Life in a Shrinking World: Changes in Altitudinal Distributions of Alpine Mammals due to Climate Change.
The effects of increased global temperatures are being measured in many biological systems. Given the complexity of biological systems, their responses to a changing climate are difficult to predict. Physiologic processes are particularly susceptible to temperature, leading to an optimal range of temperatures where animals live. As global temperatures increase, species will be exposed to a changing range of potentially stressful temperatures, especially in species currently living at their thermal limits (alpine species). Warming temperatures may force alpine species to move to higher elevations to maintain thermoneutrality. Ultimately, if temperatures increase as predicted, alpine mammals may be unable to move higher and may face localized extinctions.
We plan to test the hypothesis that, in response to warming temperatures, alpine mammals are shifting their ranges to higher elevations to stay within their optimal physiologic temperature range. We will measure the metabolic thermoneutral zone of alpine mammals at four montane sites in the western U.S. and use these physiologic data in conjunction with current climate models to predict range shifts in alpine mammals. We will verify our predictive models using historic range data, current distributions, and recent temperature changes. The proposed study will focus on small diurnal mammals (chipmunks, ground squirrels, pikas) as they are prolific, exhibit a range of thermal requirements, and are easy to work with. We propose that responses to increased temperatures will differ by species and location, with specialist and high-altitude species being the most responsive to increased temperatures.
The proposed study will provide sorely needed information on basic thermal requirements of alpine mammals and will generate physiologically relevant models of future changes in the altitudinal ranges of these species. Rather than simply documenting range shifts, this study will link those shifts to physiologic requirements. This information will be critical to management agencies and provide important information on the speed that species changes are occurring. This study will also begin to incorporate important physiologic information that can be used in future studies to build more complex models of species habitat requirements and enable managers to design physiologically meaningful species conservation plans.
Our study will be conducted within two distinct physiographic regions of the United States: The Sierra Nevada of California and the Rocky Mountains of Colorado and Wyoming. We will conduct our studies at paired national parks located within each of these two regions representing a north-south transect. Yosemite (southern site) and Lassen (northern site) National Parks will be used in the Sierra and Rocky Mountain Biological Laboratory and Grand Teton National Park within the Rockies. We chose these locations because they have experienced a century or more of protection which will isolate species within their boundaries from other confounding anthropogenic disturbances. These parks represent the best remaining “natural” ecosystems and the greatest concentration of accessible alpine ecosystems. We are working on obtaining permission to work inside the parks, however, if we cannot obtain permission we will work in National Forests immediately adjacent to the parks.
We will conduct our study on 12 potential species of diurnal, alpine mammals living within the parks, consisting of chipmunks (Neotamias), ground squirrels (Spermophilus), and the American pika (Ochotona princeps). We will conduct this study over two years visiting the parks in the Rocky Mountains in year one and the parks in the Sierra Nevada in year two. Year three will utilize the metabolic data to create species range maps and verify the changes using historical species distributions.