Polar Bears Facing Double Whammy

July 21, 2003 — -- The mightiest predator in the remotest corner of the globe appears to be falling prey to a double dose of environmental ills. The source: The far-away industrialized world.

The Arctic polar bear faces retreating ice packs at Earth's northern polar cap, which have jeopardized the animal's ability to hunt seal, leading to weight loss, studies show. And now a range of chemical contaminants blown in from industrialized regions appear to be collecting in the bear's remaining fat stores.

The combination, say scientists, threatens the animal's longevity.

"As the animals lose fat, the remaining fat has higher concentrations of pollution," said Andrew Derocher, a polar bear expert with the University of Alberta in Edmonton, Canada. "When you start to add one stressor to another, the detrimental effect can become much greater."

Derocher, who has studied polar bears in the Arctic for the past seven years with the Norwegian Polar Institute, assessed recently that retreating ice flows at Earth's northern reaches could drive the polar bear to extinction within 100 years.

The bears, whose Latin name, Ursus maritimus, means "sea bear," evolved about 200,000 years ago from brown bear and use sea ice as a floating platform to catch prey — mainly seal. Studies suggest this polar ice has been retreating at a rate of about 9 percent per decade.

Meanwhile, as the top predator in the harsh ecosystem at the top of the world, the polar bear is unusually vulnerable to ingesting a slew of chemical contaminants.

Weather mapping has shown the cool Arctic regions act as a giant sink for air streams flowing from all points south. In what is known as the grasshopper effect, chemicals repeatedly evaporate and condense, falling back to the ground.

Many end up at the Arctic, after rising and falling and riding thousands of miles on cool air streams. As air streams reach the frigid regions around the North Pole, moisture cools, condenses and falls to Earth. The chemicals then linger for long periods in snow and ice at the pole since low temperatures prevent evaporation. Here they can be ingested by wildlife.