The Heat Is Online

Study Finds Big Rise in Polar Bear Mortality

Polar bear survival rate falls as climate warms: study
Reuters News Service, Nov. 16, 2006

ANCHORAGE, Alaska (Reuters) - Polar bear cubs in Alaska's Beaufort Sea are much less likely to survive compared to about 20 years ago, probably due to melting sea ice caused by global warming, a study released on Wednesday said.


The study, published by the U.S. Geological Survey, estimated that only 43 percent of polar bear cubs in the southern Beaufort Sea survived their first year during the past five years, compared to a 65 percent survival rate in the late 1980s and early 1990s.


"The changes in survival of cubs are very dramatic," said the study's author Steven Amstrup, polar bear project leader for the USGS Alaska Science Center.


The falling survival rate comes as a warming climate has melted much of the sea ice off Alaska's northern coast, limiting polar bears from hunting for food at the ice's edge, Amstrup said.


"The things we're observing are consistent with a population that is undergoing nutritional stress," said Amstrup. "We can't say definitively it's because of changes in the sea ice, but we don't know what else it would be."


The study also found that adult male polar bears captured after 1990 were smaller than those captured before then.


Co-authored by one of Amstrup's USGS colleagues and a scientist with the Canadian Wildlife Service, the study provides information that might be used by federal officials who are considering a proposal to give polar bears protections under the Endangered Species Act.


Environmentalists have petitioned the U.S. Fish and Wildlife Service to classify the bears as threatened because of new difficulties they are facing from the warming Arctic climate.


A decision on the threatened listing is due by December 27, said Fish and Wildlife Service spokesman Bruce Woods.