Trumpeter swans are among the species that, by 2050, are not expected to be able to live in most of their current territory, according to a report. Photo: Elaine Thompson/Associated Press
The Baltimore oriole will probably no longer live in Maryland, the common loon might leave Minnesota, and the trumpeter swan could be entirely gone.
Those are some of the grim prospects outlined in a report released on Monday by the National Audubon Society, which found that climate change is likely to so alter the bird population of North America that about half of the approximately 650 species will be driven to smaller spaces or forced to find new places to live, feed and breed over the next 65 years. If they do not — and for several dozen it will be very difficult — they could become extinct.
The four Audubon Society scientists who wrote the report projected in it that 21.4 percent of existing bird species studied will lose “more than half of the current climactic range by 2050 without the potential to make up losses by moving to other areas.” An additional 32 percent will be in the same predicament by 2080, they said.
Among the most threatened species are the three-toed woodpecker, the northern hawk owl, the northern gannet, Baird’s sparrow, the rufous hummingbird and the trumpeter swan, the report said. They are among the 30 species that, by 2050, will no longer be able to live and breed in more than 90 percent of their current territory.
“Common sense will tell you that with these kinds of findings, it’s hard to believe we won’t lose some species to extinction,” said David Yarnold, the president of the National Audubon Society. “How many? We honestly don’t know. We don’t know which ones are going to prove heroically resilient.”
Can the birds just move? “Some can and some will,” Mr. Yarnold said. “But what happens to a yellow-billed magpie in California that depends on scrub oak habitat? What happens as that bird keeps moving higher and higher and farther north and runs out of oak trees? Trees don’t fly. Birds do.”
The report’s predictions are based on both United Nations estimates of the effects of climate change in 2050 and 2080, and on two voluminous surveys of birds: the Audubon Society’s own Christmas bird count, which thousands of volunteers have worked on for decades, and a more general annual survey of breeding birds. The latter was started by the federal government in 1914; amateur birders began the Christmas bird count a few years earlier.
“The notion that we can have a future that looks like what our grandparents experienced, with the birds they had, is unlikely,” said Gary Langham, the study’s chief author, in an interview. The impact of climate change, he said, will not just harm birds already considered endangered — it is as likely to decimate birds that have robust populations now.
“This whole other threat tends to undo successes we’ve had in the past,” Dr. Langham said.
Terry Root, a Stanford University biologist who specializes in the impact of climate change on the geographic distribution of species, said she found the conclusions in the Audubon survey disturbing indeed. “If we are losing as many species as this is saying, what’s going to happen to all the insects they eat?” she said. “There are going to be winners if you move a species out of a region, and these winners might be mosquitoes and spiders.”
Alternatively, Dr. Root said: “Maybe other avian species will grow in abundance and take up the space. We don’t know.”
On Tuesday, the United States Fish and Wildlife Service and the Smithsonian Institution are scheduled to release their annual state of the birds report, which is also expected to describe declines in bird populations and threats from changing ecosystems. Laury Parramore, a spokeswoman for the Fish and Wildlife Service, said in a statement on Monday that the Audubon Society’s work “provides a tool to help predict future bird distribution and ranges” that will help guide her agency’s conservation plans.
Birds could feel the impact of a changing climate in different ways. Drought in Southern California is blamed for a sharp drop in breeding among California raptors, perhaps because a lack of water is killing the insects and small rodents they feed on.
Puffins, whose reintroduction off the Maine coast had largely been a success story for the Audubon Society, have shown signs of declining both off the American coast and in countries like Iceland and England, perhaps because of climate-driven changes in the ocean food web.
“Every species of plant and animal is very well-tuned to what it does for a living,” Dr. Langham said. “A bird in the desert can’t go to the boreal forest. Everything about every organism is finely tuned.”
On the bright side, Dr. Langham said, his report shows that many species will continue in their current abundance and, mostly, their current locations: American robins, red-tailed hawks, western scrub jays, western meadowlarks, northern cardinals and northern mockingbirds.
And at least one species, popular among poets and jilted lovers, is expected to flourish as warming takes its course, Dr. Langham said. “You want to know what climate change sounds like?” he asked. “It’s the sound of a mourning dove — their climate potential is going to increase.”
Other species may or may not be able to adapt. For example, the brown pelican, a Gulf Coast resident, could move northward and inland, Dr. Langham said, adding, “But really with any bird that shows new climate space opening up, it is far from certain that any bird is going to capitalize on that potential.”
Dr. Langham called for a revised conservation strategy that focuses not only on species in immediate trouble, but those likely to suffer as climate forces them out of their current homes. The Audubon report, he said, is “a framework to focus on which species are predicted to be sensitive and where they are likely to move, and importantly, where they are likely not to move.”
Mr. Yarnold of the Audubon Society said that birds were resilient, but that climate change will test their limits. “We just don’t know whether they’ll be able to find the food sources and the habitat and cope with a new range of predators,” he said. “Maybe they’ll all be incredibly hardy and find ways to survive.”
But, he added, “That doesn’t seem likely, given, one, the number of birds affected, and two, the pace at which these things are happening.”
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