polar bearCanada's western Hudson Bay could lose its population of polar bears (Ursus maritimus) in as little as a decade, according to new research by biologist Andrew Derocher and others from the University of Alberta (U.A.).

Derocher tells Yale Environment 360 that the polar bears in western Hudson Bay have lost 25 percent of their population in the past three decades. During that time, the animals' average body weight has dropped by 27 kilograms and females have lost 10 percent of their body length.

Much, if not all, of this has been caused by the loss of sea ice in the region. Polar bears rely on this ice for hunting and rearing their young. Hudson Bay polar bears now spend three more weeks on land than they did three decades ago, for a total of nearly five months, during which time they are unable to hunt, burning off two pounds of fat per day.

According to calculations by Derocher and his team, led by U.A. mathematical biologist Peter Molnar, the western Hudson Bay polar bears could die out in 25 to 30 years, or maybe in as few as 10 if there are several years in a row with low sea-ice conditions. "One of the things we found was that the changes in this population could happen very dramatically," Derocher said. "And a lot of the change could come within a single year if you just ended up with an earlier melt of sea ice."

Globally, there are 19 populations of polar bears. The population in Hudson Bay is one of the most accessible by humans, and has therefore been studied more heavily than most.

Photo: Polar bear, via Wikipedia