Mammals may not get to cool climates in time

A new study is the first to consider whether mammals will actually be able to move to those new areas suitable for mammals before they are overrun by climate change. Carrie Schloss, University of Washington research analyst in environmental and forest sciences, is lead author of the paper in the Proceedings of the National Academy of Sciences. “We underestimate the vulnerability of mammals to climate change when we look at projections of areas with suitable climate but we don’t also include the ability of mammals to move, or disperse, to the new areas,” Schloss says. Indeed, more than half of the species that scientists have in the past projected could expand their ranges in the face of climate change will, instead, see their ranges contract because the animals won’t be able to expand into new areas fast enough, says co-author Joshua Lawler, associate professor of environmental and forest sciences. In particular, many of the hemisphere’s species of primates—including tamarins, spider monkeys, marmosets, and howler monkeys, some of which are already considered threatened or endangered—will be hard-pressed to outpace climate change, as are the group of species that includes shrews and moles. Winners of the climate change race are likely to come from carnivores like coyotes and wolves, as well as the group that includes deer and caribou, and one that includes armadillos and anteaters. The analysis looked at 493 mammals in the Western Hemisphere ranging from a moose that weighs 1,800 pounds to a shrew that weighs less than a dime. The study considered climate change, but not other factors that cause animals to disperse, such as competition from other species. To determine how quickly species must move to new ranges to outpace climate change, researchers used previous work by Lawler that reveals areas with climates needed by each species, along with how fast climate change might occur based on 10 global climate models and a mid-high greenhouse gas emission scenario developed by the U.N. Intergovernmental Panel on Climate Change. The researchers coupled how swiftly a species is able to disperse across the landscape with how often its members make such a move. In this case, the scientists assumed animals dispersed once a generation. It’s understandable, for example, that a mouse might not get too far because of its size. But if there are many generations born each a year, then that mouse is on the move regularly compared to a mammal that stays several years with its parents in one place before being old enough to reproduce and strike out for new territory. Western Hemisphere primates, for example, take several years before they are sexually mature. That contributes to their low-dispersal rate and is one reason they look especially vulnerable to climate change, Schloss says. Another reason is that the territory with suitable climate is expected to shrink and to reach the new areas animals in the tropics must generally go farther than in mountainous regions, where animals can more quickly move to a different elevation and a climate that suits them. Those factors mean that nearly all the hemisphere’s primates will experience severe reductions in their ranges, Schloss says, on average about 75 percent. At the same time, species with high dispersal rates that face slower-paced climate change are expected to expand their ranges. “I think it’s important to point out that in the past when climates have changed—between glacial and interglacial periods when species ranges contracted and expanded—the landscape wasn’t covered with agricultural fields, four-lane highways and parking lots, so species could move much more freely across the landscape,” Lawler says.