Published this week in the online edition of the Proceedings of the National Academy of Sciences, the study found that clearings for cropland averaged twice the size of clearings for pasture and conversion occurred rapidly with more than 90 percent of clearings for cropland planted in the first year following deforestation.

Over the four year study period, deforestation for large-scale cropland accounted for 17 percent of forest loss in large clearings. However, area deforested for cropland and the mean annual soybean price in the year of forest clearing were directly correlated, suggesting that deforestation rates could return to higher levels seen in 2003-2004 with a rebound of crop prices in international markets, the authors say.

"There has been a lot of debate recently about the role of large-scale agriculture in Amazon deforestation, said University of Maryland geographer Ruth DeFries, who led the study. "This study on one hand refutes the claim that agricultural intensification does not cause new deforestation. On the other hand, it shows that clearing for pasture rather than intensive mechanized agriculture remains the dominant cause of deforestation in the state of Mato Grosso, DeFries said.

The team combined deforestation maps, field surveys and satellite-based information to see what happened to large plots (greater than 60 acres) of rainforest after they were cleared. Clear areas were characterized as cropland, cattle pasture, or re-growing forest in the years following initial clearing in Mato Grosso, the Brazilian state with the highest rate of both deforestation and soybean production since 2001.

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