Polar bears and climate change
Polar bears, known as iconic symbols of climate change, are facing significant threats to their survival primarily due to the loss of sea ice caused by global warming. Initially, conservation efforts in the 1970s led to population recovery, but recent studies indicate that their habitat is shrinking, affecting their ability to hunt for their primary prey, the ringed seal. As sea ice diminishes, polar bears have increasingly resorted to land-based food sources, which are not sufficient for their dietary needs, leading to weight loss and starvation. Furthermore, their proximity to human settlements has risen, resulting in increased conflicts and health risks for both bears and humans.
Scientific projections warn that by 2050, a substantial portion of the polar bear population could vanish, highlighting a potential decline of over 30%. Despite their classification as a threatened species under the Endangered Species Act, political debates have hindered necessary climate action aimed at reducing greenhouse gas emissions. The situation remains critical, as experts stress that immediate actions are required to mitigate climate change impacts, which not only threaten polar bears but also numerous other Arctic species. The ongoing conversation around polar bears serves as a focal point for broader discussions on environmental policy and climate resilience.
Subject Terms
Polar bears and climate change
Definition
The polar bear has become an icon of global warming. In 1973, the five "polar bear nations" (the United States, Canada, Denmark, Norway, and the then Soviet Union) agreed to limit polar bear hunting to the Inuit and other Indigenous peoples. The bear population recovered, only to face a new threat: global climate change.
Changes in sea ice, permafrost, and prey species in the Arctic and subarctic are linked to reduced body condition and smaller litter size in polar bears. In western Hudson Bay, long-term studies conducted by wildlife biologist Ian Stirling of the Canadian Wildlife Service and his colleagues documented climate warming and a significant reduction in the amount, location, and persistence of sea ice adjacent to the shore. The polar bear is heavily dependent on the ringed seal as a food source. Its usual hunting technique requires sea ice. A bear will locate the breathing hole of a seal and then ambush the animal when it comes up for air or will prey upon young seals in their dens. As sea ice diminishes, bears are less able to catch their prey. In 2024, scientists found that polar bears living on land had been unable to adapt to land-based food sources such as bird eggs, berries, and grass, and thus faced rapid weight loss and starvation.
Hungry polar bears waiting on shore for sea ice to form have become a problem for human communities, invading northern villages and encountering human hunters. At one time, this increase in sightings was interpreted as evidence of increasing numbers and used to justify higher quotas for the taking of polar bears. The modern consensus is that polar bears are increasingly attracted to human settlements by trash and other potential food sources due to a decline in their natural hunting conditions. The interaction between bears and humans further threatens the bear population, bringing disease and harmful behavioral changes, as well as the killing of bears that pose threats to humans.
Significance for Climate Change
A series of studies coordinated by the United States Geological Survey (USGS) and released on September 7, 2007, predicted that two-thirds of polar bears would perish by the year 2050. All polar bears in Alaska would be gone. The studies—conducted by American and Canadian scientists—used conservative assumptions to project the loss of sea ice due to global warming. At the time of the 2007 USGS studies, there were an estimated twenty thousand to twenty-five thousand polar bears worldwide. In 2015, the International Union for Conservation of Nature and Natural Resources (IUCN) projected that the global polar bear population would decline by more than 30 percent by 2050. Studies on climate change and polar bears by the USGS were blocked and faced political opposition under the administration of President Trump. In 2019, the population was estimated at 22,000 to 31,000, according to the nonprofit World Wildlife Fund.
Because the polar bear, Ursus maritimus, is thought to have evolved from the brown bear, Ursus arctos, 200,000 years ago, some have suggested that the polar bear might reverse course and adapt to and live in the terrestrial ecological niche now occupied by the brown bear. However, brown bears are primarily vegetarian, whereas polar bears are primarily carnivorous. Brown bear claws are adapted for digging, and polar bear claws are for grabbing and holding prey. Polar bears are slow to reproduce, and it is unlikely that they could change both their behavior and their physical characteristics quickly enough to cope with disappearing sea ice. Sea ice is central to the life of a polar bear. It provides a habitat for prey animals and hunting, mating, and denning sites for the bears themselves. In western Hudson Bay, for example, polar bears gather on the shore each year to wait for sea ice to form.
While polar bears and their response to global warming have been studied longer and in greater depth than has other Arctic species, they are far from the only animal affected by a changing climate. Gray whales migrating south to their breeding grounds off the coast of Mexico have recently appeared to be emaciated, suggesting a shortage of their normal diet of tube worms and amphipods in their summer feeding grounds of the Bering and Chukchi Seas.
Other marine animals that are affected by the loss of sea ice and climate warming in the Arctic include ringed seals, bearded seals, ribbon seals, sea lions, walruses, narwhals, fish, and many seabirds. Biologists have only begun to study how these creatures will respond to the profound changes in their habitat. Polar bears—known to eat dead whales washed up on the shore as well as other carrion—might benefit temporarily from the die-off of marine animals but will suffer eventually as their prey species are reduced.
On May 14, 2008, the polar bear was listed as threatened under the provisions of the Endangered Species Act, and it remains at this status in 2023. This designation is one step down from that of endangered species and offers less protection from human activities. However, Dirk Kempthorne, then secretary of the interior under President George W. Bush, made clear that the Department of the Interior would not allow the polar bear’s plight to be used to justify limits on greenhouse gases (GHGs) saying: "When the Endangered Species Act was adopted in 1973, I don’t think terms like 'climate change’ were part of our vernacular." The act, he said, "is not the instrument that’s going to be effective" in dealing with climate change.
Images of polar bears have been used by conservation groups to advocate reductions in GHGs in hopes of slowing and perhaps reversing global warming and also in fund-raising by these groups. Global warming skeptics complain that such images appeal to emotion and not to reason and demand further proof that a warming climate will result in great reduction and even extinction of polar bear populations by the middle of the twenty-first century.
In the 2010s, it became increasingly clear that the threat posed to polar bears by climate change was indeed backed up by science. In early 2017, the US Fish and Wildlife Service lent its support to the argument that declining sea ice was the primary threat to polar bears and suggested decisive action to halt the warming of the Arctic was necessary to prevent the species extinction. Experts agreed that limiting greenhouse gas emissions would improve the survival chances of polar bears but noted that the apparent climate change skepticism of the administration of President Donald Trump meant immediate action was unlikely. Conversely, President Joseph Biden took immediate efforts to fight climate change by rejoining the Paris Climate Agreement in January 2021, bringing new hope to renewed efforts to fight climate change.
Bibliography
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