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A Change in the Weather: How will Plants and Animals Respond to Climate Change?
“A Change in the Weather: How will Plants and Animals Respond to Climate Change,” Workshop at the 1999 Ecological Society of America Meeting, Spokane, WA, 9 August 1999.
Climatic changes are known to have had major impacts on ecosystems, as paleo-ecological evidence indicates that vegetation, wildlife and insects have all undergone drastic reorganizations during ice age/interglacial transitions. During such natural transitions, the average rate of climatic change on a sustained global basis was about one degree C per thousand years; however, the lower range estimate for anthropogenic climate change in the next century is one degree C (and the high end estimate about five degrees C), so many ecologists have expressed serious concerns about the potential impacts. Wildlife connections to climate changes have traditionally been understudied. Fortunately, this tradition is being reversed with an increasingly large number of studies showing not only that wildlife may be expected to be sensitive to climatic shifts of the magnitudes projected, but that wildlife may already be demonstrating discernible changes with recent climatic variations. For example, some migratory birds may be arriving in their summer ranges earlier and Edith’s Checkerspot butterfly seems to have shifted its range northward and upward in elevation.
The National Wildlife Federation (NWF) has sponsored the research activities of young researchers on this topic. The goal of the Chancellor Estate Fellowships in Climate Change and Wildlife is to promote the scientific study of how global warming may affect wildlife and habitats by providing fellowships to graduate students for research on the impacts of climate change on U.S. ecosystems and individual wildlife species.
To highlight the cross-disciplinary research of the NWF Fellows and other young researchers working on the impacts of climate change on wildlife, ESA and NWF co-sponsored a workshop at the 1999 ESA Annual Meeting in Spokane, WA. The workshop, “A Change in the Weather: How Will Plants and Animals Respond to Climate Change?,” was co-organized by Stephen Schneider, Stanford University, Francisca Saavedra, University of Maryland, Patricia Glick, National Wildlife Federation, and Lori Hidinger, Ecological Society of America.
Stephen Schneider introduced the workshop by stating that as scientists we have two obligations: (1) to produce peer-reviewed research to improve the understanding of nature and (2) as citizens, to share our views, distinguishing opinion from science, and strive to make a difference in the world. He noted that the research presented at the workshop filled the first obligation and could serve as the basis of fulfilling the second one.
Patricia Glick stressed the importance of supporting sound science and building a bridge between science and public policy. NWF looks to play a clear and important role in bringing the issue of climate change “home” to the American public. Part of this effort will be the publication of an edited volume of the scientific research conducted by the Chancellor Estate Fellows.
One way of determining how wildlife is responding to climate change is to compare current data on species abundance in an area to historical data on species abundance in the same area. Rafe Sagarin, University of California, Santa Barbara, discussed research he has been conducting in Monterey Bay comparing abundances of macroinvertebrates in a rocky intertidal community between surveys conducted in 1931-33 and 1993-96. The early surveys were conducted by W. G. Hewatt at the Hopkins Marine Station along an ecological transect through the intertidal zone from high to low tide and this same transect was resampled by Sagarin sixty years later. This resampling allowed him to quantify a change in density of species along the transect, with some increasing, others decreasing, and others unchanged. If these species are divided by historic geographic range relative to the study site, it becomes apparent that the “southern” species are increasing and the “northern” species are decreasing. Daily long-term temperature records from the Hopkins Marine Station indicate a small annual increase in nearshore ocean temperature. These results are consistent with the predicted effects of climate warming: if a species exists in a “climatic envelope” which moves north due to climate change, then there will be a change in the distribution of that species as it moves north with its “climatic envelope” or goes locally extinct if it cannot.
Wildlife depend of vegetation for habitat and forage. As U.S. climates change, the spatial distribution of vegetation will change and ultimately impact wildlife. Elena Shevliakova, Carnegie Mellon University and Princeton University, discussed her efforts to model the impacts of climate change on vegetation distribution. She determined the relationship between climate and the spatial location of 13 vegetation types and using four climate change scenarios, predicted probable changes in vegetation distribution and composition. All four models predicted numerous changes in the Northeast, Appalachians, and West. Under each scenario, some species disappear and others increase. When she compared losses of species, Shevliakova found mostly a loss of trees and an expansion of desert shrubs. These climate induced changes will have impacts on wildlife that depend of these vegetation types.
Butterflies can be used as model systems for understanding the biological effects of climate change. Jessica Hellman, Stanford University, stated that butterflies are ideal models to use in climate change research because their biology is well known, their population dynamics are sensitive to climate, and they are good candidates for generalizing to other herbivorous insects. We can use our knowledge of how butterflies respond to build predictions of climate change effects. Using the Bay Checkerspot butterfly as an example, Hellman investigated when and how in its life cycle climate change is most likely to have an impact (either through direct or indirect effects). She discussed how to build biological mechanisms into mathematical models which will allow us to predict changes in population size under elevated temperatures. A mechanism-oriented modeling framework using well-studied biological systems can explore a range of potential climate change effects and allow us to understand general impacts and sensitivities and suggest effective management prescriptions in the face of change.
A possible response of a species to rapid climate change is to track the climate by shifting its range. Lisa Crozier, University of Washington, studied the leading edge of a species that is doing just that, the native grassfeeding Sachem skipper (Atalopedes campestris). This insect has been undergoing expansion on the western side of its range—north from California to Washington and then east to eastern Washington—and is successfully overwintering in southeast Washington. Crozier investigated whether this expansion was linked to climate change or tied to a temporary warming trend in the Pacific Northwest. Summer conditions are favorable for this skipper outside its range, but winter conditions are not. This may be a transient expansion that will be pushed back with the next cooling trend, but additional warming could allow more permanent expansion.
Temperature increases due to climate change are having an impact at high altitudes. Francisca Saavedra, University of Maryland and Rocky Mountain Biological Laboratory, discussed her research on the potential impact of climate change on the phenology and reproduction of Delphinium nelsonii (Ranunculaceae), an early source of nectar on which hummingbirds and butterflies rely. Saavedra noted that flower number is directly related to winter snowfall (decreased snowfall leads to decreased flower number). To look at the possible relationship between climate change and fitness, she conducted two experiments—a snow removal experiment and a warming experiment. Plants that had snow removed from them (to mimic less snowfall) flowered and peaked earlier, but stayed open the same length of time as the control plants. Plants that flowered earlier had heavier seeds, a likely increase in fitness. Plants that were warmed (to mimic earlier snowmelt) had decreased densities and also decreased numbers of flowers per plant, decreasing their fitness. These experiments and observations of natural populations demonstrate that yearly snowpack affects the timing and blooming of D. nelsonii. Climate warming should lead to earlier blooming of D. nelsonii which could impact its pollinators and other plants that rely on those pollinators.
Climate change impacts on one species will not only impact that species, but also others in the same ecosystem. Laurie Koteen, Yale School of Forestry and Environmental Studies, told a story of climate, a fungus, a tree, a squirrel, and grizzly bears in the Greater Yellowstone Ecosystem. Koteen has been researching climate change impacts on a pathogen range shift and the consequent impact on wildlife. The white bark pine blister rust, an exotic species ravaging white pines, spreads only under specific climate conditions. The white bark pine produces large nutritious seeds collected by squirrels and stored in large middens which are, in turn, raided by grizzlies. These seeds provide an important food source and are available at a critical time. How will future climate change impact the spread of the white bark pine blister rust, the seed set of white bark pines, and grizzly mortality? When the seed crop is low, grizzlies tend to roam more which increases their interactions with humans and their chance of being killed. Increased blister rust events with climate change is more significant at lower elevations, but higher temperature peaks at high elevations could lead to a greater spread of the pathogen in the white pine of the Greater Yellowstone Ecosystem.
Eric Sanford, Oregon State University, also discussed climate change impacts on the community level. Tolerances to temperature vary among species within the same community and future warming may cause communities to disassemble. Temperature change may influence populations indirectly by affecting species interactions. Sanford investigated possible links between climate change and keystone predation in a rocky intertidal system. If keystone predators are sensitive to temperature, then small temperature changes could result in large community impacts. The rocky intertidal communities of the Pacific Northwest are well described, as is its keystone species, the seastar, which maintains community diversity through predation on mussels. However, predation by seastars is sharply reduced during changes in temperature (e.g., cold water upwellings). These upwellings are sensitive to climate and their frequency and intensity may be impacted by future climate change which could transform the community dynamics.
Climate change is only one of the stresses ecosystems face, another is biological invasions. How will climate change and species invasions interact? Will shifts occur in the range, distribution and density of invasives with climate change? Erika Zavaleta, Stanford University, addressed this question using fire ants as a case study. Fire ants spread out from points of invasion and much of this spread has been southward, with any northward spread being relatively slow. If the slowing of northward spread is related to the climate tolerance limit of the fire ant, what will happen with climate change? Will the ant be able to increase it’s northward spread? While fire ants do have some cold hardening and super cooling capacity, freezing is lethal and foraging ceases below 15 decrees C. With warming, we would expect expansion of the northern range of fire ants. For every invasive species which will increase its range with warming, are there others that will decrease? In looking at 50 invasive species in the U.S., 24 were cold limited, 24 were uncertain, and 2 were heat limited. This suggests that a number of invasive species will increase their ranges with warming while only a few will contract.
These studies and others are part of a growing body of evidence that small temperature changes are likely to have impacts on natural systems. Climate change presents a different challenge than other anthropogenic changes because there is no way for an individual manager to deal with it to restore the system, no matter how many resources are available. In her concluding remarks, Camille Parmesan, University of California Santa Barbara, proposed that we need to build options into reserve design and habitat conservation plans to deal with potential climate change impacts.
How then to take the science and translate it to policy? The National Wildlife Federation is working to make the research of these you scientists accessible to the public. Wildlife touches a responsive chord for millions of Americans, and if we show them a reason to care about climate change, together we can move toward policy changes. For more information on the upcoming publication of these studies, contact the National Wildlife Federation, 202-797-6898, 202-797-5486 (fax), glick@nwf.org.
Lori Hidinger
Program Manager
Sustainable Biosphere Initiative
Ecological Society of America
Washington, DC
Patricia Glick
Coordinator
Climate Change and Wildlife Program
National Wildlife Federation
Washington, DC
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