Julie Palakovich Carr Graduate Student under Ron Moen and Jerry Niemi, Biology
Canada lynx (Lynx canadensis) is a medium sized carnivore and a member of the cat family (Felis). It is a species well adapted to the cold temperatures and deep snows of the boreal forests of Alaska and Canada, as the animals have thick fur and large feet. Lynx also occur in a few places in the lower 48 states of the U.S., including in northeastern Minnesota. Lynx primarily eat snowshoe hares. Lynx prefer to live and hunt in regenerating conifer forest stands approximately 20-40 years old as well as mature forest.
Canada lynx are federally protected in the lower 48 states under the Endangered Species Act. They were listed as a threatened species in 2000 due to the low abundance of animals in the southern portion of their range. This listing has prompted research into the ecology of this species. One of the major concerns for the continued survival of this species in its southern range is global climate change.
Climate change and lynx
Global climate change is a manmade climate phenomenon in which global air temperatures are rising over time due to a buildup of carbon dioxide and other greenhouse gases in the Earth’s atmosphere. As the Earth warms other aspects of our planet are changing, including rising sea levels and changes in precipitation patterns. As climate changes, the geographic range of species are predicted to change. This will most likely occur as a northward movement by each species. These predicted changes create a concern that some species may no longer occur where they do presently. This could be true for Canada lynx, especially in Minnesota, given that the species occurs at the southern extreme of its range in the contiguous U.S.
Climate change will likely impact Canada lynx in several ways. Higher summer temperatures could cause heat stress in animals or may cause them to avoid activity at the hottest times of the day. Higher winter temperatures could cause more precipitation to fall as rain instead of snow. Lynx are adapted to hunt in deep snow and declines in snow depth may allow bobcats to invade the range of lynx, causing increased competition between the species.
The purpose of this project is to visualize historic and predicted future changes in temperature and snow depth across the range of Canada lynx in order to plan for the continuing conservation of this species.
Three climate variables were modeled across the range of Canada lynx in Canada and the United States: average summer temperature, average winter temperature, and average maximum winter snow depth. Summer was defined as June, July, and August; winter was defined as December, January, and February. Data for the U.S. was obtained from the National Climatic Data Center (www.ncdc.noaa.gov) and for Canada from Environment Canada (www.climate.weatheroffice.ec.gc.ca). All data was obtained for individual weather stations. Data from the U.S. was largely only available after 1948, therefore two historic time periods were modeled: 1950-1975 and 1975-present. Maximum snow depth was used instead of mean snow depth because data for mean snow depth was not available for the U.S.
The data for each climate variable was visualized in ArcMap (ESRI) at each weather station. To create a continuous map of each climate variable from point data at individual weather stations, the data was interpolated. I used inverse distance weighted interpolation to predict the climate data at locations where weather stations did not exist. The data was then clipped to the extent of the range of Canada lynx.
Climate predictions were taken from online maps created by the Canadian government (www. atlas.nrcan.gc.ca/site/english/maps/climatechange/scenarios). These global predictions of changes in summer and winter temperature and precipitation were made for 2050 and 2100. All changes are relative to the period of 1975-1995. I saved each map as a jpeg, imported them into ArcMap, and then rectified the images to make them spatially explicit. The maps were then digitized to improve image quality. Lastly, the map algebra tool was used create maps of predicted temperature and snow depth.
The final maps for each of the three climate variables were saved as jpegs and imported into Image Ready in order to become animations. Separate animations were created for each climate variable. Each animation consisted of four frames (i.e. time periods): 1) 1950-1975, 2) 1975-present, 3) 2050, and 4) 2100. The final animations were exported from Image Ready as QuickTime movies.
Winter temperature has warmed and is expected to warm further throughout the entire range of lynx. Similarly, summer temperatures have warmed in the last 30 years and are predicted to continue to rise. Alaska may become a refuge for lynx given predicted cooling in 2100.
Snow depth has not changed greatly to date nor does it appear to change much in the future. However, these results should be regarded with caution as maximum snow depth is modeled. Average snow depth may change over time. Also, generalizations from this data are limited by the methods employed to predict future snow depth, namely assuming a constant ratio of rain to snow depth. Also, future warming will likely cause more precipitation to fall as rain instead of snow and also cause further melting of snow.
Implications for lynx
Climate has already started to change throughout the range of Canada lynx and is predicted to continue to do so during the next century. Warming winter and summer temperatures, especially in the southern portion of the species range, will likely have the largest impacts on lynx. If temperatures warm to the extent predicted, the future of lynx in the lower 48 states is at jeopardy.