The most magnificent forest system on Earth is for sure the Amazon rainforest: it covers 1.6 million square miles (4 million square km) only in Brazil (60 % of the country's area).

Largely unexplored, it stores 20 % of the world's fresh water and about 30 % of the world's plant and animal species, many still unknown for science.

But the global warming may put an end to the world's largest remaining biological paradise, turning it into a grassy savanna in less than a century. A drop in the rainfall combined with increased temperatures will change the ecology of the area.

"We are working with two scenarios: a worst case and a second, more optimistic one," said Jose Antonio Marengo, a meteorologist with Brazil's National Space Research Institute.

"The worst case scenario sees temperatures rise by 5 to 8 degrees until 2100, while rainfall will decrease between 15 and 20 %. This setting will transform the Amazon rain forest into a savanna-like landscape," Marengo said.

"That scenario supposes no major steps are taken toward halting global warming and that deforestation continues at its current rate", Marengo said.

The other possibility requires the governments to take more aggressive actions to stop global warming.
"It would still have temperatures rising in the Amazon region by 3 to 5 degrees Celsius and rainfall dropping by 5 to 15 %," Marengo said.

"If pollution is controlled and deforestation reduced, the temperature would rise by about 5 degrees Celsius in 2100," said Marengo.

"Within this scenario, the rain forest will not come to the point of total collapse."

The study, begun in 2004 and scheduled till 2010, tries to project climatic changes that will affect Brazil over the next 100 years.

To avoid the worst possibility, industrialized nations must intensely mobilize to decrease emissions of greenhouse gases, but, by its side, Brazil should reduce deforestation and burning in the Amazon area.

Burning trees releases about 370 million tons of greenhouse gases annually (about 5 % of the world total).

About 20 % of the Amazon forest has already been cut down and the rate of deforestation is still alarming, even if it has decreased in the recent years.