Polar Bears Becoming Thinner & Having Less Cubs Due To Melting Sea Ice

A new study published in Ecological Applications found that polar bears are becoming thinner and not having as many cubs as a result of melting sea ice in their habitat, reported CNN.

Polar bears rely on sea ice for hunting seals, making dens, mating, and traveling. As sea ice continues melting at alarming rates in the Arctic and earlier in the season, polar bears have less space and less time to eat and produce offspring, leading to a decline in their populations. The polar bear is already listed as a vulnerable species, which is one step from endangered.

Study author Kristin Laidre, who is a professor of aquatic and fishery sciences at the University of Washington, made a statement about the study's findings.

"Climate-induced changes in the Arctic are clearly affecting polar bears. 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."
Laidre added that seeing how melting sea ice affects polar bears could provide insight into how it will affect other species as well. She said that the polar bears inhabit a seasonal ice zone, meaning that the ice melts completely during the warmer months.
"Bears in this area give us a good basis for understanding the implications of sea ice loss."

Talini (L), a 9-month old 160-pound polar bear cub, swims with her mother Barle at the Detroit Zoo's Artic Ring of Life exhibit August 25, 2005 in Royal Oak, Michigan.
Getty Images | Bill Pugliano

The researchers tracked the movements of adult female polar bears living in Greenland over two periods of time in the 1990s and 2010s. Between 2009 to 2015, the bears were seen spending an average of 30 more days on land than they did during the 1991 to 1997 period. The scientists believe that this is because sea ice is melting faster and sooner in the year, effectively land-locking the polar bears.

When there's less sea ice, the polar bears wait on land until the ice builds up again for them to travel out into the sea and hunt seals. Without sea ice, the bears don't get enough to eat and become thinner. Of the 352 bears that were studied, not even 50 were considered fat, a marker of how well their body can keep them warm in the freezing temperatures.

"When the bears are on land, they don't hunt seals and instead rely on fat stores," Laidre explained. "They have the ability to fast for extended periods, but over time they get thinner."

In addition to becoming thinner, polar bears were also found to have less offspring, most likely due to their inability to find enough food to sustain them and their developing cubs.

Researchers warn that a massive conservation effort is needed to prevent the polar bear from moving to an endangered species level and eventually becoming extinct.