Scientists have shown, for the first time, that changes in a large-scale climate system can synchronize population fluctuations in multiple mammal species across a continent-scale region. The study, to be published in the 14 November 2002 issue of the journal Nature, compares long-term data on the climate system known as the North Atlantic Oscillation with long-term data from Greenland on the population dynamics of caribou and muskoxen, which are large mammals adapted to breeding in the Arctic.
"The Arctic can provide useful early-warning signals for the rest of the world because the species that live in this sensitive region are expected to be among the first to show the effects of the Earth's changing climate," says Eric Post, assistant professor of biology at Penn State University, who is a coauthor of the study along with Mads C. Forchhammer, associate professor of ecology at the University of Copenhagen in Denmark. "Here we have a very simple system with a very clear signal: two species on opposite sides of a continent that never mix, never compete for food, and have no common predators, yet their population dynamics are synchronized. The only thing they have in common is the large-scale climate system that influences weather throughout the northern hemisphere," Post comments.
Post and Forchhammer studied seven herds of caribou and six herds of muskoxen in Greenland, where the two species live on opposite costs and are separated by an impassable continent-wide ice sheet spanning about 600 miles (1,000 kilometers) at its minimum width. "We chose to study these two species in Greenland because their complete physical and ecological separation rules out the alternative explanations that have confounded previous studies of the role of climate in synchronizing population dynamics, leaving only weather as the controlling factor," Post explains.