Drifting pollution affecting Arctic wildlife

Canadian polar bears have been growing thinner and there are fewer new cubs

By Environmental News Network staff

(ENN) -- The warming of the Canadian Arctic region over the last two decades could be making life worse for polar bears, according to research published recently in New Scientist magazine.

Researchers Nick Lunn and Dennis Andriashek of the Canadian Wildlife Service have been studying polar bears around Churchill on the shores of Hudson Bay in Canada. Their study is one of the most detailed audits of any wild animal population anywhere, according to the magazine.

Twice a year, in March and September, Lunn and Andriashek go bear-tagging. Recently, their research has revealed that the bears they study have been growing thinner and there are fewer new cubs. The researchers are blaming changes in the offshore ice for these effects and say a catastrophe may be imminent.

Polar bears spend much of their lives on the ice floes along the Canadian coast. They feed mainly on young ringed seals and life is generally easy. But as the ice melts and they are forced onto land, finding food gets more difficult. With the food scarcity, adult bears may lose as much as a third of its body weight over the summer, according to the article.

This weight loss affects their reproduction. Annual births per adult dropped from 0.99 to 0.84 from the early 1980s to now. During the same period, average weight for the bears also declined according to New Scientist.

Some scientists theorize that the bears are being affected by pollutants such as PCBs, which travel to polar regions in the atmosphere and then accumulate in the food chain.

Last year, researchers in Norway's remote Svalbard islands reported they found seven female polar bears with vestigial male organs. Research team leader Andrew Derocher believed the anomaly may have been caused by toxic chemicals.

The Svalbard archipelago are at a crossroads of air and ocean currents bringing pollution from distant industrial sites in Europe, North America and even Asia.

PCBs dissolve readily in animal fat, such as blubber, and stay there. A polar bear's favorite food is seal blubber.

However, the level of PCBs -- polychlorinated biphenyls -- in the Svalbards is at least 2.5 times higher than in Canada's polar bear territory, Derocher said.

Ian Stirling, head of the Churchill research program, believes that instead of PCBs, a more likely explanation is the melting of ice floes in the Canadian region.

"The final weeks before the ice melts in Hudson Bay are a critical time for the bears -- and possibly the key to their continued survival. Adult bears out on the ice do most of their feeding at this time," according to New Scientist.

"Stirling estimated that if the ice broke up even one week earlier than normal, typical female fears would come ashore 10 kilograms lighter and return at the end of the summer 34 kilograms lighter. They would produce and wean fewer cubs.

In the short term, global warming could be good for bears further north, says Stirling, because the break-up of permanent ice would provide a better habitat for seals. But round Hudson Bay, he believes the bears could already be on a knife-edge. "The first impact (of warming) on polar bears will be felt at their southern limit, in Hudson Bay," he says.

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