Meltdown: Arctic wildlife is on the brink of catastrophe

Polar bears could be decades from extinction, a survey into global warming has found. Steve Connor reports on the crisis that threatens the polar ice-cap

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Polar bears, the biggest land carnivores on Earth, face extinction this century if the Arctic continues to melt at its present rate, a study into global warming has found. The sea ice around the North Pole on which the bears depend for hunting is shrinking so swiftly it could disappear during the summer months by the end of the century, the Arctic Climate Impact Assessment (ICIA) says.

Polar bears, the biggest land carnivores on Earth, face extinction this century if the Arctic continues to melt at its present rate, a study into global warming has found. The sea ice around the North Pole on which the bears depend for hunting is shrinking so swiftly it could disappear during the summer months by the end of the century, the Arctic Climate Impact Assessment (ICIA) says.

Scientists in the study believe the survival of the estimated 22,000 polar bears in the region is hanging by a slender thread as they suffer the double whammy of chemical pollution and dwindling feeding territories. Polar bears traditionally hunt on floating sea ice for seals and other quarry. But the ice has retreated significantly during summer, so the carnivores are having to swim further from one floe to another in search of quarry.

As a result of this extra effort, many bears are failing to build up the necessary fat reserves during the important hunting period of spring and early summer to take them through the bitterly cold winter months when females nurse their young. The sea ice in the Hudson Bay area of Canada, for instance, breaks up about two and a half weeks earlier than it did 30 years ago, Ian Stirling of the Canadian Wildlife Service said.

The rapid and unprecedented shrinkage of the ice, and the extra burden it places on the animals, has resulted in the polar bears here weighing, on average, 55lb less than they did in the 1970s. And the bears have long become more than a nuisance in Churchill, Manitoba, on the shore of Hudson Bay. They are frequently tranquilised and flown back north.

Scientists at the World Wildlife Fund said that, if that continues, many of the polar bears in the Hudson Bay area will be so thin within the next 10 years that they could become infertile. Lara Hansen, chief scientist at the WWF, said: "If the population stops reproducing, that's the end of it."

Separate studies have already shown that toxic pollutants are building up in the fat of polar bears in a way that could affect their ability to reproduce. WWF scientists say these toxins are affecting the bears' immunity to infections.

The ACIA is the product of four years' work by more than 250 scientists from Britain, the United States and many other industrialised countries. Its 139-page report, presented to a scientific conference this week in Reykjavik, found climate change is affecting the Arctic more than many other regions. For instance, scientists estimate that the polar region is warming at up to 10 times the rate of the world as a whole.

In Alaska, western Canada and eastern Russia, average winter temperatures have risen as much as 3C or 4C in the past 50 years, and they are projected to increase by a further 7C, or 13C, over the next 100 years.

Robert Corell, of the American Meteorological Society, who chaired the assessment, said global warming is already affecting the native Arctic people as well as the unique wildlife of the region. "The Arctic is experiencing some of the most rapid and severe climate change on Earth," he said. "The impacts of climate change on the region and the globe are projected to increase substantially. The Arctic is really warming now. These areas provide a bellwether of what's coming to planet Earth."

Several computer models of how the sea ice is shrinking were examined and the scientists concluded that at the very minimum half the summer sea ice will disappear by 2100, with some models showing an almost total melt. The assessment adds: "This is very likely to have devastating consequences for some Arctic animal species such as ice-living seals, walruses and Arctic char, and for local people for whom these animals are a primary food source. Should the Arctic Ocean become ice-free in summer, it is likely that polar bears and some seal species would be driven toward extinction."

But it is not only polar bears and ringed seals that are threatened. Native people are also having to cope with a dramatic change to their lifestyle, Chief Gary Harrison of the Arctic Athabaskan Council, said. "Our homes are threatened by storms and melting permafrost, our livelihoods are threatened by changes to the plants and animals we harvest. Even our lives are threatened, as traditional travel routes become more dangerous."

Countries bordering the Arctic, notably Russia, Greenland and Canada, are already planning for the time when the north-west and north-east shipping routes are open all year round. Russia especially is expected to benefit hugely from the control of a year-round shipping route between Japan and Europe which will cut thousands of miles off present-day trade routes. Another possible change will result from the melting of the winter ice covering the Barents Sea which is probably the coolest, purest and richest stretch of salt water in the world. The corresponding increase in sunlight and phytoplankton in the Barents Sea will trigger the growth of even richer fishing grounds for cod and other commercially important species, bringing further industrial incursions into this pristine world.

Arctic sea-ice naturally thickens in the winter and melts in the summer but the balance has shifted significantly towards melting in recent years. Scientists estimate the period of melting has increased by about five days every decade over the past 50 years, with the result that the ice has got thinner and is beginning to retreat rapidly. The phenomenon was first recognised by the American military who closely monitored sea-ice thickness when its nuclear-powered submarines sailed under the North Pole during the 1950s.

A comparison of sea-ice measurements made during 1958-76 with 1993-1997 found it had thinned by 42 per cent. An analysis of similar data gathered by British submarines between 1976 and 1996 found a 43 per cent thinning of Arctic sea-ice.

Further measurements suggest sea ice has reduced from an average thickness of four metres to just under three metres in the past 30 years. Satellite measurements suggest that the area covered by sea-ice has diminished by about 4 per cent per decade, an apparently smaller rate of decline because sea-ice has to get thinner before it begins to retreat in surface area. Peter Wadhams, a specialist in Arctic sea-ice at the Dunstaffnage marine laboratory in Oban, made many of the measurements of sea-ice thickness while he was a civilian scientist on board the Royal Navy submarines during their secret voyages under the North Pole. Some things have changed for ever since, he said. One change, for instance, is the disappearance of the Odden ice tongue, a huge spit of ice that formed off eastern Greenland each winter.

The Odden ice tongue, like all sea-ice, was considered an important driving force in the circulation of the ocean currents. As ice forms from salt water, salt is rejected, which causes a rise in salinity. This cold, dense, salty water sinks to the bottom of the sea, helping to drive the movement of deep ocean currents.

The Odden ice tongue was last seen in 1997, and its disappearance suggests that this important engine of ocean circulation could be slowing, Professor Wadhams said.

"The ice-covered seas represent the cold end of the enormous heat engine that enables the Earth to have temperatures suitable for human life over most of its surface," he said. Melting sea ice threatens to disrupt these ocean "conveyor belts" of water. The worst scenario for Britain could be the collapse or movement further south of the warm Gulf Stream, which could cause us to experience a climate similar to that of Newfoundland, which reguarly freezes in winter.

Mark Serreze, of the University of Colorado at Boulder, said satellite monitoring of the entire Arctic region reveal that there are few doubts the phenomenon is real, and warming is proceeding at a rate eight times faster than at any time in the past 100 years. Melting sea-ice does not contribute to increases in sea levels because it floats, but the melting of the Greenland ice sheet can cause sea levels to rise by as much as seven metres. There are signs that this process has begun, althought total melting is likely to take up to 1,000 years.

As the ice cover retreats, one fear is that it will reduce the amount of sunlight naturally reflected from the Earth back into space. In other words, a world with little or no Arctic sea ice will become even warmer as more sunlight is absorbed by the ground to heat the atmosphere. Another possible "positive feedback" resulting from a warmer climate in the Arctic could result from the release of huge amounts of methane gas locked in the permafrost of the northern hemisphere.

Molecule for molecule, methane is far more effective at trapping heat, due to the greenhouse effect, than carbon dioxide. Again, scientists are worrying that a warmer Arctic could lead to runaway global warming as more and more greenhouse gases are released into the atmosphere.

The ACIA said a warmer polar region will not only result in the possible extinction of the polar bear and other species. It will present serious challenges to the health and survival of some native peoples and their cultures.

"During the next 100 years, climate change is expected to accelerate, contributing to major physical, ecological, social, and economic changes, and the assessement has documented that many of these changes have already begun," it warns.

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