Climate Fact: Mammals on the Move
In Brief: Warming across the state of Michigan has been followed by an influx of species formerly inhabiting lands to the south.
The Great Lakes region is an ecological “transition zone.” To the north lie boreal forests dominated by conifer trees. To the southwest lie oak savannas and prairies, and to the southeast lie deciduous oak-hickory woodlands. When the climate changes – average temperatures rise or rainfall in a given location changes – animals that are adapted to those conditions will often move to find the conditions for which they are best suited. Temperatures have warmed in the Great Lakes region over the past 30 to 40 years. Since 1985, surface temperatures on Lake Superior have been warming by an average of 1.2 degrees Fahrenheit per decade. Spring conditions are on average arriving earlier in the year and winters are milder, with average minimum temperatures up to 7.4 degrees Fahrenheit warmer than they were in the late 1960s. As a result of these warming conditions, species better adapted to the conditions that were prevalent to the south of Michigan several decades ago – and are now normal in Michigan today – have moved into the state or have expanded their once marginal populations there. Woodland deer mice, for example, used to be dominant throughout the northern part of the Lower Peninsula, but have declined in number since white-footed mice moved in from the south. Flying squirrels, eastern chipmunks and opossums are now common or even abundant in parts of Michigan where they were largely unknown in the 1950s and 1960s.
Seasons: Winter, Spring, Summer, Fall
Source: Myers, P et al. “Climate-induced changes in the small mammal communities of the Northern Great Lakes Region.” Global Change Biology 15 (2009): 1434-1454.
