Climate change is starving polar bears into extinction, according to research published Monday that predicts the animals will all disappear by 2100.
In some regions, they are already caught in a vicious downward spiral, with shrinking sea ice cutting short the time bears have for hunting seals, scientists reported in Nature Climate Change. Their declining body weight undermines their chances of surviving Arctic winters without food, the scientists added.
“The bears face an ever longer fasting period before the ice refreezes and they can head back out to feed,” Steven Amstrup, who created the study and is chief scientist of Polar Bears International, told AFP.
On current trends, the study concluded, polar bears in 12 of 13 subpopulations analyzed will have been killed within 80 years by the fast pace of change in the Arctic, which is warming twice as fast as the planet as a whole.
Even if humanity were able to cap global warming at 2.4 Celsius, about half-a-degree above Paris Agreement targets, but still hugely ambitious, it would probably only delay the polar bears’ collapse.
“That is still way above anything polar bears have faced during one million years of evolutionary history,” said Amstrup. The threat is not rising temperatures per se but the animal’s inability to adapt to a rapidly shifting environment.
Their habitat is melting
“If somehow, by magic, sea ice could be maintained even as temperatures increase, polar bears might be fine,” Amstrup said by email. “The problem is that their habitat is literally melting.” Polar bears spend most of their lives on the sea ice of the Arctic Ocean.
There are approximately 25,000 polar bears left in the wild today. The challenge to their survival has long been understood, but the new study — building on pioneering work by Amstrup a decade ago — is the first to put a timeline on their likely extinction.
A male bear, for example, in the West Hudson Bay population that is 20 percent below its normal body weight when fasting begins will only have enough stored energy to survive about 125 days rather than 200 days.
New-born cubs are even more exposed, according to the study, especially when mothers have not fattened up enough to provide nourishing milk.
“We cannot build a fence to protect sea ice from rising temperatures,” said Amstrup. “The only way to save them is to protect their habitat by halting global warming.”