Polar bears in Baffin Bay, between Canada’s Baffin Island and Greenland’s west coast, are skinnier and having fewer cubs as the sea ice they depend on melts, according to a new study.
Researchers at the University of Washington in the U.S., and others in Canada, Greenland and Norway, compiled the data from a combination of satellite tracking and visual observations, comparing polar bears in the 1990s with their habits and population in more recent years.
For the current population, they found that as sea ice has ebbed, the amount of time polar bears spend on land increased, which curtailed their attempts to find food, stay healthy and reproduce, according to the study published in the journal Ecological Applications.
“We know that sea ice, which is where the bears need to be, is decreasing very rapidly,” Kristin Laidre, a professor and Arctic ecologist at the University of Washington and lead author of the study, said in a statement from NASA’s Earth Observatory. “When there’s no sea ice platform, the bears end up moving onto land with no or minimal access to food. Our research looked at how these changes affect their body condition and reproduction.”
The backdrop is stark. In recent decades, sea ice concentrations have dropped by 13% per decade since 1979 as global temperatures warmed, NASA noted, with Arctic regions warming twice as fast as the rest of the world. This means sea ice forms later in the fall and breaks up earlier in the spring.
“Climate-induced changes in the Arctic are clearly affecting polar bears,” said Laidre, an associate professor of aquatic and fishery sciences, in a statement from the University of Washington. “They are an icon of climate change, but they’re also an early indicator of climate change because they are so dependent on sea ice.”
Baffin Bay is home to a subpopulation of polar bears that stick to that region, the researchers noted. They tracked the movement of adult female bears, assessed litter sizes and gauged the bears’ general health between the 1990s, and the years between 2009 and 2015.
They studied 43 adult females in Baffin Bay from 1991 to 1997, and 38 females from 2009 to 2015, as NASA’s Earth Observatory noted. The bears follow sea ice as the season unfolds, which brings them to Baffin Island in the fall at the ice’s lowest extant, the researchers found. When the ice forms again, they can return to Greenland.
However, the ice is taking its time coming back, forcing the bears to spend a month more on land than they have in the past.
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