New research says some animals can't move fast enough to find the new habitat they'll need to survive in a warming world.

Share story

As climate change transforms their habitat, some animals are already on the move. But a new analysis from the University of Washington warns that many species won’t be able to run fast enough to survive a warming world.

On average, about 9 percent of the Western Hemisphere’s mammals migrate too slowly to keep pace with the rapid climate shifts expected over the next century, says the study published Monday in the Proceedings of the National Academy of Sciences. In some areas, including parts of the Appalachian Mountains and the Amazon basin, nearly 40 percent of mammals may be unable to reach safe haven in time.

“It’s another warning sign that the climate is changing, and that not all plants and animals are going to be able to deal with it,” said co-author Joshua Lawler, associate professor of environmental and forest science at the UW.

The species most at risk include the monkeys of Central and South America and tiny creatures such as shrews and moles. Deer, elk and big carnivores such as wolves and coyotes stand a better chance, because they evolved to cover long distances.

The study is the first to combine climate-change projections with estimates of how rapidly mammals shift their ranges.

“This paper does a really nice job of taking that critical next step,” said David Ackerly, of the University of California, Berkeley. Ackerly was not involved in the UW project, but his lab laid some of the ground work by estimating the rate at which temperature changes are expected to sweep across the landscape as rising concentrations of greenhouses gases warm the planet.

Over the past decade, scientists have discovered that moving day is already here for a wide range of species. Mountain moths are fluttering upslope to cooler temperatures and some butterflies have shifted their territories more than 130 miles.

American pikas, which were never found above 7,800 feet at the turn of the 20th century, now live at elevations nearly 2,000 feet higher.

The UW scientists focused their analysis on 493 mammal species, from moose to the 2-inch-long pygmy shrew. The researchers estimated the animals’ migratory rates based on body size and how quickly they reproduce.

Individual rabbits may not travel far from their birthplace, but if every generation moves a little bit, the species as a whole can cover a lot of ground. New World monkeys, which take several years to mature, disperse more slowly.

The team combined 10 computer models to estimate the most likely range of temperature changes over the next 100 years, said lead author Carrie Schloss.

Some of the results were surprising. While temperatures spikes are expected to be most pronounced at northern latitudes, many of the imperiled species live near the equator. One reason for their poor outlook is that tropical creatures are adapted to an environment where temperatures rarely change, Lawler explained.

Also, flat terrain, such as the Amazon basin and the Central United States, forces animals to travel farther to find cooler or more hospitable climes.

Mammals who live near mountains might have an easier time, Lawler said. They don’t have to climb far to find relief from the heat. That’s contrary to earlier studies that concluded mountain-dwelling animals might be in more danger of extinction.

If the new analysis is right, mammals of the Pacific Northwest don’t have much to worry about. In Western Washington and Oregon, the ocean is expected to moderate climate change, Lawler said. Effects are likely to be more severe in the Inland Northwest, where habitats such as sagebrush steppe are already on the edge.

The scientists admit their study presents an oversimplified view of the real world. It doesn’t account for shifts in the other factors that influence mammals’ distribution, such as competition and predation. Nor does it account for species’ ability to adapt to changing habitat.

The scientists did try to make the picture more realistic by factoring in some of the barriers mammals will face as they set out for greener pastures — things such as roads, shopping malls and cities. In many cases, the analysis found species that would otherwise win the race with climate change will falter in the face of these modern obstacles.

But the analysis also points to ways people might be able to reduce the impact of climate change — in addition to cutting back emissions, Schloss said. If it’s possible to identify choke points that block animal migrations, corridors could be built to ease the creatures on their way.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com