October 13, 2005

Dry days in the Amazon rain forest.

It's the worst drought in 40 years, with water levels in some rivers 15 meters [49 feet] lower than normal. According to researchers, the probable culprit is rising temperatures in the North Atlantic, which may be caused by global warming.

Low water on the Amazon

A boat makes tries to make its way through a section of the Amazon River suffering from lower water levels near Uricurituba, in northern Brazil, on Tuesday, Oct. 4, 2005. [Photo: AP/A Critica/Euzivaldo Queiroz]

The unusually dry weather has taken everyone — including scientists by surprise. Usually, droughts in the region are associated with El Niņo, which periodically warms the southern Pacific and wreaks weather havoc world-wide. But this year hasn't seen an El Niņo form. What scientists have detected, however, is a warming of the surface temperatures in the North Atlantic — warming which was responsible for this year's numerous severe hurricanes. The low pressure systems that result from this warming cause high pressure in areas further south, such as the Amazon basin. These high pressure systems tend to have fewer rainclouds and, obviously, drop less rain.

The Amazon Basin shows wide seasonal variation in rainfall, [Paul Lefebvre of the Woods Hole Research Center in the US] points out. But with the wet season not due to begin until December, local communities are fearful that the current lack of water may harm fish supplies and increase the risk of disease.

Drought in the Amazon could also stunt tree growth and make the forest more susceptible to burning — both of which could have global implications for climate.

Studies by Lefebvre's colleagues show that drought conditions can cut the amount that trees grow by a quarter, which would in theory prevent the forest's ability to soak up carbon.

If this happens, the Amazon could conceivably become a carbon 'source', pumping out carbon dioxide faster than it can absorb it, Lefebvre says. More carbon dioxide in the atmosphere could raise world temperatures even further, making droughts even more damaging in the future.

Forest burning, often used to remove insect pests or encourage grass growth for grazing animals, could also fall into a similar vicious cycle, Lefebvre says. "Fire damage sets up a process where the forest becomes more susceptible to the next burn," he says. Local governments have tried to limit the number of burning permits issued, but many people are too poor to afford them, and so ignore the regulations.

The ultimate fear is that the Amazon forest — often touted as an invaluable piece of armour against climate change — could become part of the problem rather than a key element of the solution. Droughts make it more likely that it will become a net source of greenhouse gases to the atmosphere, rather than mopping them up.

"From hearing what people are saying, I'm quite alarmed," Lefebvre admits. "It's an interesting time to be studying this, but it's not good news."

Via news@nature.com.

Posted by Magpie at October 13, 2005 01:01 PM | Environment | Technorati links |

Wow. Just wow.

Posted by: Mary at October 13, 2005 11:26 PM

Holy hell. We are SO in for it. Why does the handbasket have to be sitting on the porch at the gates of doom before you can get anyone motivated?

Posted by: natasha at October 13, 2005 11:44 PM

Do you people have even a clue of how stupid you sound?
One volcano eruption puts more fumes in the air than all the engines in the world ever have combined.
What am I wasting my typing for.
Please get a life.

Posted by: lycfyg-LQ at October 14, 2005 04:20 AM