As the Arctic ice melts, less Greenland caribou are being born and the population's mortality rate is higher.
The changing climate and melting ice has changed the timing of plant growth, which has affected the animal's lifestyles and has resulted in a lower production rate of caribou calves, a Penn State press release reported.
Eric Post, a Penn State University professor of biology, started observing the local plant growth and its effect on the number of caribou calf births two decades ago.
"I initially was interested simply in determining how closely timed the calving season was to the onset of vegetation green-up," Post said. "Without a thought as to how this relationship might be affected by climate change."
Over the years, Psot has noticed the plant life pops up earlier every year, but the same is not true in terms of calf births.
"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, the decrease in sea-ice coverage has been linked to higher temperatures in the Arctic inland. "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."
The caribou, which have been thriving on the land for over 3,000 years, usually arrive from their annual migration to feed on the plants around calf-birthing time.
"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. "The animals show up expecting a food bonanza, but they find that the cafeteria already has closed."
Plants adjust their growing time to the weather, but caribou's reproductive systems don't do the same.
"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.
The research pair also used data from the 1970s to see how the caribou trends had changed over time.
"This comparison allowed us to look for signs of trophic mismatch in the same caribou population over 30 years ago," Post said.
"We found an interesting contrast to the current state of caribou calving in relation to spring green-up," he 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 and his colleagues plan to see how the rapidly melting ice is interfering with other local animal populations.
"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.
