Polar Bears in Warmer Times

In the barren lands of snow and ice, further north than many Canadians have ever trekked, is the world of the polar bear — a large, white hunter, dependent on the Arctic sea ice.

An estimated 25 000 polar bears live throughout the circumpolar Arctic within the jurisdiction of five countries: the United States, Canada, Denmark (Greenland), Norway and Russia. Each signed the Agreement on the Conservation of Polar Bears and Their Habitat in 1973, in an effort to protect this endearing symbol of the north. The agreement states that "each Contracting Party shall take appropriate action to protect the ecosystems of which polar bears are a part, with special attention to habitat components such as denning and feeding sites and migration patterns, and shall manage polar bear populations in accordance with sound conservation practices based on the best scientific data."

As the home to about two-thirds of the world's polar bears, Canadians share a large responsibility to protect this species.

A New Threat

Although not in immediate danger of extinction, polar bears currently face threats common to all large predators: human encroachment on their habitat, illegal hunting, and through chemical contaminants in their prey. However, polar bears are facing a new threat; climatic change that is reducing the amount of sea ice cover in the Arctic and, in more southerly areas such as Hudson Bay, changing the timing of freeze-up and break-up.

Average winter temperatures in the Canadian Arctic have increased as much as 3 to 4 degrees Celsius in the past 50 years, and the recent Arctic climate impact assessment projects even larger increases in the region in the century ahead. Some climate models are projecting a complete loss of summer sea-ice cover above the Arctic Circle by the end of this century.

Since 1978, the total amount of ice cover has declined by about 14 per cent. At the present accelerated rate of warming in the Arctic, ice might be gone by the middle of the 21^st century and the polar basin may be largely ice-free in as little as 100 years.

Sea ice is a significant component of the Arctic marine environment; a large reduction or the disappearance of ice from some areas will fundamentally alter the ecosystem. Species that rely on sea ice, such as polar bears, will be particularly vulnerable to a warming climate.

Hudson Bay Polar Bears

Some of the first signs of the effects of climate change on polar bears are being seen in western Hudson Bay where the ice is now melting an average of two and a half weeks earlier than in the mid-1970s.

In Hudson Bay, all ice melts completely in the summertime, unlike the ice further north. Hudson Bay polar bears rely on their ability to hunt seals over the winter and spring in order to store large amounts of fat, as much as 200 kilograms, before being forced ashore for three and one half to four months while the bay is ice-free. A pregnant female can go eight months on land without food and needs to store enough fat for herself and produce enough milk for her cubs as well.

There is a strong relationship between break-up of the sea ice and the condition of the bears when they come ashore. Early melt shortens the time that bears are able to feed on ringed seals – their main food source. Research shows that Hudson Bay polar bears are now coming ashore about 15 per cent lighter, than they did 20 years ago.