A new study published in the Communications Earth and Environment journal highlights a dire prediction: polar bears in Canada’s Hudson Bay could face extinction if global temperatures increase by 2°C.
Key Findings
- Hudson Bay: A crucial habitat for a significant population of polar bears (Ursus maritimus), Hudson Bay is a seasonally ice-covered inland marginal sea of the Arctic Ocean.
- Seasonal Ice Cycle: Each July, the summer sea ice retreat forces polar bears onshore, where they rely on fat reserves during a fasting period until the ice re-forms in winter, allowing them to hunt seals again.
- Ice-Free Periods: Historical data shows that from 1979 to 2014, Hudson Bay had an average ice-free period (IFP) of around 128 days. In regions like Foxe Basin, the IFP was shorter, while it extended up to 165 days in eastern Hudson Bay and 150 days in western Hudson Bay, near Churchill, Manitoba.
Impacts of Climate Change
- Rising Temperatures: Over the last 30 years, Hudson Bay has warmed by more than 1°C. This warming trend has led to earlier sea ice melt in spring and later ice formation in fall, extending the ice-free period by approximately a month.
- Fasting Challenges: During the extended ice-free period, polar bears primarily fast, occasionally feeding on marine mammal carcasses or hunting caribou. However, prolonged fasting leads to significant weight loss—1 to 2 kg per day.
Population Decline
- Historical Decline: Polar bears in Hudson Bay historically fasted for about 120 days, maintaining a healthy population. However, the extension of the IFP has led to a noticeable decline in polar bear numbers, particularly in western Hudson Bay.
- Recent Trends: Between 2016 and 2021, the polar bear population in Hudson Bay decreased by 27%, compared to an 11% decline between 2011 and 2016. The population is now roughly half of what it was in 1987, with significant reductions in adult females, young bears, and cubs.
Future Projections
- CMIP6 Insights: The latest projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6) suggest a more detailed and concerning future for polar bears. If global warming is limited to 2°C above pre-industrial levels, the ice-free period may be kept under 183 days in western and southern Hudson Bay, offering some hope for adult polar bear survival.
- Long-Term Outlook: Despite this potential mitigation, the extended ice-free periods have already severely impacted polar bears, making extirpation in this region a significant possibility.
Policy Implications
This study underscores the urgent need for comprehensive climate action to mitigate the impacts of global warming on vulnerable species like polar bears. Policymakers must consider these findings in their climate change strategies to ensure the survival of these iconic Arctic predators.