Warming may already doom the polar bears

THE NEWS TRIBUNE
Last updated: September 13th, 2007 01:22 AM (PDT)

As the planet slowly heats up, the arctic sea ice – where the bears hunt – is receding. Its edges break up a little earlier every year, on average. If this continues, the summer melt will advance by seven or eight days a decade.

Because the bears feed on seals and other prey they find on the ice, they eat during winter and spring. They wait out the summer and fall – subsisting on stored fat – until the ice comes back.

With the thaw beginning earlier, the bears have less time to eat. Researchers have found that the average weight of polar bears is dropping, as is the survival rate of cubs.

A new study by the U.S. Geological Survey, released last week, has projected such trends into future decades. The USGS researchers reached a shocking conclusion: Two thirds of all polar bears may disappear by mid-century. The bears now ring the Arctic, but the thaw may leave few of them surviving outside of the islands north of Canada.

All of Alaska’s bears would die out under this scenario – which is based on conservative climate assumptions.

These animals are one of the wonders of nature. They are the largest land carnivores on the planet; some weigh more 1,000 pounds, and one is recorded as weighing more than 2,000. They take prey as large as beluga whales.

They are self-aware enough to cover their black noses with their white paws – completing their wintry camouflage – as they wait for seals to surface at breathing holes. The females are architects: They excavate multi-chambered, carefully ventilated dens under the snow, in which they give birth.

It is hard to imagine such iconic creatures vanishing from most of their historic habitat. But that’s just one of the countless disasters global warming appears likely to wreak upon the Earth’s ecosystems.

Unfortunately, the buildup of greenhouse gases in the atmosphere cannot be quickly reversed by cutting the emissions of those gases. Global warming has a momentum that will continue for many decades even with the most heroic efforts to stop it. If the USGS projections are right, most polar bears will vanish no matter what humanity does.

The chief hope, as far as the bears go, is that the climate will eventually cool again soon enough to let the surviving bears repopulate their original habitat. That’s but one of many good reasons for the United States to get serious about global warming.

Originally published: September 13th, 2007 01:22 AM (PDT)