Warmer Atlantic Waters Triggered Katrina and Amazonian Drought

http://www.bloomberg.com/apps/news?pid=20601130&sid=aNQf_jdH_4n8&refer=environment

By Jeremy van Loon

March 5 (Bloomberg) -- Warmer water in the Atlantic spawned an increase in the number of severe storms in the Caribbean in 2005, including Hurricane Katrina, and had an unexpected impact on the world’s largest tropical rain forest: drought.

The milder waters in the second-biggest ocean caused such arid conditions in the western and southern parts of the Amazon that younger trees died and growth in older ones slowed. That then turned a rain forest that normally absorbs 500 million tons of carbon dioxide a year into a net emitter of the greenhouse gas blamed for global warming, scientists said.

The Amazonian forest, in one dry year, released 900 million tons of CO2, reversing its usual role in climate change dynamics, ecologist Oliver Phillips of the University of Leeds said in an interview. There were few visible indications of the drought and the results run counter to the notion that intact forests are vast absorbers of CO2 at all times, he added.

“It didn’t take much for the Amazon to become a source of carbon emissions rather than a sink,” Phillips said. “This shows that it doesn’t take a catastrophic change of climate for the forest to become a net contributor of emissions.”

The results of the study of the impact of the drought on the Brazilian forest by a team of scientists including geographers, biologists and climatologists appears today in Science. The team is examining whether the trees quickly returned to net absorbers of carbon following the drought.

Logging, Fires

The sensitivity of forests to fluctuations in climate may harm efforts to reduce carbon emissions. Destruction of forests by logging and fires to clear land for farming contributes a fifth of annual CO2 emissions while at the same time the intact trees consume almost as much in the process of photosynthesis.

With the world’s forests shrinking daily by an area the size of Washington, D.C., envoys at ongoing UN-led climate- change talks are looking at ways to save tropical forests and include their carbon absorption in a new global-warming treaty to replace the Kyoto Protocol. Proposals include providing money or carbon credits for countries with large tracks of wooded areas such as Brazil and Indonesia for keeping the trees intact.

“There is a lot of uncertainty about how forests are adapting,” said David Huberman, an expert on conservation incentives at the International Union for the Conservation of Nature in Gland, Switzerland. “This study would be a call for caution. We don’t know how forests will react to climate change and conservation is clearly a solution.”

Trees Stop Growing?

The findings by Phillips and his 67 co-authors at 40 institutions come two weeks after Phillips’ fellow University of Leeds researcher Simon Lewis said tropical rain forests will likely slow their absorption of carbon dioxide in the coming decades due to aging.

Older trees will probably stop growing for the same reasons they did in 2005 after Katrina devastated New Orleans -- warmer temperatures and less available water, the study showed.

Phillips and the other researchers examined more than 100 plots throughout the Amazon and measured 100,000 trees and recorded tree deaths. They also made note of changes in weather.

Forests are also under threat by logging. The world loses about 50,000 square kilometers (19,305 square miles) of primary forests annually, mostly in the tropical regions of South America, Africa and Asia, the UN’s Environment Program has said.

At 6 million square kilometers (2.3 million square miles), the Amazon forest is 15 times as large as California and contains one-fifth of all species on Earth.

http://www.sciencedaily.com/releases/2009/03/090305141625.htm