Tropics insects 'face extinction'

Many tropical insects face extinction by the end of this century unless they adapt to the rising global temperatures predicted, US scientists have said.

Researchers led by the University of Washington said insects in the tropics were much more sensitive to temperature changes than those elsewhere.

In contrast, higher latitudes could experience an insect population boom.

The scientists said changes in insect numbers could have secondary effects on plant pollination and food supplies.

In the research published in Proceedings of the National Academy of Sciences, the US scientists studied how temperature changes between 1950 and 2000 had affected 38 species of insects.

Unlike warm-blooded animals, cold-blooded organisms cannot regulate their body temperatures by growing a coat of fur or shedding it when it gets warm. They are instead limited to either seek shade when hot or sun themselves when cool.

The scientists predicted such species would struggle to cope with the 5.4C rise in tropical temperatures expected by 2100.

"In the tropics, many species appear to be living at or near their thermal optimum, a temperature that lets them thrive," said Joshua Tewksbury of the University of Washington.

"But once temperature gets above the thermal optimum, fitness levels most likely decline quickly and there may not be much they can do about it," he added.

Although some species might be able to migrate uphill and towards higher latitudes, or evolve to cope with the warmer climate, others might eventually die out, the scientists said.