Left alone, it was assumed, the world's rain forests would not only flourish but might even rescue us from disaster by absorbing the excess carbon dioxide and other planet-warming greenhouse gases.

billion metric tons of carbon into the atmosphere each year - making forests the leading source of greenhouse gases

More than paradise lost, a perishing rain forest could trigger a domino effect - sending winds and rains kilometers off course and loading the skies with even greater levels of greenhouse gases - that will be felt far beyond the Amazon basin.