I’ve seen those images of polar bears stranded on small islands of ice and heard that some are now dying by drowning. How are other wildlife populations affected by global warming?
—Jessie Walters, via e-mail
Most researchers agree that even small changes in temperature are enough to send hundreds if not thousands of already struggling species into extinction unless we can stem the tide of global warming. And time may be of the essence: A 2003 study published in the journal Nature concluded that 80 percent of some 1,500 wildlife species sampled are already showing signs of stress from climate change.
The key impact of global warming on wildlife is habitat displacement, whereby ecosystems that animals have spent millions of years adapting to shift quickly. Ice giving way to water in polar bear habitat is just one example of this. Another, according to The Washington Post, is the possibility that warmer spring temperatures could dry up critical breeding habitat for waterfowl in the prairie pothole region, a stretch of land between northern Iowa and central Alberta.
Affected wildlife populations can sometimes move into new spaces and continue to thrive. But concurrent human population growth means that many land areas that might be suitable for such “refugee wildlife” are already taken and cluttered with residential and industrial development. A recent report by the Pew Center for Global Climate Change suggests creating “transitional habitats” or “corridors” that help migrating species by linking natural areas that are otherwise separated by human settlement.
Beyond habitat displacement, many scientists agree that global warming is causing a shift in the timing of various natural cyclical events in the lives of animals. Many birds have altered the timing of long-held migratory and reproductive routines to better sync up with a warming climate. And some hibernating animals are ending their slumbers earlier each year, perhaps due to warmer spring temperatures. To make matters worse, recent research contradicts the long-held hypothesis that different species coexisting in a particular ecosystem respond to global warming as a single entity. Instead, different species sharing like habitat are responding in dissimilar ways, tearing apart ecological communities millennia in the making.
And as wildlife species go their separate ways, humans can also feel the impact. A World Wildlife Fund study found that a northern exodus from the United States to Canada by some types of warblers led to a spread of mountain pine beetles that destroy economically productive balsam fir trees. Similarly, a northward migration of caterpillars in the Netherlands has eroded some forests there.
According to Defenders of Wildlife, some of the wildlife species hardest hit so far by global warming include caribou (reindeer), arctic foxes, toads, polar bears, penguins, gray wolves, tree swallows, painted turtles and salmon. The group fears that unless we take decisive steps to reverse global warming, more and more species will join the list of wildlife populations pushed to the brink of extinction by a changing climate.