Polar bears in southern Hudson Bay could become extinct as soon as the 2030s because of thinning sea ice that helps them find food, according to a new study.
“We knew the loss of Arctic sea ice would be a catastrophe for polar bears, but this could be the first subspecies to disappear,” said Julian Straub, lead author of the study published in the journal Nature on Thursday. Communication Earth and the Environment.
Last month, in the eastern half of Hudson Bay, the world’s most studied polar bear habitat, The ice is gone A month earlier than usual.
Polar bears are used to about four months of ice-free weather before the ice reforms and they can hunt blubber-rich seals from the pack ice, but the presence of sea ice doesn’t guarantee that polar bears can hunt: the ice must be thick enough to support polar bears.
Previous studies have looked at the extent of sea ice to determine the species’ viability, but Dr Straub and her colleagues used climate models from the Intergovernmental Panel on Climate Change. Latest Report The idea is to predict when the remaining ice will be too thin for bears to hunt.
There’s no consensus on how much ice is needed to support an adult male polar bear, but the study based its field surveys on a benchmark of about 10 centimetres (just under four inches).
Polar bears do a good job of dealing with ice with minimal resources: they crawl, move on their bellies, and spread their limbs as far apart as possible to distribute their weight evenly over the ice. But sometimes they still fall through the ice. This isn’t usually a problem for polar bears, who are good swimmers, but it’s a bigger problem when they’re hunting seals, as hitting the ice is like an alarm bell, alerting the seals to the presence of a predator.
Jeffrey York, senior director of research policy at the Polar Bear Institute and co-author of the study, said polar bears need thick ice because they have to sprint to catch seals. Sea ice, which is highly saline, is more plastic and resilient than glass-like freshwater ice. But other experts say 10 centimeters is a stretch.
“We’re always looking for a benchmark we can use,” says Andrew Desrochers, a biology professor at the University of Alberta, “but 10 centimetres is pretty thin. You can’t land a helicopter on that ice. It needs to be about twice that thick for polar bears to actually use it.”
Elizabeth Kruger, the World Wildlife Fund’s manager for the Arctic, said the modeling was less severe than expected. “It’s actually pretty daunting,” she said.
The ice-free season is currently about a month longer than polar bears are accustomed to. Research suggests The ice-free period Extend to 6 monthsEven the hardiest Hudson Bay bears, typically healthy adult males, would struggle to survive.
Polar bears are known as indicator species, predicting the health and viability of the entire Arctic ecosystem. The combination of reduced sea ice and reduced snowpack has a significant impact on ringed seals, a favorite food of polar bears, because with less than 32 centimeters of snow, the seals have a harder time keeping their pups alive in their dens.
Last year, global temperatures temporarily rose to 1.5 degrees Celsius above pre-industrial levels. Under the Paris Climate Agreement, countries agreed to try to keep global warming below that level to avoid the worst effects of global warming. While the rise in temperature is not permanent, Dr Straub and other scientists say polar bears in the region cannot survive if temperatures rise more than 2.1 degrees Celsius above pre-industrial levels.
Currently, about Half the number of polar bears As in 1987, a similar event was observed in western Hudson Bay.
“Our best analysis suggests that polar bears will survive until the end of the century,” Desrochers said, referring to the 19 subspecies that live throughout the Arctic, “but in Hudson Bay, that’s highly unlikely.”
Hudson Bay bears are unlikely to move from their habitat even if conditions worsen. First Nations and Inuit communities may be forced to change their traditional methods of hunting polar bears at some point just to protect bear populations. Towns may have to figure out ways to stop bears from targeting human food in times of crisis to minimize human-bear conflicts. Longer-term possibilities include distributing polar bear food, but Dr. Desrochers said that method would not be able to sustain the population indefinitely.
“There is no other solution that can be done to manage the population in the long term other than addressing greenhouse gas emissions,” Dr Desrochers said.
