Scientist warns of climatic threat to polar bears

Noted polar bear scientist Dr. Ian Stirling has won the Northern Science Award for 2003.

The award is presented every year to a person or a group of indigenous people who, through their work, make a significant contribution to the advancement of knowledge and understanding of the Canadian North.

Stirling, who studies polar bears in the Beaufort Sea and western Hudson Bay, has been with the Canadian Wildlife Service for more than 30 years. His research on polar bears has been particularly important in understanding the effects of climate change in the Arctic.

“What I really want to do is not look just at the bears themselves, but at the bears as part of the marine ecosystem and as indicators of things that are changing – even if we don’t know quite what’s happening,” Stirling said in an interview from his office in Calgary.

Stirling believes if the climate warms sufficiently for Hudson Bay to be ice-free most of the year, then it’s likely polar bears will disappear from that part of the world.

Stirling has studied polar bear dens that lie along the Hudson Bay coast, a region that is getting warmer and drier and affected by forest fires. Lightning often starts these fires, and the dens, which are carved into peat, burn easily – another blow to the polar bears’ Arctic habitat.

“Overharvesting is curable. You just don’t harvest as many for a while and let the population recover, but it’s hard for a population to recover from climatic warming. Climatic warming is the greatest overall threat to polar bears at the moment,” Stirling said.

He said contaminants that affect both reproduction and the immune system are also damaging polar bear populations in areas such as the northern Svalbard Islands, Greenland and Russia.

Stirling was drawn to the Western Hudson Bay polar bears because these animals are unique to the Arctic. They fast for four to eight months, depending heavily on hunting during the sea ice season.

He found that, as a result of the reduction in sea ice in Hudson Bay over the past 20 years, the polar bears have less time to hunt and are returning to land in poorer condition. Bears are leaner, smaller and less able to find food to survive.

The weight for both male and female polar bears has declined, and female bears are having fewer cubs.

Their diet has also changed from ring seals, which are ice-dependent, to other kinds of seals – which may prove to be a life-saving technique for hungry bears.

In Hudson Bay, ice melts completely in the summer, so every bear in the population has to come ashore and live on its stored fat reserves for four months, and the pregnant females for eight months. Preying on harbour seals and bearded seals helps them out in the short term.

“It may make things spin out a little bit more if there are more harbor seals or bearded seals around to access,” Stirling said.

Stirling has been receiving specimens collected by hunters from Arviat that show the ring seals killed are older than was once the case. This could mean fewer ring seal pups are being born.

“We don’t really know what’s that’s about. Things in nature don’t usually change in a linear fashion, like push button A and you get reaction A. All sorts of other things come into play,” Stirling said.