Vast shift in bird species expected from warming
Published 4:00 am, Wednesday, September 2, 2009
Birds of a feather will no longer flock together, and some California species will face extinction as a result of global warming, according to a study released Tuesday by PRBO Conservation Science.
The study, which predicts how birds in California will adapt to changing climatic conditions, says there will be a dramatic change in the pecking order of the avian world over the next 60 years.
In one fell swoop, the changes in bird habitats and behavior between now and 2070 will equal the evolutionary and adaptive shifts that normally occur over tens of thousands of years, according to researchers with PRBO, also known as the Point Reyes Bird Observatory.
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"What we found is that not only will species shift and communities change, but the composition of communities in certain places will not resemble anything we see today," said Diana Stralberg, a landscape ecologist and the lead author of the report, "Reshuffling of Species With Climate Disruption: A No-Analog Future for California Birds?"
"Species will exist in different and unusual combinations," she said. "Food and prey might not be available, and there may be unanticipated interactions with other species, including predators."
The study predicts a scramble among bird populations for new flocking partners and habitats, which will undoubtedly ruffle a few feathers. Some birds will be pushed toward extinction as they struggle against unfamiliar avian competitors, strange predators and unpredictable prey.
-- Species including the California thrasher, rufous-crowned sparrow and ash-throated flycatcher will move to the Point Reyes Peninsula as it gets drier and less foggy. Those birds will then commune with strangers like the purple finch and black-throated gray warbler.
-- The distribution of the white-crowned sparrow, a black-and-white bird that likes coastal scrublands, including Point Reyes, will decline 76 percent, meaning they will be found in fewer places as temperatures rise.
-- The distribution of the varied thrush, a large, robinlike bird from the Pacific Northwest that often spends winters in California, will decline 87 percent.
-- The distribution of the yellow-billed magpie, commonly found in oak woodlands only in California, will decline by 32 percent.
-- Of the five bird species, including fox sparrows, Clark's nutcrackers and MacGillivray's warblers, that will see the greatest percentage declines in distribution, only one, the white-crowned sparrow, is not a forest-dwelling species. The distribution of some species, like acorn woodpeckers, will actually increase.
John Wiens, PRBO's chief conservation science officer, said what happens to birds could happen to us all.
"Birds are nature's barometers," said Wiens, who co-wrote the study. "If birds occur in different combinations in the future, it's likely that other organisms such as insects and plants will as well. The reshuffling of bird assemblages that we project may just be the tip of the iceberg."
The study, which will be published today in the Public Library of Science journal PLoS ONE, was conducted by scientists with PRBO, Stanford University, UC Santa Cruz and the Klamath Bird Observatory. They studied 60 birds from various California habitats, including oak woodlands, conifer forests, grasslands, riparian and coastal scrub.
The research team used models designed to predict changes in the snowpack, rainfall, plant and tree distribution between now and 2070 and compared that to the bird populations in California.
The study predicts that some groupings of bird species will move together while others will shift separately. Many birds will move north out of the hot, dry Central Valley or shift their ranges closer to the coast. Others will move to higher elevations in the mountains, searching out lower temperatures, moisture and prey, Stralberg said.
"They'll be trying to adapt," Stralberg said. "The problem is they may or may not adapt."
Scientists have long predicted major changes in the ecosystem as a result of climate change. Reduced snowmelt is expected to change the types of trees and vegetation and have lasting impacts on birds, animals, insects and even the microscopic pathogens that infect them.
The study is part of a modeling effort that will eventually include analysis of up to 300 bird species in California. Stralberg said she hopes the work inspires a more collaborative effort to protect ecosystems instead of just individual species.
"It's not a fair playing field, so we should try to intervene," she said. "There may be things that we can do to help more species survive."