Global warming has extended the destructive reach of humankind. Plants and animals far from human habitation are now threatened by the climate change resulting from the carbon we release into the atmosphere through the burning of fossil fuels. In fact, according to a new study, global warming may surpass other by-products of human activity, such as deforestation, in driving species into extinction.

Forester Jay Malcolm of the University of Toronto and his international team of conservation professionals looked at the changes to vegetation types, or biomes, in 25 so-called hot spots--unique ecosystems with a wide range of endemic species. The researchers modeled what would happen to the plants in these areas if the atmospheric concentration of carbon dioxide doubled in the next 100 years.

Under a number of scenarios--ranging from broadly defined biomes in which species were able to spread away from impacted areas to highly sensitive biomes whose species could not move at all--anywhere from hundreds to tens of thousands of plant and animal species were lost. "Climate change is rapidly becoming the most serious threat to the planet's biodiversity," Malcolm says. "This study provides even stronger scientific evidence that global warming will result in catastrophic species loss across the planet."

Areas most at risk, according to this study, include the tropical Andes, southwest Australia, California and South Africa, primarily because these areas present the least opportunity for species to migrate away from the problem. For example, South African animals are blocked by the ocean from moving farther south in response to a different climate.

Describing their work in the current issue of Conservation Biology the scientists note that the findings back similar results from other studies. And limited research into more widespread biomes showed comparable extinction rates. "The hot spots studied in this paper are essentially refugee camps for many of our planet's most unique plant and animal species," adds co-author Lee Hannah of Conservation International. "If those areas are no longer habitable due to global warming then we will quite literally be destroying the last sanctuaries many of these species have left."