The scientists told a geoscience conference in Vienna they already predict fires will increase and could spread to previously fire-free parts of the world as the climate changes.

"An increase in fire may be the greatest early impact of climate change on forests," Brian Amiro from the University of Manitoba said late on Wednesday.

"Our forests are more likely to become a victim of climate change than a saviour," he added.

Last year more than 200 wild fires swept across parts of southeastern Europe, destroying homes and devouring woodland. In Greece 65 people died.

Amiro said global warming will cause more fires which as they burn contribute to global warming by producing greenhouse gases.

"Fire avoids environmental extremes, like the deserts, tundra and rainforests," said Max Moritz from the University of California, Berkley.

"But there are some predictions which show there could be fires in deserts and there are worries they may occur in tropical rainforests if they were drier," he said.

Forests are natural carbon stores, some built up over millions of years, but as they burn they release the carbon quickly in the form of carbon dioxide.