Svalbard Polar Bears Maintain Body Condition Despite Rapid Sea Ice Loss, Study Finds
In a surprising twist for climate science, polar bears in the Norwegian Arctic archipelago of Svalbard have not lost body condition despite experiencing rapid sea ice habitat loss due to global warming. This finding, published in the journal Scientific Reports, challenges previous assumptions about how these iconic predators are responding to environmental changes.
Unexpected Resilience in a Warming Arctic
Researchers from the Norwegian Polar Institute and the University of Alberta analysed data from 1,188 records of 770 adult polar bears collected between 1992 and 2019. They measured the "body composition index," an indicator of fat reserves and overall physical health. Contrary to expectations, the study revealed that after initial declines from 1995, the body condition of both male and female polar bears increased from around the year 2000 onwards.
This improvement occurred even as the number of ice-free days in the region surged by approximately 100 over the same period. The Barents Sea around Svalbard, home to one of 20 polar bear populations across the Arctic, has warmed at a rate of up to 2°C per decade, losing sea ice more than twice as fast as other bear habitats.
Adapting to New Prey Sources
Lead author Jon Aars from the Norwegian Polar Institute expressed his astonishment at the results. "If I had been told in 2003 that bears in Svalbard would have access to sea ice two months less on average from 2000 to 2019, I would have predicted they would be skinnier, with potential effects on survival and reproduction," he said. "Instead, we see the opposite—bears are now in better condition."
The researchers attribute this resilience to the bears' ability to exploit alternative food sources on land as sea ice diminishes. Key factors include:
- Increased reindeer populations: Bears have been taking more reindeer, whose numbers have risen significantly.
- Walrus carcasses: Recovery and growth in walrus populations provide additional sustenance.
- Harbour seals: Hunting of harbour seals in West Svalbard has become more common as their populations expand.
- Summer foraging: Bears also consume eggs and birds during the warmer months.
This dietary shift means polar bears are spending more time on land without the ability to hunt their traditional prey, ringed seals, on sea ice. Yet, they have managed to compensate effectively, at least in the short term.
Contrasting with Other Populations and Future Warnings
The findings from Svalbard stand in stark contrast to studies of other polar bear populations, where sea ice loss has been linked to declining body condition and shrinking numbers. Co-author Andrew Derocher from the University of Alberta noted that this highlights the diversity among polar bear groups. "Bears in this region appear to be experiencing short-term buffering to climate impacts due to diverse and new prey types," he explained.
However, scientists caution that this resilience is likely temporary. As sea ice continues to retreat, the bears' ability to maintain their condition may wane. Aars warned, "It is likely that body condition will decline in the future, as sea ice loss will continue. What is uncertain is when this will happen."
Derocher echoed this sentiment, emphasising that the buffering effect is not a long-term solution. John Whiteman, chief research scientist at Polar Bears International, added that while the big picture for conservation remains clear—polar bears depend on sea ice, which is disappearing—this study illustrates the substantial variation in how ice loss has affected bears in different areas thus far.
Ecological Shifts and Broader Implications
The adaptation of Svalbard's polar bears is already having ripple effects on local ecosystems. Increased predation on bird colonies and other wildlife suggests polar bears are becoming a more prominent part of the terrestrial ecosystem than in the past. This shift underscores the complex and sometimes unexpected ways species respond to climate change.
Despite the current stability in body condition, researchers stress that ongoing monitoring is essential. The study serves as a reminder that while some populations may show temporary resilience, the overarching threat of climate change to Arctic habitats and their inhabitants remains severe and pressing.
