Climate Change May Be Indirectly Threatening Caribou In The Arctic
October 1, 2013

Climate Change May Be Indirectly Threatening Caribou In The Arctic

Lee Rannals for - Your Universe Online

New research indicates that caribou may be indirectly affected by climate change due to sea-ice loss in the Arctic.

Researchers, publishing a paper in the journal Nature Communications, say that melting sea ice is leading to fewer caribou calf births and higher calf mortality in Greenland. The team was able to link the melting Arctic sea ice with changes in the timing of plant growth on land, which in turn led to lower production of calves in the area.

Eric Post, a Penn State University professor of biology, and Jeffrey Kerby, a Penn State graduate student, said that data has revealed an increasingly earlier start to the plant growing season, which is a change that has not been matched by earlier calving by caribou in the area. The decline in sea ice has also been associated with increases in local temperature inland in many parts of the Arctic.

"We therefore hypothesized that sea-ice decline was involved in local warming and the associated advancement of the growing season for plants at the study site, and so we set out to test that hypothesis," Post said in a statement.

Evidence shows that caribou have used this area in Greenland as a calving site for over 3,000 years. Caribou typically arrive from their west-to-east migratory journey to search for young plants to eat around the time the animals give birth.

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

The researchers said that while plants respond to warmer temperatures and other changes in the climate by adjusting the timing of their growth, caribou continue to give birth at nearly the same time during the spring.

"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 and Kerby included information from a 1970s study of caribou calving and calf survival at the same site by Danish biologists Henning Thing and Bjarne Clausen. This older study allowed the team to look back for signs of trophic mismatch in the same caribou population over 30 years ago. Post said that they used these older statistics and compared it to their more recent findings.

"We found an interesting contrast to the current state of caribou calving in relation to spring green-up," Post said. "Rather than a trophic mismatch, the observations by Thing and Clausen suggest a high state of trophic match associated with later onset of the plant growing season. As a result, the data from the late 1970s indicate very high calf production in this population at that time."

Post said he plans to study other ecological communities living near sea ice in future research.

"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 concluded.