Reindeer do not survive on the carrots left out by excited children on Christmas Eve.

During winter in the Arctic, reindeer eat lichens and plants they find beneath the snow. But erratic winter weather can make it hard for them to get to their food.

“We might get a snowfall in October, but then it will rain, and then it will freeze, and then it might snow again, and then it might rain again, and then freeze again, and … then the lichen and other winter fodder will be encased in ice,” says Bruce Forbes of the University of Lapland in Finland.

This alternating rain and snow is not unusual. But he says that as the climate warms, “what’s new is the intensity of the rain, the extent of the area over which it rains heavily, and then the thickness and impenetrability of the ice crust.”

If the ice is very thick, reindeer cannot break through it to reach their food, so they can starve.

“We’re talking tens of thousands of animals starving in individual events,” Forbes says.

Many Indigenous herders in the Arctic depend on reindeer for their livelihoods, so the losses are devastating for the animals and human communities, too.

Reporting credit: Sarah Kennedy/ChavoBart Digital Media.