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Applying the Science

With so many stacked goals already associated with our work, can we really add the facilitation of climate-driven species movement to the pile?

By Jennifer Dowdell & Amy Nelson

If you work to protect and regenerate ecological systems, design robust and resilient communities, and plan for the conservation of natural resources, chances are you already integrate adaptation to climate change into your work. Whether you are restoring oyster reefs that also help protect coastal communities from storm surges, developing integrated water strategies for increasingly arid sights, or planning for coastal habitat movement associated with sea level rise, you likely have rising tides and temperatures and decreasing water tables and snowpacks in mind. But what about climate-driven species movement? As the body of knowledge on this topic grows, are we practitioners allowing it to inform our work? With so many stacked goals already associated with our work, can we really add the facilitation of climate-driven species movement to the pile?  If one of those goals is biodiversity (and honestly, when is it not?) we’d better.

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Many already have. Planners, managers, and designers are beginning to apply knowledge about projected, climate-driven species movement to their work in ecological restoration, conservation planning, and regenerative design. As we learned from Wildlands Network and from our interview with researcher Josh Lawler, many conservation organizations and natural resources agencies are using climate and species movement prediction models to guide decisions about which land to acquire and conserve. For example, the Washington Department of Fish and Wildlife’s use of the Columbia Plateau Analysis (prepared by Washington Wildlife Habitat Connectivity Working Group) enabled them to identify and target a habitat concentration area for future translocation of the Sharp-tailed Grouse.

Others are applying a variety of adaptive strategies that promote the conservation and protection of biodiversity and ecosystem services. Here, we highlight some examples.

Conserving populations with higher genetic diversity or more flexible behaviors

Understanding and enhancing species resilience to changing conditions is considered an important adaptation strategy. Through a closer examination of species’ genetic and behavioral responses to the pressures of climate change, scientists are gaining more insights to inform our understanding of species survival and flexibility. Species that can adjust in response to environmental degradation will be more resilient in the long term. The challenge is to understand the nuances of a species’ genetic traits and behaviors (termed “survival traits”) in order to know whether or not they are flexible enough to move or survive within changing systems. This information could then help scientists develop conservation plans to deal with climate change.

Research examining species genetics and behavioral traits for flexibility run the gamut, from studies of mayflies and other aquatic insects in the foothills of the Rockies, where scientists are realizing that some populations may be even more vulnerable than first thought; to the study of coral reefs in Mexico, where some coral species have shown the ability to create large fat reserves that help them withstand bleaching and other high stress events associated with warming waters. This is particularly important since corals serve as critical habitat for thousands of species in tropical waters.

In another example of studying genetic and behavioral flexibility two species of the African striped mouseRhabdomys pumilio and Rhabdomys dilectus, were studied to better understand their resilience in light of changing climate across Southern Africa, where warming is leading to increased aridity. Behaviors differ between the two species, ie., group-living versus solitary behavior. Adaptive social behaviors allow one species (R. pumilio) to reproduce in both solitary and communal breeding scenarios, thus allowing for greater resilience if the populations are stressed and community dynamics change. The study showed that although both species face the possibility of extinction under extreme conditions, they can survive if they use their potential for social flexibility. Furthermore, in one scenario, the species that lives in the western part of the study area displaces the eastern species because of its origins in a slightly drier areas (and its associated physiological adaptation to arid habitats). This could perhaps lead to an understanding of steps needed to promote the conservation of certain populations that show more adaptive and resilient behaviors, and how the absence of social flexibility may be a constraint for survival under increased pressures of climate change.

Habitat manipulation/restoration

Sycan Marsh Preserve ©The Nature Conservancy

An understanding of the movement of bull trout (Salvelinus confluentus) in response to climate change is informing the way Craig Bienz, Program Director at The Nature Conservancy’s Sycan Marsh Preserve in Oregon has approached habitat restoration.  According to Benz, changes in mean annual water temperature of only 1–3°C may influence bull trout dispersal or displacement such that their range is reduced by as much as 40%. With annual temperatures expected to rise between 2.2°C and 4.8°C, and with the threat of extreme and prolonged droughts, the future looks grim for this already threatened species. “Increased atmospheric temperatures will exacerbate the effects of loss of riparian vegetation and ongoing stream-water withdrawals,” said Benz, “resulting in higher stream temperatures and further fragmenting and reducing bull trout habitat.” On top of all that,  said Bienz, “higher temperatures may also reduce snowpack and will probably alter flow regimes and sediment loads, potentially burying gravel essential for spawning.”

Bull trout (Salvelinus confluentus) ©The Nature Conservancy

Fortunately, Bienz and his colleagues have implemented several bull trout habitat restoration initiatives with climate change and ecosystem process in mind. “We are increasing connectivity within the watershed and stream network by removing barriers to dispersal, thereby allowing fish to move in response to changes in stream temperature,” said Bienz. By removing water-control structures, they are also restoring the historic hydrologic regime, which will, according to Bienz, allow the stream to expand, contract, and move through its floodplain, potentially buffering the impacts of projected changes in stream flow over the coming century. They have also increased riparian vegetation and restored hardwoods in riparian areas to provide microhabitats. The efforts are paying off. “We have seen an increase in salmonid habitat,” said Bienz. “Summer stream temperatures now decrease more than 3°C through reaches where there was previously an increase, and beaver (Castor canadensis) populations increasing over 80%. These changes should benefit bull trout regardless of the exact nature of climate change, and thus can be undertaken despite the uncertainty in the magnitude of temperature changes and projected changes in precipitation.”

Replanting with ecotypes better suited for future climates

Climate-driven species movement can come into play when selecting plants for ecological restoration projects. “I do think about it when developing planting plans where there is potential to prepare for a future shift in plant community,” said Biohabitats environmental scientist Bryon Salladin. For a recent stream restoration project, for example, Salladin proposed a concept that included planting bald cypress (Taxodium distichum) in an area of Maryland’s Coastal Plain that is on the northernmost tip of the species’ current range. “Although bald cypress is native to warm, humid climates,” said Salladin, “its northern limit is actually caused by ice damage to seedlings. As the climate warms, that ice becomes less of a factor at that site.”

Biohabitats Landscape ecologist Kevin Grieser, who develops many planting plans for stream and wetland restoration projects in northeast Ohio and southwestern New York, takes a similar approach. “Based on climate change scenarios, the general shift in forest type in these areas is from Maple-Beech-Birch to Oak-Hickory,” said Grieser, “so that is often reflected in my plant lists.” Species movement in response to climate change also helps guide decisions about species to include or exclude from planting plans. For projects in southwestern New York, where the white spruce (Picea glauca) is at the southern end of its range, you typically will not find the species in any of Grieser’s plans.  According to Grieser, many entities and individuals are looking to purchase plant material from regional nurseries to the south or in slightly warmer climates than the actual restoration location.

In the southern U.S., a program called PINEMAP, a collaboration 50 scientists, educators, and Extension professionals from 11 southeastern land grant universities and the USDA Forest Service, is working to develop and disseminates knowledge that enables southern U.S. forest landowners to adapt forest management approaches and plant improved varieties of loblolly pine (Pinus taeda), to increase forest resilience and sustainability under variable climates. The program integrates research, extension, and education.

Preserving Climate Strongholds

Another strategy being considered by The Nature Conservancy (TNC) is the conservation and preservation of natural climate strongholds. These are locations that have been identified as having a certain set of characteristics that allow them to withstand the impacts of climate change and ensure the survival of a diverse array of species – providing diverse environmental conditions and corridors that promote local movement and linkages to alternative habitats. Climate strongholds, considered highly resilient and biologically diverse, also provide important sources of clean drinking water, fertile soils, other important ecosystem services.

TNC recently identified a swath of land in the southeastern US that has the capacity to provide important climate strongholds as climate change continues to exert pressure on sensitive habitats and populations. The areas considered the most resilient show the most complexity in topography, geological characteristics, and ranges in elevation. These diverse locations, found from Florida to Tennessee, West Virginia and Virginia, also lack large networks of roads, urban areas, and other barriers that act as natural migration of plants and animals (what they termed “permeability of landscapes”).

Many of the most resilient landscapes identified in the TNC study are found in the Appalachian ranges and other spots that provide a variety of conditions, from hot slopes, to cool coves, wet basins and dry flats. The high elevation forests of the Southern Blue Ridges had particularly impressive density of climate strongholds.

It was noted that the “position and context of the Cumberland and Blue Ridge Mountains, the large river systems linking the Piedmont to the coast, and the host of connections that run through the state of Alabama give them significance with respect to maintaining connections and movements that we previously did not recognize.” There is a plan for the Nature Conservancy to review the data over the next two years to better understand linkages that can create a “connected network of resilient areas” and the TNC is now working on a similar study to identify strongholds in the Pacific NW, results are expected by the end of the year.

Scientists note that now that these locations of ecological resilience and diversity have been identified there should be planning strategies and policies developed to protect and preserve these areas, protecting them from future development, pollution, and other pressures. The results are starting to be used by land managers (nonprofits and government agencies alike) as a blueprint for targeting land and water management for the greatest conservation results.

In-situ conservation

Ex-situ strategies involve conservation of species outside of their native habitats, usually in a zoological park, preserve or botanical garden. This often includes seed storage, captive breeding, or DNA storage. The main purpose of these collections are the “rescue and preservation of threatened genetic material and the breeding of species for potential reintroduction in their native habitats” in order to ensure the survival of a species that is on the brink of extinction. Living organisms in ex-situ collections are often managed according to strict scientific and horticultural standards to maximize their value for conservation. The main purpose of ex-situ practices are to maintain biological and genetic diversity in light of many pressures.

Zoos and botanic gardens are the most well-known examples of this type of conservation strategy, but there are also facilities like the Smithsonian’s Conservation Biology Institute (SCBI) in Front Royal, Virginia, where research and breeding is undertaken to maintain genetic diversity and provide reserves for highly endangered species from across the globe in large-scale, controlled environments. At places like SCBI, larger numbers of a given population can be studied in order to better understand and promote long-term sustainability of threatened species.

The SCBI is also an active member of a consortium of large research institutions and breeding centers that jointly maintain and manage more than 25,000 acres of land. Conservation Centers for Species Survival (C2S2) were formed for the express purpose of protecting endangered wildlife species, providing large areas of space and similar habitat conditions for species that are not surviving in their native habitats in the wild, and providing scientists an opportunity to study these sensitive species in unprecedented ways within a controlled and safe environment. The centers range from the Smithsonian’s location in Front Royal, VA to locations in Texas, California, Florida and Ohio. Their efforts support species recovery and potential reintroduction into the wild of genetically sustainable populations.

According to David Wildt, PhD, a senior scientist who heads the SCBI’s Center for Species Survival, ex-situ populations are developed for a number of reasons:

  • As an insurance population to retain genetic diversity
  • To generate knowledge and a deeper understanding of reproductive traits in a controlled and semi-natural environment (in ways that could never be done in the wild)
  • To use animals to inspire and educate the general population about the importance of conservation efforts
  • To support species for future reintroduction into the wild

One of the most notable stories of species recovery that the SCBI played a role in is the reintroduction of the black-footed ferret in the Western U.S. At one time it was thought that the black footed ferret was extinct. It was rediscovered, only to find that there were only 18 animals left. SCBI studied the species and their reproductive traits, reintroducing a population that has since grown to over 300 animals living in the wild again.

While climate change is not the primary driver for the majority of the conservation efforts being undertaken at the SCBI there is one fairly high profile example at the intersection of climate change research and reproductive research. For many years Dave Wildt has led reproductive studies of giant pandas in collaboration with Chinese scientists, in order to try to resolve ex-situ breeding challenges and promote long-term sustainability of panda populations. Chinese scientists have been working with Wildt to better understand and promote reproductive success of the Giant Panda in order to conserve this flagship species, which is a national icon and a keystone species in China. A parallel study led by Wildt’s colleague Melissa Songer has more recently focused on integrating spatial habitat information with climate models in China. The goals of Songer’s study are to better understand the effects of climate change on available panda habitat, predict how habitat will shift, and better understand what land will need to be preserved in order to promote habitat availability for shifting populations. The model shows that climate change could reduce available panda habitat by 60% within the next 70 years. Most suitable habitat will not occur near current preserves and thus the creation of new protected areas will be tantamount to the long-term viability of panda populations in the wild.

The Chinese, in partnership with their U.S. counterparts, have successfully worked to increase the panda population, rebounding from approximately 120 pandas in captivity in the 1990s to over 375 pandas in captivity in 2014. A key aim is to make sure the population is demographically and genetically secure before reintroducing them in the wild. This climate study will provide guidance for where reintroduction will need to occur.

Assisted migration

One of the more controversial strategies considered for the protection and preservation of vulnerable species is the relocation of vulnerable species to new locations, before their historical ranges become completely inhospitable due to effects of climate change. The aim is to preserve ecosystems, communities or individual species that are experiencing rapid decline (and ultimately risk extinction) by helping them move to locations where they may have a chance at survival. This is particularly important for species where their rate of migration cannot keep pace with modern climate change (trees and plants), or where corridors associated with potential migration are blocked by human barriers in the form of large scale development or urbanization, highways, cities, etc.

This practice, which goes by a variety of names, including assisted migration, assisted colonization, managed relocation, or rewilding, is applied with varying degrees of human intervention.  It can occur as an assisted population migration (where seed sources are relocated within current ranges), an assisted range expansion (moved from current ranges), or an assisted species migration (when a species is moved far from their original ranges to a location where they can ideally survive and thrive). Unlike other types of conservation strategies this involves humans not only deciding where a species will go, but actively working to move that species to a place where it may have never existed before.

??????????????????There are a multitude of potential risks associated with bringing a species to a location where it doesn’t currently exist. First, there is the risk of it becoming invasive or disturbing a given ecosystem’s equilibrium. There is also the risk of disrupting historic evolutionary and ecological processes. And there is no guarantee that the relocated species will thrive or survive after being moved to new locations that are not their native habitat. The concept of assisted migration also raises serious ethical dilemmas for some, regarding the concept of humans playing the role of “planetary manager. However, scientists who have been studying the implications of assisted migration often consider the alternative, continued extinctions and loss of biodiversity. One study recently explained that we may be coming to time where humans must play in supporting novel ecosystems that support biodiversity through more active conservation strategies.

A growing number of studies examining the potential for assisted migration.  For example:

In the case of the Florida torreya (Torreya taxifolia) a group of environmental activists and citizen scientists (known at the Torreya Guardians) have led efforts over the last decade to find locations where this species could likely thrive outside of its rapidly diminishing native habitat, along a stretch of the Apalachicola River’s headwaters near southern Georgia. The species began to decline in the late 19th century, when it was heavily logged and used for fuel. In the mid-1900s, it began dying off. Many attributed the rapid decline to a mysterious disease, the cause of which no one could identify.  The tree has declined 99% in the last century and today, it is struggling to survive. There is some evidence in the fossil record that it had once survived in more northern stretches of forest and so in the interest of protecting biodiversity there has been an effort to find a new location for this tree species to take hold. Lee Barnes, a horticulturalist who has been active in the relocation efforts, explains that one doesn’t want to risk losing a species for which we are still learning what services it could provide, whether that be as part of the intricate web of an ecosystem of dependant organisms or for food/medicinal properties that we have yet to find. To this end there are currently seeding efforts on private properties in North Carolina, Georgia, South Carolina, Michigan, Ohio and Northeast. Ideally, according to Barnes, “we will be able to rewild the species.”

Jason Smith & Florida torreya (Torreya taxifolia) ©Jason Smith

Jason Smith, associate professor of forest pathology at the University of Florida’s School of Forest Resources and Conservation would rather these efforts wait for science. In 2012, Smith and his colleagues have discovered that the real culprit in the decline of Florida torreya is a species of fungus called Fusarium torreyae. Smith believes the pathogen is not native to the U.S. and he fears that well-intentioned efforts to move the Florida torreya to the southern Appalachians could result in the spread of the fungal disease to other species.

“We are all concerned about how to best manage what is arguably the most critically endangered tree in America, and citizen science is great, but is has to be supported and driven by the scientific community.”

Many scientists are in support of further study of the potential for assisted migration although they consider it an action of last resort. The growing body of literature on this subject suggests there are indeed still many questions to consider, including the following.

  • How are decisions made about candidate species for assisted migration and why? What are the priorities? Are there ecosystem services to be maintained? Genetic populations? Economic priorities?
  • Where are species moved and what is the process to decide the end location?
  • How does assisted migration interface with the more traditional strategies of conservation planning, ex-situ and in-situ approaches?
  • Who are the players making the decisions about assisted migration and how can they be coordinated for optimized function and biodiversity goals?
  • How is assisted migration or relocation handled across jurisdictional boundaries?
  • What about moving entire networks of species instead of individual species?
  • What sorts of monitoring protocols are put into place to study populations that have been moved, to make sure they are not having adverse effects in their new homes?

There is no single, one-size-fits-all adaptive strategy for facilitating climate-driven species movement as part of our work in conservation and restoration. Nor are the potential approaches limited to those mentioned in this article. Other concepts, such as transformative restoration,which involves taking advantage of climate-driven invasive species movement by replacing areas the retreat with plants native to surrounding regions, are out there, too.  As the climate changes, more strategies will undoubtedly emerge.




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