Without a concerted effort to reduce greenhouse gas emissions, some populations of polar bears will feel the burn of global warming as soon as 2025, scientists warned in a new study.

The research, released Tuesday from the United States Geological Survey, used updated scientific models to determine how different emissions levels would affect global temperatures and thus the Arctic ice that is the polar bear’s habitat.

It may already be too late to avoid hurting polar bears, regardless of whether emissions fall. The researchers found that climate change could reduce the population of 8,500 polar bears in Alaska, Russia, and Norway—a third of the global population—within a decade.

So, Why Should You Care? Other polar bear–populated regions are also expected to see declines, according to the study. But the Polar Basin Divergent Ecoregion that includes Alaska will be hit the quickest and the hardest, according to Todd Atwood, the study’s lead author and head of the USGS Polar Bear Research Program. The reason? That particular region is experiencing some of the most rapid declines in the availability of summer sea ice. Polar bears need that sea ice to hunt their favorite meal—seals—and also to mate and give birth.

“Arctic-wide, the sea ice melt season—the length of time between sea ice breakup in summer and freeze-up in fall—has lengthened at a rate of five days per decade since 1979,” Atwood said.

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The study considered two scenarios to see how polar bears in four Arctic regions would fare. The first scenario analyzed how polar bears would do if the rise of global greenhouse gas emissions was halted by 2040 to avoid catastrophic climate change. The second scenario assumed emissions would rise at the current rate.

The results showed that polar bear populations in two regions—the Divergent region and the Seasonal Ecoregion—along Canada’s Hudson Bay—could see large declines in polar bear populations much sooner than expected if emissions don’t fall.

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The study determined only whether population sizes “decreased” from current levels or “greatly decreased.”

The study also looked at what kind of effects other environmental stressors—such as shipping, oil and gas exploration, disease, and contaminants—could have on the species. “Those had only negligible effects on polar bear populations compared to the much larger effects of sea ice loss and associated declines in their ability to access prey,” Atwood said.