al. 2011).
        When favorable climate develops beyond its existing range, yellow-cedar may be particularly slow to migrate because of its low reproductive capacity (Harris 1990). The previously mentioned genetic study is designed to test the Holocene migration of yellow-cedar, which we suspect is slow and still proceeding toward the northeast. Yellow-cedar is absent from much of the widespread forested wetland in these areas, even though the conditions appear to be favorable for yellow-cedar and may have been so for thousands of years. Yellow-cedar may benefit from some assistance in migration to speed the colonization of new habitats as the climate warms.
        Assisted (or facilitated) migration is the deliberate movement by humans of genotypes and species into areas in which the projected climate is believed to be associated with high probabilities of persistence. These activities can be controversial, because widespread movements of species can be interpreted as fostering the introduction of invasive species that could bring unanticipated consequences. Assisted migration may be required for species with narrow resource requirements or poor dispersal ability (Warren et al. 2001), such as yellow-cedar. As a cautious step, we conducted a trial planting of yellow-cedar near Yakutat, Alaska, (an area of discontinuous occurrence for yellow-cedar but still within its range limits; Hennon and Trummer 2001) to test the survival and growth of yellow-cedar where it did not previously grow. The first-year survival rate was over 90%, which suggests that the targeted expansion of yellow-cedar is possible.
    2016 UPDATE: New USFS technical report: "A climate adaptation strategy for conservation and management of yellowcedar in Alaska", by Paul E. Hennon et al., 382 pages in pdf
    DESCRIPTION: A conservation and management strategy for yellow-cedar in Alaska is presented in the context of climate change. This document has four sections. Section 1 covers the ecology and silvics of yellow-cedar, as well as other background information. Section 2 outlines knowledge on the extensive mortality to yellow-cedar, including the role of climate. Section 3 describes opportunities for the conservation and active management of yellow-cedar on lands that are considered either suitable or unsuitable for yellow-cedar. Section 4 uses risk models and yellow-cedar distribution data to evaluate, quantify, and map areas of habitat suitability for yellow-cedar, both now and predicted through the year 2100. Yellow-cedar at risk of forest decline by the end of the century varies considerably by geography in coastal Alaska. Some areas are already heavily affected by decline, and risk is not expected to increase appreciably. Other areas are currently unaffected but are expected to develop decline. Still other areas are expected to remain healthy. This report provides a vulnerability assessment and the scientific foundation for conservation and active management of yellow-cedar on suitable and vulnerable lands. Specific management considerations are presented regionally and for 33 separate geographic zones where yellow-cedar grows in coastal Alaska. NOTE: This report has a PALEOECOLOGY section and excellent photographs. Sample: "If palynological evidence is correct in placing yellow-cedar to these dates, the average generation time (defined as years required for offspring to replace parent in stand) for yellow-cedar is probably measured in hundreds of years, and only 15 to 50 generations of trees separate modern-day populations from the founding events that gave rise to these stands. The high genetic variability of yellow-cedar in Alaska shows no evidence of a genetic bottleneck, and is consistent with yellow-cedar occupancy in Alaska throughout the Pleistocene. . . The end of the Little Ice Age in the mid-to-late 1800s was associated with the onset of yellow-cedar decline, which we have dated as beginning in about 1880–1900 (see section 2). The ages of mature yellow-cedar trees, whether they are dead or still living, indicate that most regenerated and attained upper canopy status during the Little Ice Age. We hypothesize that this favorable climate allowed yellow-cedar to regenerate prolifically, even at low elevations, where it would later be most vulnerable to decline. Therefore, yellow-cedar forests are composed of trees that regenerated and grew during a favorable climate, but have since been subjected throughout portions of the range to a different climate that exposes them to fine-root freezing injury and decline."
         ASSISTED MIGRATION PROJECT OF YELLOW-CEDAR: "The movement of a species to a new suitable climate, called assisted migration, is an approach to expand a species' range. As a species declines and dies in part of its range, there may be new locations, sometimes called the leading edge, where the climate becomes suitable. Assisted migration may be necessary for some species of trees that cannot migrate rapidly enough to keep pace with a changing climate. In 2009, a new planting trial was initiated in Yakutat, Alaska, to determine if yellow-cedar could be regenerated and grow in a new, but suitable, environment. This location was selected because it is farther north and accumulates deep snowpacks over the winter. It is important to note that Yakutat is not outside of yellow-cedar's range because yellow-cedar extends northwest into Prince William Sound. Third-year survival surveys, conducted in 2012, showed 80-percent survival. Another planting trial, a common garden study, was initiated in 2010 to compare yellow-cedar growth rates, foliar terpenes, and freezing resistance. Four different sites, 3 on Prince of Wales Island at a range of elevations and 1 on the mainland at Echo Cove north of Juneau, and 16 different seedlots were included in the study design." NOTE: The geographic expression of Yellow-cedar forest mortality is unusual because "Yellow-cedar decline is now known to occur along a north-south axis that covers more than 6 degrees of latitude, or about 600 miles. This mortality is not known to occur furthur south in British Columbia, Washington, Oregon, or California." Mortality was more common among larger trees but also occurred in trees with diameters as small as 6 in. Tree species other than yellow-cedar typically do not show elevated mortality rates in stands affected by yellow-cedar decline. Yellow-cedar decline was known to occur only in older, unmanaged forests until recently, when silviculturist Greg Roberts of the Wrangell Ranger District noticed dying yellow-cedar in young-growth forests on Zarembo Island in southeast Alaska. He and colleagues assessed this situation initially in the summer of 2013.
       The dying and recently dead yellow-cedars had been previously selected as crop trees in the 38-yr-old precommercially thinned stand. Symptoms of dying trees in the young-growth forest mirrored the classic symptoms of dying mature trees: dead coarse roots, necrotic phloem lesions extending from coarse roots vertically up the lower bole, and entire crowns dying as a unit with proximal (inner) foliage the first and distal (tip) foliage the last to die. Also, as is common on nearly dead or recently dead mature trees, the galleries of the bark beetle Phloeosinus and mycelial fans and rhizomorphs of the fungus Armillaria were found on young yellow-cedars in this stand. The dead and dying young-growth yellow-cedar trees were found in the wetter portions of the stand, as indicated by tree sizes and understory plants, another similarity with yellow-cedar decline in unmanaged forests. Dead mature yellow-cedar stands were observed around these affected young-growth stands, suggesting that landscape position, including elevation, is conducive to decline development. Plot data reveal that this spread tends to occur along a hydrologic or slope gradient, with long-dead trees in central areas with poorly drained soils and more recently killed or dying trees around the periphery on sites with better drainage. Stands at the northern limits of yellow-cedar decline in southeast Alaska from Slocum Arm to Klag Bay on the outer coast of Chichagof Island have a south-to-north sequence of older, recently killed, dying, and healthy yellow-cedar stands. Initially, fine roots die, followed by small-diameter root mortality and the formation of necrotic lesions on coarse roots.

    The forests of coastal Alaska are expected to have the largest increase in frost-free days of anywhere in North America during the 21st century as the winter climate crosses the snow-rain threshold. Temperatures averaged near freezing during the winter months of the 20th century at weather stations located near sea level in southeast Alaska. With heavy year-round precipitation, this near-freezing winter temperature regime suggests that modest warming would dramatically reduce snow accumulation. Despite the potential for a warming regional climate and less snow accumulation, the close proximity of southeast Alaska to the mainland continental climate in adjacent British Columbia and Yukon Territory still allows cold air to be pushed over yellow-cedar forests during high-pressure weather events in the spring. This juxtaposition of climates produces mild maritime weather that maintains the physiological activity of yellow-cedar and reduces snow, but also allows for periodic infiltration of cold continental conditions that inflict injury.
        Forest management strategies on certain land ownerships and land use designations can take several forms, such as the movement of tree species from various genetic sources through assisted migration and the favoring of conditions for a species through active management. This latter method has promise in coastal Alaska. In this area silvicultural techniques of planting or thinning can be used to increase the presence of yellow-cedar on productive soils where it would otherwise be less competitive with western hemlock and Sitka spruce.
    VIDEO: Tracking Yellow Cedar Decline in Southeast Alaska (3 min)


  • REDWOOD TREES NORTH TO OREGON - David Milarch has been collecting branchlets from some of the "champion" trees of various species, especially in the USA. Because redwoods resprout from the base for many decades after the trunk is cut, he has collected clones of some of the biggest (long cut) specimens of historic times — and he is planning now to plant some of those clones "in areas that might be safer for the trees if the globe heats up, a process known as assisted migration." This was reported in The Oregonian ,"Ancient redwoods, giant sequoias to be 'archived' on Oregon coast", 27 Nov 2012. AND TO BRITISH COLUMBIA: "Prehistoric trees may help a B.C. forest fight climate change" - 23 July 2015 popular news article reports landowners in southern B.C. are planting redwoods from California and dawn redwoods from China (both of which occur in Canadian fossil record of 55 million years ago). Forest researcher Sally Aitken of UBC comments that choosing seed stock of current species from more southerly realms is a more moderate form of "assisted migration" that she is experimenting with. EDITOR'S NOTE: November 2016, Connie Barlow submitted a proposal to University of Washington's Center for Creative Conservation, to initiate a Redwood and Sequoia Inventory for Puget Sound Region, as for more than a century landscapers have been planting both California species into the Pacific Northwest — where they not only seem to be thriving, but naturalizing into nearby forests.

  • GIANT SEQUOIA ASSISTED MIGRATION EXPERIMENT. The largest family-owned lumber company in California, Sierra Pacific Industries, has for nearly half-a-century been experimenting with planting California's native Giant Sequoia northward from its relictual range in the southern Sierras into the northern Sierras and the southern Cascade Mountains of northern California.
         The FIGURE BELOW was adapted by Connie Barlow (red and green borders added) from a 2013 poster presentation by forester Glenn Lunak (employed by Sierra Pacific), delivered at the Southern Sierra Nevada Change Adaptation Workshop in Visalia Calif. Click the title to access online Lunak's poster (and figure):
    "Preserving Giant Sequoia Genetic Resources through Forest Management in the Face of Climate Change". Also see the 21-page, richly illustrated "Giant Sequoia Genetic Conservation Plan Progress Report of Sierra Pacific Industries (updated July 2015)".

    Journalist Zach St. George reports (in 2015), during a field visit with Lunak:

    Lunak's boss first came up with the idea at a conference on giant sequoias, but Lunak is in charge of planning and implementing the program. In 2010, the company started collecting cones from sequoia groves. Lunak says it aims to collect seeds from groves each year, waiting for storms to knock down fresh cones. A nursery sprouts and grows the seedlings, 20,000 or so from each grove. . .

       . . . . In many areas across the company's holdings, previous owners planted sequoias as an experiment or out of curiosity, as Lunak did in the 1980s. These trees have allowed him to evaluate areas where the new groves can be expected to do well. The trees grow naturally only between about 4,000 and 7,000 feet of elevation, and always mixed with sugar pine. Roughly hewing to those criteria, Sierra Pacific plants the seedlings in a mix with native species, between 20 to 40 percent of the total, creating more than a dozen new groves per original grove, each bearing the full genetic diversity of its parent community. "What is the climate going to be doing fifty, 100, 200, 500 years from now?" Lunak says. "By replicating these grove representatives in numerous growing environments, we know some won't do well, but by growing across this range of environments, we feel we will be successful in preserving the genetics of these groves over the long term." Eventually, if all goes to plan, there will be more than 1,600 of these groves spread across the northern Sierra Nevada and southern Cascades, covering some 32,000 acres, compared to the roughly 47,000 acres of natural sequoia groves. As the company thins and harvests other trees, it will favor the sequoias, Lunak says, leaving them to grow fat and old.


    Note: For details on Sequoia's preference for SW-facing slopes and its ability to grow very well northward of its historically native range, see J. Kitzmiller and G. Lunak 2012, "Growth of Giant Sequoia Compared to Ponderosa Pine and Other Mixed-Conifers in California Plantations", Western Journal Applied Forestry 27: 196-204.

    EXCERPTS: Our results provide basic knowledge that could be used for both Sequoia conservation and production forestry. . . The project leader designated 131 plantations established between 1952 and 2005 from inventory records [or Sierra Pacific Industries], without prior knowledge of performance, to represent the range of ages, geographic locations, and site conditions where Sequoia was planted usually with one to three other conifer species. . . Results: Sequoia grew significantly taller in 27% of the plantations, while Ponderosa Pine grew significantly larger in only 5%. Sequoia grew significantly larger in dbh in 43%, while Ponderosa Pine exceeded Sequoia in only 6%. Thus Sequoia displayed significant growth superiority 5 to 7 times more often than Ponderosa Pine. In a subgroup of 47 older (19 + yr) plantations, Sequoia was unsurpassed by Ponderosa Pine in dbh. . .In the north region, northeast aspects had similar growth of Sequoia and Ponderosa Pine, while the others, especially the southwest aspect, favored Sequoia. . . Discussion: The performance results of within-pair size differences support the proposition that Sequoia is the fastest-growing conifer on the best sites in the Sierra Nevada Mountains outside the natural range of Sequoia. Sites that favored Sequoia most were in southern latitudes, on moist high quality sites with low stand densities, along middle slopes, and facing southwest. These areas should best sustain Sequoia in California's summer-dry climate, and perhaps in changing climates. Although soil data were not included in our study, the deeply fractured, weathered bedrock of decomposed granitic soils typical of southern Sierra Nevada may also play a role in providing additional late-season moisture to the deep-rooted Sequoia. . . By mid-to-late summer when available soil moisture is largely used up, most pines and firs have already completed shoot growth and set winter buds. However, Sequoia's indeterminate shoot growth pattern allows crown expansion to continue as long as conditions are favorable.

    EDITOR'S NOTE: 2015 news article on people planting redwoods and metasequoia on Canada's Cortes Island in northern Puget Sound: "Prehistoric trees may help a B.C. forest fight climate change": Kellhammer is raising redwoods, among other species, on Cortes to see how they'll adapt to the warmer future predicted from climate change. "What we're imagining is that trees that are now happier further south will actually be happier further north as anthropogenic climate change speeds up," Kellhammer says. Some of Kellhammer's decade-old Metasequoias, for example, reach over 10 metres in height.

    "Giant redwood trees planted in Cornwall to make forest - by Christian Nordquist, 16 March 2016. Excerpt: "Forty giant coast redwood trees from California have been planted on Monday at the Eden Project in Cornwall, southwest England. It is the first time this species has been planted in Europe. As the saplings grow, they will form an avenue of goliaths along the main entrance road to Eden. Eden's group of twenty-seven apprentices helped plant the trees, together with Eden's horticulture team, forty children from the local Lanlivery CP School, and Eden's co-founder Sir Tim Smit. The first sapling to be planted was a clone of the Fieldbrook Stump, the remains of a well-known redwood from northern California that was felled in 1890, when it was approximately 3,500 years old. The children made a 109-foot circle — the circumference of a fully grown redwood — on the day the saplings were planted."

  • "Giant sequoias outside their natural range" - website, Monumental Trees, posts extensive lists (by continent) of where sequoias have been planted and are thriving. It begins:
    Shortly after its discovery during the gold rush in the middle of the 19th century, the giant sequoia (Sequoiadendron giganteum) was planted extensively outside its natural range, especially in Europe. The success of its introduction depends very much of the resemblance of the region's climate to that up in the Californian mountains. The tree grows very well in the wetter parts of Europe like the U.K., and certain parts of Canada, Australia, and New Zealand, while it does not grow very well in the eastern part of the US or not at all in the tropics or cold areas like the northern parts of Scandinavia or Russia. Trees can withstand temperatures of -25 degrees F (-31 degrees C) or colder, for short periods of time providing the ground around the roots is insulated with either heavy snow or mulch. Outside its natural range, its foliage suffers from damaging windburn. The tree does not appreciate too arid soils or humid, hot summers.
        Giant sequoias are very successful in the Pacific Northwest from western Oregon north to southwest British Columbia, with fast growth rates. In Washington (Seattle area) and Oregon, it is common to find giant sequoias that have been successfully planted in both urban and rural areas.. In the northeastern USA there has been some limited success in growing the species, but growth is much slower there, and it is prone to fungal diseases due to the hot, humid summer climate there. Specimen examples grow in arboretums in Pennsylvania and Rhode Island.

    Biggest Sequoia Trees in Washington State

    See GiantSequoia.com - Washington State for photos + list

    Editor's Note: a 2016 article in The Guardians, "Amid California's historic drought, ancient sequoias show signs of stress", includes these clips:

    Worst off are the forests south of the Sierra Nevada, almost all of which are "in huge trouble," according to Asner. He's mapped significant mortality in the low and mid-elevation forests in the Sierras, and found evidence of widespread stress in northern California as well, though it's less extreme than in the south. The least stressed forests are near the Oregon border and at high altitudes in the Sierras. . . His findings, as well as the results from Stephenson's ground surveys, will be used to calibrate Asner's data. Collectively, they'll piece together a picture of the sequoias' health that will be unprecedented for land managers here.
        Dropping leaves is a water conservation strategy, and it might help a sequoia maintain a good water supply to the foliage that remains. "It's not a desirable thing for a tree to have to lose up to half of its foliage," Ambrose says, "but it is an indication that they do have mechanisms to deal with severe drought." The team will also look for spatial patterns in the die-back and try to explain why certain areas are more sensitive than others. That would help park managers prioritize efforts to protect sequoias when the drought lifts. They could use prescribed fire to thin certain parts of the forest and reduce competition for water, for instance.
        . . . Sequoias are resilient, and this isn't the first drought the ancient trees have endured. But it is a different kind of drought because temperatures are warmer. Heat intensifies drought by robbing plants and soils of additional moisture. And already, Stephenson says, "it seems to have put extra stress on sequoias." After noticing the die-back last fall, Stephenson searched park records for mention of similar foliage loss during the droughts of the 1920s and 30s, which impacted California as well as the Great Plains. "During the Dust Bowl period, they did see a lot of pines dying," Stephenson says. "But not a whisper of anything going on with the sequoias. We couldn't find any reference to anything like this being seen in the past."
    Editor's Note: Autumn 2016 the University of Washington's new transdisciplinary Center for Creative Conservation invited preliminary proposals from individuals and organizations beyond the university for projects that would engage in "mutual learning, risk-taking, and action on pressing conservation needs." Inspired by the sheer number and vibrancy of California-native sequoias and redwoods she encountered as landscape plantings in the Pacific Northwest (some naturalizing into nearby forests), Torreya Guardians founder Connie Barlow submitted a proposal (2 pages in pdf): "Redwood and Sequoia Inventory for Puget Sound Region".

  • "California tree die-off rate increases 114 percent in a year" - Nov 2016 news report. EXCERPT: "This is disturbing and downright scary," said Tim Krantz, a professor of environmental studies at the University of Redlands. "This has huge ramifications, not just for plants and animals, but for all of us in California," he said. These massive forest die-offs, followed by devastating wildfires, will clear away the regulator and moderator of rainwater, he said. Without trees and other vegetation, when rain does fall, it will not be effectively held so it can trickle into groundwater. It will just wash away, Krantz said. Climate change is happening so fast, he said, that plants won't have time to adjust. "Baja California is moving our way," he said. The majority of the 102 million dead trees are located in 10 counties in the southern and central Sierra Nevada region. The Forest Service also identified increasing mortality in the northern part of the state, including Siskiyou, Modoc, Plumas and Lassen counties. As the state enters the sixth year of drought, water-starved trees have lost their ability to fight off bark beetles and disease, Barrows said. This is compounded by the rapid warming of winter temperatures, caused by global warming, which would turn the winter season into a continuation of the bark beetles' breeding season, he said.

  • ARIZONA CYPRESS Cupressus arizonica glabra, currently south of the Grand Canyon, needs to leap the Grand Canyon by 2030 - Warwell, Rehfeldt, and Crookston 2012 conclude: "In response to global warming under the IS92a scenario, the realized climatic niche space of Arizona smooth cypress should shift about 200 to 350 km northwest of its contemporary location (Figures 3B, 3C, 3D). The area occupied should increase by about 1.5 and 2 times its contemporary size in decades 2030 and 2060, respectively (Table 4). In decade 2090, the area decreases to 1.2 times the contemporary size as the distribution shifts to northern Nevada and southwestern Colorado. In all three future decades, the contemporary realized climatic niche space is expected to be prominent in valleys where the Arizona, Nevada, and Utah borders meet. This includes the Virgin Mountains in Nevada, an area where naturalized populations of the subspecies have been observed (Charlet 1996)."
        Meanwhile the subspecies currently east of Bakersfield CA will no longer survive in its current habitat by 2060: "By decade 2030, the Paiute cypress realized climatic niche space will lie outside its contemporary distribution. By 2060, the realized climatic niche space of this subspecies occurs exclusively in Oregon."
        Note: The importance of maintaining the genetic diversity within the Arizona Cypress complex during climate change is grounded in this 1997 background document: "Quantitative Analyses of the Genetic Structure of Closely Related Conifers with Disparate Distributions and Demographics: The Cupressus Arizonica Complex", by Gerald E. Rehfeldt. He concludes that: "perpetuation undoubtedly will require human intervention, particularly in the face of rapid climate shifts (see Wigley and Raper, 1992). The two primary human roles most likely will be to assist migration by maintaining the appropriate habitat and providing the genotypes appropriate to those habitats."

  • TECATE CYPRESS (formerly Cupressus forbesii Jeps., currently Hesperocyparis forbesii (Jeps.) Bartel or Callitropsis forbesii (Jeps.) D.P. Little). A 2012 paper in Global Change Biology employs species-distribution and bioclimatic-envelope modelling of this endangered, endemic species of southern-most, coastal California to delineate the importance of considering how climate change might threaten a species physiologically but also amplified by increasing fire frequency. "Evaluation of assisted colonization strategies under global change for a rare, fire-dependent plant", by Helen M. Regan et al.:
    EXCERPTS: Tecate cypress is representative of a common functional group of plants found in most Mediterranean ecosystems: long-lived obligate seeders. It is an ideal case study because it is rare and highly threatened, it occurs in a landscape fragmented by urban growth and other land-use changes, its life history cycle is dependent on fire regime which is also expected to change with climate change, it is a poor disperser and large reductions in its populations are likely, deeming global extinction in the next century possible in the absence of intervention... Reproduction occurs almost entirely through the seed released from canopy-stored cones during fires that simultaneously kill all adult trees.
         Discussion: In view of the fact that many managers are already considering implementation of assisted colonization programs, there is a clear need for research that evaluates the potential success and the uncertainties of these strategies (McLachlan et al., 2007; Ricciardi & Simberloff, 2009). An important result of our study, therefore, is that any evaluation of assisted colonization needs to account for the fact that impacts of climate change are unlikely to occur in isolation; and thus a research framework is needed that considers assisted colonization in light of the impacts of interacting threats. In particular, our results show that for a long-lived Mediterranean obligate seeder, implementing assisted colonization to mitigate the effects of distribution shifts or contractions due to climate change will be useless if the prevailing threat of frequent fire is not moderated... Hence, future management must consider what can be done to protect Tecate cypress stands, whether translocated or natural, from experiencing damaging fires at short intervals... Although our results show a dramatic effect of fire frequency on Tecate cypress persistence, it is possible that small subpopulations may continue to persist in isolated areas, or fire refugia, which remain unburned even though surrounding areas burn with high frequency... We echo the caution expounded in McLachlan et al. (2007) that common garden experiments should be considered to garner insights about potential competition in recipient and donor patches.


  • WHITE PINE IN EASTERN NORTH AMERICA - "Climatic niche, ecological genetics, and impact of climate change on eastern white pine (Pinus strobus): Guidelines for land managers", by Dennis G. Joyce and Gerald E. Rehfeldt, 2013, Forest Ecology and Management.
    EXCERPT: "The Intergovernmental Panel on Climate Change has presented unequivocal evidence that the climate is changing (IPCC, 2007). Over the last 30 years, the mean global temperature has increased by 0.6 degrees C. During this same time period, isotherms marking the average annual temperature have moved pole-ward about 160 km, and the inertia of the global climate system ensures an additional warming of 0.4 degrees C over the next two decades (IPCC, 2007). If greenhouse gas emissions continue at the current business-as-usual rates, the speed of isotherm movement will at least double in the latter half of the current century (Hansen, 2009)
        Over the 21st century, the magnitude of climate shifts is expected to exceed the ecological amplitude of many tree species, eventually leading to extirpation over substantial portions of contemporary ranges (Barns, 2009; Iverson et al., 2008; Kirschbaum and Fischlin, 1996).
        Especially at middle to northern latitudes, persistence of tree species is projected to be contingent, in large part, on colonizing emergent suitable habitat beyond the northern limits of contemporary distributions (Williamson et al., 2009). But, post-glacial migration rates of North American tree species (McLachlan and Clark, 2004; McLachlan et al., 2007) are a small fraction (less than 2%) of the rate climate gradients are shifting (Hansen, 2009). A seed-dispersal simulation model applied to five species of trees native to the eastern United States indicated that there is only a small probability of colonization at distances beyond 20 km (Iverson et al., 2008).
        The conclusion drawn by many authors is that many North American tree species will experience range contraction at the trailing southern edges with little prospect of effective stochastic range expansion to the north (Barns, 2009; Iverson and Prasad, 1998; Iverson et al., 2008; Keenan et al., 2011; Ledig et al., 2010; Rehfeldt, 2004; Rehfeldt and Jaquish, 2010; Thomas, 2004; Thuiller, 2003). In the face of these conclusions, forest managers are challenged to choose the most appropriate management options for maintaining and enhancing productive forests. Preparing to mitigate adaptational and dispersal lags through assisted redistribution of native tree species is fundamental component of this challenge (Ledig et al., 2010). While the challenge is clear, the task is daunting.
        Eastern white pine is one of the most commercially valuable trees in eastern North America. It is most abundant in a broad latitudinal band extending from northwest Ontario, Minnesota and Wisconsin eastward to the New England states and the Maritime Provinces (Iverson et al., 2008). The natural range also extends southward primarily along the Appalachian Mountains reaching its southern limits in Georgia. It occurs on nearly all soils within its range, but is most competitive on well drained sandy soils of low to medium site quality (Wendel and Smith, 1990).
        The entire southern half of the contemporary spatial and genetic distribution of P. strobus is projected to be extirpated by mid-century as habitat deteriorates. Where habitat remains suitable, the cumulative stresses of increasing maladaptation of endemic climatypes elevates both acute and chronic population susceptibility to insect and disease attack, and will likely lead to ineffective seed production. Under these projections, multiple-generation persistence of populations in the contemporary distribution will be the exception. And, projecting the emergence of suitable habitat in the future does not imply occupancy. Indeed, projected geographic shifts for P. strobus are at least two orders of magnitude greater than estimates of post-glacial dispersal rates in trees (McLachlan and Clark, 2004; McLachlan et al., 2007). The effectiveness of stochastic colonization is dubious, but extensive population decline and extirpation in the contemporary distribution is inevitable.
        Silviculture programs of the twenty first century are faced with the daunting tasks of conserving the existing resource in the short term by mitigating the elevated stress associated with climate warming and focusing reforestation on a redistribution of species and genotypes to the appropriate array of climates. (Rehfeldt et al., 2006). . . As the climate changes, populations such as the Virginia provenance may be suitable for transfer into Ontario to address adaptation concerns.
        The consistency of the projected redistribution for both the climate and ecological genetic profiles places Pinus strobus on a growing list of temperate and boreal tree species that appear to be poorly equipped to persist in their contemporary distribution as the climate warms. The magnitude and speed of climate change is projected to lead to widespread range recession; preclude requisite adaptation of populations in situ; and exceed the capacity of marginal populations to colonize increasingly disjunct emergent suitable habitat. It seems clear that maintaining optimal growth and productivity of P. strobus as the climate warms will require substantial artificial reforestation efforts focussed on matching climatypes to suitable habitat.


  • WHITEBARK PINE - an excellent review paper (2015) also provides citations to the key previous papers on this keystone species of the mountains of western North America: "Assisted Migration and Latitudinal Limitations of Whitebark Pine", by Jesse Wood, 2015. Arbutus Review.
    ABSTRACT: Whitebark pine, a high alpine tree species, is limited up to 55 degrees N despite uncolonized suitable habitat that exists in Northern British Columbia. It is unclear what limits its northward distribution. Whitebark pine is dependent upon a bird species, Clark's nutcracker, for its seed dispersal, therefore, the bird's limitations must be examined. As optimal seed caching sites are located in recently burned sites, this paper hypothesizes that the fire regime in northern forests is not conducive for the creation of these sites. Assisted migration projects must focus more attention to long-term regeneration by addressing the needs of Clark's nutcracker.

    EXCERPT: Assisted Migration: An Emerging Restoration Technique - Due to its unique high alpine range, slow reproductive maturation, and its poor competitive ability, whitebark pine is unlikely to become an invasive species if transplanted in an assisted migration project (McCaughey & Tomback, 2001; McLane & Aitken, 2012). As very few species, especially conifers, can endure the harsh high alpine conditions at which whitebark pine grows, it poses little threat to the native vegetation; rather, it creates microclimates more conducive for the colonization of other species (Tomback et al., 2001). Rather than create temporal guidelines based upon the species reproduction, Bower and Aitken (2008) suggest geographical and temperature guidelines for transporting seedlings: up to 1.9C in mean annual temperature of the coldest month in the northern region and 1.0C in the Rocky Mountain region. This translates to 505 kilometers northward in the northern region of the province and increased elevation of 320 meters in the Rocky Mountain region (Bower & Aitken, 2008). These guidelines increase the likelihood of seedling establishment and decrease the potential for cold-related injuries. Along with the seed transport temperature guidelines given above, Bower and Aitken (2008) recommend avoiding the transfer of seeds between mountain ranges and caution against exceeding the temperature guidelines as doing so may lead to maladaptation (traits that become more harmful than helpful). Translocating seeds from multiple locations may have adverse effects on the local population, reducing local adaptation, productivity, and health (Aitken & Whitlock, 2013). However, in the face of climate change, it could be beneficial to facilitate assisted migration of individuals to promote adaptation to the changing climate (Aitken & Whitlock, 2013). Mahalovich et al. (2006) found that each seed zone they examined had enough genetic diversity (having rust resistant and cold hardy seedlings) to facilitate breeding and restoration programs. Due to the high mortality rates caused by the White Pine Blister Rust, rust-resistant and cold hardy genotypes need to be identified and collected for migration following the temperature guidelines established by Bower and Aitken (2008).

  • WHITEBARK PINE (news articles and essays on conflict with 1964 Wilderness Act)
  • "Climate Change Creates Challenges For A Wilderness Pine Tree", by Devan Schwartz, 2014.

  • "Comments on the Quartz Mountain Whitebark Pine Planting Preliminary Environmental Assessment (EA) from Wilderness Watch".

  • "Whitebark Pine Restoration Project" (Scotchman Peaks Wilderness, Idaho), by Friends of Scotchman Peaks Wilderness, 2016.

  • "Handle with Care" by Emma Marris.

  • PINE TREES IN NEW JERSEY THREATENED BY NATIVE PINE BEETLE DUE TO WARMER WINTERS - "In New Jersey Pines, Trouble Arrives on Six Legs", 1 December 2013 report in New York Times. Excerpt: In an infestation that scientists say is almost certainly a consequence of global warming, the southern pine beetle is spreading through New Jersey's famous Pinelands. It tried to do so many times in the past, but bitterly cold winters would always kill it off. Now, scientists say, the winters are no longer cold enough. The tiny insect, firmly entrenched, has already killed tens of thousands of acres of pines, and it is marching northward. Scientists say it is a striking example of the way seemingly small climatic changes are disturbing the balance of nature. They see these changes as a warning of the costly impact that is likely to come with continued high emissions of greenhouse gases. The disturbances are also raising profound questions about how to respond. Old battles about whether to leave nature alone or to manage it are being rejoined as landscapes come under stress.

  • AMERICAN CHESTNUT - American Chestnut once was a dominant canopy tree of deciduous forests of the eastern USA. In early 20th century, an Asian blight killed virtually all individuals (though many keep regenerating from ancient rootstock, only to die back before maturation and seed production). "Bringing Back the American Chestnut Tree", by Blair Caldwell (journalist), 22 November 2015, Upper Michigan's Source, reports on the planting of American Chestnut and backcrossed Asian-American Chestnut in the upper peninsula of Michigan. Excerpt:
    Around 50 people came together Sunday to see this American Chestnut tree take its place in Houghton. The tree is known for its sweet and protein-filled nuts and grows to be around 100 feet tall and about five feet in diameter.
         "Its native range is in Appalachia, so southeastern USA," said Karena Schmidt, lab manager of the greenhouse and soil lab in the School of Forestry at Michigan Tech. "But with our climate changing a bit, this tree has every potential to actually do well and be a part of our forest canopy here, and so we are participating in something called assisted migration."
         The American Chestnut was once plentiful until chestnut blight was introduced to the species. In a nutshell, it cut off the tree's water supply. Michigan Tech's School of Forestry has worked hard to ensure their newly planted chestnuts have the chance to mature. "We're also including in these plantings a few individuals that have been crossed with Chinese chestnut, which is resistant and then backcrossed to American Chestnut so that they only have about a 16th of a genetic constitution of the Chinese tree," said Terry Sharik, Dean in the School of Forest Resources and Environmental Science at MTU.


  • MAGNOLIA species

      
  • "Magnolia grandiflora L. Range Expansion: A Case Study in a North Carolina Piedmont Forest, by Jennifer A. Gruhn and Peter S. White, 2011, Southeastern Naturalist, offers a useful analogy for how Florida Torreya can be viewed as becoming "naturalized" to North Carolina — evident in the grove of elder planted trees in Highlands, North Carolina having naturally given rise to seedlings and saplings in its forested vicinity.

    While unintentional, the natural dispersal and establishment of Southern Magnolia beyond its planting in the arboretum at Chapel Hill, is a fine example of poleward "assisted migration" of a southerly native species in this time of rapid climate change.

  • "Horticultural escape and naturalization of Magnolia tripetala in western Massachusetts: Biogeographic context and possible relationship to recent climate change", by Jesse Bellemare and Claudia Deeg, 2015, Rhodora.
    EXCERPTS: During the 2014 field season, eight new locations of Magnolia tripetala escape from horticulture and naturalization were documented in Franklin and Hampshire counties in the Connecticut River Valley region of western Massachusetts. These records constitute a substantial expansion of the documented adventive occurrence of M. tripetala in western Massachusetts, where only four locations had previously been reported. In addition, although most earlier reports of adventive occurrences of M. tripetala in New England have constituted only single, isolated individuals, and the species has been described as occurring mostly at forest edges and in thickets, the new locations reported here include five sites with substantial, multi-individual populations of M. tripetala spreading into mature, intact forest vegetation. Based on herbarium records and our consultation with regional botanists, it appears that only four other locations with substantial naturalization by M. tripetala populations have been documented for New England in recent decades. Taken together, these records suggest M. tripetala may become a more common exotic tree species in the region in coming years.
         . . . Of particular note, five of the eight new Magnolia tripetala records in Franklin and Hampshire counties represent sites with vigorous naturalized populations, including numerous seedlings, saplings, and reproductively active trees established in intact forest vegetation. . . It is also notable that the new Magnolia tripetala naturalization sites reported here for western Massachusetts occurred across a broad range of forest types and environmental settings. For example, two naturalization sites in Amherst were situated in wet, Acer rubrum-dominated woods, whereas the site in South Hadley occurred on a steep, conifer-dominated slope under Tsuga canadensis and Pinus strobus. In Easthampton, M. tripetala was naturalizing in a post-agricultural Pinus strobus stand, whereas the naturalized population in Deerfield occurred in the understory of a forest dominated by Acer saccharum. These locations showed evidence of on-site reproduction and seedling establishment even under relatively closed canopy conditions — characteristics that will likely facilitate further spread of this species into intact forest habitats in the region. The ecological breadth evident among the sites also suggests that the niche requirements of M. tripetala may be broadly met in forested habitats in the region. That being said, limited seed dispersal appears to have allowed only localized spread to date, mostly in the vicinity of reproductively active horticultural trees (e.g., within 10s to a few 100 meters), rather than scattered widely across the landscape.


    Umbrella magnolia (wild) in northeast Alabama. (photo by C. Barlow)
       . . . Consistent with local evidence of dispersal limitation, it is noteworthy that the native range of Magnolia tripetala is entirely restricted to areas south of the formerly glaciated portions of the eastern US. This type of distribution pattern is quite common among many small-ranged forest plant species and is suggestive of large-scale dispersal limitation (Bellemare and Moeller 2014). Despite its more southerly native distribution, M. tripetala performs quite vigorously in horticulture in the northeastern US, approx. 300 to 400 km beyond its native range-edge in Pennsylvania (Cullina 2002). Indeed, the escape and naturalization of M. tripetala in the region might be viewed as evidence that its fundamental niche requirements are met in New England, even though it is not native to the region (Sax et al. 2013).

    . . . The pattern of relatively synchronous escape and establishment of this southern tree species in the last 20 to 30 years seems most consistent with a link to recent climatic warming in the northeastern US. . . Investigation by Greller et al. (2011) of Magnolia spp. naturalizations on Long Island, NY, has also suggested that climate warming in the past two decades has been a key factor related to the recent establishment and spread of M. acuminata, M. macrophylla, and M. tripetala in that region.
         . . . Research on the escape and naturalization of Magnolia tripetala and other plant species that are native to the US, but exotic in New England, is continuing at Smith College, and the corresponding author would appreciate hearing of any new field observations.

    EDITOR'S NOTE: An excellent journalistic article featuring this Bellemare and Deeg 2015 paper on Umbrella Magnolia was published April 2016 online in Yale Environment 360 and also in Resilience. Written by Janet Marinelli, "As World Warms, How Do We Decide When a Plant is Native?, ends with this paragraph:

    "While scientists grapple with the implications of escaped magnolias, there is poetic justice that a plant from the Dickinson homestead has sparked the discussion. Although the view of enduring wilderness championed by Thoreau and John Muir came to dominate conservation thinking, Emily Dickinson, who perceived the beauty and destructive capacity of nature all around her, may be the more appropriate literary icon for an age of climate disruption."


      LEFT: One of several images from "Recent declines of Populus tremuloides in North America linked to climate", 2013, James. J. Worrall et al., Forest Ecology and Management.

    Excerpts: "Because early, warm springs can advance phenology, climate change is expected to increase the exposure of trees to damage by spring frost. Indeed, aspen phenology in Alberta has advanced 2 weeks over the last 70 years, and exposure to spring frost has consequently increased. Thus, the large and damaging events in Arizona in 1999 and Utah in 2007 may become more common. Cycles of thawing and freezing during winter dormancy can injure plants in a variety of ways, generally referred to as winter injury. Warm periods deharden buds, twigs, cambium, sapwood, or roots, leaving them vulnerable to freezing temperatures that follow. Thaw-freeze cycles also cause winter cavitation of xylem vessels, to which aspen is relatively susceptible. Like spring frost, incidence of thaw-freeze events will likely increase with climate warming."

  • "ASPEN, Climate, and Sudden Decline in Western USA", G.E. Rehfeldt et al., 2009, Forest Ecology and Management.

  • "Assisted migration to address climate change: recommendations for aspen reforestation in western Canada", Laura K. Gray et al., 2011, Ecological Applications 21:1591-603
    EXCERPTS: "We find it useful to differentiate the movement of species far outside their range for conservation purposes (assisted colonization), and population movement within a species range or somewhat beyond the leading edge (assisted migration). Under this definition, assisted migration would usually apply to common and widespread species for the purpose of maintaining ecosystem health and productivity, whereas assisted colonization aims at conserving endemic or range-restricted species. Although there are exceptions, this definition largely reflects previous usage of terminology in conservation biology (e.g., Hunter 2007, Hoegh-Guldberg et al. 2008, Ricciardi and Simberloff 2009) and forest resource management (e.g., Millar et al. 2007, O'Neill et al. 2008b, McKenney et al. 2009). For both assisted migration and assisted colonization, the contentious issue is the risk of unintended consequences associated with large-scale management interventions as well as a lack of rigorous scientific knowledge to guide the movement of species or genotypes. While predictive habitat modeling and observed biological impacts suggest an obvious general need for assisted migration (e.g., Parks and Bernier 2010 and associated conference papers), we usually do not know if this need applies to a particular population of a species, and where exactly appropriate target habitat would be under uncertain future climates.
        "Our view is that assisted migration of common species is a promising and effective climate change adaptation strategy with good chances of successful implementation. First, movement of planting stock is already a well-established management practice in reforestation programs, although the current principle of seed transfer is to limit the distance of seed movement to ensure that reforestation stock is well adapted to planting environments (Ying and Yanchuk 2006). Second, there is a substantial body of research on how populations of commercially important tree species are adapted to local environments (Morgenstern 1996), and we can further draw on existing programs for commercial forestry species that monitor forest growth and health to determine the need for assisted migration (Parks and Bernier 2010). Third, robust predictive habitat models to reliably guide assisted migration are far easier to develop for common species than for rare endemics that lack census data for model parameterization (Kadmon et al. 2003). Fourth, most common tree species have a high degree of within-population genetic variation in addition to substantial environmental plasticity (Hamrick 2004). Slightly missing the optimal habitat of a planting stock in an assisted migration program is therefore unlikely to have serious consequences. Lastly, implementing assisted migration at a large scale requires little or no additional financial resources when put into operation through existing reforestation programs.
         In a case study for aspen in western Canada, we develop a framework to guide assisted migration that draws on reciprocal transplant experiments to detect adaptational lag of populations, remote sensing to identify populations that are potentially vulnerable to climate change, and predictive habitat modeling to target assisted migration efforts both in terms of species choice and at the level of locally adapted populations within a species. Our intention is to develop more dependable guidelines for assisted migration by synthesizing information from a variety of data sources and by drawing on independent modeling, experimental, and empirical research approaches.
         "A measure of observed climate change was calculated as the difference between the 1961-1990 climate normal and the 1997-2006 decadal average, which corresponds to the period when trees were grown in the reciprocal transplant experiment Climate projections for the sample sites for the 2020s, 2050s, and 2080s were generated by overlaying projections from general circulation models expressed as difference from the 1961-1990 normal period.&nbdp;. . Although accounting for within-species genetic structure in bioclimate envelope modeling has previously been proposed (e.g., Botkin et al. 2007), to our knowledge this is the first study that implements this idea. A final practical advantage is that the ecosystem modeling units are also the framework for current natural resource management prescriptions, and model projections can therefore be directly linked to a set of applicable management practices under anticipated future climates.
         "The average climate during the decade 1997-2006 when trees of the reciprocal transplant experiment were grown in the field is substantially warmer and drier than the 1961-1990 reference period. Temperature increases were more pronounced in the north than in the south, with more warming in winter than in summer temperatures. Observed temperature trends approximately correspond to patterns described in the IPCC fourth assessment report (IPCC 2007) and also match regional climate change projections by general circulation models for the 2020s in direction and magnitude. In contrast, observed precipitation trends are opposite in direction to projections by most general circulation models. The trend toward drier climate conditions was more pronounced in winter, and together with warmer winter temperatures have resulted in major reductions in precipitation as snow.
         "Aspen is currently most frequent in the Northern Boreal zone and the western portion of the Boreal Plains of Alberta. The majority of model runs, however, project a complete loss of habitat for aspen over much of this area. In contrast, the Foothills and the Taiga Plains are projected to maintain aspen habitat. Also, moderately high aspen frequencies and low probability of habitat loss are expected along a band across the Boreal Plains that originates in the Rocky Mountain Foothills and crosses Alberta in a northeast direction. Interestingly, projected habitat shifts for the 1997-2006 decadal average approach model projections for the 2020s quite closely. Notably, aspen appears to have already lost climatically suitable habitat along the southern fringe of its distribution .
         "Adaptational lag refers to a mismatch of genotypes and environments, caused by a relatively fast environmental change and a comparably slow evolutionary response (Matyas 1990). Adaptational lag is not uncommon, and is in fact part of any evolutionary change through directional natural selection. Even if adaptational lag does not pose a threat to a species' overall survival, it is a concern for forest management because it can result in suboptimal growth, poor forest health, and high rates of tree mortality. Even though these impacts could be viewed as a natural part of evolutionary change, proactive climate change adaptation strategies should aim at maximizing forest health and productivity through intervention.
         Although reciprocal transplant experiments can theoretically be used to determine optimal transfer distances for seed sources (Wang et al. 2006b, O'Neill et al. 2008a), we propose that bioclimate model projections are a better and safer approach to make such inferences. Bioclimate envelope models have many limitations that have been thoroughly discussed (e.g., Hampe 2004, Araujo and Guisan 2006, Botkin et al. 2007). However, many of these limitations do not apply in a reforestation context. For example, management practices can 'migrate' as rapidly as bioclimate envelope model results suggest. Also, competition and species interactions are usually controlled through spacing of plantations and choice of planting stock. Perhaps most importantly, the limitation that bioclimate envelope models project the realized niche and not the fundamental niche of tree species turns out to be an advantage in a reforestation context.
         "Another disadvantage of using data describing the fundamental niche of tree populations from common garden trials has been mentioned before. Long-term evolutionary fitness is not necessarily reflected by growth measured in short-term common garden trials. In contrast, the realized niche inferred from distribution data should be a reasonable approximation of environmental conditions under which a species (or populations of a species) are competitive in the long term. . . In Table 4 we list the most appropriate climatic regions where seed should be obtained for reforestation.
         Nevertheless, from an applied perspective, the combined information from GCM projections, climate trends that have apparently materialized, and observed biological response make a strong case for implementing adaptation strategies in the southern fringe of the Boreal Plains, and the Dry Mixedwoods of the Northern Boreal region. Reforestation programs should rely on more drought-tolerant species or genotypes in the future, and aspen forestry should concentrate on the moister and more northern ecosystems.
         "Does this suggest that we should develop relatively 'short-sighted' adaptation strategies, i.e., focus on the 2020s projection and dismiss longer-term projections as too uncertain for practical resource management? We think the answer to this question is 'Yes.' Despite consideration of their long lifetime, it is important to realize that the most vulnerable phase of trees remains their seedling and sapling stage. In a changing environment, we should not focus on optimizing planting stock for maximum growth during mid-rotation, when this means that seedlings planted today will not survive because climate conditions predicted for the 2050s have yet to materialize. The high degree of uncertainty in longer-term climate projections is an additional argument to develop adaptation strategies for the immediate future with a 10-20 year planning horizon.
         "To end on a positive note, we also would like to point out that for northern regions, climate change may be associated with opportunities as much as challenges to forest resource management. Results from the reciprocal transplant experiment suggest that major gains in productivity could be achieved by matching genotypes to new environmental conditions through assisted migration, arguably exceeding projected gains from current genetic tree improvement programs.

  • "Past and ongoing shifts in Joshua tree distribution support future modeled range contraction" by Kenneth L. Cole et al., Ecological Applications, 2011.
       EXCERPT: The future distribution of the Joshua tree (Yucca brevifolia) is projected by combining a geostatistical analysis of 20th-century climates over its current range, future modeled climates, and paleoecological data showing its response to a past similar climate change. As climate rapidly warmed 11,700 years ago, the range of Joshua tree contracted, leaving only the populations near what had been its northernmost limit. Its ability to spread northward into new suitable habitats after this time may have been inhibited by the somewhat earlier extinction of megafaunal dispersers, especially the Shasta ground sloth. All of the models project the future elimination of Joshua tree throughout most of the southern portions of its current range. Although estimates of future monthly precipitation differ between the models, these changes are outweighed by large increases in temperature common to all the models. Only a few populations within the current range are predicted to be sustainable. Several models project significant potential future expansion into new areas beyond the current range, but the species' historical and current rates of dispersal would seem to prevent natural expansion into these new areas. Several areas are predicted to be potential sites for relocation and assisted migration.

     The Joshua tree example used here does have an added complication in that its migrational capacity to respond to changing climates seems to be extremely limited. There are no historical records of Joshua tree invasions into new habitat and even few documented instances of recent seedling establishment. Although the rapidly warming climate of the early Holocene (Steffensen et al. 2008, Cole 2010) would seem to have opened up vast new areas of potential range to the north, the fossil record does not record any significant northward expansion over the last 11,700 years. These facts coalesce with morphological observations of the plant's indehiscent fruits and the abundance of fruits and seeds in fossil ground sloth dung to support the concept that the species' current mobility is constrained by the earlier extinction of the Shasta ground sloth and other possible seed vector(s) (Janzen and Martin 1982, Lenz 2001).
         Although it is likely that some of these un-sampled areas with high levels of future climate potential, such as Nellis Air Force Base, are already occupied by Joshua tree, they could serve an important conservation function in the future. But other areas further from the current range in central Nevada, northwestern Arizona, and southwestern Utah could hold high potential for future relocation efforts, should such activities prove desirable and possible. Managed relocation, also known as assisted migration or assisted colonization, has become a controversial topic for conservation (Hoegh-Guldberg et al. 2008). Fortunately for Joshua tree, a majority of the areas predicted to be sustainable, within migrational range, or potential assisted migration sites, are already on federal lands or other protected areas.

    See also USGS press release: "Uncertain Future for Joshua Trees Projected with Climate Change".

    A superb 2013 photo-essay including staff interviews at Joshua Tree National Park is "Preventing a Joshua Treeless National Park". See also "Park Not Suitable for Joshua Trees" by James W. Cornett in The Desert Sun 24 September 2015. Cornett summarizes 20 years of observations of a Joshua Tree population in Death Valley National Park, which is thriving. In contrast to the struggling trees in Joshua Tree National Park, the study site records a northern population in a landscape in which the combination of high elevation and flat absorptive surface provisions this yucca with cooler temperatures and more opportunity for desert rain to sink into the soil. See also a 2015 National Geographic article, "Climate Change Threatens an Iconic Desert Tree".

    Finally, a 2006 paper by Rehfeldt et al. provides the technical empirical and modeling background to the Tree Atlas interactive tool offered by USFS online: "Empirical Analyses for Plant-Climate Relationships in the Western United States". In it, the 2030, 2060, 2090 maps of species future range shifts (owing to climate change forecasts) are depicted for more than a dozen species. One such species is the Saguaro cactus (Carnegiea gigantic), signature "tree" of the Sonoran Desert. What one sees is that, by 2090, the livable habitat for the Saguaro will likely shift entirely northward of its current range — completely overlapping the northern-most range of where the Joshua Tree (Yucca brevifolia) is found today. If so, then where should Joshua Tree be helped in migrating to? See image below:

  • "Joshua Trees Nearly Wiped Out by 2100?" by Jessica Marshal, 25 March 2011, Discovery News.
    "Ken Cole of the U.S. Geological Survey in Flagstaff, Ariz., and an interdisciplinary group of colleagues used information about the current distribution of Joshua trees combined with climate models to predict where the trees may be by 2070 to 2099." Using Pleistocene evidence in extinct ground sloth dung, data on the lack of recent reproduction in Joshua Tree National Monument (California), this tall member of the Yucca plant type, becomes the "poster plant" for "assisted migration" in the American West. Joshua Tree National Monument was, as it turns out, created too close to the southern edge of the 20th-century range of Joshua Trees, and thus may be doomed to loss of its namesake plant. See also, "Joshua Trees Losing Ground, Fast".

  • "Ground Truthing" blog post by Chris Clarke, 17 January 2008
    Revisits a previous blog on the possible extinction of California's Joshua Tree, owing to an inability to disperse and thus track climate changes. In this blog, Clarke mentions the work of Torreya Guardians in assisting migration of a critically endangered tree in eastern North America.

  • "Outlook Bleak for Joshua Trees" NPR online article and "All Things Considered" audio, 4 February 2008
    Interview of scientists and managers working in Joshua Tree National Park; prospects for the extirpation of Joshua Trees in the park as climate changes; the role of extinct ground sloths in past seed dispersal of this tallest of all yuccas. Audio interview of a trip to a cave looking for sloth dung.


  • "Climate Change and Forests of the Future: Managing in the Face of Uncertainty,", by Constance I. Millar et al., Ecological Adaptations, 2007.
    EXCERPT: Establish 'neo-native' forests. Information from historical species ranges and responses to climate change can provide unique insight about species responses, ecological tolerances, and potential new habitats. Areas that supported species in the past under similar conditions to those projected for the future might be considered sites for 'neo-native' stands of the species. These may even be outside the current species range, in locations where the species would otherwise be considered exotic. For instance, Monterey pine (Pinus radiata), endangered throughout its small native range, has naturalized along the north coast of California distant from its present native distribution. Much of this area was paleohistorical range for the pine, extant during climate conditions that have been interpreted to be similar to expected futures in California. Using these locations for 'neo-native' conservation stands, rather than removing trees as undesired invasives, is an example of how management could accommodate climate change. (p. 2148)
  • "Relative vulnerability to climate change of trees in western North America" by Michael J. Case and Joshua J. Lawler, 2016, Climatic Change.
    EXCERPT: "Following disturbances, managers have a number of possible options, such as facilitating a change in species composition. This can be accomplished by identifying and planting more resilient genotypes of a species (e.g., a more drought tolerant genotype) or perhaps even planting a different species. Assisted colonization, also referred to as managed relocation or assisted migration, is becoming an increasingly accepted adaptation strategy in response to climate change (Lawler and Olden 2011). Some are already experimenting with assisted migration of tree species in some areas of North America (Schmidtling 2001, Erickson et al. 2012, Marris 2009), a trend that may increase in fragmented landscapes and with species that have limited dispersal abilities (Williams and Dumroese 2013). . . Climate change presents a particularly difficult challenge for natural resource managers who will need to make decisions about which species should receive the benefits of limited funding. Vulnerability assessments, such as the one demonstrated here, are one of the tools that resource managers have at their disposal to better prepare for this uncertain future. Our approach, of quantifying inherent sensitivity, projected climatic changes, and adaptive capacity can facilitate, not only the identification of species that are relatively more vulnerable, but it can also identify the key aspects of vulnerability, which if addressed, could promote resilience in the face of climate change."
  • "The Tree Coroners": To Save the West's Forests, Scientists Must First Learn How Trees Die" - in-depth article focusing on USA southwestern forest species stressed by heat and drought, by Cally Carswell, 9 December 2013, High Country News.

  • "Darcy's Law Predicts Widespread Forest Mortality Under Climate Warming" - by Nathan McDowell and Craig Allen, May 2015, Nature Climate Change. Excerpts: "Tall trees of old-growth forests are at the greatest risk of loss. . . Planting of southerly and low-elevation genotypes into more northerly or higher-elevation landscapes is another forward-looking adaptation approach to increase the resiliency of future forests to warming and extreme droughts."

  • "Seed dispersal in changing landscapes" by Kim R. McConkey et al., 2012, Biological Conservation
    EXCERPTS: There is evidence for a growing, global, seed dispersal crisis, which has so far been masked, by the long life-span of perennial plants. Plant populations that are neither being dispersed, nor regenerating in situ, may persist for decades in an apparently healthy state (Guimarčes et al., 2008). These 'living dead' are, at least for now, still living, so their rescue is low down on the long list of conservation priorities. At the same time, the role of 'assisted migration' — artificial dispersal — as a solution for expected future problems is being debated in the conservation literature without any clear understanding of the potential for unassisted migration (Hoegh-Guldberg et al., 2010; Sax et al., 2009; Vitt et al., 2010). It is apparent that improved communication between seed dispersal researchers and conservation practitioners could benefit both sides. Our aim here is to synthesize current understanding of the interactions between seed dispersal and the major drivers of global change in order to identify key gaps that require further research and to provide useful guidance to conservation practitioners. We start by reviewing existing knowledge and identifying knowledge gaps, and then follow this by suggestions for how our current understanding of seed dispersal processes can be incorporated into conservation planning and management. . . The speed of movement needed to track predicted temperature changes in the 21st century has a global mean of 1.69 km a year or 169 km per century (Chen et al., 2011), which is beyond the capacity of most long-lived woody plants as well as many plants of other life forms (Corlett, 2009; Nathan et al., 2011). Much faster movements will be required in the lowland tropics, where the temperature gradient is almost flat. In these cases, assisted migration may be the only option.

  • "How Fast Can Trees Migrate?" by Jacquelyn Gill, (blogpost) 8 May 2013
    Excellent overview with online links to the recent history, challenges, opportunities, and current issues on this question — especially drawing from the paleoecological literature focusing on pollen data.

  • "Forests Not Keeping Pace with Climate Change" by Zhu, Woodall, and Clark, Global Change Biology, November 2011
    EXCERPT of press release: The study found no consistent evidence that population spread is greatest in areas where climate has changed the most; nor do the species' response patterns appear to be related to seed size or dispersal characteristics. "Warm zones have shifted northward by up to 100 kilometers in some parts of the eastern United States, but our results do not inspire confidence that tree populations are tracking those changes," says Clark, who also holds appointments at Duke as a professor of biology and statistics. "This increases the risk of serious lags in tree migrations."

  • "Assisted migration could help plants find a new home" by Laura Nielsen (for Frontier Scientists blog in) Anchorage Daily News, 28 August 2013
    Excellent short overview of the current discussion on assisted migration, with some examples from northern plant biomes.

  • "Assessing the potential for urban trees to facilitate forest tree migration in the eastern United States" by C.W. Woodall et al., 2010, Forestry Ecology and Management - helpful charts showing large urban areas of northeastern USA that have tree species in plentiful plantings north of their native range (e.g., Sweet Gum (Liquidambar) planted in New York City is 2 degrees latitude farther north; Southern Live Oak and Water Oak planted in Boston are 8 degrees and 5 degrees, respectively, farther north). Caveat: Ability of those individuals to actively move seed into surrounding wild forests is low; thus suburban plantings and outward plantings by landscapers will be more important to facilitate assisted migration in pace with climate change.


    FORESTS OF MEXICO

     

    Mapped predictions of mean annual temperature (degree Celsius) for digitized elevations on a 1 km grid, for (a) contemporary climate and (b) 2090 climate, using output from the Canadian Center for Climate Modeling and Analysis model, scenario A2. Maps presented in Saenz-Romero et al., 2010, "Spline models of contemporary, 2030, 2060 and 2090 climates for Mexico and their use in understanding climate-change impacts on the vegetation, Climatic Change.

  • "Abies religiosa (Oyamel Fir) habitat prediction in climatic change scenarios and implications for MONARCH BUTTERFLY conservation in Mexico", 2012, Saenz-Romero et al., in Forest Ecology and Management CONCLUSION: "The predicted suitable climate niche for A. religiosa will diminish rapidly over the course of the century: a decrease of 69.2% by the decade surrounding 2030, 87.6% for that surrounding 2060, and 96.5% for 2090. To realign genotypes to the new locations of those climates for which they are adapted, the distribution of A. religiosa would need to shift upwards 300 m by 2030. The only feasible way for migration of this magnitude to be accomplished in such a short time is by the adoption of assisted management strategies. By the end of the century, suitable habitat for the monarch butterfly may no longer occur inside the Monarch Butterfly Biosphere Reserve. Research is needed on appropriate techniques for successfully transferring contemporary populations of A. religiosa to higher altitudes and poorer site conditions than those at which they currently exist. Research is also needed on whether monarch butterfly migrating populations would overwinter on A. religiosa transferred to new sites or on other species transferred to sites currently inhabited by A. religiosa."      

    DEC 2015 UPDATE: "To Protect Monarch Butterfly, A Plan to Save the Sacred Firs", by Janet Marinelli, Yale Environment 360, December 2015, reports that a small assisted migration project for moving Oyamel Fir upslope has already begun:

    EXCERPT: Mexican scientists are pinning their hopes on a plan to move the species progressively higher up local mountainsides in a race to save these firs and the butterflies that depend on them. "We have to act now," says the plan's architect, Cuauhtemoc Saenz-Romero, a forest geneticist at the Universidad Michoacana de San Nicolas de Hidalgo. "Later will be too late, because the trees will be dead or too weak to produce seeds in enough quantity for large reforestation programs." When the rainy season arrived last summer, a few hundred seedlings were planted at 11,286 feet, where habitat suited to oyamel fir trees is expected to be by 2030. . . Early studies determined that trees growing at a particular altitude are genetically different from populations at other elevations. Seed was collected along an altitudinal gradient to capture genetic diversity, and then germinated. The planting this past summer was designed to test which of 10 genetically distinct populations — a shift upwards of almost 1,500 feet in altitude for some of the seedlings — would fare best.

    As keynote speaker for the Nov 2015 Texas Butterfly Festival, Cuauhtemoc Saenz-Romero was quoted in the popular press:

    "'Conservation' can no longer mean we should look and not touch. Rather, we will have to consider unprecedented, perhaps unimaginable, interventions in order to save both the fir forest and the monarch. Since we cannot move the mountain, we have to move the forest. We call this assisted migration. In this case, we must attempt to relocate this micro-habitat to a higher elevation that currently lacks resources such as organic soil above 4,000 meters, but this is where the trees need to be — if they are to survive and sustain the monarchs that depend upon them."
         When asked who will undertake this enormous challenge, Romero says it will most likely be citizen conservationists. This is especially true for the Monarch, where citizens have organized to address deforestation, preserve habitat, plant milkweed and publicize the devastating effects of herbicides and pesticides. "Across Mexico and the United States, informed and interested citizens are provoking change more rapidly than government. It is truly remarkable! It is also very late. We now have climate with no contemporary analogues — nothing to which we may compare current ecological circumstances. For this reason conservationists, especially, must abandon the idea that Nature should be allowed to operate autonomously. Instead, we must do everything in our power to help her adapt, because there is no time for an evolutionary course correction."

  • NEWS REPORTS OF 2016 MONARCH BUTTERFLY FESTIVAL (in Mexico and San Antonio TX)
    "Butterfly Festival Emerges at Instituto Cultural de Mexico" - Oct 2016. News report in San Antonio paper includes quotes by key Mexican forester Cuauhtemoc Saenz-Romero, who "proposes a radical action to 'move the forest' up 300 meters in altitude by gathering the seeds of the Oyamel trees in Michoacan and engaging in a reforestation effort. 'We need to act now. If not, the forests (over time) will become like a savannah — just grassland,' he explained. 'I know it sounds radical but our models indicate this is what we have to do.'"

    "Experts: Climate Change Threatens Monarch Butterfly Migration" - Oct 2016. News report of the 2016 Monarch Butterfly conference, includes this quote by panelist Katharine Hayhoe: "Without a doubt, the butterflies can adapt if they have the time," Hayhoe added. "The question is if they can change within the time that they have to because of climate change. Some ask, 'Are we trying to interfere in nature?' The answer is yes, but we are already interfering. Taking action to help may be the only way that the Monarch migration survives in the time they have been given."



    Above figure in Considerations for restoring temperate forests of tomorrow: forest restoration,
    assisted migration, and bioengineering
    , by Dumroese et al. 2015.

  • "Altitudinal assisted migration of Mexican pines as an adaptation to climate change", by D. Castellanos-Acuna et al., 2015, Ecosphere.

       Three economically and ecologically important species of native pine were tested in common gardens in semi-wild forest upslope (southeast aspect) from their parent trees. The three species were Pinus devoniana, Pinus leiophylla, Pinus pseudostrobus.

    EXCERPTS: "It has been projected in Mexico that, by the decade centered on the year 2030, there will be an increase in mean annual temperature of 1.5 degrees C, and a decrease of 7% in precipitation. . . Since the year 2010, numerous individuals of these low-altitude populations have already exhibited signs of decay, apparently due to climate change related stresses; in sites with shallow soils and southern aspects, unusual dry season heatwaves have caused severe defoliation, accumulation of dead branches, and death in some individuals."
        "The results suggest that an assisted upwards migration of 300 m in altitude, in order to approach a realignment of the populations to the climate projected for the decade centered around the year 2030, appears to be a viable strategy with which to accommodate the effects of climate change."

  • THREE RARE, ENDEMIC SPRUCE IN MEXICO:
       The 3 spruce are Picea martinezii, Picea mexicana, Picea chihuahuana (along with Picea engelmannii in AZ and NM for comparison). "Projections of Suitable Habitat for Rare Species Under Global Warming Scenarios", by F. Thomas Ledig et al., 2010, American Journal of Botany.

    Conclusion: "The results are important for conservation of these species and are of general significance for conservation by assisted colonization. We conclude that our procedures for producing models and projecting the climate niches of Mexican spruces provide a way for handling other rare plants, which constitute the great bulk of the world's endangered and most vulnerable flora."

    Editor's summary notes, with quoted excerpts:

    1. BROAD IMPLICATIONS. This paper is not behind a paywall: it is highly recommended to all foresters, academic contributors to the assisted migration issue, and climate-vegetation modelers.

    2. CLIMATE MODELING. This is a very technical paper with excellent graphics. The methodology section is detailed. It demonstrates (a) the high utility/reliability of established modeling techniques for predicting species-specific habitat shifts owing to climate change and (b) the need for expedited action for tree species whose confined, disjunct populations identify them as Pleistocene relicts.
  • (Page 981) "The Random Forests algorithm of Breiman (2001) is of demonstrated robustness for predicting the contemporary realized climate niche from climatic variables (Iverson et al., 2005; Rehfeldt et al., 2006). Our contribution to statistical modeling with this algorithm has been to extend the approach to rare species by: (1) assuring that data recording the absence of a taxon in the training data set represent the full climatic range of locations where the species does not occur, (2) using a single model for multiple taxa, thereby increasing the amount of absence data incorporated into the training data for a single forest, and (3) using values of local importance to assure that critical variables were not inadvertently lost during stepwise elimination procedures. The result was a model of extraordinary fit."
  • (Page 970) "We conclude that our procedures for producing models and projecting the climate niches of Mexican spruces provide a way for handling other rare plants, which constitute the great bulk of the world's endangered and most vulnerable flora."
  • (Page 971) "We believe that the three species of Mexican spruce are emblematic of the challenges that Mexico will face in implementing management to prevent extinctions due to global warming."
  • (Page 971) "By separating the mitotypes of Chihuahua spruce, we make one of the first attempts to take intraspecific genetic variation into consideration when projecting future distribution of climate niches."
  • (Page 985) "The results illustrate some important considerations for conservation in general. One is that transient disappearance of habitat, as in Mexican spruce, may complicate conservation efforts. Although models may project suitable climate at some future time, in the shorter term, suitable habitat may be lacking. This implies that some species will need interim preservation in seed banks or botanic gardens to bridge the gap between contemporary and future habitat. Second, suitable habitat under a global warming scenario may not move northward. Although counterintuitive, suitable climate may appear southward, as in our projections for Martinez and Mexican spruces and the northern mitotype of Chihuahua spruce. Third, a species is not a uniform monolith, and it may be necessary to consider intraspecific genetic differences. Not all populations of a species will necessarily respond the same. Our example shows that the two mitotypes of Chihuahua spruce respond to climate change in contrasting ways; the range contracts southward for the northern mitotype and northward for the southern mitotype."
  • 3. PLEISTOCENE RELICT CONIFERS. Genus Picea, spruce, is a cold-climate, forest canopy species in high latitudes (especially boreal zones) or high elevations and cool ravines (montane). Not surprisingly, the three species of spruce in Mexico are found only as small, disjunct populations and are projected to be extremely vulnerable to climate change:
  • (Page 971) "All three species are considered endangered, are relicts of the last glaciation, and the only representatives of the largely boreal genus Picea to reach such southern latitudes in North America. Chihuahua spruce extends just south of the Tropic of Cancer (Ledig et al., 2000b). Chihuahua spruce and Martinez spruce grow in cool, temperate, montane forests. Chihuahua spruce, in particular, occurs mostly on sites exposed to direct sun for only brief periods of the day, usually in the bottom of arroyos or at the foot of barrancas at elevations between about 2100 m and 3000 m a.s.l. Martinez spruce is found between about 1800 m and 2500 m a.s.l. Mexican spruce is found in the subalpine zone on the tops of the highest peaks and ridges of northern Mexico, above 3100 m a.s.l."
  • (Page 971) "We conclude that the scattered stands of spruces in the Sierra Madre Occidental and Sierra Madre Oriental are relicts of the last glacial period and that Holocene warming resulted in the extinction of spruce in the Valley of Mexico and contraction of the range northward. In addition, the lower elevational range of Chihuahua spruce in the Sierra Madre Occidental contracted upward at least 510 m in elevation between 13000 yr BP and the present (Ortega- Rosas et al., 2008)."
  • 4. PRECIPITATION IS KEY VARIABLE. Habitat shifts arising from most of the climate projections used in this study turned not so much on projected warming but on projected shifts in precipitation.
  • (Page 979) "Variation is obscured when GCM projections are presented as a composite. While variation among the three GCMs for temperature variables was relatively slight, that for precipitation was large (Saenz-Romero et al., in press), and of the eight climate variables used as predictors, five were interactions involving precipitation."
  • 5. SITE-SPECIFIC FACTORS NOT MODELED. Implementation of modeling results requires awareness of additional site-specific factors not considered in the model:
  • (Page 971) "Chihuahua spruce and Martinez spruce grow in cool, temperate, montane forests. Chihuahua spruce, in particular, occurs mostly on sites exposed to direct sun for only brief periods of the day, usually in the bottom of arroyos or at the foot of barrancas at elevations between about 2100 m and 3000 m a.s.l. Martinez spruce is found between about 1800 m and 2500 m. Mexican spruce is found in the subalpine zone on the tops of the highest peaks and ridges of northern Mexico, above 3100 m a.s.l. (see Fig. 1 and detailed description in Ledig et al., 2000b)."
  • (Page 983) "The predicted suitable areas include more than the actual present distributions. This is common in models where suitable habitats are predicted based on climate alone. Many other factors may restrict where a species actually occurs, e.g., substrate, interactions with other species, or restrictions on seed dispersal (e.g., Pearson and Dawson, 2003; van Zonneveld et al., 2009). We believe that microsites, such as the bottom of shaded barrancas and arroyos for Chihuahua spruce and high elevation, summer fog, and winter snow for Mexican spruce, are necessary within the climatically suitable areas. Such microsites are much narrower than the habitat predicted in Figs. 2-5, because, in the case of Chihuahua spruce, the climate model is not yet capable of microtopographic projections, and in the case of Mexican spruce, three data points cannot possibly depict the extent of the suitable habitat. Yet, it is also true that species do not occur in all places ideally suited to them. In other words, a portion of the errors of commission are due to correctly predicting niche space that is, by chance, not occupied."
  • 6. COUNTERINTUITIVE: CLIMATE DRIVES SPRUCES SOUTH IN MEXICO. Because Mexico's tallest mountains (the big volcanos near Mexico City) are far to the south of the current range of spruce, it seems counter-intuitive that as climate change proceeds the spruce wink out in the north, while new habitat opens for them in the south (at exceedingly high elevations). Note: The model did not include landscapes north of the Mexico border, so it is possible that suitable habitat would appear in the USA or Canada.
  • (Page 970) "Contrary to intuition, habitat did not develop to the north for any of the Mexican taxa; rather, climate niches for two taxa re-materialized several hundred kilometers southward in the Trans-Mexican Volcanic Belt. The climate niche for a third Mexican taxon shrank drastically, and its two mitotypes responded differently, one of the first demonstrations of the importance of intraspecific genetic variation in climate niches."
  • (Page 984) "Contrary to the common notion that suitable habitat will open in northern latitudes, predicted suitable climate niches for two of the spruces of Mexico in the years 2060 and 2090 would open in the south, on the highest mountains of the Trans-Mexican Volcanic Belt in central Mexico."
  • 7. GENETIC ADAPTATION: INADEQUATE. There is strong evidence that the spruce genus in Mexico is incapable of undergoing adequate genetic adaptation to track climate change this century.
  • (Page 984) "The predictions of range loss do not take into account the potential for genetic adaptation (e.g., Skelly et al., 2007). However, the history of spruce in Mexico seems to make the possibility of adaptation unlikely. Some spruce occurred around Mexico City (about 700 km further south than the present distribution of the genus), but disappeared during the Holocene ca. 7500 yr BP (Lozano-Garcia et al., 1993). If spruce failed to adapt to the early Holocene warming that occurred over a few millennia, it seems unlikely to respond to current climate change which is occurring at an accelerated tempo."
  • (Page 984) "In addition, adaptation requires suitable genetic variants (Kellermann et al., 2009), and genetic diversity is low in Chihuahua spruce and Martinez spruce (Ledig et al., 1997, 2000a). Genetic diversity in Mexican spruce is only moderate (Ledig et al., 2002) and less than half that found in the closely related Engelmann spruce (Ledig et al., 2006). In general, genetic diversity decreases with range occupied, as in California conifers (Ledig, 1987) and, perhaps, in plant species in general (Hamrick and Godt, 1996). The raw material for evolution appears lacking in many narrowly distributed species. . . In Scots pine (Pinus sylvestris L.), it might take 13 generations to adapt to climate change (Rehfeldt et al., 2002), but 13 generations in a tree species is on the order of millennia, whereas pronounced warming will occur on the scale of decades.
  • (Page 984) "The high level of ovule abortion in all three spruces of Mexico and, therefore, low seed yields, is also a handicap to colonization. Inbreeding leads to aborted ovules in conifers (Franklin, 1970). Aborted ovules ranged from 36 to 47% in the three populations of Mexican spruce, which suggests very high inbreeding coefficients of 0.73 to 0.84 of a possible maximum of 1.00 (Flores-Lopez et al., 2005). The problem of inbreeding is even worse in Chihuahua spruce and Martinez spruce than in Mexican spruce. The relatively small size of populations and their isolation apparently have contributed to unusually high levels of selfing for a conifer. Based on genetic structure rather than ovule abortion, selfing is 41-60% for Martinez spruce (Ledig et al., 2000a), 85-100% for two small populations of Chihuahua spruce (Ledig et al., 1997), and 19-41% for Mexican spruce (Ledig et al., 2002)."
  • 8. DISPERSAL CAPACITY: INADEQUATE. Populations of the spruce genus in Mexico are incapable of dispersing to new habitats that will open up for them.
  • (Page 984) "For simplicity, we will use the term colonization to refer to the process of dispersal and colonization that results in changes in species' distribution and use the phrase gene flow to refer to exchange of genes among populations via pollen or seed movement. For most species, lack of information makes it difficult to predict colonization responses (Neilson et al., 2005). However, the future rate of climate change is likely to exceed the colonization rates of most plant species (Davis and Zabinski, 1992). Predicted suitable climates in 2030, 2060, or 2090 based on current realized climate niches for the spruces of Mexico seem too distant from their present distribution and lacking in connectivity to allow any reasonable expectation of natural colonization. . . The high endemism of the subalpine habitats in the Sierra Madre Oriental suggests that the vegetation there was not linked with the Trans-Mexican Volcanic Belt during the Pleistocene (McDonald, 1993)."
  • (Page 984) "Even short distances between populations of spruce in Mexico seem to preclude gene flow via either pollen or seed, especially for Chihuahua spruce. On average, the number of migrants per generation among populations of Chihuahua spruce was estimated as only 0.43 to 0.76, depending on the method of calculation (Ledig et al., 1997). These are low rates, but even they are overestimates of the actual rate of gene exchange because they reflect past contact between populations, not current gene flow. Therefore, there seems little likelihood of seed dispersal even among relatively close, contemporary populations of Chihuahua spruce. The estimated number of migrants per generation is higher in Martinez spruce, but lower than expected for conifers, which suggests that dispersal between contemporary populations of Martinez spruce probably does not occur either."
  • 9. THE TIME TO ACT IS NOW.
  • (Page 971) "Delay or inaction is not an option. A point would be reached where seed production was at such a low level that establishing ex situ populations would be impossible. Therefore, early action is needed and the first step is to project where threatened species might find suitable habitat in future decades."
  • 10. FUTURE HABITATS ARE ONLY SHORT-TERM. Suitable habitats to serve as recipient zones for assisted colonization of Mexican spruce within Mexico offer only short-term solutions. By the end of this century, the models predict extinction or severe contraction for all three spruce species within the borders of Mexico. Indeed, the speed of climate/habitat shifts is so rapid that a newly migrated population may have no time to produce even one seed crop before ongoing climate change destroys their capacity. A previous (2002) paper by Ledig et al. ("Genetic diversity, mating system, and conservation of a Mexican subalpine relict, Picea mexicana") advocates for trans-national seed transfer: "The most serious threat to Mexican spruce may be global warming, because stand management can do nothing to prevent it. Already restricted to the highest sky islands in northern Mexico, there is nowhere that Mexican spruce can migrate to escape warming temperatures. Ex situ conservation is the only option to offset the effects of global warming. Seeds should be collected and divided among several seedbanks for long-term storage. Cuttings should be collected and multiplied by cloning to establish field genebanks, probably in the United States or Canada."



    A GLOBAL PERSPECTIVE ON FORESTS: "The role of forest genetic resources in responding to biotic and abiotic factors in the context of anthropogenic climate change", R. Alfaro et al. (international co-authors), 2014, Forest Ecology and Management

    EXCERPTS: "Given the pivotal role of trees in ecosystem function, abrupt climate change impacts on them may thus have profound consequences for forests as a whole (Whitham et al., 2006). Irreversible loss of ecosystem integrity and function may follow, with replacement by new non-endemic ecosystems (Gunderson and Holling, 2002; Mooney et al., 2009).
        Assisted migration involves human movement of tree seed and seedlings from current locations to sites modelled to experience analogous environmental conditions in the future (Guariguata et al., 2008; McLachlan et al., 2007). Such movements may be latitudinal, longitudinal or altitudinal, and are designed to reduce extinction risks for those species not able to naturally migrate quickly enough, and to maintain forest productivity (Heller and Zavaleta, 2009; Marris, 2009; Millar et al., 2007). Assisted migration may be undertaken over long distances, or just beyond the current range limit of particular genotypes and populations, or within the existing range (Winder et al., 2011). A gradual form of assisted migration could consist of reforestation of harvested sites with seed from adjacent locations likely to be better adapted to the planting site under future climate (e.g., in the Northern hemisphere, using seed from sources to the south; in mountainous regions using seed from lower elevations).
        Another challenge to assisted migration that is specific to long-living perennials is that, where climate is changing quickly, large differences in conditions may be observed over an individual trees lifespan. To find species or genotypes well adapted to conditions at establishment and at productive maturity (e.g., for some species, perhaps a century later) may therefore be difficult. In order to achieve a proper balance, the interval to production/maturity needs to be considered, and multiple stepped translocations over time may be required (Soto-Correa et al., 2012). In addition, changes to pest outbreak risk could simultaneously occur as a result of climate change, and this should be factored into assisted migration decisions (Murdock et al., 2013).
         Another useful approach is to conduct assisted migration on assemblages of species with positive interactions that reduce climate risks. For example, a 'first-stage' species may be planted as a nurse crop to provide protection from temperature extremes for a second tree. Such an approach has been applied to Abies religiosa (Kunth) Schltdl. et Cham., using the leguminous shrub Lupinus elegans Kunth as a nurse plant for seedlings (Blanco-Garcia et al., 2011). Within species, assisted gene flow, where genes are exchanged between populations by moving individuals or gametes, has also the potential to control and reduce mal-adaptation (Aitken and Whitlock, 2013).
         Assisted migration responses to climate change that are based on greater dependency on the trans-national exchange of forest genetic resources require an appropriate policy and legislative environment to support transfer, including by the harmonisation of phytosanitary requirements, as noted by Koskela et al. (2009). At a national level, policies defining seed zones will need to be modified to allow the assisted migration of genetic material within nations. Countries developing national forestry action plans should also be encouraged to specifically include genetic level responses to climate change in their plans, which has sometimes, but not always, been the case to date (Hubert and Cottrell, 2007).
         As in previous climate change episodes, forest genetic resources will recombine to produce new variants, which through natural or assisted selection will produce the genotypes required to continue providing the ecosystem services that societies need from forests. But, as climate change progresses it will be important to monitor the adaptation of trees, stands and ecosystems, and to intervene with efforts to support adaptation where needed.


    FORESTRY VIDEOS ON ASSISTED MIGRATION

      

    In 2008, the Climate Change Resource Center of the U.S. Forest Service assembled a dozen research foresters at the leading edge of translating climate change science into "adaptation" responses for forest managers. These scientists delivered excellent short talks captured on video. The result is a superb, free online learning tool: ADAPTING TO CLIMATE CHANGE: A Short Course for Land Managers". "Assisted Migration" as an important adaptation strategy for foresters is specifically mentioned by Constance Millar. Similarly, Jill Baron encourages experimentation (in which lack of success in small-scale adaptation projects would be regarded as helpful learning experiences, not failures). See also MILLAR 2015 video: "The Role of Assisted Migration in Climate Adaptation Planning: When and Where to Employ It".


        January 2014, Connie Barlow (founder of Torreya Guardians) launched on youtube an EDUCATIONAL VIDEO SERIES on Assisted Migration that extends the learnings and experience within Torreya Guardians to potentially apply to private landowners throughout the USA who want to begin experimenting on their own lands with helping even common tree species (especially large-seeded species dependent on rodents for range extension) to move northward in anticipation of climate change — climate change that may push habitable ranges northward faster than the trees can "move" on their own. This newly suggested activity for citizen naturalists: Leaf a Legacy.

    Access: "Climate, Trees, and Legacy VIDEOSERIES".
    Episodes: 01 - Introduction; 02 - Lessons of Torrey Pine; 03 - Lessons of Joshua Tree; 04 - Lessons of Arizona Cypress; 05 - Rocky Mountain Trees in Climate Peril; 06 - Becoming Passenger Pigeon; 07 - Alligator Juniper Assisted Range Expansion; 08 - Foresters Outpace Conservation Biologists in Climate Adaptation


          
  • VIDEO: Climate Change Prompts Tree Deaths: Australia and the World (2012)

    11-minute video of 2012 produced by Australian television. Superb introduction to how increases in heat and drought contribute to tree deaths of an unprecedented scale. This video focuses on Australia, but also looks at the western USA, the Amazon forest, and elsewhere. The implications: Trees with slow natural rates of dispersal (anything other than wind-blown seeds) will require human-assisted migration of more heat-adapted populations of the same species or altogether different species.


  •       
  • VIDEO: Whitebark Pine Assisted Migration Trial in Canada & Alaska (2012)

    by Sally Aitken. Key topics include:

    26:52 - assisted migration section begins

    51:08 - the polarized debate on assisted migration

    56:03 - moving whitebark pine beyond its current range

    01:01:21 - risks of action v. inaction

    See also McLane and Aitken 2011, "Whitebark Pine Assisted Migration Trial", which says, "Whitebark pine will be extirpated from most of its current range over the next 70 years."


  •       
  • VIDEO: Will My Forests Look Good in those Genes? (2014) by Sally Aitken, 46 minutes.

    BACKGROUND: British Columbia plants some 250 million seedlings per year as part of their forest management and timber harvest program (95% of forests in British Columbia are publicly owned). Studies are underway via the AdapTree multi-disciplinary research program (led by UBC prof Sally Aitken), who gives a powerpoint presentation in this 2014 webinar video.

    KEY LEARNINGS: Forests subject to timber harvests will have a climatic advantage over unmanaged forests in that re-plantings will occur with "portfolios" of genotypes selected from wide-ranging populations of the same species that are projected to function well in anticipated climate change scenarios. Western Canadian forests are the subject of this research, which does not yet include non-commercial tree species.


  •       
  • VIDEO: Greater Yellowstone Research: Whitebark Pine and Clark's Nutcracker Mutualism (2012)

    12-minute video of fieldwork by Taza Schaming, with excellent visuals of dead and dying Whitebark Pines and the key role played by Clark's Nutcracker in prying open the cones and then burying the seeds.


  •       
  • VIDEO: Whitebark Pine Ecology: Management of an Ecosystem in Decline (2012)

    38-minute video of 2012 illustrated talk by Dan Reinhart, ecologist of Yellowstone National Park. By clicking left, you will begin at 08:48 timecode, where the talk begins.

  • VIDEO: "Forest Trees in Climate Peril" - 45-min presentation by Connie Barlow to conservation audience in Prescott AZ, 2014.




    PLEISTOCENE REWILDING and Taxon Substitution for Ecological Restoration

  • "Science for a Wilder Anthropocene: Synthesis and future directions for trophic rewilding research" by Jens-Christian Svenning and 10 co-authors (including C. Josh Donlan, lead author of the original Pleistocene Rewilding papers in 2005 and 2006 (linked below), Proceedings National Academy of Science, 2015.
    ABSTRACT EXCERPT: Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. EDITOR'S NOTE: Newcomers to Pleistocene Rewilding will do well to begin online research by not only reading this 2015 paper but also by consulting the references as an ideal way to survey previous papers.

         Paul S. Martin originated the concept of Pleistocene Rewilding and Taxon Substitution in the 1970s. You can learn more about his early work in that field by accessing this page: Tribute to Paul S. Martin.

    The VIDEO at left is an illustrated version of a 1996 phone interview Connie Barlow did with Paul specifically about his "Pleistocene Rewilding" concept.

  • "Is the Climate Right for Pleistocene Rewilding? Using Species Distribution Models to Extrapolate Climatic Suitability for Mammals across Continents", by Orien MW Richmond et al., PLoS One 5(9): e12899. doi:10.1371/journal.pone.0012899
    ABSTRACT begins: Species distribution models (SDMs) are increasingly used for extrapolation, or predicting suitable regions for species under new geographic or temporal scenarios. However, SDM predictions may be prone to errors if species are not at equilibrium with climatic conditions in the current range and if training samples are not representative. Here the controversial "Pleistocene rewilding" proposal was used as a novel example to address some of the challenges of extrapolating modeled species-climate relationships outside of current ranges. Climatic suitability for three proposed proxy species (Asian elephant, African cheetah and African lion) was extrapolated to the American southwest and Great Plains using Maxent, a machinelearning species distribution model.

  • "Rewilding North America" by Josh Donlan and 11 other authors, Nature, 18 August 2005 (2 pages).
    Content: The first advocacy article ("commentary") by prominent conservation biologists that proposes "rewilding" close-kin of some of the large mammals that went extinct in North America at the end of the Pleistocene, 13 thousand years ago by reintroducing close relatives or proxies.

  • "Pleistocene Rewilding: An Optimistic Agenda for the 21st Century" by Josh Donlan and 11 other authors, American Naturalist, November 2006, vol 168: pp 660-681.
    Content: This is the long and fully developed version of the 2005 paper, by the same set of authors. Abstract: Large vertebrates are strong interactors in food webs, yet they were lost from most ecosystems after the dispersal of modern humans from Africa and Eurasia. We call for restoration of missing ecological functions and evolutionary potential of lost North American megafauna using extant conspecifics and related taxa. We refer to this restoration as Pleistocene rewilding; it is conceived as carefully managed ecosystem manipulations whereby costs and benefits are objectively addressed on a case-by-case and locality-by-locality basis. Pleistocene rewilding would deliberately promote large, long-lived species over pest and weed assemblages, facilitate the persistence and ecological effectiveness of megafauna on a global scale, and broaden the underlying premise of conservation from managing extinction to encompass restoring ecological and evolutionary processes. Pleis tocene rewilding can begin immediately with species such as Bolson tortoises and feral horses and continue through the coming decades with elephants and Holarctic lions. Our exemplar taxa would con- tribute biological, economic, and cultural benefits to North America. Owners of large tracts of private land in the central and western United States could be the first to implement this restoration. Risks of Pleistocene rewilding include the possibility of altered disease ecol- ogy and associated human health implications, as well as unexpected ecological and sociopolitical consequences of reintroductions. Estab- lishment of programs to monitor suites of species interactions and their consequences for biodiversity and ecosystem health will be a significant challenge. Secure fencing would be a major economic cost, and social challenges will include acceptance of predation as an over- riding natural process and the incorporation of pre-Columbian eco- logical frameworks into conservation strategies.

  • "Pleistocene Rewilding" New York Times Magazine article by Alan Burdick, 12/11/05.
    Content: Summary of one of the NYT's pick-of-the-year best ideas.

  • "Pleistocene Dreams" Orion Magazine, Point of View editorial by Josh Donlan, July 2008.
    A biophilia, soul-centered, and future-generational plea for beginning the bold task of megafaunal Pleistocene Rewilding.

  • "Rewilding with large herbivores: The importance of grazing refuges for sapling establishment and wood-pasture formation" Biological Conservation by C. Smit et al., 2015.
    Abstract: Rewilding is a novel nature management type that aims at restoring natural processes with minimal human intervention. It is increasingly employed on abandoned agricultural lands in Europe, but empirical studies are scarce. Rewilding may lead to formation of wood-pastures, arguably the primeval landscape in parts of Europe before Neolithic times. We investigated sapling establishment, a key process for wood-pasture formation, in the Oostvaardersplassen: Europe's oldest large-scale rewilding area, with high densities of free-roaming large herbivores. We transplanted saplings of pioneers, spiny shrubs, and hardwood species and studied how herbivore accessibility (grazed control, partial and full exclosure), vegetation type (tall roughs; short lawns) and soil-tillage (mimicking wild boar rooting) affected sapling survival for four years. No single sapling survived in grazed controls, while survival in exclosures was 25%. Differences in survival between partial and full exclosures were minor, indicating that reduced herbivore access is sufficient for sapling survival. We conclude that rewilding with herbivores can successfully form wood-pasture landscapes on abandoned agricultural land as long as grazing refuges are present that allow for sapling establishment. As grazing refuges are generally lacking on abandoned agricultural lands, where most rewilding is foreseen, we recommend that future projects consider the presence — or creation — of grazing refuges.

  • "Rewilding Megafauna: Lion and Camels in North America?" an interview with Connie Barlow, by actionbioscience.org, March 2007.
    Content: Lengthy interview with Connie Barlow discussing the Pleistocene megafaunal rewilding concept. Very useful links to other related articles and audios at the end.

  • Transcript of 11/20/09 Science podcast on on the concurrent paper in the journal, "Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America" by Jackquelyn L. Gill et al.
    ABSTRACT of paper: Although the North American megafaunal extinctions and the formation of novel plant communities are well-known features of the last deglaciation, the causal relationships between these phenomena are unclear. Using the dung fungus Sporormiella and other paleoecological proxies from Appleman Lake, Indiana, and several New York sites, we established that the megafaunal decline closely preceded enhanced fire regimes and the development of plant communities that have no modern analogs. The loss of keystone megaherbivores may thus have altered ecosystem structure and function by the release of palatable hardwoods from herbivory pressure and by fuel accumulation. Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions and during the B√łlling-Aller√łd warm period. Human impacts remain plausible, but the decline predates Younger Dryas cooling and the extraterrestrial impact event proposed to have occurred 12,900 years ago.

  • "Where the Wild Things Were" by Daniel Cossins in The Scientist, May 2014.
    Survey of ongoing rewilding projects of large animals, mostly in Europe.

  • "Resolving lost herbivore community structure using coprolites of four sympatric moa species" by J.R. Wood et al. in PNAS, Aug 2013.
    ABSTRACT EXCERPT: Knowledge of extinct herbivore community structuring is essential for assessing the wider ecological impacts of Quaternary extinctions and determining appropriate taxon substitutes for rewilding. Here, we demonstrate the potential for coprolite studies to progress beyond single-species diet reconstructions to resolving community-level detail. . . Our results show that moa lack extant ecological analogs, and their extinction represents an irreplaceable loss of function from New Zealand's terrestrial ecosystems.

  • "Pleistocene Dreams" by J. C. Hallman in Seach Magazine, May/June 2008.
    Content: Lengthy report on the author's visits to talk with some of the leaders in Pleistocene Rewilding movement.

  • "Pleistocene Park: Where the Auroxen Roam" by Andrew Curry. 2008. Wired Magazine 16.10
    Content: A long report of the rewilding of Europe's endangered native bison to a 500 acre preserve in Latvia that will also contain other surrogates for Pleistocene megafauna.

  • "Return of the Devil Could Aid Small Mammals in Australia" Conservation Magazine 2015
    Proposal to bring back to Australia (rewild) the TASMANIAN DEVIL, which had been extirpated from Australia approx. 3,000 years ago (possibly by the dingo that arrived on the continent 3,500 to 5,000 years ago. The dingo has been extirpated on large segments of Australia by cattle ranchers. Returned devils might serve the remaining ecosystem by its standing as a top predator. Source: Hunter D.O. et al. "Reintroduction of Tasmanian devils to mainland Australia can restore top-down control in ecosystems where dingoes have been extirpated." Biological Conservation DOI: 10.1016/j.biocon.2015.07.030

  • "Conservation Biology: Reflecting the Past" by Emma Marris, Nature 462, 30-32 (2009)
    Tag line: Unsatisfied with merely halting environmental destruction, some conservationists are trying to reconstruct ecosystems of the past. Emma Marris travels back in time with the rewilders.

  • "Role of Ecological History in Invasive Species Management and Conservation by C. Josh Donlan and Paul S. Martin, Conservation Biology, 1 February 2004
    Conclusion: "Nativeness, place, and history are central to the science, strategies, and aesthetics of biodiversity. Currently, a post-Columbian bias blinds us from a paleoecological view of North America, a vista with widespread policy implications. The attention of the public, long enchanted with dinosaurs, needs to shift to our indigenous Pleistocene patrimony. We lost and cannot replace the Ornithischia. We can resurrect and along the way help save the Proboscidea."

  • "Resurrecting Extinct Interactions with Extant Substitutes" by Christine J. Griffiths et al., Current Biology 21(8), April 26, 2011
    Summary: Rewilding with taxon substitutes, the intentional introduction of exotic species to replace the ecosystem functions of recently extinct species, is one way to reverse ecosystem dysfunction following the loss of species interactions [2]. This is highly controversial [3], in part because of a lack of rigorous scientific studies [4]. Here we present the first empirical evidence of an in situ rewilding project undertaken as a hypothesis-driven ecosystem management option. On Ile aux Aigrettes, a 25-hectare island off Mauritius, the critically endangered large-fruited endemic ebony, Diospyros egrettarum (Ebenaceae), was seed-dispersal limited after the extinction of all native large-bodied frugivores, including giant tortoises. We introduced exotic Aldabra giant tortoises, Aldabrachelys gigantea, to disperse the ebony seeds. Not only did the tortoises ingest the large fruits and disperse substantial numbers of ebony seeds, but tortoise gut passage also improved seed germination, leading to the widespread, successful establishment of new ebony seedlings. Our results demonstrate that the introduction of these exotic frugivores is aiding the recovery of ebonies. We argue for more reversible rewilding experiments to investigate whether extinct species interactions can be restored.
       See also: authors' press release; BBC News Online; Mail Online (UK); Discovery News.

  • "Rewilding Pragmatism" by Martin Lewis, Breakthrough Journal, Summer 2015.
    A historian associated with the Breakthrough Institute puts "rewilding" in the context of the "ecomodernist" perspective. The central example is the prospect of "rewilding" grizzlies into the Diablo Range east of San Francisco, using fencing and strong management, along the lines of Africa's Kruger National Park.

  • "On the Use of Taxon Substitutes in Rewilding Projects on Islands" by Dennis M. Hansen, Islands and Evolution, 2010, 33 pages in PDF.
    In-depth survey of the most advanced on-the-ground example of "rewilding" that has occurred to date, written by one of the principal scientists leading the effort. Hansen writes, "I believe islands offer some of the best-suited scenarios to rapidly advance our empirical understanding of rewilding and exploring the use of taxon substitutions in conservation and restoration."

  • "The Use of Extant Non-Indigenous Tortoises as a Restoration Tool to Replace Extinct Ecosystem Engineers" by Christine J Griffiths et al, Restoration Ecology, 2010.
    Content: We argue that the introduction of non-native extant tortoises as ecological replacements for extinct giant tortoises is a realistic restoration management scheme, which is easy to implement. We discuss how the recent extinctions of endemic giant Cylindraspis tortoises on the Mascarene Islands have left a legacy of ecosystem dysfunction threatening the remnants of native biota, focusing on the island of Mauritius because this is where most has been inferred about plant-tortoise interactions. There is a pressing need to restore and preserve several Mauritian habitats and plant communities that suffer from ecosystem dysfunction.

  • "On the Use of Taxon Substitutes in Rewilding Projects on Islands" by Dennis M. Hansen, 2010, chapter in Islands and Evolution, Perez-Mellado et. al, eds.
    Extract: "I hope the examples here, as well as the case studies, will illustrate the potential for taxon substiution to rapidly move beyond the status of gimmck and become an integral part of restoration schemes for some of the most degraded habitats on our planet."

  • "Ecological History and Latent Conservation Potential: Large and Giant Tortoises as a Model for Taxon Substitutions" by Dennis M. Hansen et al. Ecography: 33: 272-84 (2010)
    ABSTRACT: Starting in the late 1970s, ecologists began unraveling the role of recently extinct large vertebrates in evolutionary ecology and ecosystem dynamics. Three decades later, practitioners are now considering the role of ecological history in conservation practice, and some have called for restoring missing ecological functions and evolutionary potential using taxon substitutes  extant, functionally similar taxa  to replace extinct species. This pro-active approach to biodiversity conservation has proved controversial. Yet, rewilding with taxon substitutes, or ecological analogues, is now being integrated into conservation and restoration programmes around the world. Empirical evidence is emerging that illustrates how taxon substitutions can restore missing ecological functions and evolutionary potential. However, a major roadblock to a broader evaluation and application of taxon substitution is the lack of practical guidelines within which they should be conducted. While the International Union for Conservation of Nature's reintroduction guidelines are an obvious choice, they are unsuitable in their current form. We recommend necessary amendments to these guidelines to explicitly address taxon substitutions. A second impediment to empirical evaluations of rewilding with taxon substitutions is the sheer scale of some proposed projects; the majority involves large mammals over large areas. We present and discuss evidence that large and giant tortoises (family Testudinidae) are a useful model to rapidly provide empirical assessments of the use of taxon substitutes on a comparatively smaller scale. Worldwide, at least 36 species of large and giant tortoises went extinct since the late Pleistocene, leaving 32 extant species. We examine the latent conservation potential, benefits, and risks of using tortoise taxon substitutes as a strategy for restoring dysfunctional ecosystems. We highlight how, especially on islands, conservation practitioners are starting to employ extant large tortoises in ecosystems to replace extinct tortoises that once played keystone roles.

  • "Bolson Tortoises of the Pleistocene assisted to move north to New Mexico" New Mexico Wilderness Alliance, Rewilding Institute Website, January 2008.
    Content: 37 Bolson Tortoises (larger than a desert tortoise) were moved from a private ranch in Arizona to protected lands in New Mexico where they are being bred and managed expressly for "rewilding" into their former habitat.

  • "Beyond Historic Baselines: Restoring Bolson Tortoises to Pleistocene Range", by Joe Truett and Mike Phillips, in Ecological Restoration, June 2009, pp 144-151.
    Abstract: Ecological restoration in North America traditionally has strived to return ecosystems to some semblance of the early historic (post-Columbian) condition. Emerging alternative paradigms recognize the large impacts exerted by pre-Columbian peoples, the ever-changing nature of ecosystems regardless of anthropogenic effects, and the possibility of using other benchmarks. Recently, the Turner Endangered Species Fund initiated a project to restore the endangered bolson tortoise to an area in southern New Mexico within its late Pleistocene, but not historic range. Justifications included the likelihood that prehistoric humans extirpated it from New Mexico, the presence of habitats similar to those in its current range in Mexico, and escalating threats to species there. . . Restoring imperiled species to prehistoric ranges has some precedent in North America and, we believe, merits increasing consideration as historic ranges of some species offer increasingly less security.

  • "Mauritius: Back to Wildlife [Tortoises]" article in The Guardian Weekly Online, 22 September 2008.
    Content: Aldabran Giant Tortoises used as proxies for the Mauritius giant tortoises that had been exterminated. "Rewilding" a small island near Mauritius with these giant tortoises.

  • "Rodrigues Island: Hope thrives at the Franćois Leguat Giant Tortoise and Cave Reserve" by David A. Burney, Madagascar Conservation and Development, June 2011.
    2-pages illustrated review of a tortoise restoration project on the island of Rodgrigues, and how the tortoises are helping to restore highly endangered native plants.

  • "Conservation and restoration of plant-animal mutualisms on oceanic islands" by Christopher N. Kaiser-Bunbury et al, Perspectives in Plant Ecology, Evolution and Systematics, 2010.
    13 pages, with color illustrations, on island restoration and rewilding efforts focusing on using congenerics or other species proxies where extinctions preclude restoring historically native species with whom extant native plants coevolved.

  • "Seed Dispersal and Establishment of Endangered Plants" on Oceanic Islands and the Use of Ecological Analogues", www.PLOSone, by Dennis M. Hanson et. al, May 2008.
    Content: Meshes "ecological anachronisms," conservation biology, rewilding of ecological proxies/analogs, and assisted migration/colonization, in a landmark paper that experimentally demonstrates the ecological viability and conservation value of introducing Aldabran tortoises to the oceanic island of Mauritius as ecological proxies (seed-dispersal agents) for Mauritian tortoises that were driven into extinction by humans.

  • "Rewilding Large Herbivores: The importance of grazing refuges for sapling establishment and wood-pasture formation" - by Christian Smit et al., 2014, Biological Conservation.
    EXCERPT: Rewilding may lead to formation of wood-pastures, arguably the primeval landscape in parts of Europe before Neolithic times. We investigated sapling establishment, a key process for wood-pasture formation, in the Oostvaardersplassen: Europe's oldest large-scale rewilding area, with high densities of free-roaming large herbivores. We transplanted saplings of pioneers, spiny shrubs, and hardwood species and studied how herbivore accessibility (grazed control, partial and full exclosure), vegetation type (tall roughs; short lawns) and soil-tillage (mimicking wild boar rooting) affected sapling survival for four years. No single sapling survived in grazed controls, while survival in exclosures was 25%. Differences in survival between partial and full exclosures were minor, indicating that reduced herbivore access is sufficient for sapling survival. Editor's note: I recall encountering photos in a paper showing how wild Malus trees established and grew tall, despite intense grazing, if the seed happened to germinate within an established hawthorn thicket.

  • "Rewilding Megafauna: Lions and Camels in North America?" interview with Connie Barlow, March 2007.
    Content: in-depth interview on Pleistocene Rewilding: its conservation potential and ethical and ecological justifications.

  • "Rewilding America, Pleistocene Style" The Monitor's View, Christian Science Monitor, 30 August 2005.
    Content: Editorial generally supportive of the August 2005 paper in Nature.

  • "Should Humans Give 'Hot' Animals a Hand?" by staff, Daily Democrat (Woodland, CA), 24 January 2007.
    Content: Lots of quotes from Dr. Mark Schwartz on the assisted migration issue.

  • "Restoring America's Big, Wild Animals" by Josh Donlan, Scientific American, June 2007.
    Lead author of the "Pleistocene Rewilding" paper originally published in Nature writes for a popular audience and responds to criticism that has emerged.

  • "Bring Elephants to Australia?" by David Bowman, Nature, 2 February 2012.
    Proposes introducing elephants and bringing back a proxy (Komodo dragon) for a giant extinct lizard in an effort to control rampant wildfires energized by alien grasses and alien predators of native marsupials. For excellent commentary and background on this paper, see: Australia's Newest Firefighters: Elephants?" by Nidhi Subbaraman.

  • "Big Animal Extinction 'severed nutrient arteries'" by Mark Kinver, BBC News, 12 August 2013.
    "The demise of big animals in the Amazon region 12,000 years ago cut a key way that nutrients were distributed across the landscape, a study has suggested. Researchers say animals such as huge armadillo-like creatures would have distributed vital nutrients for plants via their dung and bodies."

  • "Bringing Back Europe's Prehistoric Beasts" by Jens-Christian Svenning, Scientific American.com, June 2007.
    Proposes rewilding the endangered Asiatic lion into Europe.

  • "Pleistocene Rewilding" webpages
    Ongoing reports, news articles, and blog entries on this topic, posted at the The Rewilding Institute website.

  • "Pleistocene Rewilding" WIKIPEDIA entry
    Wikipedia entry, with photos and references, on this topic.

  • "The North Atlantic Ocean: Need for Proactive Management", by John C. Briggs. Fisheries, April 2008. Vol 33, pp. 180-184.
    For those of us considering the importance of "assisted migration" of species impacted by climate change, or outright "rewilding" of species or surrogates to regions in which they lived thousands of years ago, this paper is something to ponder. Here the author proposes that the collapses of fisheries in the North Atlantic may be irreversible without infusion of new species diversity, and that much is to be gained (and little risked) by introducing North Pacific fishes into the North Atlantic. The deep-time discussion of "The Great Trans-Arctic [Marine] Biotic Interchange" (which began 3.5 million years ago when the Bering Land Bridge was transgressed by marine waters), is crucial reading for those of us working with entirely terrestrial biotas.

  • "Rewilding Megafauna: Lions and Camels in North America?" Interview with Connie Barlow
    Interview published on the Action Bioscience website, an education resource of the American Institute of Biological Science

  • "Cloning Mammoths for Pleistocene Rewilding" blogpost
    Useful blogpost and comments on the possibility of cloning frozen mammoth DNA from flesh or sperm.

  • "Michael Archer: How we'll resurrect the gastric brooding frog, the Tasmanian Tiger"
    17-minute video from the TEDx "De-Extinction" series of talks, 2013.

  • "George Monbiot: For more wonder, rewild the world"
    15-minute video from TEDx, featuring the ecological benefits of bringing wolves back to Yellowstone, and advocacy for bringing back the extinct megafauna and how plants alive today in Europe seem adapted to elephants and rhinoceros. "Rewilding offers us the hope that our silent spring could be replaced by a raucous summer." And from an online essay: "Understorey trees such as holly, box and yew have much tougher roots and branches than canopy trees, despite carrying less weight. Our trees, in other words, bear strong signs of adaptation to elephants. Blackthorn, which possesses very long spines, seems over-engineered to deter browsing by deer; but not, perhaps, rhinoceros."

  • "Doom of the elephant-dependent trees in a Congo tropical forest"
    2013 paper by David Beaune et al, published in Forest Ecology and Management. On how extirpation of forest elephants in the Congo is diminishing or eliminating seed dispersal of forest trees have fruits that evidence the "megafaunal dispersal syndrome."


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