Shift Happens

Climate change might be more accurately called climate creep. As temperatures rise everywhere, ecosystems will redistribute.  Plants and animals will move in order to “stay comfortable” just as you would move to another room if it got too hot.  Heat moves from the equator out and up, so whole ecosystems should move toward the poles, or into higher elevations. Average global temperatures rose 0.8C over the last century, with the majority of that change coming in the last 40 years.10  The current rate of global average temperature increase translates to an average change velocity, or climate creep, of 0.42km/year for any given ecosystem.12

Idealized Performance curve from Nature.com

The need for organisms to move in the face of climate change is often tied to thermal performance curves.  A thermal performance curve is simply a measure of an organism’s ability to perform essential life functions at various temperatures. When a creatures environment lies at either extreme of its thermal range it will be unable to expand its range any further. Global warming opens up new land for populations at their lower critical limit by warming areas previously too cold, but at the same time puts great stress on organisms already at their upper critical limit. Those who are unable to keep up with the speed of change will face real trouble.

A common tool for assessing an organism’s ability to survive climate change is to look at its dispersal ability: the product of both the time it takes a generation to birth the next and the distance each successive generation can travel.17  When you compare a creatures ability to disperse with the velocity of change for their ecosystem you get a good sense of who will be left behind and who is at great risk for extinction.

For both the Lynx and the bobcat this kind of risk of assessment doesn’t yield much concern.  The bobcat’s impressive dispersal score of 14.83 km/yr is more than enough to keep place with even the fastest moving climates, like the Mangrove forests in Florida, which show a change velocity of .95 km/yr and are the second fastest moving environment on earth.17,12  The Canadian Lynx is in just as good a situation when you just compare the raw numbers. The boreal forests the Lynx calls home shows a change velocity of .43 km/yr compared to the cat’s dispersal rate of 11.70km/yr.17,12  Even the snowshoe hare, whose success greatly impacts the success of the Lynx, doesn’t have much to worry about with a dispersal rating of 2.40 km/yr.17 

Climate change velocities by biome from Loarie et al 2009

One interesting issue presented for the Lynx is the speed of change for its current environment and the speed of change for the environment that spans its entire northern boundary.  The boreal forests are having their range pushed northward at .43km/yr, but the Tundra are only moving at .29 km/yr.12  This difference in change velocities will cause an overall condensing of this biome as its southern reaches move north but its northern reaches are unable to push into the cold hard ground of the tundra.  Under current conditions the habitat of the lynx will shrink 1.4 km every decade.  That means contraction equal to one and a half football fields along its entire southern boarder every year.