This is the desperate struggle of polar bears to find food in the melting Arctic. Science

In a world where climate change is altering natural habitats at a rapid pace, polar bears have become one of the symbols of the fight for survival. Summers are getting longer, the planet’s temperature is rising and ice is shrinking. When the frozen blocks of the Arctic disappear, bears spend more time on land, where food is harder to find, as their traditional hunting strategies that take advantage of sea ice become less effective. A study was published today in nature communication It presents a picture of the challenges that the 25,000 polar bears left on the planet face in order not to die of starvation.

In the period of late spring and early summer, polar bears use sea ice as a hunting platform. They primarily feed on seals that are giving birth and weaning their babies during the same season. When the ice melts, Arctic giants have to slow down as much as possible to save energy. A team of scientists led by Anthony Pagano, a wildlife biologist with the United States Geological Survey, observed polar bears up close for three weeks in the summer. To achieve this, they placed collars equipped with cameras and GPS on twenty bears in western Hudson Bay, Manitoba (Canada). The population in the region has declined by about 30% since 1987 and the ice-free period has increased by three weeks since 1979, leaving bears on land for about 130 days in the past decade.

After analyzing the images, they found that bears try different strategies for feeding and maintaining energy reserves, including scavenging and resting at levels similar to grizzly bears when entering hibernation. Of those who were active, 70% ate terrestrial foods such as berries, herbs and bird carcasses. Three bears dared to swim long distances to find food in the water and although two of them found the remains of a beluga and a seal, they were unable to eat them while swimming or bring them to land.

Regardless of their strategy of eating or resting, there was a steady loss of body mass and 19 of the 20 lost an average of 1 kilogram per day. “Continued increases in the duration of heat on land will be associated with increased risk of starvation,” Pagano says. “No strategy will allow polar bears to exist on land for more than a certain period of time. “Even the bears that were looking for food lost weight at the same rate as the bears that were lying down,” says Charles Robbins, director of the Bear Center at Washington State University and a co-author of the study.

It has been speculated that polar bears can adapt to the ice-free season by searching for terrestrial food, but studies show that it is not so easy to find and it does not provide them with the nutrients or energy they need, so they In the end one will have to suffer from famine. David Nogues Bravo, a macroecologist at the Center for Macroecology, Evolution and Climate at the University of Copenhagen, who did not participate in the study, points out that food shortages “reduce the possibility of maintaining generational replacement” and adds that “terrestrial Food provided them some energy gain, but ultimately they had to expend more energy to access those resources.

The ice covering the Arctic reaches its lowest level every September and each year is less than the previous one. According to NASA data based on multiple satellites, the polar caps have expanded at a rate of 12.6% each decade since the 1980s. A 2023 study supported by observations from NASA and ESA satellites estimates that ice-free September will occur for the first time between 2030 and 2050. And if greenhouse emissions are not reduced, by 2100 the Arctic region will spend half the year without ice.

The study’s findings have important implications for polar bear conservation, but also invite us to examine the impacts on the Arctic’s marine and terrestrial ecosystems. According to Nogues, the presence of these long-term hunting animals in terrestrial areas has indirect effects on other species such as birds. He adds, “Bears are able to eat dozens of eggs in a short period of time and reduce the chances of survival of these bird populations.”

It is not new that polar bears are in serious danger of extinction. Surprisingly, due to melting sea ice, the number of children is declining drastically and adults are facing starvation. “I have seen polar bears in the Arctic and it is bleak to see the path to possible functional extinction of this species in the near future,” says Nogues, who emphasizes that it is important to take “biodiversity” into account. The crisis and the climate crisis are not two separate crises, but two sides of the same coin.”

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