How Is Wildlife Affected by Global Warming?

Even Small Climate Changes Can Send Hundreds into Extinction

Polar Bear, Penguins and Seal on a Small Island of Ice. Getty Images

A reader of Earth Talk wanted to know about wildlife populations affected by global warming, including polar bears that appear to be stranded on small islands of ice.

First, the polar bear-stranded-on-ice images are misleading. Polar bears are powerful swimmers and negative effects of climate change on their population will come from losing access to their prey, not from being stuck on small pieces of ice.

Most researchers do agree that even small changes in temperature are enough to stress hundreds of already struggling species, many into extinction. 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.

How Global Warming Affects Wildlife

The key impact of global warming on wildlife is habitat disruptions, whereby ecosystems that animals have spent millions of years adapting to rapidly transform in respond to climate change, reducing their ability to fulfill the species' needs. These habitat disruptions often are due to changes in high temperatures, low temperatures, or water availability, and often a combination of the three. In response, growing conditions change, and the vegetation community shifts. 

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 fragmented and already cluttered with residential and industrial development. Our cities and roads can be obstacles preventing plants and animals from moving into these alternative spots.

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. 

Shifting Life Cycles and Global Warming

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 - a pattern called phenology. 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.

Global Warming Effects on Animals Affect People Too

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.

Which Animals Are Hardest Hit by Global Warming?

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.

EarthTalk is a regular feature of E/The Environmental Magazine. Selected EarthTalk columns are reprinted on About Environmental Issues by permission of the editors of E.

Edited by Frederic Beaudry.