A major international report says the increasingly rapid loss of Arctic sea ice is already taking a toll on polar bears and Canada should reconsider its decision not to include the mighty predators on its list of endangered species.
The Polar Bear Specialist Group, which met over the weekend in Copenhagen, Denmark, has concluded that the overall condition of the world's 19 polar bear populations is deteriorating. The group is part of the International Union for the Conservation of Nature, one of the world's largest environmental science networks.
The group says that the number of bear populations in decline is eight -- up from five in its last report in 2005. Three populations are considered stable compared with five previously.
Only one population is increasing. Information on seven populations is still too scarce for scientists to draw solid conclusions.
The report released Monday suggests an "unprecedented" loss in sea ice, which bears use as a seal-hunting platform, is behind the trend.
Group chairman Erik Born points to evidence from around Churchill, Man., where sea ice is now breaking up about three weeks earlier than it used to.
"They've been weighing and measuring polar bears and they've been able to demonstrate there is a clear downward trend in the body mass of adult females," Born said from Copenhagen. "There is also evidence (of) decreased survival of very old bears and younger bears which can be linked to the change in sea ice."
Born, a biologist from the Greenland Institute of Natural Resources, said evidence suggests the same story is playing out across the Arctic.
"It's a pretty good correlation that this is what will happen in other polar bear populations that suffer from decrease in sea ice. I think it's fair to assume that this is what will happen in other places."
Sea ice reached a record low in 2007 and is also well below average this summer. A study released last week found that the extent of ice cover averaged less in the 20th century than in any time during the last 800 years.
Nor is disappearing sea ice the only threat the bears face.
The report found rising levels of mercury, a potent neurotoxin, in bear bodies. As well, at least one population -- the Baffin Bay bears of Canada and Greenland -- is probably being overhunted, although Inuit hunters in that area have long disputed that.
Because of the amount of uncertainty involved with counting polar bears, the polar bear group has kept its estimate of the global population at between 20,000 and 25,000. About two-thirds of those are believed to live in Canada.
Still, Born said, Canada should reconsider a review that recommended polar bears not be considered an endangered species. At least some of Canada's 13 populations should be reclassified, he suggested.
"The review was looking at polar bear populations as a whole and not recognizing that there are different populations of bears in Canada that might be affected differently. It would make more sense if they took it population by population."
Baffin Bay is one group that should be considered endangered, he said.
The report also says decisions on the status of different populations should be made in light of increasing climate change, a factor missing from the initial evaluation from the Committee on the Status of Endangered Wildlife in Canada.
"The 2008 COSEWIC report does not quantitatively evaluate the threat of global warming, especially predicted changes in sea ice, on polar bear subpopulations," the report says.
A spokesperson for Environment Minister Jim Prentice was not immediately available for comment.
Monday's report recommends polar bear populations should be assessed every five years instead of once a decade because of the increasing speed of climate change.
Born emphasizes that there are still seven populations about which scientists know very little.
Polar bear research is expensive and difficult. The great white hunters are spread across a range of 17 million square kilometres, an area about the size of Russia, in which a couple of badly timed storms can wipe out an entire field season.
Born also recognizes that polar bear research has become highly politicized. Environmental groups use the beasts to promote the fight against climate change; those who favour northern development point out that there are still plenty of bears around.
That doesn't change anything for him, said Born.
"We have people all over the world who make polar bears an icon. It makes the debate in the media very uncomfortable, but I don't think it changes the scientific work."
