According to a study published in Conservation Biology, climate change, exacerbated by habitat loss, could cause up to 30 percent of land-bird species (which include the vast majority of all bird species) to go extinct worldwide by the year 2100.
The study is one of the first analyses of extinction rates to incorporate the most recent climate change scenarios set forth earlier this year in the reports of the Intergovernmental Panel on Climate Change (IPCC), which shared the Nobel Peace Price with Al Gore.
“Of the land-bird species predicted to go extinct, 79 percent of them are not currently considered threatened with extinction, but many will be if we cannot stop climate change,” says Cagan Sekercioglu, a senior research scientist at Stanford University and lead author of the study.
“Vegetational shift is the key issue here,” Sekercioglu said. “Birds will follow the shift in habitat.” All plants have certain temperature and precipitation requirements that they need to flourish. As lowlands become too warm for some species, higher slopes that were formerly too cool become better suited to their needs, and the distributions of plants slowly move upward. That shifting of populations renders bird species vulnerable to a host of complications.
As birds move upslope, their potential habitat decreases, as the circumference of a mountain is typically smaller near the summit than at its base. And once the summit of a mountain becomes too hot for a species or its preferred vegetation type, the habitable area is reduced to nothing. “It`s like an escalator to extinction,” says Sekercioglu.
Rising temperatures may also play a role in other environmental dangers. For example, as Hawaiian mountains become warmer, mosquitoes carrying avian malaria, to which most native bird species have no immunity, are moving upslope, invading the last refuges of birds already on the brink of extinction.
Due to the remoteness of the mountains and a lack funding for ornithological studies in most tropical countries, there are few data on these birds’ responses to climate change. Crucial remote sensing data are also becoming less available, as government satellites like Landsat age and as image distribution moves increasingly to the relatively expensive private sector.
“Our best guess is that climate change effects, exacerbated by habitat loss, will result in about 400–550 land bird extinctions by 2100, based on a 2.8 °C warming. Climate change will affect intact montane (and polar) habitats most and its victims will mainly be those species not presently threatened by habitat loss. Large numbers of species, thus-far largely unaffected by human actions, are in danger of extinction from climate change.”-Blackwell Publishing Ltd.
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