A study of Santa Cruz, Bolivia, which used NASA satellites and computer models, reports that cutting down tropical forests and converting grasslands to crops may inadvertently warm those local areas. According to the research, forest canopies create wind turbulence that cools the air, and native grasslands are better adapted to the tropics than crops, in ways that also have a cooling effect.

Lahouari Bounoua, a researcher at the University of Maryland (UMD), College Park, Md., and NASA's Goddard Space Flight Center (GSFC), Greenbelt, Md., used a computer model to show that temperatures in January may have warmed on average by about 1 degree Fahrenheit in the last 25 years, solely because native forests and grasslands in Santa Cruz were replaced with crops. Co-authors in this interdisciplinary study of land cover and climate changes included University of Maryland researcher, Ruth DeFries, NASA GSFC/UMD scientist Marc Imhoff and NASA GSFC researcher Marc Steininger.

"It's important to understand the effects of changing land cover in the tropics, because unlike the past, future deforestation is likely to occur in tropical and sub-tropical regions," said Bounoua.

The Santa Cruz region has one of the highest rates of concentrated deforestation in the world over the last 20 years, a recent study by co-author Steininger found.

According to the computer model, in places where tropical forest species were replaced by crops, nighttime temperatures dropped slightly, while daytime local temperatures rose by 3.6 degrees Fahrenheit (F) or 2 degrees Celsius. Forests have high canopies with varied surfaces, and the movement of winds over these rough surfaces creates turbulence and cools the air. Low, even croplands on the other hand create less turbulence from winds and don't cool the air as much, the researcher
'"/>

Contact: Krishna Ramanujan
kramanuj@pop900.gsfc.nasa.gov
301-286-3026
NASA/Goddard Space Flight Center
21-Aug-2003