Wildlife as Indicators of Climate Change

Glaciers are receding, seasons seem to be getting longer, and many areas in the western United States are undergoing drought. In fact, mean air temperatures have increased by approximately 0.6 degrees C globally during the past 100 years. And, according to Intergovernmental Panel on Climate Change (IPCC) reports, air temperature is expected to continue warming globally from 1.4 to 5.8 degrees C during the 21st century. However, some still aren’t certain if climate change is a long term event or temporary trend. Why not look at those that will be most affected by the impacts of climate-change on our Rocky Mountain ecosystems? Wildlife.

Scientists and their partners at the USGS Northern Rocky Mountain Science Center (NOROCK) are doing just that. Two studies funded by a new USGS initiative on Global Climate Change and Wildlife Science are underway to examine how climate change may be impacting the habitats of native fish and ungulate species. The goal of both projects is to provide tools that will help wildlife managers predict potential climate change induced impacts on wildlife throughout the Rocky Mountains and the interior western United States.

Fish Species

State and federal agencies and non-governmental organizations are increasingly consumed with the recovery and restoration of native trout and salmon throughout the western United States. Almost all of the native inland cutthroat species, grayling and bull trout have been proposed for listing under the Endangered Species Act and a number are currently listed as “Threatened”.

Trout, grayling, and char historically inhabited a variety of freshwater habitats (streams, rivers, lakes, ponds, reservoirs), but have declined due to habitat degradation, fragmentation, and introductions of nonnative species. The remaining intact populations of native trout, char, and grayling species are largely restricted to small, fragmented headwater habitats. Recent localized extinction of these small populations caused by wildfires and subsequent floods have highlighted their vulnerability.

Complicating these issues is global warming and associated climate change, which are likely to increase air and water temperatures, increase the risk of catastrophic fire, change the timing and quantity of water from snowpack, increase winter flooding in some areas, and provide habitat conditions that favor introduced species. Understanding how effects of climate change will influence habitat for native fish is critical for effective management and recovery of these species.

NOROCK fisheries researchers and project collaborators from USGS, US Forest Service, and Trout Unlimited are studying how global warming and associated climate change may drive landscape scale impacts that affect the fresh water habitats of key native fish species. Specific research questions the team will explore include:

• What is the geographic distribution of target species or populations in relationship to current temperature and flow regimes?
• How are the flow and temperature regimes likely to change in response to a warming climate, and which habitats and populations will be affected most?
• How will these large-scale changes in climate affect native salmonid distributions across the western United States?
• How well does the relationship between climate and salmonid distribution reflect actual measurements in a basin?

Outputs of the project are:

1. Develop a database including all existing species distribution and habitat information, and air and water temperature data.
2. Develop maps defining existing and projected future distributions of native salmonids factoring in anticipated temperature, hydrology, and non-native impacts alone and in combination.
3. Develop an open file report of this analysis that would include data analysis, maps and forecasts for each of the species listed.
4. Preparation of a scientific journal article that synthesizes the work.
5. Distribution of information through a series of workshops and meetings with resource managers to update them on the projected change scenarios.

By developing these types of forecasting tools, researchers can assist wildlife managers in predicting potential climate change induced impacts on various fish species throughout the Rocky Mountains and the interior western United States.

Ungulate Species

The ecology of hoofed big-game species in the northern Rocky Mountains, known as ungulates, is strongly influenced by climate. Climate change impacts summer precipitation, winter snow pack, and the timing of spring green-up, all of which control animal physiology, demography, diet, habitat selection, and predator prey interactions. However, the degree of response to these impacts from animals such as elk, moose, mule deer, and pronghorn antelope is uncertain.

In the northern Rocky Mountains, ungulates are managed by state and federal agencies and funding of management programs are supported by the sale of hunting licenses and other tourism related activities such as fishing licenses and camp ground fees. Thus, impacts of climate change can not only directly impact ungulate species, but also the ability of managers to promote conservation through hunting and tourism; a direct hit on the economies of many western states.

NOROCK scientists and collaborating scientists from the Wyoming Cooperative Fish and Wildlife Unit at the University of Wyoming, the USGS Earth Resources Observation and Science (EROS) Data Center, Penn State University, and Humboldt State University, will study how global climate change may impact ungulate species. Scientists will examine how climate change induced events such as decreased snow pack, early spring conditions, and increased drought may alter species migration routes and population numbers, influence disease prevalence such as brucellosis in feed grounds, and impact abundance of vegetation such as aspen.

Key research questions that will be examined include:

• What is the influence of climatic variation (snow pack and plant productivity) on Rocky Mountain ungulate population dynamics, recruitment, and human harvest (hunting)?
• How does climate influence elk migration patterns, and how do migration patterns influence elk aggregation on feed grounds and their transmission and maintenance of brucellosis?
• How does climate influence elk foraging decisions during winter and the impact of elk herbivory (grazing) on the regeneration of aspen, a declining deciduous component of the Greater Yellowstone Ecosystem (GYE) forests?

Outputs of the project include datasets and models which will be made available to federal, state, tribal, and local government agencies, as well as to scientist at universities and non-governmental organizations and useful for other researchers and wildlife managers. Datasets and models include: 

1. Vegetation greenness data will be compared within and between years, correlated with weather station data, and tested to see if it impacts the timing of ungulate movement between winter range or feedgrounds and summer range.
2. SNOTEL data in the southern GYE will be examined for potential influence on both animal movement and vegetation productivity.
3. Population models for five species of ungulates across Wyoming will be used to summarize existing data and forecast potential impacts of climate change to allow managers to alter their decisions and maintain desired populations.

The long term goal of the project is to provide the tools for natural resource managers to facilitate a better, science-based understanding of how climate change can impact various ungulate species within the region.  

Implications

Through both projects, USGS scientists and their partners will address important issues surrounding how global climate change may impact ecosystems throughout the northern Rocky Mountains. Sound science will enable natural resource managers to be better prepared when addressing management issues surrounding regional wildlife habitat and population changes associated with global climate change. For information specific to each project, please contact: