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Conserving Biodiversity in a Changing Climate

Abstract


Climate change is already having significant impacts on species and ecosystems in a variety of ways including forcing species range shifts, altering phenology and interactions among species, and degrading habitat quality. In addition, climate change may exacerbate non-climate stressors by increasing the magnitude of the stressor or by reducing the ability of a species to cope with the stressor. Non-climate stressors include habitat loss and degradation, invasive species, pests, pathogens, and pollution.


Addressing the growing threat to biodiversity brought about by rapid climate change will require new approaches to natural resource management and conservation. Adaptation strategies being developed can be characterized as those that 1) resist the impacts of climate change; 2) increase the resilience of systems; or 3) allow or facilitate the transformation to a new state of the system. Strategies include restoring the ecological processes that maintain systems, conserving a network of sites that encompass a variety of ecological settings, and restoring landscape connectivity to allow species to shift their ranges in response to climate change.


Implementing adaptation strategies is necessary for conserving biodiversity, but will not be sufficient. If climate change continues unabated, the projected rate and magnitude of change will make these adaptation efforts ever more costly and less effective. 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.


Conserving Biodiversity in a Changing Climate

An article by Rick Schneider

Originally published in Prairie Fire Journal, 2015


Climate change is already having significant impacts on species and ecosystems and these are likely to increase considerably in the future. 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, non-profit conservation organizations, and universities, has been working to develop and implement strategies to help species adapt to climate change. Action is needed now to reduce the impacts of climate change and help sustain our natural heritage.


Effects of Climate Change on Species and Ecosystems


Climate is one of the primary factors determining the distribution of wild plants and animals. 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. 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 which are at the southern limit of their range here, while we will gain species from states to the south of us. For example, 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 invasive species, 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 such as cropland, highways, dams, and cities. This development forms a barrier to the movement of many species and will inhibit 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 not responding uniformly 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 non-climate stressors such as habitat loss and degradation, invasive species, pests, 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, the non-climate stressors may reduce the ability of a species to cope with climate change. The recent mountain pine beetle epidemic is 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 and made them more susceptible to the beetle attack. These outbreaks have decimated nearly 50 million acres of forests in the western U.S. and Canada. Reducing the impacts of non-climate 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. Climate changes 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 stream flows and an increase in the frequency of streams and wetlands drying up. Finally, increases in air temperature will result in increases in water temperature, causing a reduction in suitable habitat for cold-water dependent species such as blacknose shiner and trout. 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 evaluated.


Adaptation Strategies


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 the preservation of historical conditions to 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 which 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. Climate change has caused a significant increase in fire frequency and size in recent decades in the western U.S. 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 as the climate changes. 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. The canyons on the north-facing side of 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 landscape connectivity, to allow species to shift their distribution in response to climate change. During past climate changes, the primary way that species responded was to follow the climate to which they were adapted. The current amount of habitat fragmentation in the Great Plains will be a barrier to movement for many species. In a number of areas, connectivity between existing intact landscapes can be restored and maintained. However, restoring connectivity will be an enormous challenge in the tallgrass prairie region where less than 2% 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. 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 pre-industrial 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. 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 (http://www.wildlifeadaptationstrategy.gov/) provides an excellent overview of climate change impacts on biodiversity and strategies to address those impacts.



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