GENEVA • Polar bears could see their numbers dwindle by nearly a third by mid-century, a top conservation body has said, warning that climate change poses the greatest threat to the king of the Arctic.
The International Union for the Conservation of Nature (IUCN) said a reassessment of the status of the polar bear in its famous Red List of threatened species confirmed the giant mammal's status as "vulnerable".
The IUCN said there were currently between 22,000 and 31,000 polar bears globally, but warned their numbers were likely to shrink fast with the rapid loss of their sea ice habitat due to global warming.
"We're expecting more than a 30 per cent loss over the coming 35-40 years," Ms Dena Cator of the IUCN's Species Survival Commission said.
The travails of polar bears, which no longer have as many floating ocean perches from which to hunt seals, have been well documented. The IUCN pointed out that if more than five months of the year are ice- free, the bears are forced to fast for longer, "which is likely to lead to increased reproductive failure and starvation in some areas".
This is alarming, as recent studies show Arctic sea ice is disappearing faster than most climate models had predicted. Some parts of the Arctic are now expected to cross the five-month ice-free threshold by the middle of the century, while the Canadian Arctic archipelago is expected to take until the end of the century to reach that point.
"Based on the latest, most robust science, this assessment provides evidence that climate change will continue to seriously threaten polar bear survival," IUCN chief Inger Andersen said.
Warming Arctic temperatures could also reduce the habitat and increase the chances of disease among species that polar bears prey on, including ice seals, the organisation warned.
Environmentalists said the IUCN findings were not surprising and highlighted the urgency of reining in climate change.
Ms Sybille Klenzendorf, a biologist in the World Wildlife Fund's species conservation division, appealed for immediate action by world leaders at a key United Nations climate summit in Paris next month.
"We need climate change action in Paris to slow the warming," she said, warning that the bear's decline was symbolic of the dangers climate change poses to the planet.
The polar bear, she said, "is the canary in the coal mine. These changes are coming and we need to act, and hopefully there is still time to change the situation".
Ms Klenzendorf and other environmentalists stressed that climate change was impacting on the world's 19 polar bear populations differently, with those farthest south suffering the most.
Bear populations in Canada's western Hudson Bay and Norway's Svalbard archipelago are among those most at risk, according to Mr Magnus Andersen, an expert at the Norwegian Polar Institute.
Populations farther north are far less vulnerable and in some cases are even benefiting from the changes brought by a warming climate, he said. The thinning and more broken ice creates more biomass, which helps increase fish stocks, providing more and bigger fish, which in turn fatten and grow the populations of seals - polar bears' favourite meal.
Beyond shrinking sea ice habitats, climate change is also increasing other threats to polar bears. The retreat of the polar ice cap has opened up sea routes through the Arctic and has allowed more resource exploration, thus increasing pollution.
In September, countries bordering the Arctic agreed to a 10-year Circumpolar Action Plan for Polar Bears aimed at ensuring the survival of the majestic creatures in the wild.