PARIS, April 10 (AFP) — Global warming will severely disrupt wildlife half-a-century from now but few species are likely to die out during this time, a study published Thursday in the British science journal Nature suggests.

The study predicts how the 1,870 species of mammals, birds and butterflies in Mexico will react to a warmer climate by 2055, using two estimates — one high, the other low — of the likely temperature rise.

Both scenarios predict “severe ecological perturbations,” in which Mexico’s habitat will change dramatically over the next five decades.

Many areas will become uninhabitable for some species because they will become too hot or dry, but some areas, such as previously cooler highland regions, could in theory be opened up for habitation.

“Relatively few” species will become extinct, but all are likely to live in a much smaller geographical range than before, the study says.

This is because species facing a threatened habitat do not disperse universally across the country to colonise the newly opened-up areas.

Instead, they either cannot flee at all or gradually migrate to the nearest available habitat.

The study, led by Townsend Peterson of the University’s of Kansas’ Natural History Museum, is one of the first detailed attempts to predict how wildlife will cope with global warming.

In a phone interview with AFP, Peterson said that he estimated 2.4 per cent of Mexico’s 334 native species of mammals, birds and butterflies faced extinction by 2055 because their colonised habitats would shrink by 90 per cent or more.

He cautioned, though, that the picture is more complex than it seems.

The figures do not include especially vulnerable species such as amphibians, which are water-dependent and have little capacity to migrate.

Another big unknown was the effect of habitat change on the complex ecological system, he said.

Thousands of species — predators and prey, hosts and parasites — will live cheek-by-jowl in smaller, highly condensed areas. This made for a precarious balance that could be easily disrupted.

“It could be like the game of pickup sticks, in which thin, little sticks are pulled out of a pile, until eventually one is pulled out and the whole thing cascades down,” Peterson said.

“I suspect that ecosystems are like that. You can only perturb them so much before there is a cascade.”

Climate experts concur, with few exceptions now, that the earth’s temperature is rising as a result of burning oil, gas and coal. These “fossil” fuels release carbon dioxide as a by-product of combustion, and the gas hangs invisibly in the atmosphere, trapping heat from the sun.

Still under debate is how fast the warming will occur and what effects this will have on the world’s climate system and its flora and fauna.

The study’s temperature variations were an increase of 1.6 to 2.5ºC (2.9 to 4.5ºF) by 2055 and an annual decline in rainfall of 70 to 130mm (2.8 to 5.2 inches).

It did not factor in big climate events, such as storms, droughts and El Niños, which many experts say will become more frequent as global warming bites.