Climate Change: Polar Bears face starvation threat as ice melts

Polar bears face starvation as the Arctic sea ice melts

Some polar bears face starvation as the Arctic sea ice melts because they are not able to adapt their diets to living on land, scientists have found.

The iconic Arctic species typically relies on catching ringed seals on ice floes offshore for their sustenance. However, in a warming world where ice is vanishing, many bears are now spending more time on land, consuming bird eggs, berries, and grass. 

Unfortunately, the transition to a land-based diet leads to rapid weight loss, heightening the risk of death. While polar bears have symbolized the threat of climate change in the Arctic, the situation for this species is intricate. 

The decline in bear numbers until the 1980s was primarily due to unsustainable hunting, but with increased legal protection, their numbers have rebounded. Presently, the most significant threat to polar bears is the rise in global temperatures, as their survival is intricately linked to the frozen Arctic seas.

These seas serve as platforms for hunting ringed seals, rich in fat, especially in late spring and early summer. However, as many parts of the Arctic experience increasing ice-free periods during warmer months, the bears face challenges. 

For instance, in Western Manitoba, where the study occurred, the ice-free period extended by three weeks between 1979 and 2015. Researchers monitored 20 polar bears over three years during the summer months, collecting blood samples, weighing the bears, and fitting them with GPS-equipped video camera collars.

This enabled scientists to document the movements, activities, and dietary habits of the animals.

During ice-free summer months, polar bears employed various survival strategies, with some prioritizing rest and energy conservation. The majority attempted to forage for vegetation, berries, or swam in search of food. Both approaches proved unsuccessful, with 19 out of the 20 bears in the study experiencing body mass loss, reaching up to 11% in some cases, averaging one kilogram per day.

Lead author Dr. Anthony Pagano from the US Geological Survey in Alaska noted that regardless of the strategy employed, there was no tangible benefit in prolonging the bears' survival on land.

Co-author Charles Robbins from the Washington State University Bear Center emphasized the fundamental differences between polar bears and grizzly bears, stating, "They're very, very different."

Of the three bears that took to the water, two found carcasses of dead animals but spent only a brief time eating, as they were too fatigued from their efforts. One sub-adult female discovered a dead beluga whale, taking a couple of bites but mainly using it as a buoy to rest on.

A notable observation was that one bear gained 32kg in weight. Researchers believe this bear, who spent much time resting and conserving strength, was fortunate to encounter an animal carcass.

While prior research has outlined the challenges posed by climate change in the coming decades, this new study raises crucial questions about the species' adaptability. Other researchers suggest that the impacts of climate change on polar bears may vary depending on location. 

Jon Aars from the Norwegian Polar Institute, not involved in the study, mentioned that while polar bears might disappear from areas with future sea ice loss, some regions may maintain suitable conditions for bears for many decades. The study, providing insights into the challenging conditions faced by bears if sea ice continues to disappear, has been published in Nature Communications.

Source: BBC