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Climate change creates winners and losers among birds

A recent study published in Science and led by Stephen Willis and Philip Stephens, compared bird migrations in North America and Europe. They discovered that some bird species are adapting well to conditions associated with climate change, while populations of other species are declining. A reporter covering this story interviewed me for my opinion on the research. See her work, below.


Climate change creates winners and losers among birds

Pola Lem, E&E reporter

Published: Friday, April 1, 2016

Birds of a feather flock together, it's said -- and where climate change is concerned, bird species on both sides of the Atlantic are responding in similar ways.

That's the finding from a new study published yesterday in the journal Science, which shows rising global temperatures are creating winners and losers in the bird world. Some species are thriving, while others are scrambling to adapt, according to the U.K.-based research team.

Using climate records for the period 1980 to 2010, scientists led by Stephen Willis and Philip Stephens, both of Durham University, examined 145 common bird species in Europe and 380 common bird species in the United States. After accounting for factors like variations in habitat and migratory behavior, they found climate change explains the differences in population trends between species favored or handicapped by rising temperatures.

Wrens have been increasing in northern European areas where winters are becoming milder but declining in some southern countries where summers have been getting hotter and drier. Photo courtesy of Stephen Willis, Durham University.

"What's so critical about this -- in and around the '70s, scientists estimated a major uptick in increasing global temperatures -- that, in some ways, is a key turning point for asking the question, what happens to organisms following that uptick?" said Charles Davis, a professor of evolutionary biology at Harvard University's Center for the Environment.

Davis, who also co-directs Harvard's herbaria, which include more than 5 million specimens of algae, bryophytes, fungi and vascular plants, was not involved in the study. He praised the wealth of data gathered in it, something he said isn't available to "plant people" like himself.

"It's simply, hands-down, an amazing sort of collection of data that both amateurs and professionals have assembled over the last 30, 40 years to understand where birds live and how that's changed," said Davis.

Frank La Sorte, a researcher at the Cornell Lab of Ornithology, also lauded the efforts of volunteers in collecting data, and called the study "novel" in scope.

"It's the first of its kind that does an intercontinental comparison," La Sorte said of the analysis.

The study opens the door for new lines of inquiry, he said, like how landscape differences in either continent will affect birds' ability to adapt.

U.S. birds may be better off

Whereas birds in Europe live in a place with a long history of land-use change -- with forests being cut down for fields and replanted again over and again over centuries -- North American birds face a less human-dominated environment. Birds in the United States also have the advantage of more open territory in colder regions.

"Birds in North America can respond to climate change by going north because there's plenty of available land, whereas in Europe, if they go north, they'll run into the ocean," he said.

The question of how different species will adapt to shifting habitat is also a practical one, said Elizabeth Ellwood, an ecologist at Florida State University.

"It sounds maybe obvious on the surface, but when you look into the literature, you find that birds are notoriously different in their responses to things like climate change," she said.

So it's a lucky thing for birds that their responses to climate change can fit into two broad categories, winners and losers, Ellwood said.

"When it comes to land managers and conservation biologists wanting to help species, the more we can generalize, the better we are able to address numerous species at a time," she said.

It's all about killing -- or in this circumstance, saving -- more birds with one stone.

If science suggests that many species move farther north, said Ellwood, that tells conservationists to allocate more land toward the northern end of species ranges rather than the southern end.

"That may be the greatest benefit we can provide to them -- that may be the place to put our efforts," she said.

Hurting skies and pocketbooks

Those conservation methods may come into play for species like the American robin, which is already showing a broader move north. At home in suburban lawns across the United States, the robin is on the downturn in Southern states like Mississippi and Louisiana but is more populous in north-central states like the Dakotas, the study suggests.

And it's not just birds on the wing, said Jack Fellows, director of the Climate Change Science Institute at the Oak Ridge National Laboratory.

Populations of some insects have soared in recent years, a result of higher survival rates over milder winters. In the case of the bark beetle, that advantage means entire forests are getting eaten up.

"We have hundreds of thousands of acres of dead trees in Colorado. That's habitat loss for all kinds of species, including birds," he said.

As insects like the bark beetle multiply, it's tough to tell whether birds will benefit, since populations of other organisms, like bacteria, could also rise, said Fellows.

The worry is also a financial one. He pointed to places like Great Smoky Mountains National Park, the most-visited national park in the United States, whose forests have been ravaged by an exploding beetle population.

"This also goes to our pocketbooks," Fellows said. "You start losing birds in national parks and it's not just a tragic loss -- it also impacts local economies."

Still, he said, current changes are merely a taste of what's to come.

"It's pretty subtle at this point," Fellows said, "but the changes associated with climate change really start showing up about 2020 or 2030."

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