In
southeast Greenland, a genetically unique and isolated population of polar
bears has been discovered.
Scientists
who examined and followed the bears discovered that they are able to survive
despite having limited access to sea ice – which is vital for polar bears – by
relying on freshwater ice provided by Greenland's ice sheet.
The
bears were described in a study published in the journal Science on Thursday.
In
a statement, lead study author Kristin Laidre, a polar research scientist at
the University of Washington's Applied Physics Laboratory, said, "We
wanted to survey this region because we didn't know much about the polar bears
in Southeast Greenland, but we never expected to find a new subpopulation
living there."
“We
wanted to survey this region because we didn’t know much about the polar bears
in Southeast Greenland, but we never expected to find a new subpopulation
living there,” said lead study author Kristin Laidre, a polar research
scientist at the University of Washington’s Applied Physics Laboratory, in a
statement.
“We
knew there were some bears in the area from historical records and Indigenous
knowledge. We just didn’t know how special they were.”
An icy necessity
Traveling
far, the 19 known polar bear populations rely on sea ice to hunt their prey,
like ringed seals, and sit near breathing holes to capture their prey. The
calories provided by seals can help them store energy for months when food and
sea ice is more scarce.
As
the Arctic warms more than twice as quickly as the rest of the earth, sea ice
is swiftly melting and disappearing. When the sea ice melts, polar bears must
go to land, which limits their dietary options.
Meanwhile,
polar bears in southeast Greenland prefer to stay close to home, thus they have
developed a unique adaptation to their surroundings. Polar bears have access to
river ice and some restricted access to sea ice, which helps them catch seals,
despite being isolated by the Greenland ice sheet, mountains, open water, and
fast-flowing coastal currents.
Between
February and late May, bears can exploit sea ice. They hunt seals on the
freshwater ice when it breaks away from the ice sheet for the rest of the year.
"As
a result of climate change, polar bears are at risk of losing their ice."
"This new population gives us some insight into how the species can
survive in the future," said Laidre, who is also an associate professor of
aquatic and fishery sciences at the University of Washington.
"However,
we must use caution when extrapolating our findings because the glacier ice
that allows Southeast Greenland bears to survive is not present throughout the
Arctic."
In
March 2015, an adult mother polar bear and two 1-year-old pups stroll on
snow-covered freshwater glacier ice. - Kristin Laidre/University of Washington
The
environment of southeast Greenland is a unique, small-scale climate refuge
where the bears can survive, and similar habitats can be found along
Greenland’s coast and the Norwegian island of Svalbard.
“These
types of glaciers do exist in other places in the Arctic, but the combination
of the fjord shapes, the high production of glacier ice and the very big
reservoir of ice that is available from the Greenland Ice Sheet is what
currently provides a steady supply of glacier ice,” said study coauthor Twila
Moon, deputy lead scientist at the US National Snow and Ice Data Center in
Boulder, Colorado, in a statement.
“In
a sense, these bears provide a glimpse into how Greenland’s bears may fare
under future climate scenarios,” Laidre said. “The sea ice conditions in
Southeast Greenland today resemble what’s predicted for Northeast Greenland by
late this century.”
Aerial research
The
new study is comprised of 30 years of historical data from Greenland’s east coast
and seven years of new data from the southeastern coast. The latter is a remote
region with sharp mountains, heavy snow and unpredictable weather, making it
difficult to study.
The
research team spent two years consulting with polar bear subsistence hunters,
who hunt for survival, rather than sport, in eastern Greenland. The hunters
were able to share their expertise and contribute samples for genetic analysis.
The
researchers, working with the Greenland Institute of Natural Resources in Nuuk,
Greenland, were able to study and track the bears using helicopters as the
researchers flew over sea ice, estimating that there are a few hundred bears
living in the remote area. This is similar to other small populations of polar
bears elsewhere.
Female
polar bears in southeastern Greenland are smaller than those in other parts of
the country. Smaller bears also have fewer cubs, which could be related to
their looking for partners as they wander around the surrounding fjords and
mountains. However, the researchers won't know for sure until they receive more
data from the bears' long-term surveillance.
Bears
either travel through fjords on ice or climb mountains to reach other fjords.
Half of the 27 bears tracked during the investigation floated south by mistake
for an average of 120 miles (190 kilometers), stranded on small ice floes
caught in the strong East Greenland coastline current.
A
fjord in southeast Greenland is shown filled with open water in April 2016. -
Kristin Laidre/University of Washington
Once
the bears had a chance, they just hopped off of the ice and trekked back to the
fjord they call home. Created by glaciers, fjords are long, narrow, deep sea
inlets found between high cliffs.
“Even
with rapid changes happening on the ice sheet, this area in Greenland has the
potential to continue to produce glacial ice, with a coast that may look
similar to today, for a long time,” Moon said.
The
researchers warn, however, that this habitat may not be enough for other polar
bears suffering in the wake of the climate crisis.
“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,” Laidre said.
“But
I don’t think glacier habitat is going to support huge numbers of polar bears.
There’s just not enough of it. We still expect to see large declines in polar
bears across the Arctic under climate change.”
Uncertain future
The
researchers assume that polar bears in southeast Greenland have evolved in
isolation for hundreds of years. According to the study authors, the oldest
written record of bears in this place originates from the 1300s, while the
first recorded mention of bears in the region's fjords dates from the 1830s.
The
polar bears' whereabouts are unclear. Researchers aren't sure if the number is
constant, growing, or shrinking, but Laidre believes that more monitoring will
show what the future holds for this unusual species.
The
polar bears in southeastern Greenland are so genetically different as a result
of their isolation that the researchers propose that they be classified as the
species' 20th subpopulation. And Greenland’s government will make any decisions
regarding protection for the bears.
Three
adult polar bears can be seen using the sea ice during the limited time when it
is available in April 2015. - Kristin Laidre/University of Washington
“Preserving
the genetic diversity of polar bears is crucial going forward under climate
change,” Laidre said. “Officially recognizing these bears as a separate
population will be important for conservation and management.”
Meanwhile,
sea ice continues to decline in the Arctic, which greatly reduces survival
rates for most polar bear populations going forward.
“Climate
action is the single most important thing for the future of polar bears,”
Laidre said.
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