PARIS • Polar bear numbers could drop a third by mid-century, according to the first systematic assessment of how dwindling Arctic sea ice affects the world's largest bear.
There is a 70 per cent chance that the global polar bear population - estimated at 26,000 - will decline by more than 30 per cent over the next 35 years, a period corresponding to three generations, said the study released yesterday.
Other assessments have reached similar conclusions, notably a recent review by the International Union for the Conservation of Nature (IUCN), which tracks endangered species on its Red List.
The IUCN classified the sea-faring polar bear - also known as Ursus maritimus - as "vulnerable", or at high risk of extinction in the wild.
But the new study, published in the Royal Society's Biology Letters, is the most comprehensive to date, combining 35 years of satellite data on Arctic sea ice with all known shifts in 19 distinct polar bear groupings scattered across four ecological zones in the Arctic.
Percentage by which the global polar bear population might decline by over the next 35 years.
"Polar bears depend on sea ice for most aspects of their life history," the study notes. Most importantly, they use it as a floating platform to hunt seals, which can outswim them in open water.
Researchers led by Mr Eric Regehr of the US Fish and Wildlife Service in Alaska projected three population scenarios out to mid- century, and all of them were grim.
The first assumed a proportional decline in sea ice and polar bears.
Despite year-to-year fluctuations, long-term trends are unmistakable: The 10 lowest Arctic ice extents over the satellite record have all occurred since 2007.
The record low of 3.41 million sq km in 2012 was 44 per cent below the 1981-2010 average.
This week, the US National Snow and Ice Data Centre reported that sea ice extent in October and November was the lowest registered for both months. The culprit is global warming, which has raised the region's surface temperatures by more than 2 deg C compared with the pre-industrial era level.
On current trends, the Arctic could see its first ice-free summers sometime in the 2030s, according to climate scientists.