Polar bear populations in and around Alaska are declining due to continued melting of sea ice and Russian poaching, according to reports released by the US Fish and Wildlife Service.
Fewer polar bears have survived in the southern Beaufort Sea, which extends from northern Alaska to parts of Canada, and in the Chukchi and Bering Seas between northwestern Alaska and Russia, the agency's draft population assessments show.
Officials say the drop among the Chukchi and Bering bears is likely steeper than for those in the Beaufort, due to a more dramatic melt of sea ice -- which the bears need to travel and forage for food -- and an illegal Russian hunt believed to be killing 150 to 250 bears a year.
The assessments, though incomplete, are disturbing, said an attorney with the Center for Biological Diversity, which petitioned and later sued the federal government to add polar bears and walruses to the US Endangered Species Act list.
"That information, when you look at it, paints a pretty grim picture for the species," attorney Brendan Cummings said.
The United States officially recognised polar bears as an endangered species last year as a result of the warming Arctic climate, which has wiped out much of the summer sea ice critical to the animals' survival.
Russian poaching, believed to be spurred by a market for bear hides, represents what the Fish and Wildlife Service describes as a potential compounding threat to the population, said Bruce Woods, the agency's spokesman in Alaska.
"Of course, since it's illegal hunting, it's very difficult to quantify," Woods said.
There was an estimated 0.3 percent annual decline in the polar bear population in the southern Beaufort Sea between 2001 and 2007, with the total numbers likely hovering between 1,397 and 1,526 animals, according to the draft assessments.
It has been more difficult to study the Chukchi and Bering population, which stretches across the border, although the Fish and Wildlife Service has determined the minimum population there is about 2,000 animals, according to the assessments.
The worldwide polar bear population is generally believed to be about 20,000 to 25,000, according to the International Union for Conservation of Nature, which lists the species as "vulnerable".
The recent declines in the Alaska area follow decades of growth and stability that started in 1972 when the United States outlawed sport-hunting of polar bears. Prior to the ban, sportsmen killed hundreds of Alaskan polar bears annually, often using aircraft to track the animals.
The Fish and Wildlife Service also issued preliminary population information showing the Pacific walrus, another marine mammal dependent on sea ice, had been impacted by habitat warming.
A reliable overall population estimate for the Pacific walrus, under consideration for Endangered Species Act protection, is expected to be released by early 2010, Woods said.
Cummings, however, expressed frustration at the delay.
"By the time they get around to issuing a complete population estimate for the walrus, it'll likely be out of date," he said. "We don't need to know how many walruses there are, because if there's no sea ice, there's no walrus habitat, and we're going to lose the walrus."