WASHINGTON (AP) – A meticulous re-creation of a 3-year-old study of birds on a mountainside in Peru has given scientists a unique opportunity to show how the change in climate is pushing species away from the places to which they are better adapted.
Surveys of more than 400 bird species in 1985 and later in 2017 found that populations of almost all had declined, eight disappeared altogether and almost all had moved to higher elevations in what scientists call "an escalator to the extinction. " "
"Once you move as far as you can go, there is no other place left," said John W. Fitzpatrick, the study's author and director of Cornell's Laboratory of Ornithology. "On this particular mountain, some populations of climbing vines were literally eliminated."
It is not certain if the birds changed ranges due to temperature changes or indirect impacts, such as changes in the ranges of insects or seeds from which they feed.
These findings, published Monday in the Proceedings of the National Academy of Sciences, confirm what biologists had suspected for a long time, but had little opportunity to confirm. The existence of a 1985 bird study on the same mountain gave scientists a rare and useful baseline.
Previous research has documented habitats of birds and other species that rise in height or latitude in response to warming temperatures. But Mark Urban, director of the Center for Biological Risk at the University of Connecticut, who was not involved in the study, said he was the first to demonstrate what climate change models predicted: that rising temperatures will cause local extinctions.
"A study like this where you have historical data you can go back and compare to is very rare," Urban said. "As long as the species can disperse, you will see species marching towards the mountain, until the escalator becomes a stairway to heaven."
In 1985, Fitzpatrick established a base camp next to a river that runs down a mountain slope in southeastern Peru, with the objective of cataloging the habitat ranges of the tropical bird species that lived there. His team spent several weeks moving up and down the Cerro de Pantiacolla, using fine nets called fog nets to catch and release birds, and keeping detailed diaries of birds that captured, saw or heard chirping in the forests.
Two years ago, Fitzpatrick passed his magazines, photos and other records to Benjamin Freeman, a postdoctoral fellow at the Center for Biodiversity Research at the University of British Columbia. Freeman, who has been researching tropical birds for more than a decade, set out to recreate the trip in August and September 2017. Using old photos of views of the mountains, his team located the same base camp.
Freeman largely recreates Fitzpatrick's path and methodology to see what happened in the intervening years, a period in which average temperatures in the mountain increased 0.76 degrees Fahrenheit (0.42 degrees Celsius). Because the mountain is on the edge of a national park, the area had not been disturbed.
In addition to deploying 40-foot (12-meter) fog nets on the slopes, Freeman's team placed 20 boxes of microphones on the mountain to record bird squeaks that might not be easily seen.
"We found that bird communities were moving down the slope to reach the climatic conditions they originally adapted to," said Freeman, the study's lead author. Near the top of the mountain, bird species moved upward at 321 feet (98 meters), on average.
"We believe that temperature is the main switch to explain why species live where they live on the slopes of the mountains," Freeman said. "A large majority of the species in our study were doing the same thing."
Birds adapted to live within narrow temperature bands, in regions without large seasonal variations, may be particularly vulnerable to climate change, Fitzpatrick said. "We should expect that what is happening on this mountaintop is happening more generally in the Andes and other tropical mountain ranges," he said.
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