Global warming has already caused extinctions in the most sensitive habitats and will continue to cause more species to disappear over the next 50 to 100 years, according to a new study.

The study, conducted at the University of Texas at Austin and published online Wednesday in the Annual Review of Ecology, Evolution and Systematics, also predicted that species will not evolve fast enough to prevent extinction.

"This is absolutely the most comprehensive synthesis of the impact of climate change on species to date," said biologist Dr. Camille Parmesan, the study's author, in a release Wednesday.

Parmesan reviewed more than 800 scientific studies on the effects of human-induced climate change on thousands of species.

"Because there are now so many papers on this subject, we can start pulling together some patterns that we weren't able to before," she said.

Previously published studies predicted that global warming would most severely affect species restricted to cold climate habitats, such as the Earth's poles or mountain tops, as well as habitats with narrow temperature tolerances, such as tropical corals.

Less than a decade later, those predictions have proved accurate, Parmesan said.

"We are seeing stronger responses in species in areas with very cold-adapted species that have had strong warming trends, like Antarctica and the Arctic. That's something we expected a few years ago, but didn't quite have the data to compare regions."

The most sensitive species are going extinct or shifting their ranges geographically as their original habitats become inhospitable, the data found.  

Last month, a 700-page report commissioned by the British government warned of the extinction of 20 to 40 per cent of wildlife species unless the issue of climate change is immediately addressed.

Global warming deniers 'out of step': UN chief

The studies Parmesan analyzed also show that some species — those with short generation times like insects — are evolving in response to climate change, but not in ways that could prevent extinction.

"To really come up with something new that's going to allow a species to live in a completely new environment takes a million years," she said.

She said some good news can be found, in that some species had a few individuals adept at moving, indicating some populations are evolving better dispersal abilities.

The study comes as UN Secretary-General Kofi Annan told the UN conference on climate change Wednesday that those who would deny global warming or delay taking action against it are "out of step" and "out of time."

"Let no one say we cannot afford to act," Annan declared, in a clear reference to those, including the Bush administration, who contend that reducing global-warming gases would set back economies too much.

With files from the Associated Press