Few Caribou Births in Greenland Linked to Sea Ice Melt

Melting sea ice in Greenland may be leading to fewer caribou births and higher calf mortality, according to new research linking the loss of sea ice with changes of the timing of plant growth on land.

Researchers from Penn State University report that sea ice melt spurs the early growth of plants, which goes on to affect the feeding patterns of caribou. The caribou are reportedly bearing fewer offspring, which the researchers, writing in journal Nature Communications, link to the sea ice melt.

"I initially was interested simply in determining how closely timed the calving season was to the onset of vegetation green-up," said Penn State biologist Eric Post, "without a thought as to how this relationship might be affected by climate change."

Post has spent the past two decades conducting research on Greenland. He said that as he observed an increasingly earlier start to the plant growing season, a corresponding shift in caribou calving has not been observed.

"Until this study, identifying the environmental driver of this change has been the biggest challenge, one that we're getting a better understanding of now that we have more years of data," Post said, adding that the ongoing decline of sea ice has been linked to increases in local temperatures, leading the researcher to hypothesize that sea ice decline was linked to local warming and the corresponding early plant growth.

When the plants are young they are at peak nutrients, which are beneficial to caribou.

"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 researcher Jeffrey Kerby. "The animals show up expecting a food bonanza, but they find that the cafeteria already has closed.

"This scenario is what we call a trophic mismatch -- a disconnect between the timing of when plants are most nutritious and the timing of when animals are most dependent on them for nutrition," Kerby said.

Post said the scenario highlights how interconnected all the pieces of the ecosystem are.

"Sea ice is part of a broader climate system that clearly has important effects on both plants and animals. Exactly how sea-ice decline might affect species interactions in this and other types of food webs on land in the Arctic is a question that deserves greater attention," Post said.