Polar bears have long been the poster species for the damaging effects of climate change, but a new study suggests they may get along just fine, even in the absence of sea ice.
A previously unknown population of polar bears has been found living in south-east Greenland, and rather than hunting seals from sea ice, they make do with hopping on to chunks of freshwater ice that calve off glaciers.
The remote region had been poorly studied until now because of its unpredictable weather, jagged mountains and heavy snowfall, which makes the area inaccessible.
But a seven-year project has found a few hundred polar bears thriving on the freshwater ice floes, suggesting that the species could survive the sea-ice melts predicted with global warming.
“If you’re concerned about preserving the species, then yes, our findings are hopeful – I think they show us how some polar bears might persist under climate change,” said lead author Kristin Laidre, professor of aquatic and fishery sciences at the University of Washington.
“The sea ice conditions in south-east Greenland today resemble what’s predicted for north-east Greenland by late this century.
“These bears provide a glimpse into how Greenland’s bears may fare under future climate scenarios.
The polar bears were found to be physically and genetically distinct from other species, which researchers believe is because they are hemmed in by mountains, the Denmark Strait, the East Greenland coastal current and the Greenland Ice Sheet.
Body measurements suggest that adult females are smaller than in most regions. They also have fewer cubs, which may reflect the challenge of finding mates in the remote landscape of fjords and mountains.
Unlike other polar bears, the community also prefers to stay in one place, rather than venturing far over sea-ice to hunt. Satellite tracking showed that when 27 bears accidentally floated 120 miles on ice floes caught in a coastal current, they swam to land and walked back home.
“They are the most genetically isolated population of polar bears anywhere on the planet,” said co-author Professor Beth Shapiro, of the University of California, Santa Cruz and investigator at the Howard Hughes Medical Institute.
“We know that this population has been living separately from other polar bear populations for at least several hundred years, and that their population size throughout this time has remained small.”
'A steady supply of ice'
The landscape means that the south-east Greenland bears have access to sea ice for only four months, between February and late May, but for the remaining two-thirds of the year, they hunt seals from chunks of freshwater ice breaking off the Greenland Ice Sheet.
But researchers say the fact that bears can survive suggests that marine-terminating glaciers, and especially those regularly calving ice into the ocean, could become climate sanctuaries as ocean ice melts.