The golden toad (Bufo periglenes) has the tragic honour to be the first identified species to go the way of the dodo because of, in all probability, greenhouse gases.

The colourful amphibian made its home in a tiny area, measuring only four square kilometers (a third of square mile), in the Monteverde cloud forest, a pristine nature reserve in Costa Rica.

The secretive species, discovered only in 1964, had only a narrow window of opportunity to reproduce, during brief storms during the April-June rainy season that create temporary puddles, allowing male and female toads to congregate.

But warmer weather and a couple of seasons without rainstorms caused the toad population to crash in 1987. Not a single specimen has been seen in more than 15 years.

Where the golden toad went, other species are doomed to follow, says John Lanchbery of Britain's Royal Society for the Protection of Birds (RSPB).

"There is substantial and compelling evidence that the degree of climate change which has already occurred has affected both species and ecosystems, sometimes adversely," Lanchbery reported earlier this month at a conference on climate scientists in Exeter, England.

"It appears very likely that [other] species will increasingly become extinct and ecosystems will be lost with little further change in the climate."

Global warming, also called the greenhouse effect, is the term for a rise in Earth's surface temperature caused by carbon gases emitted by fossil fuels, which trap the heat from the Sun.

The Kyoto Protocol, which takes effect on Wednesday, is the first international treaty to tackle the pollution, although the impact -- even if the pact is enacted in full -- will barely make a dent in the problem.

Since 1900, Earth's surface temperature has warmed by 0.7-0.8 C, and a rise of another 5 C (9 F) may occur by the end of the century if emissions are unchecked.

But even an increase on half of that scale could be catastrophic, given that thousands of species are already endangered.

One of them is the polar bear, which according to research by the environmental group WWF could be wiped out in just over 20 years.

Polar bears go out on ice sheets to hunt for seals. So shrinking polar ice sheets means they will have less time to hunt for food and build up their stores of fat, which are essential for survival during the summer.

According to a study published in the British science journal Nature in January 2004, a middle-of-the-range rise in temperature would cause the extinction of between 15 and 37 percent of 1,000 species in six regions that are rich in biodiversity.

The principal threat comes from loss of habitat and available food, and is especially dangerous because the change is compressed into decades rather than hundreds of years, said Isabelle Chuine of France's National Centre for Scientific Research (CNRS).

"The timescale is just too fast. Many species will be unable to adapt in time," she told AFP.

Progressive warming is already starting to change migratory patterns, a complex phenomenon that starts with the first link on the food chain.

Lanchbery gave the example of the North Sea, a region well studied by European climate experts.

Warmer water in the North Sea has hit the abundance of plankton, in turn affecting the population of sand eels, a small fish that is the staple diet for many local seabirds. In consequence, arctic terns, kittiwakes, guillemots and sea skuas last year suffered a cataclysmic breeding failure.

"The long-term risk is that local populations of these species could get wiped out," said Philippe Dubois of France's League for the Protection of Birds (LPO).

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