HUGE swathes of the Amazon jungle could be destroyed by drought this century, even if nations make a massive effort to slow down global warming, according to a paper presented at the Copenhagen Climate Congress.

"The Amazon report used computer models to calculate the effects of rising temperatures on the rainforest and found that if temperatures rose by 2 degrees by the middle of the century - considered a conservative prediction - between 20 and 40 per cent of the rainforest would die. If temperatures rose by 3 degrees, three-quarters of the forest would die and transform into grassland.

"On any kind of pragmatic time-scale, I think we should see the loss of the Amazon forest as irreversible," Dr Chris Jones, a lead researcher at the meteorological office's Hadley Centre, told the conference.

"The study, due for publication in the journal Nature Geoscience, was the first to measure the expected loss of trees in the Amazon as a result of climate change. The forest contains about 10 per cent of the world's land-based carbon sinks, and earlier studies have shown changes there would affect the earth's climate.