Polar bears 'will vanish in 60 years'

They are the symbol of the Arctic wilderness, undisputed monarchs of their frozen land. But in 60 years the polar bear will probably have all but vanished, a victim of man-made climate change, a report due to be published this week will reveal.

And by 2080, global warming will have melted the last Arctic pack ice, according to the latest projections by scientists. As it thins and declines, today's population of 22,000 polar bears will go with it, unable to feed themselves or raise their cubs. They are likely to survive only in zoos, if at all.

That is the conclusion by experts on the species working at the Norwegian Polar Institute, which a report by the Worldwide Fund for Nature is expected to confirm this week.

Pack ice is crucial for the survival of the bears, so highly specialised they are unlikely to be able to operate effectively on land.

According to Peter Wadhams, professor of ocean physics at Cambridge University, observations from submarines show the ice has thinned by 40 per cent - from an average of 4.8 metres (16feet) 20 years ago to just 2.7metres (nine feet) today.

"There will come a point when the ice will be too thin for the bears to use," he says. "At that point, I expect the population will crash."

Global warming projections by the University of East Anglia's Hadley Centre suggest pack ice will disappear entirely from Spitzbergen - between Norway and Greenland, which is home to Europe's largest breeding population of polar bears - between 2030 and 2050. It will vanish from the rest of the Arctic, including what will then be their last strongholds in Canada, between 2060 and 2080.

According to the Norwegian group, pollution from oil exploration and chemicals that reduce fertility also threaten the bears. However, the effects of climate change will, they say, be inescapable.

"There is little doubt that polar bears are being, or will be, negatively affected by the effects of climate change via changes to their habitats," a spokesman said.

"Bears may be forced on shore for extended periods and forced to rely on stored fat. If these periods become excessively long, mortality will increase. Such changes are already thought to be occurring in western Hudson Bay.

"Further, young cubs which are unable to swim long distances may suffer greater mortality. If ice patterns change, existing den areas may be unreachable. Because polar bears must walk against the moving ice (like walking the wrong way on an escalator) increased ice movements will increase energy use and reduce growth and reproduction."

According to Dr Ian Stirling of the Canadian Wildlife Service, the other leading centre for research on the species, there is evidence climate change has brought rain in winter to Northern Canada and Spitzbergen. That has caused the snow banks in which the females build their breeding dens to collapse, suffocating mothers and cubs.

Early break-up of Arctic pack ice in spring is also seriously affecting the bears' physical condition. "It shortens the time bears have to feed on ringed seals, at the very best time of the year," he says. "Over the last 20 years, the bears have lost approximately 15 per cent of their body weight."