Temperatures are rising faster in the Arctic than anywhere else in the world, giving green vegetation a stronger foothold in the typically icy region. While a greener Arctic could help suck some excess carbon dioxide out of the atmosphere, dark vegetation also absorbs more sunlight, which could help to speed up global warming. You might think all that extra vegetation would at least be a good thing for plant-munching animals like caribou, which need to eat up to 12 pounds of grass and other plants every day, but a new study suggests a greener Arctic is bad for caribou as well.
A team of researchers from the United States and Norway tracked 11 herds of caribou over a 35-year period. During that time, temperatures in the Arctic soared, sea ice retreated, and vegetation thrived. Comparing herd populations alongside these other factors, the researchers found that, as the amount of plant biomass in the summer time increased, the caribou populations fell.
The problem, the authors speculate, is that the wrong kinds of plants are thriving in the warming Arctic. Shrubs that contain toxins as a defense mechanism against herbivores—like birch and alder—have a competitive advantage over edible species. The more land these shrubs cover, the less space there is for lichen to grow—a winter staple for the caribou.
Caribou are just one of many species threatened by global warming, many of which are only found in the Arctic. Arctic foxes, polar bears, bowhead whales, and narwhals are all in trouble, according to the World Wildlife Fund, not to mention the roughly four million humans living in the Arctic.