In a surprising turn of events, polar bears within Norway’s Svalbard archipelago are exhibiting an increase in body fat and weight, even as the surrounding sea ice diminishes. Svalbard, situated in the Arctic Ocean, is experiencing warming at a rate seven times faster than the global average.
The sea ice in the northern Barents Sea, a critical hunting ground for these bears stretching between Svalbard and Russia’s Novaya Zemlya, now persists for two months less during winter and spring compared to two decades ago. This environmental shift forces the bears to undertake extensive swims of up to 300 kilometers between their ice-based hunting areas and the terrestrial snow dens on the islands where they give birth.
Despite these challenges, a study led by Jon Aars of the Norwegian Polar Institute revealed that the average size and weight of the Svalbard polar bear population have actually increased since the year 2000. This finding presented a notable surprise to the researchers involved.
Aars described the situation in Svalbard as “good news” locally, while cautioning that this positive observation does not extend to all polar bear populations. “But if you want bad news, you can just go and look somewhere else where you have very, very firm evidence that climate change is impacting polar bears negatively,” he stated.
Global Variations in Polar Bear Populations
The polar bear, a large and solitary predator, is distributed across the Arctic in twenty distinct populations, making accurate population counts exceptionally difficult. While numbers are reported to be declining in certain regions like Alaska, Canada, and Greenland, other areas seem to maintain stable or even growing populations. Data for nine of these populations remains too insufficient to draw firm conclusions.
Specifically, the polar bear population in the Barents Sea, estimated to have ranged from 1900 to 3600 individuals two decades ago, is currently believed to be stable or possibly increasing. The research initiative, which commenced in 1995, involved immobilizing 770 bears using dart guns fired from helicopters. Field teams would then land to measure the bears’ length and, using chest girth measurements, estimate their weight.
Shifting Hunting Strategies and Diet
Analysis of the collected data indicated a decline in the bears’ body condition up to the year 2000, followed by an improvement through to the end of the observation period in 2019. Scientists surmise that the reduction in sea ice might be inadvertently aiding the bears’ hunting success. During spring, when ringed seals give birth to pups on the ice, polar bears typically hunt them to build vital fat reserves for the ice-free months.
Furthermore, these bears appear to be adapting by exploiting new and varied food sources. The roughly 250 individuals that remain on the islands during the ice-free periods are reportedly hunting bearded seals and harbor seals along the coast. The presence of harbor seals, in particular, is increasing in Svalbard due to the warming climate.
These bears, referred to as “local bears,” have also been observed engaging in opportunistic feeding by raiding duck and geese colonies for eggs and have been seen hunting reindeer from a growing cervid population. The carcasses of walruses, another species experiencing an increase in the region, can provide sustenance for extended periods.
Adaptability and Future Uncertainty
Jouke Prop from the University of Groningen in the Netherlands commented on the Svalbard bears’ unexpected adaptability, suggesting that “extinction is delayed.” He characterized their behavior as “crazy things” indicative of a species under pressure, acknowledging that while these strategies might not be universally successful, they could sustain the population in Svalbard for a period.
It is suggested that the polar bear population in Svalbard may not yet have reached the archipelago’s carrying capacity, especially considering that Arctic nations prohibited hunting them for hides and zoological specimens in 1973. However, warming temperatures are beginning to disrupt the foundational elements of the Arctic food chain, starting with algae that grow on the underside of sea ice.
“It will be very difficult to support a reasonable population of polar bears if sea ice disappears,” Prop warned. Echoing this concern, Aars noted that a critical threshold exists, beyond which the continued loss of sea ice will inevitably have a negative impact on polar bears in Svalbard.