For most animals, adapting to climate change won’t mean evolving new ways to stay cool—they’ll just pick up and move to cooler habitats. It’s how the world’s fauna survived climatic changes in the past, but this time the journey will be more difficult thanks to a relatively new challenge: a continent-wide obstacle course of roads, cities, farms, and other man-made barriers. To get around these obstructions, animals will need natural pathways, known as wildlife corridors, that people create by connecting isolated habitats. But before we can identify and plan these pathways, we first need to know what routes the animals will take.
A mezmerizing animated map published this week by the Nature Conservancy attempts to show where exactly these corridors might be as animals weave their way to cooler climates. By combining the projected movements of nearly 3,000 species of birds, mammals, and amphibians (represented by blue, pink and yellow lines, respectively, and shown in full below), the map highlights the major migratory routes wildlife will take—along with the lands that need preservation—to make these journeys possible. (Check out Audubon's Birds and Climate Change Report to see future range maps for more than 300 bird species.)
The basis for the map is a data set put together in 2013 by a group of climate scientists. Their goal was to plot the current ranges of 2,903 vertebrates (more than half of which are birds) and then predict where each will end up if they want to stay cool 70 years from now. But predicting migration routes is more complicated than just drawing a straight line between two points; the animals will want to avoid all those previously mentioned obstacles while also spending as much time in undeveloped land as possible. So the researchers overlaid a land-use map to show human development and predict the routes animals would most likely take if forced from their current habitats. All this data was then used to create the final animation. Each swirly line represents a common pathway that many animals will need by the end of the century to reach the cooler climates
“We traced the little routes that would best avoid human impacts on the landscape to get to suitable climates,” says Josh Lawler, a University of Washington ecologist who led the research illustrated by the map. “By overlaying all those routes, we were able to get an idea of how species might move from one place to another.”
A quick glance at the map reveals an obvious—and somewhat expected—pattern: Animals will travel north to cooler areas by largely sticking to mountain chains. The most prominent route funnels animals from the Eastern half of the country along the Appalachian Mountains and north into Canada. Low-lying areas in the Great Plains, Deep South, Rust Belt, and all along the Eastern Seaboard are expected to undergo significant warming. They're also highly developed. As a result, animals will have few options but to flee into cooler areas along mountaintops, where they’re less likely to run into farms, towns, and cities.
The western U.S. features more escape routes, although most also track cool, high mountain peaks. In a few spots, the routes form small spirals. “It looks like they’re going down the drain almost,” Lawler says. These spirals point to high-elevation spots that could serve as refuges for species over the next century—or possibly turn into traps. “If the temperatures keep going up and the climate keeps changing, those species will no longer be able to survive there, so they’re kind of dead ends,” he says.
While the map shows projections for birds, amphibians, and mammals, birds have a big advantage: wings. Unlike earth-bound fauna, most birds can fly over obstacles to reach cooler areas—a fact the map does not take into account. Migratory birds in particular are unlikely to rely on natural corridors, as they’re used to scanning the landscape for suitable habitat and adjusting their routes as needed.
However, some bird species are unwilling or unlikely to risk crossing open spaces to find better habitat. “It’s the resident birds that particularly avoid edges and use interiors that will have more trouble moving and for which these pathways will be more important,” Lawler says. If non-migratory birds need to move north, they’ll need a well-connected landscape to do so.
An example of one such bird is the Red-cockaded Woodpecker, a federally endangered species that rarely leaves the protected canopy of longleaf pine forests in the southeastern U.S. When the woodpeckers are ready to start their own family clusters, they typically carve out new nest cavities within a mile of their birthplace—a preference that could slow their adaptation to climate change. Nick Haddad, a North Carolina State University ecologist, is currently studying whether the Red-cockaded Woodpecker will use wildlife corridors to travel north if ousted by warm temperatures. “The question is: Can they get there?” he says. “And that’s when the corridors, the actual structure of landscapes, become absolutely essential.”
As it stands, the woodpecker could be in trouble if it does have to move. Forest patches in the southeastern U.S. are deeply fragmented. A recent study found that plants and animals living in just 2 percent of Eastern natural areas will be able to easily move through connected lands to escape warming temperatures, compared with 41 percent of natural areas out West. And that’s likely to get worse: Urban areas such as Charlotte, Atlanta, and Raleigh are developing quickly. “Once highways go in, once cities are built, then that’s a permanent block to migration," Haddad says.
With more and more people moving back to urban areas, it will be important to responsibly manage sprawl with the future migratory routes of animals in mind. Maps such as this one are important for recognizing how we might do this, but it’s not just urban planners and land managers who can create wildlife corridors—anyone with a backyard can cultivate habitat welcoming to birds and other wildlife. Of course, greater proactive efforts to reduce the contributing factors to climate change are also necessary. “It’s also critical that we also reduce emissions to give those species that will have a harder time keeping up a chance,” Lawler says.