More than half of cropland expansion between 1980 and 2000 occurred at the expense of natural forests, while another 30 percent of occurred in disturbed forests, reported a Stanford University researcher presenting Saturday at the annual meeting of the American Association for the Advancement of Science (AAAS) in Chicago.
Holly Gibbs, formerly of the University of Wisconsin-Madison, reached her conclusion after analyzing more than 600 satellite images from the United Nations Food and Agricultural Organization (FAO) and other organizations.
"What we found was that indeed forests were the primary source for new croplands as they expanded across the tropics during the 1980s and 1990s," Gibbs explained. "Cropland expansion, whether it's for fuel, feed or food, has undoubtedly led to more deforestation, and evidence is mounting that this trend will continue."
"This is a major concern for the global environment," she continued. "As we look toward biofuels to help reduce climate change we must consider the rainforests and savannas that may lie in the pathway of expanding biofuel cropland."
Oil palm plantations and logged over forest in Malaysian Borneo. While much of the forest land converted for oil palm plantations in Malaysia has been logged or otherwise been zoned for logging, expansion at the expense of natural and protected forest does occur in the country. Reserve borders are sometimes redrawn to facilitate logging and conversion to plantations.
Conversion of natural ecosystems for production of biofuel feedstocks like corn and sugar cane for ethanol, and soy and palm oil for biodiesel, can result in substantial greenhouse gas emissions since these croplands sequester less carbon than the forests and wetlands they replace. For example the production of a single ton of palm oil on land converted from peat forest in Indonesia can result in 25 to 70 tons in carbon dioxide emissions from clearing of vegetation, draining of swampy soils, and burning.
Gibbs says the FAO is currently in the process of gathering data that will reveal the impact of the recent biofuels boom on forests and other ecosystems. She hopes the data can be used to influence policy makers to steer future agricultural expansion towards abandoned and degraded agricultural lands rather than forests.
"I think that biofuels may have a critical place in our future energy plan, but the way that we're currently going about producing biofuels could have a lot of unintended consequences," she said. "The new administration should carefully consider the full consequences of any energy plan to make sure we protect the carbon stored in rainforests as well as reduce our fossil fuel emissions."
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The report also looked at forest clearing in Riau, on the island of Sumatra, and Papua, which is part of New Guinea. In Riau, 38.5 percent of its total forest area has been allocated for conversion into plantations, of which 1.5 million hectares consisted of palm oil plantations. In Papua, 480,000 hectares had been cleared and allocated for growing oil palm. 
