A problem of Amazonian proportion

'Alarming' Amazon Droughts May Have Global Fallout : NPR: "The world's largest tropical forest, the Amazon, experienced something rare last year — a drought. It wasn't the earth-cracking kind of drought that happens in the American Southwest or the Australian outback, but it did stunt or kill lots of trees.

It was the second such drought in the Amazon in five years, and forest scientists are trying to understand why these droughts are happening, and what their effects will be for the planet.

The 2005 drought in the Amazon was so unusual that scientists called it a '100-year event' — something supposed to happen only once a century.

"This is what's quite alarming — that we've seen these two very unusual events," says Simon Lewis, a forest ecologist at the University of Leeds in Great Britain, who watched both droughts hit the Amazon. Lewis notes that several of the computer models that calculate the effects of climate change do predict that parts of the planet are going to get drier.

"And those two unusual events are consistent with those predictions that suggest that the Amazon may be severely impacted over the next few decades by these droughts," he says.

How Droughts Affect Forests

Writing in the journal Science, Lewis and his scientific team say the droughts are probably caused by the northward movement of especially warm water in the Atlantic Ocean. That shift carries moisture north, robbing big chunks of the Amazon of rain it normally would get."