Polar bears are getting fatter in the fastest-warming place on Earth

Polar bears have been getting bigger even as sea ice disappears in Norway’s Svalbard archipelago, the fastest-warming place on Earth – but scientists don’t expect the good times to last.

The northern Barents Sea, which lies between Russia’s Svalbard and Novaya Zemlya in the Arctic Ocean, is warming seven times faster than the globe as a whole. Sea ice around Svalbard lasts two months less in winter and spring than it did twenty years ago. Bears now have to swim 200 to 300 kilometers between hunting grounds on the ice and snow burrows on the islands where they give birth.

But the average size and weight of Svalbard’s bears have increased since 2000, a finding that surprised Jon Aars of the Norwegian Polar Institute, who led the study.

“We should consider this good news for Svalbard,” he says. “But if you want bad news, you can just look elsewhere where you have very, very strong evidence that climate change is negatively impacting polar bears.”

This wide-ranging solitary predator is divided into 20 populations across the Far North, where it is extremely difficult to count. Although its numbers are declining in parts of Alaska, Canada and Greenland, they appear stable or increasing in other places. For nine of the populations, the data are too rare to be precise.

The Barents Sea population, estimated twenty years ago at between 1,900 and 3,600 bears, is considered stable, even growing. Starting in 1995, Aars and his colleagues tranquilized 770 bears with dart guns from helicopters. They jumped on the snow or ice to measure their length and, to estimate their weight, their chest circumference.

Trend analysis showed that this body condition decreased until 2000, then increased until observations ended in 2019.

In spring, when ringed seals give birth on sea ice, polar bears hunt them to build up fat reserves for the ice-free months. Aars and his colleagues think the shrinking ice area could make these seals easier to find.

Bears are also exploiting new food sources. The approximately 250 individuals that remain on the islands when the ice recedes could hunt more bearded seals along the coast, as well as harbor seals, which are spreading to Svalbard as the climate warms.

These “local bears” are increasingly raiding duck and goose colonies in search of eggs, and they have been seen chasing reindeer from a growing deer population. Walrus carcasses, another increasing species there, can provide weeks of feasting.

Svalbard’s bears are more capable of adapting than scientists thought, “so extinction is delayed,” says Jouke Prop of the University of Groningen in the Netherlands.

“They’re a desperate species. They do crazy things,” he said. “It doesn’t work everywhere, but it can work for a while” in Svalbard.

Polar bears may still not have reached carrying capacity on the archipelago after Arctic countries banned hunting them for their pelts and zoo specimens in 1973. But warming is starting to disrupt the food chain, which begins with algae under sea ice, Prop warns.

“It will be very difficult to maintain a reasonable population of polar bears if the sea ice disappears,” he says.

“There will be a threshold, and… polar bears in Svalbard will be negatively affected by the continued loss of sea ice,” says Aars.

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