As sea ice melts, caribou calves go hungry

We’ve heard plenty of bad news about how sea-ice loss affects polar bears. But scientists have now found that the disappearance of Arctic sea ice is tough on animals living inland as well. Through a chain reaction, the ice melt changes the timing of plant growth, making it harder for caribou calves to find food.

The team studied a site in the mountains near Kangerlussuaq, Greenland, which caribou may have been using as a breeding ground for thousands of years. The animals migrate to the area in May or June, and the calves munch on newly-emerged plants.

From 2002 to 2011, the researchers noted when half of the plant species at the site began to grow. That date crept 1.6 days earlier each year, or a total of 16 days over the decade-long study, the team reports in Nature Communications. But the caribou didn’t keep up: The animals continued to give birth at roughly the same time every year.

As the gap between calving and plant growth widens, calves are more likely to die young, the authors say. “Since plants are emerging earlier in the year, they tend to be older and past their peak nutritional value by the time the hungry caribou arrive to eat them,” said study co-author Jeffrey Kerby of Penn State University in a press release. “The animals show up expecting a food bonanza, but they find that the cafeteria already has closed.”

How is this related to sea ice? Arctic sea ice declined from 1979 to 2011, with a particularly steep drop starting in 2000. Ice loss is linked to higher inland temperatures, and that warming triggers earlier plant growth. The lesson: When studying the effects of ice melt, people need to pay attention not just to species that directly depend on the ice but to landlubbers as well. Roberta Kwok | 2 October 2013

Source: Kerby, J.T. and E. Post. 2013. Advancing plant phenology and reduced herbivore production in a terrestrial system associated with sea ice decline. Nature Communications doi: 10.1038/ncomms3514.

Image © Jeffrey Kerby