A Yale University study examines the movements of 406 migratory bird species in North America and finds that most birds are not moving fast enough to keep up with rising temperatures.
As rising global temperatures alter ecosystems around the world, animal species typically have two choices: adapt to changing local conditions or flee to cooler climates. Ecologists have long assumed that the world's bird species are best equipped to respond to climate change pressures simply because they have the ability to fly to higher altitudes or toward the global poles.
But a new Yale study finds that few bird species are able to escape the realities of a warming world.
the findings Published on May 28 in the journal Nature Ecology and Evolution.
“They can’t move fast enough or far enough to keep up with the pace of climate change,” said Jeremy Cohen, the study’s lead author. He is an associate research scientist in Yale’s Department of Ecology and Evolutionary Biology and a member of co-author Walter Jetz’s lab.
Jetz, a professor of ecology and evolutionary biology in Yale's Faculty of Arts and Sciences, is also director of Yale Center for Biodiversity and Global Change and the Jack and Laura Dangermond Scientific Chair of the E. O. Wilson Biodiversity Foundation.
Cohen and Jetz analyzed data on the movements of 406 North American bird species collected from citizen observers over two decades, as well as corresponding local temperature changes. They found that many of the assumptions they had made about how bird species respond to climate change were correct. During the summer, for example, bird species moved an average of 40 to 50 miles north during the period covered by the data—sometimes moving to higher elevations. And, on average, the northward movement helped the birds avoid a temperature increase of about 1.28 degrees Celsius—or about half the temperature increase they would have experienced if they had stayed in place.
But, on average, birds still experienced a 1.35°C increase in temperature during the summer months compared to temperatures in their original home range. During the winter months, birds had only minimal success in limiting their exposure to warming, experiencing only 11% less warming than if they had not moved north. In winter, birds experienced an average of a whopping 3.7°C increase in temperature over the 20 years, reducing their potential exposure by only half a degree through their northward movement.
The ability of birds to escape higher temperatures also varied by species. Overall, more than 75% of birds were able to move to slightly cooler climates in response to warming temperatures. But some species, such as the cactus wren, which is native to deserts and arid systems in North America, did not move at all, making them more vulnerable to climate-driven changes in their environmental niches. These climate-driven “niche shifters,” known as climate-driven “niche shifters,” may be limited in their ability to fly or prevented from leaving their current home environment or competing for it in new locations due to specific habitat needs and ecological dependencies.
The researchers found that bird species capable of long-distance flight were most successful in limiting their exposure to warmer climates and maintaining their historical climate niches. These included the blue-winged warbler, which traveled more than 160 miles north and experienced two degrees less warming than if it had stayed in place. But even these birds are facing temperatures that exceed those they knew in their original range 20 years ago.
For species that are much less mobile than birds, such as reptiles and mammals, the options for escaping rapid warming are even more limited.
Climate change is widening the gap between the climatic niche into which species have evolved over thousands of years and what they experience in their native regions, the authors say.
“In a unique, well-studied terrestrial system, we find that even a highly mobile group, like birds, cannot move fast enough to keep up,” said Jetz. “This raises deep concerns about the ability of all other, less mobile and less familiar species to survive in a warmer world. Much better understanding and management of the most likely victims of climate change – those most ecologically and geographically connected – is needed to stave off a looming extinction crisis.”
The research was funded in part by the EO Wilson Biodiversity Fund to advance the Hemisphere Project.
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