Global climate change will have winners as well as losers. The widespread and adaptable red fox has expanded its range northward over the past 70 years, but the fox's impact on its northern neighbors remains uncertain.
The arctic fox (Alopex lagopus) lives where many animals can't: in bitterly cold and often food-scarce tundra. Its small size means it doesn't need much food to get by. But in a warming Arctic there's more to eat, and the new bounty attracts the arctic fox's southern neighbor—the much bigger red fox (Vulpes vulpes).
Red foxes hadn't occupied the tundra in the past partly because it was too cold; with their longer ears and limbs, they lose heat faster than their Arctic cousins. But the temperature in the Arctic has risen between 2 and 3°C (3.6-5.4°F) in the past 50 years, making the region more hospitable to the red fox.
Can the red fox and arctic fox coexist? No one knows for certain, but in some areas arctic fox numbers decrease when red foxes move in. And when the two species are in pens together, red foxes take over the best denning, resting, and feeding areas. However, the arctic fox will likely survive in Greenland, where it is relatively common and unthreatened—and where the red fox is rare.
Fossil evidence suggests that competition with the red fox may not be the arctic fox's only climate-induced problem. Today, the arctic fox is restricted to the tundra regions in the Northern Hemisphere. During the last glaciation, the foxes—and the tundra—existed as far south as modern Belgium, Germany and southwestern Russia. Experts on fox fossils conclude that when the glaciers retreated, southern populations didn't—or couldn't—simply move with the tundra back north. Instead, they went extinct. To some, this suggests that moving north to escape warming temperatures may not be an option for some arctic fox populations.