Why do longer ice-free seasons increase the risk of starvation for polar bears?

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Jasper National Park: grizzly bear — bear Grizzly bear in Jasper National Park, western Alberta, Canada.

Longer ice-free seasons increase the risk of starvation for polar bears because sea ice serves as their primary platform for hunting seals, their essential prey.1

As global warming causes sea ice to melt earlier and freeze later, polar bears are forced to spend more time on land, where they lack access to their high-energy seal diet. While these bears may attempt to forage for alternative food sources like berries or seabird eggs, these options are lower in quality and require significantly more effort to obtain than hunting seals on the ice. Consequently, the reduction of their hunting habitat directly limits their ability to maintain necessary energy levels, leading to increased rates of starvation and declining population health.1