Even Slight Warming Harms Some Species, Experts Say

Stefan Lovgren
for National Geographic News
April 20, 2005

It seems like warmer temperatures should come as welcome relief to the caribou that roam the harsh lands of Alaska.

But global warming may be having an adverse effect on the hardened animals. The number of caribou in one of Alaska's four herds has dropped from 187,000 in 1989 to 120,000 today.

The decline, scientists suggest, could be due to warmer weather. The caribou now struggle with everything from more mosquitoes to more snow, brought on by the changing climate.

"The caribou can cope with cold temperatures," said Steve Arthur, a biologist with the Alaska Department of Fish and Game in Fairbanks. "But hot weather and insect activity interfere with their ability to feed, reducing their energy and decreasing their ability to get through the winter."

The caribou are hardly alone. Around the world many animals are struggling to cope with rising temperatures.

A National Geographic four-part TV series, Strange Days on Planet Earth, which begins tonight on PBS, links seemingly disparate phenomena—such as Alaska's caribou decline and the disappearance of species from California tide pools—to climate change.

Many scientists are questioning whether organisms can evolve rapidly enough to keep pace with climate change. Some researchers suggest that even the tiniest temperature rises could mean the difference between life and death for many animals.

Shifting Seasons

There is little doubt that the planet is warming. Over the last century the average temperature has climbed about 1 degree Fahrenheit (0.6 of a degree Celsius) around the world.

Most scientists believe the warming is due primarily to an atmospheric increase in carbon dioxide—a greenhouse gas—caused by the burning of fossil fuels such as coal and petroleum.

A United Nations panel projects that average global temperatures will rise an additional 3 to 10 degrees Fahrenheit (1.6 to 5.5 degrees Celsius) by 2099.

Alaska is at the front lines of global climate change. One report showed that temperatures have increased 4 to 7 degrees Fahrenheit (2.2 to 3.9 degrees Celsius) in some parts of Alaska in the past 50 years.

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