Washington: Global warming is likely to imperil tropical species much more than fauna in the Arctic regions, even with a slight rise in temperature.

"Many tropical species can only tolerate a narrow range of temperatures, as the climate they experience is pretty constant throughout the year," said Curtis Deutsch of the University of California and co-author of a new study.

"Our calculations show that they will be harmed by rising temperatures more than would species in cold climates. Unfortunately, the tropics also hold the large majority of species on the planet," he said.

Conversely, Arctic species might experience temperatures ranging from subzero to a balmy 16 degrees Celsius. They typically live at temperatures well below their thermal limit, and most will continue to do so even with climate change.

The study found that while temperature changes will be much more extreme at high latitudes, tropical species have a far greater risk of extinction with warming of just a degree or two.

"In the tropics many species appear to be living at or near their thermal optimum, a temperature that lets them thrive. But once it gets above this optimum, fitness levels most likely decline quickly and there may not be much they can do about it," said Joshua Tewksbury, a co-author of the study.

The scientists used daily and monthly global temperature records from 1950 through 2000, and added climate model projections from the Intergovernmental Panel on Climate Change for warming in the first years of the 21st century.

The work has indirect implications for agriculture in the tropics, which houses the bulk of the global population.

These findings have appeared in the latest edition of the Proceedings of the National Academy of Sciences.

Source : IANS