An increasing number of settlers who have moved to the country's highlands to farm in the last two decades have affected bird habitats and reduced bird populations by cutting down forests and turning grasslands into fields, The New York Times reported.
Climate change is adding to the problem, sending some populations into steep decline, researchers say.
Some scientists predict a 20 percent to 30 percent species loss if temperatures rise by 3.6 to 5.4 degrees Fahrenheit, and if some of the more extreme warming predictions come to pass the loss rate could approach 50 percent, a United Nations climate change panel says.
Tens of thousands of species living on or near mountains are vulnerable, scientists say. These species, living in habitats from the high plateaus of Africa to the jungles of Australia to the Sierra Nevada in the United States, are already experiencing climate pressures, they say.
In response to warming, animals classically move to cooler ground, but mountain species face drastic limitations.
As they move upward they must compete for less and less space on the mountaintops, where they run into uninhabitable rocky terrain or a lack of their usual foods and have nowhere farther to go.
"It's a really simple story that at some point you can't go further north or higher up, so there's no doubt that species will go extinct," Walter Jetz, professor of ecology and evolutionary biology at Yale, said.
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