Climate change is already having significant impacts on wild species and ecosystems, and these are likely to increase considerably in the future. Climate change components affecting biodiversity include increasing temperature, changes in precipitation patterns, and increases in the frequency and intensity of storms flooding, droughts, and wildfires. Natural systems provide numerous benefits to humans, including ecosystem services that sustain communities and economies. Action is needed now to safeguard species and ecosystems and the communities and economies that depend on them. Addressing the growing threats brought about by rapid climate change will require new approaches to natural resource management and conservation. The conservation community, including staff at state and federal natural resource agencies, nonprofit conservation organizations, and universities, has been working to develop and implement strategies to help species adapt to climate change. What follows is an exploration of some of the impacts of climate change, particularly in the Great Plains, and some adaptation strategies to address those impacts.
Effects of Climate Change on Species and Ecosystems
Climate is one of the primary factors determining the distribution of wild plants and animals. Desert species are found in areas where the climate is dry, while tropical rainforest species are found in areas where the climate is warm and wet. There is good evidence from the past about how species respond when the climate changes. As the world warmed following the last ice age, most species dispersed to higher latitudes or elevations, following a climate to which they were adapted. For example, most species that occurred in Nebraska at the peak of the last ice age are now found in central and northern Canada. We are seeing the same pattern under the current climate change. Hundreds of studies have documented recent shifts in species’ geographic ranges to higher latitudes or elevations. As our climate continues to change, Nebraska will lose some species that are at the southern limit of their range here, while we will gain species from states to the south of us. Surveys in recent years indicate we may have lost the tawny crescent butterfly, whose southern extent of its range was the Pine Ridge. Also, we have had a number of sightings of nine-banded armadillo in recent years, a species whose historic range was to the south of us. Some of the new arrivals will no doubt be noxious weeds, pests, and pathogens. Species are responding individually to climate change, moving at different rates and times than other species with which they currently co-occur. These individual responses will lead to changes in the species composition of natural communities, resulting in new communities that may bear little resemblance to those of today.
While some species will be able to respond to climate change by shifting their distribution, many will not. The current rate of change is many times faster than the rate following the ice age. Species with limited ability to move, such as many plants, amphibians, and invertebrates, will simply not be able to keep up as the climate to which they are adapted moves on. In addition, the natural landscape, particularly here in the Great Plains, is now highly fragmented by human development, including cropland, highways, dams, and cities. These developments form barriers to movement for many species, inhibiting their ability to respond to climate change. Those species that cannot move to more suitable locations or otherwise adapt to changing conditions will likely face local or global extinction.
The changing climate is also affecting the timing of annual events in the life cycle of species. Numerous studies have documented recent shifts in the timing of events such as migration, insect emergence, flowering, and leaf out—all driven by the earlier arrival of spring. Again, species are responding individually to climate change. Thus, there will be disruptions of ecological relationships among species as they respond to climate change in different ways and at different rates. For example, the timing of emergence of an insect pollinator may shift and become out of sync with the flowering time of its host plant. Disruption of species relationships may lead to local extinctions and have significant impacts on ecosystem structure and function.
Species are already challenged by numerous nonclimate stressors such as habitat loss and degradation, invasive species, pest, pathogens, and pollution. Climate change may exacerbate these challenges by increasing the magnitude of the stressor or by reducing the ability of a species to cope with the stressor. In addition, these stressors may reduce the ability of species to cope with climate change. The recent mountain pine beetle outbreaks, in the Pine Ridge and elsewhere, are a good example. Warmer winters have allowed for greater survival of the overwintering larvae, while longer growing seasons have allowed for additional generations each year, resulting in massive beetle outbreaks. In addition, the increase in drought and summer temperatures have stressed pine trees, making them more susceptible to beetle attack. These outbreaks have decimated nearly fifty million acres of forests in the western US and Canada. Reducing the impacts of nonclimate stressors is an important component in helping species cope with climate change.
While all ecosystems in Nebraska will be affected by climate change, aquatic ecosystems (wetlands, lakes, streams, and rivers) may be the most highly impacted. Changes in climate will alter both water quality and quantity. Increases in the frequency of high-intensity precipitation events, particularly in a landscape dominated by agriculture, will lead to increased runoff of sediments, fertilizers, and pesticides into water bodies. Increased frequency of drought and heat waves, combined with increased human demand for water, will result in lower streamflows and an increase in the frequency of streams and wetlands drying up. Finally, increases in air temperature will result in increases in water temperature, spelling trouble for cold-water dependent species such as brook trout and blacknose shiner (a state endangered species in Nebraska). A recent study from Wisconsin found that within fifty years, under a moderate climate-warming scenario, there would be a 95 percent or greater loss in suitable habitat for these two species. In an analysis by the Nebraska Game and Parks Commission, mollusks, amphibians, and small stream fishes were found to be the most vulnerable to climate change of all groups of plants and animals considered.
Climate adaptation has been defined by the Intergovernmental Panel on Climate Change as “initiatives and measures to reduce the vulnerability of natural and human systems against actual or expected climate change effects.” Adaptation strategies being developed and implemented by the conservation community can be characterized as those that (1) resist the impacts of climate change; (2) increase the resilience of systems, i.e., their capacity to absorb and recover from impacts; or (3) allow or facilitate the transformation to a new state of the system. Most conservation adaptation work to date has focused on promoting resistance and enhancing resilience. However, given the current and projected rate of climate change, there will need to be a shift in emphasis from one focusing on the preservation of historical conditions to one of anticipating and facilitating ecological transitions. In other words, we will need to manage for change, not just persistence.
One approach to building resilience in ecosystems is to restore and maintain the ecological processes that historically shaped these systems. The primary ecological processes that have shaped terrestrial Great Plains ecosystems in the past have been fire, grazing, and periodic droughts. In the last century we have greatly altered the pattern of fire and grazing on the landscape, with significant consequences for native species. For example, a century of fire suppression has transformed the Pine Ridge ecosystem from one of predominantly open ponderosa pine woodlands (maintained by frequent, low-intensity ground fires) to one of dense forests, susceptible to high-intensity crown fires. This increase in tree density has had detrimental effects on those species adapted to open woodland conditions. Climate change has caused a significant increase in fire frequency and size in recent decades in the western US. One way to increase the resilience of the Pine Ridge ecosystem, in light of increased wildfire, is to reduce the tree density and then use periodic low-intensity prescribed fire to keep fuel loads low. This will increase the likelihood that when wildfires do occur, they will stay in the ground layer and function to maintain the system. Restoring ecological processes will not only benefit current resident species and increase their persistence in the face of climate change, it will also provide suitable conditions for other species as they move northward in response to climate change. The focus is on preserving processes that ensure the continuation of diverse and functioning ecosystems, even as species composition changes.
Expanding the network of conservation areas can help to conserve the variety of ecological settings that will continue to support biodiversity and ecosystems as they shift in response to climate change. Selection of sites to be conserved should be informed by climate change considerations. Sites with greater habitat and topographic diversity will allow for species to move locally to find suitable conditions. Sites with high habitat quality and a full complement of native species are likely to be more resilient than degraded sites. It is also worth trying to identify and protect climate refugia, areas that are projected to have limited climate change and where species may persist for longer. The north-facing canyons along the Niobrara Valley are one such refugia, where a number of species persist far to the south of their main range of distribution. Streams in the Sandhills, with their consistent temperatures from groundwater input, may serve as refugia for coldwater dependent aquatic species. One approach would be to develop a network of conservation areas that would capture the geophysical diversity of the state (different combinations of topography, soils, geology). These geophysical settings are the “ecological stage” on which species interact. Conserving these “stages” and the ecological processes associated with them, can maintain biodiversity, even as the “actors” shift location over time. A carefully selected network of conservation lands will capture more of today’s biodiversity and allow for transition to changing species distributions.
In addition to conserving a network of sites, there is a need to restore connectivity between sites and across the landscape in general. During past climate changes, the primary way that species responded was to follow the climate to which they were adapted. But that response is hampered for many species by habitat fragmentation. In a number of areas, connectivity between existing intact landscapes can be restored and maintained, allowing species to shift their distribution in response to climate change. However, restoring connectivity will be an enormous challenge in the tallgrass prairie region, where less than 2 percent of the original prairie remains, typically in small, isolated patches. Here, we will need to find ways to make the working landscape more permeable to species movement.
Given the current rate of climate change, many species will not be able keep up, even if movement corridors are available. For these species, managed relocation—moving a species outside its current range to areas expected to have suitable climate in the future—may be the only answer. However, this approach is still controversial in the conservation community. There is much uncertainty about our ability to identify where suitable climate for a given species will be in the future. In addition, for most species there are large gaps in our knowledge about their ecological requirements beyond climatic factors, so identifying suitable sites will be problematic. And finally, we have ample evidence of the problems that can arise from introducing a species into an ecosystem where it did not previously occur.
Adaptation Is Necessary but Not Sufficient
Implementing adaptation strategies is necessary for conserving biodiversity, but it will not be sufficient. Even if all greenhouse gas emissions were halted today, climate scientists predict that the earth would continue to warm for several decades and then take many centuries to return to preindustrial temperatures. So it is imperative that we assist species in adapting to this new reality. However, if climate change continues unabated, the projected rate and magnitude of change will make these adaptation efforts ever more costly and less effective. The average global temperature has risen about 1.5 degrees Fahrenheit in the last century, and already we’re seeing significant impacts to species and ecosystems around the world. Climate models project that under current emissions, global temperatures will rise another 4.5 to 8.5 degrees Fahrenheit by the end of this century. The earth experienced a similar amount of temperature increase following the last ice age, but that warming occurred over a period of about eight thousand years. It is difficult to fathom the changes that would occur in the natural world with the projected rate of warming. Thus, in addition to implementing adaptation strategies, we must also slow and halt climate change by reducing greenhouse gas emissions and levels in the atmosphere. As the Intergovernmental Panel on Climate Change noted, we must learn to manage the unavoidable and we must avoid the unmanageable. To date, the conservation community has addressed climate change by focusing primarily on adaptation strategies. Going forward, we will need to put greater emphasis on addressing the root causes of climate change.
Additional reading: The National Fish, Wildlife and Plants Climate Adaptation Strategy (www.wildlifeadaptationstrategy.gov/) and Climate-Smart Conservation: Putting Adaptation Principles into Practice (www.nwf.org/) provide excellent overviews of climate change impacts on biodiversity and strategies to address those impacts.
Image Credits: Dr. Ken Dewey, School of Natural Resources, UNL