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Climate change is likely to drive up to a third of the world's plant and animal species to extinction if emissions of greenhouse gases remain unchecked, according to a new analysis of the response of such species to temperature increases.

A study in this week's Nature suggests that between 15 and 37 per cent of species could go extinct due to the global warming that is likely to occur between now and 2050. Some of these species would no longer have anywhere suitable to live. Others would be unable to reach distant regions where the climate is suitable for them.

But a rapid shift to technologies that do not produce greenhouse gases could save up to a fifth of all land species from extinction, according to the international team of scientists who carried out the analysis.

"This study makes clear that climate change is the most significant new threat for extinctions this century," says one of the researchers, Lee Hannah of Conservation International's Center for Applied Biodiversity Science in Washington DC.

"The combination of increasing habitat loss, already recognised as the largest single threat to species, and climate change, is likely to devastate the ability of species to move and survive."

More than 1,000 animal and plant species in six regions around the world, which together represent 20 per cent of the planet's land area, were considered as part of the study. The researchers used computer models to simulate how the geographical spread of these species would change in response to changing temperatures under three different climate-change scenarios.

"If the projections can be extrapolated globally, and to other groups of land animals and plants, our analyses suggest that well over a million species could be threatened with extinction as a result of climate change," says lead researcher Chris Thomas of the University of Leeds, United Kingdom.

The forecasts are for species that are predicted by the models to go extinct eventually as a result of the climate change that will occur by 2050. However, as some species respond slowly to environmental change, they will not all go extinct by 2050.

According to Klaus Toepfer, executive director of the United Nations Environment Programme (UNEP), the study "underlines again to the world the importance of bringing into force the Kyoto Protocol, the international agreement to cut back greenhouse gas emissions".

The progress of the protocol has been stalled because Russia — which needs to sign the protocol for it to come into force, given the decision of the United States not to do so  — has so far failed to ratify (see Climate change meeting ends in disappointment).

Toepfer also says that, in addition to losses to plants and animals, "billions of people, especially in the developing world, will suffer, too as they rely on nature for such essential goods and services as food, shelter and medicines".

And he warns that the figure of one million species may be an underestimate. "The Nature paper only looks at the impact on individual species, but many are interdependent," he says. "If, for example, bees and other insects that pollinate trees and flowers disappear from an area, it can lead to a ripple effect in which more and more species dependent on these insects die out."

Lera Miles, senior programme officer at the UNEP World Conservation Monitoring Centre in Cambridge, United Kingdom, and one of the study's authors, warns that immediate action is needed. "The international community needs to sit up and take notice of climate change now, and not wait for impacts to happen," she says.

Link to News and Views article in Nature: Clouded futures

Link to research paper in Nature by Chris Thomas et al

References: Nature 427, 107 (2004)/ Nature 427, 145 (2004)