By Alister Doyle, Environment Correspondent
LONGYEARBYEN (Reuters) - Time may be running out for polar bears as global warming melts the ice beneath their paws.
Restrictions or bans on hunting in recent decades have helped protect many populations of the iconic Arctic carnivore, but many experts say the long-term outlook is bleak.
An estimated 20,000-25,000 bears live around the Arctic -- in Canada, Russia, Alaska, Greenland and Norway -- and countries are struggling to work out ways to protect them amid forecasts of an accelerating thaw.
"There will be big reductions in numbers if the ice melts," Jon Aars, a polar bear expert at the Norwegian Polar Institute, said by the fjord in Longyearbyen on the Arctic archipelago of Svalbard, about 1,000 km (600 miles) from the North Pole.
Unusually for this time of year, the fjord is ice free.
Many restaurants and shops in Longyearbyen, a settlement of 1,800 people, have a stuffed polar bear or pelt -- often shot before a hunting ban from the early 1970s. Self-defense is now the only excuse for killing a bear.
Many scientific studies project that warming, widely blamed on emissions of greenhouse gases from burning fossil fuels, could melt the polar ice cap in summer, with estimates of the break-up ranging from decades to sometime beyond 2100.
Bears' favorite hunting ground is the edge of the ice where they use white fur as camouflage to catch seals.
"If there's no ice, there's no way they can catch the seal," said Sarah James of the Gwich'in Council International who lives in Alaska. "Gwich'in" means "people of the caribou", which is the main source of food for about 7,000 indigenous people in Alaska and Canada.
U.S. President George W. Bush's administration is due to decide in January 2008 whether to list polar bears as "threatened" under the Endangered Species Act.
That would bar the government from taking any action jeopardizing the animals' existence and environmentalists say it would spur debate about tougher U.S. measures to curb industrial emissions.
The World Conservation Union last year listed the polar bear as "vulnerable" and said the population might fall by 30 percent over the next 45 years. Bears also suffer from chemical contaminants that lodge in their fat.
Some indigenous peoples, who rely on hunts, say many bear populations seem robust.
"The Russians thought there's more polar bears that they're seeing in their communities, so they felt that it's not an endangered species," said Megan Alvanna-Stimpfle, chair of the Inuit Circumpolar Youth Council, of an area of Arctic Russia.
"But if we're talking about the future and there's no ice, then they are," she said.
And some reports say the melt may be quickening.
"Arctic sea ice is melting at a significantly faster rate than projected by most computer models," the U.S. National Snow and Ice Data Center said in a report on April 30.
It said it could thaw earlier than projected by the U.N. climate panel, whose scenarios say the Arctic Ocean could be ice-free in summers any time between about 2050 to well beyond 2100.
An eight-nation report by 250 experts in 2004 said "polar bears are unlikely to survive as a species if there is an almost complete loss of summer sea-ice cover."
Paal Prestrud, head of the Center for International Climate and Environmental Research in Oslo who was a vice-chair of that study, said there was no Arctic-wide sign of a fall in numbers.
But there were declines in population and reduced weights among females in the Western Hudson Bay area in Canada, at the southern end of the bears' range where summer ice has been breaking up earlier.
Mitchell Taylor, manager of wildlife research at the Inuit-sponsored environmental research department in Nunavut, Canada, said some bears in region had simply moved north.
"Hunters in many regions say they are seeing increases," he said. "It's clear that the ice is changing but it's not at all clear that the trend will continue."
Prestrud said the fate of polar bears may hinge on whether they adapt to survive longer on land in summers. In the Hudson Bay, bears often go for months without food, scavenging on birds' eggs or even on berries and roots.
"Otherwise they will end up in zoos," he said.
Aars, however, said the bears had survived temperature swings in the past: "I hear far too often that within 100 years polar bears could be extinct," he told a group of climate students in Longyearbyen.
"You will still have bays with ice for many months a year where polar bears can live," he said.
On Svalbard, bears may have become less scared of people since the hunting ban, and are more likely to see them as a meal. Aars' recommendation: don't show you are scared.
"You start shouting, or use flare shots to make a noise. Most polar bears get scared if you behave in the right way. But you have to act from the start. If you show weakness you are in trouble."