A polar bear walks across rocky ground near Wager Bay, Canada. Perhaps the Arctic’s most charismatic megafauna, polar bears face serious threats from global warming. The bears depend on sea ice as a platform from which they can hunt seals, their main prey. As more sea ice melts and polar bears are left with rocky ground like that shown in the picture, hunting for food becomes increasingly difficult for these large mammals.

Like many other species, including the great white shark, polar bears appear to be moving northward as temperatures warm. Whether these species can outrun the warming temperatures is unclear, as some scientists say that global warming will lead to the extinction of millions of species, including polar bears, and many birds and amphibians, in the next 50 years.

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Photo gallery by Chelsea Lane-Miller