Imagine you’re sitting around a fire and someone throws on another log. It bursts into flames and soon, your seat gets too hot for your liking. What do you do? You move, right?
That’s exactly what species around the world have been doing in response to climate change. One recent study found that, on average, organisms are moving away from the equator at a rate of 17 kilometers per decade, or climbing 11 meters higher, in search of cooler conditions. Of course, this rate varies between species; birds are capable of flying great distances and might simply shift the location of their wintering grounds whereas plant distributions change one seed at a time.
Life has moved in response to environmental changes throughout geologic time — it’s how many organisms survived during previous ice ages — and it’s how scientists hope some species may adapt to climate change. However, humans have now introduced a new challenge: we’ve broken up the landscape with cities and roads in ways that can make it hard for species to migrate toward habitats that suit their needs. Now, scientists have evaluated the extent of the problem in a new study, published last week in the Proceedings of the National Academy of Sciences.
The researchers first calculated how much of the United States is made up of land that’s been relatively unaffected by human development (they estimated about 45%). Then, they looked at how these plots of natural land were connected. In particular, they evaluated whether an organism could move through a series of adjacent land areas to get from their current location to somewhere cooler.
They found that, in many parts of the U.S., organisms would have a tough time. “A lot of these land areas are very fragmented and broken up,” said Jenny McGuire, a biologist at Georgia Institute of Technology and the lead author of the study, in a statement.
The situation differs dramatically between the eastern and western portions of the country. In the west, where there are large swaths of publicly owned land and lower population densities, the researchers found that 51% of natural lands are sufficiently connected to allow organisms to migrate toward friendlier climates. In the east, however, only 2% of natural land offered the same opportunity.
So the researchers asked whether establishing corridors between plots of natural land might improve the situation. Establishing corridors might involve planting ribbons of native vegetation through urban or agricultural areas, or building overpasses, which already exist in Canada, that allow animals to safely cross busy roads.
According to the researchers’ analysis, these corridors could have a powerful effect, especially in the east. Here, McGuire’s team calculated that their presence would increase the connectivity between natural lands by a factor of 13 — from 2% to 27%. They found that corridors would be particularly valuable in the southeastern U.S., where many organisms will need to migrate toward the Appalachian Mountains to find their preferred climate.
Overall, corridors up to 100 kilometers long could connect 65% of natural lands in the continental U.S. to areas of cooler climates, up from 41% today. Corridors just 10 kilometers long would still boost that number to 60%.
While helpful, the researchers note that establishing such routes would not necessarily solve the problem. In cooler places, especially small, high elevation areas, there may not be much room to accommodate newcomers, and some species simply may not be able to keep pace with warming. On the other hand, some species may not need to move, and might find ways of changing their behavior that allow them to stay put.
Regardless, the researchers say that quantifying the scale of the problem — and the benefits of potential solutions — is the first step. And corridors seem like a promising option. “Species are going to have to move in response to climate change,” McGuire said. “We can act to both facilitate movement and create an environment that will prevent loss of biodiversity without a lot of pain to ourselves.”
Learn more about behavioral adaptation in our module.
Read more about landscape fragmentation and how it impacts biodiversity at the Encyclopedia of Life Sciences.
Find out how climate change has altered habitats and how species are responding at Columbia University’s State of the Planet.
Written by Julia Rosen
Julia Rosen is a freelance science writer and PhD student at Oregon State University. She received a Bachelors degree in Geological and Environmental Sciences from Stanford University before beginning her doctoral research on polar ice cores and climate change. In between, she did her Master's in backpacking around the world and skiing. Julia is a periodic contributor to Oregon States research magazine, Terra, and helps write blog content and develop learning modules for Visionlearning.