Dec. 5 (Bloomberg) -- Climate change may cause as much as 30 percent of all land-bird species to become extinct by 2100 because food will become scarce as temperatures increase, according to a new Stanford University study.

Rising temperatures will limit the availability of plants and animals that serve as food for birds, according to the study to be published this week in Conservation Biology.

Food will be more difficult to find as lowlands become warmer and plant and animal species on which birds feed either vanish or move to higher elevations, which may put the birds in competition for food with additional species over smaller and smaller areas. Each bird species is found between specific elevations and temperature ranges that support the food it needs, and many lowland birds have no higher elevations to move to.

Birds ``are indicators of environmental health, and if you are losing big chunks of any group, that indicates that the ecosystem is breaking apart,'' said Cagan Sekercioglu, a senior research scientist at Stanford in California and the study's lead author. ``It's not going to be just birds. The same dynamics are likely to affect insects, mammals, reptiles, amphibians.''

The analysis is based on climate change scenarios reported earlier this year by the United Nations Intergovernmental Panel on Climate Change, which determined that power plants, transportation and factories contribute to global warming through the burning of fossil fuels.

The Stanford researchers modeled changes to elevation limits for more than 8,400 land birds and found that in the worst-case scenario temperatures would rise 6.4 degrees Celsius, resulting in extensive habitat loss and a loss of 30 percent of land-bird species. Even the mid-range scenario, with warming of 2.8 degrees Celsius, would result in 400 to 550 species dying off by the end of the century, according to the study.

To contact the reporter on this story: Adam Satariano in San Francisco at asatariano1@bloomberg.net

Last Updated: December 5, 2007 21:30 EST