Nature Ramble

This week…

Polar bears

Polar bears have often been used as the symbol for global warming. Who’s not familiar with this photo of what appears to be a Polar bear clinging to what is purported to be the last ice flow on the planet? If you’re not, then you aren’t spending enough time on the internet. It’s an emotive photo, and it’s design and use is meant to make us feel sorry for the plight of these magnificent animals.

OMG, the last ice flow on the planet!

But, is this the true story?

Will Polar bears become extinct?

Behind the controversy, what’s the real story about the future of polar bears?

It’s November and that time of year when the sleepy town of Churchill, Manitoba, on the western shore of Hudson Bay in Canada, turns into polar bear central.

Hundreds of polar bears, lean but lethargic – their last full meal eaten in the late spring – pass the hours wandering around aimlessly, mock fighting, or simply lying belly-up catching the dim rays of the Arctic gloaming. They are waiting until the ice freezes over and they can go and hunt seals.

Outnumbering them are the tourists who’ve flown in from around the world to get a unique “up close and personal” view of one of the Arctic’s most iconic species.

And last, but not least, there’s the scientists. While some scientists visit the “Polar Bear Capital of the World” to study the bears, others, such as Polar Bears International’s Steven Amstrup, are there because they also see a unique opportunity to inform people about the plight of polar bears.

Because polar bears, most scientists agree, are in trouble.

Human-caused global warming is causing the Arctic sea, the bears’ habitat and hunting ground, to melt and decline. If the trend of sea ice decline continues as it has done, at the rate of about 13 per cent a decade, then polar bears would suffer a loss of habitat, and consequently food.

“The best estimates we’ve got indicate that we’ll probably lose somewhere around two-thirds of the world’s bears somewhere around mid-century, just based on the simple fact that we’re losing sea ice,” says Andrew Derocher, a professor of biological sciences at the University of Alberta and past chair of the International Union for the Conservation of Nature’s (IUCN) Polar Bear Specialist Group.

The bears simply depend on sea ice to make a living, Derocher says. “No sea ice means no seals. And no seals means no polar bears.”

Skating on thin ice

Despite its size, Ursus maritimus, the largest member of the bear family, is ideally suited to life on ice, its double-layered coat and its furry-undersided paws insulating it from the chilly Arctic temperatures. A polar bear can stand up to 3 metres tall and weigh up to 600 kilograms – hardly the physique of a figure-skater – but it can move with grace and stealth across the ice surface and sneak up on its prey of ringed and bearded seals.

There are 19 subpopulations of polar bears in the world, 13 of which can be found in Canada. Some of these bears live year-round on the ice, but for populations such as the Hudson Bay bears, the ice proves an ephemeral habitat.

In this region, bears spend the winter months on the ice gorging their prey but, when the ice melts each year, they’re forced onshore where they have insufficient food until the sea ice refreezes in the fall. And as the temperatures in the Artic have risen, the sea ice has begun to melt sooner and refreeze later, leaving the polar bears stranded on land for longer lean times.

“When I first started working in Hudson Bay in the early 1980s, the sea ice would have already formed along the shore quite nicely by now,” Derocher says. “There were years when the bears were gone in the first week in November, but this year it is unlikely that we see any significant sea ice for at least a couple of weeks.”

In the last 30 years, bears have increased the amount of time they are on land by almost 30 days – staying another day longer each year – according to Amstrup. That means the bears are coming ashore to face food shortages before they have stored enough fat to last through the season, he says.

“The bears just run out of energy,” Derocher says. The longer summer fasting time impacts bear health and resilience, and influences reproduction rates, he says.

According to the United Nations’ Intergovernmental Panel on Climate Change (IPCC), ice coverage is likely to fall below one million square kilometres by 2050. The current changes, and predictions such as these, led to the listing of polar bears in the US as an endangered species in 2008.

Already the numbers of bears in the western Hudson Bay have declined, Amstrup says. “This population is near the southern extreme of the polar bears’ range and so it is one of the most vulnerable populations,” Amstrup says. “If we don’t get our act together soon we may not be able to save these bears.”

Hope or hoax?

Although most scientists appear to agree with Derocher’s grim outlook for the polar bear, there are a few that question it. One of the most vocal of these is Mitch Taylor who spent more than two decades as a polar bear researcher and manager for the Nunavut government.

“Are we just about to lose our polar bears? No we are not,” Taylor says. “We are seeing 130 years of climate warming that has increased temperature of about 0.75 degrees and that has obviously affected the sea ice, but the polar bears don’t seem to have been affected so far.”

The crux of Taylor’s argument is that the world’s polar bears are thriving, at least in terms of numbers. The current scientific consensus places the worldwide polar bear population between 20,000 and 25,000 animals, more polar bears than existed prior to the 1973 International Agreement worldwide restriction on polar bear hunting.

“This is the time the Inuit call ‘The one with most bears’,” Taylor says.

Source: BBCNews Read more