Published: September 14, 2005
Tropical Deforestation Affects Rainfall Across Globe, Study Says
Land-cover changes can help slow or speed greenhouse warming
A new study is offering insight into long-term impacts of changes caused by human development, particularly the effects on the global climate of large-scale deforestation in tropical regions.
Researchers from Duke University in North Carolina analyzed years of data using the NASA General Circulation Computer Model and Global Precipitation Climatology Project to produce several climate simulations.
According to a September 13 NASA press release, the research shows that deforestation in different areas of the globe affects rainfall patterns over a large region.
"Our study carried somewhat surprising results," said lead author Roni Avissar, "showing that although the major impact of deforestation on precipitation is found in and near the deforested regions, it also has a strong influence on rainfall in the mid and even high latitudes."
Deforestation in the Amazon region of South America, for example, influences rainfall from Mexico to Texas and in the Gulf of Mexico.
Deforesting lands in Central Africa affects rainfall in the upper and lower U.S Midwest, and deforestation in Southeast Asia alters rainfall in China and the Balkan Peninsula.
Such changes mainly occur in certain seasons, and the combined effects of deforestation in these areas enhances rain in one region and reduces it in another.
The finding contradicts earlier research suggesting that deforestation would cause a reduction in rainfall and increase in temperature in the Amazon basin but have no detectable impact on the global water cycle, which describes the existence and movement of water on, in and above the Earth.
Improved understanding of tropical forested regions is valuable because of their strong influence on the global climate. The Amazon Basin drives weather systems around the world.
The tropics receive two-thirds of the world’s rainfall, and when it rains, water changes from liquid to vapor and back again, storing and releasing heat energy in the process.
With so much rainfall, an incredible amount of heat is released into the atmosphere – making the tropics the Earth’s primary source of heat redistribution.
Land-cover changes in tropical regions can have potentially significant consequences for water resources, wildfire frequency, agriculture and related activities at various remote locations.
Depending on its nature, land-cover change also can help slow or speed up greenhouse warming.
The researchers say their results are based on numerical simulations performed with a single general circulation model and that reproducing the experiment with other computer models using different atmospheric variables would be beneficial.
Additional information on how tropical deforestation affects rainfall is available on NASA’s Web site.
Source: U.S. Department of State and NASA
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