No sea ice, no problem for these Barents Sea bears – for now
A lone polar bear swimming for hours in the ice-free Arctic has been the poster child for a warming world impacting wildlife.
But in the north of Norway, the bears of the Barents Sea are doing just fine.
Melting sea ice over decades and increasing the number of ice-free days in the region have not had the expected health effects on this specific polar bear subpopulation, According to new research published in Scientific Reports.
“The bears are doing fine there,” said co-author Andrew Derocher, a professor of biological sciences at the University of Alberta. “This may seem a little counterintuitive… until you look at the ecosystem as a whole.”
The bears appear to be adjusting to the loss of sea ice and are still able to eat what they need to survive.
In a species that is symbolically linked to the changes humans are making to the climate, experts are reminded of the variation within populations.
“We know there will be some winners in climate change. We hear a lot about losers,” said Mary Auger-Metthey, a statistical ecologist at the University of British Columbia, who was not involved in the study. “There are some animals that will take advantage of the conditions that are opening up for them.”
At the same time, experts warn that this adaptation may be temporary, and further loss of sea ice would be devastating for polar bears.
hundreds of live captures
The new research uses data from live captures of bears between 1995 and 2019 in the Svalbard archipelago, an archipelago in the Arctic Ocean and the Barents Sea, between Norway and the North Pole.
This group, one of 20 recognized sub-populations of polar bearsMade up of bears that live on land during ice-free periods and bears that roam as far as Franz Josef Land in Russia.
In total, 770 bears were studied through capture-mark-and-recapture campaigns, which involved following these bears from helicopters.
“So you fly around, you find the bear, you strike it, it goes down,” says John Aarse, lead author and senior scientist at the Norwegian Polar Institute.Te, told CBC News from Longyearbyen in Svalbard.
Height, circumference and other measurements are taken to determine body condition, which Arce calls a simple proxy for how much fat is on the bear. This could help signal health concerns before any population declines.
“This lets us know (if) there is a problem,” Auger-Methe explained, “and then we can act on a relevant timeframe for conservation.”
Because that data was collected over decades, the impacts of a warming Arctic were profound. After 2005, polar bears in the Svalbard region must deal with sea ice breaking a month earlier than usual and, on average, spend an additional hundred days in ice-free conditions.
Yet despite the initial decline, his body condition has improved and stabilized.
“It’s surprising that they don’t lose weight or that they do so well, despite us knowing that they have very little time on the sea ice,” Arce said.
diversify the menu
Part of what experts think explains the decline in body condition is the consumption of prey that is not typically part of polar bears’ diets – and potentially easier for them to access.
“There is a possibility that the area may have unusually rich alternative foods to their standard ringed seal/bearded seal diet,” suggested John Whiteman, chief research scientist at Polar Bears International, who was not involved in the research.
Arce and Derocher point to the availability of walruses, whose numbers have increased since they were protected from hunting in 1952. Polar bears also eat bird eggs and whale carcasses.
“I was actually flying at the time where you see a polar bear kill a reindeer,” Arce said. Furthermore, the availability of these other prey species on land – which do not live on sea ice – means that polar bears do not need to expend as much energy traveling to hunt.
In a rare incident, a polar bear in Churchill is caring for her offspring and another cub that is not her own. Evan Richardson, a polar bear research scientist at Environment and Climate Change Canada, is studying the family.
Climate change is still a threat
Experts are cautiously optimistic about these particular polar bears, but they don’t see successexceed all populationion.
“For Canadian polar bears, this changes nothing. Our bears are not doing well,” says Auger-Methe, adding that extensive research has studied bears in western Hudson Bay.
“It’s clear that their body condition, their survival, their reproduction are declining with the sea ice, and the same is true in the Beaufort Sea.”
They’re all the same species but Whiteman sees the short-term future of polar bears differing in different regions. Ironically, he says their long-term future is clear, as the world continues to warm from humanity’s greenhouse gases.
“At some point, you lose so much sea ice that you lose polar bears. And there’s no way to avoid that.”
Whether these Barents Sea bears will survive to the end of the century is a wild card, Derocher says.
“But I have been surprised more than once over the past 40 years studying polar bears.”
