Polar Bears Shored by Arctic Melting

Sept. 13, 2006 —  The extreme loss of sea ice in the Arctic Ocean is not only causing trouble for polar bears at sea, but on land as well.

Arctic sea ice melted at record levels last year and again in 2006, forcing the bears to spend more time on land, where they are unable to hunt their preferred food — seals.

As a result, the bears are thinner and hungrier, and foraging for alternative food sources — including garbage at human settlements. That, in turn, means polar bears are increasingly in contact with people.

It's a situation that's no good for either species.

"They’re seeking the garbage that’s there, rather than to eat the people," said sea ice researcher Claire Parkinson of NASA’s Goddard Space Flight Center. Parkinson spoke at a NASA press conference Wednesday and coauthored a paper on the polar bear troubles in the latest issue of the journal Arctic.

Still, if a garbage-seeking polar bear threatens a person, it’s legal to kill the bear, she said. The irony of the situation is that the increased encounters between bears and people have led some people in northern Canada to get the impression that polar bear populations are rising, said Parkinson.

"What we concluded in our paper is that it’s a very serious mistake to interpret increased (bear) sightings as an increase in population," said Parkinson, who worked in collaboration with Ian Stirling, a polar marine mammal researcher with the Canadian Wildlife Service in Edmonton, Alberta.

Aircraft surveys of polar bears in the Hudson Bay area studied by Parkinson and Stirling show that bears numbered about 950 in 2004 – down from 1,200 in 1989. That’s a 22 percent drop, Parkinson pointed out.

What’s more, polar bears are losing weight.

The ever-earlier spring breakup of sea ice is shortening the spring hunting season for female bears, which is probably why they getting thinner and less able to reproduce.

In the early 1980s an average female polar bear weighed in at around 650 pounds (295 kg). That’s recently dropped to less than 510 pounds (230 kg), "a significant weight loss," said Parkinson.

Studies of the timing of the ice break-up, which controls the hunting season for polar bears, show it arrives seven or eight days earlier each decade, Parkinson reported. That gradual loss of hunting and feeding time has accelerated in 2005 and 2006, as the Arctic sea ice has dropped to its lowest level ever.

Even the once-stable winter "perennial" ice, which seemed almost immune to global warming, has begun to lose ground.

"The winter ice extent was basically constant in the first 25 years of the approximately 30-year record," said Josefino Comiso, a NASA sea ice researcher. "But in 2005 and 2006 it’s much lower."

"If the winter ice retreat continues," he said, "the effect will be most profound, especially on Arctic mammals."