During 2001–2004, agricultural areas in the Brazilian Amazon forest grew by over 3.6 million hectares, but whether this cropland expansion resulted from use of land already cleared for pasture or from new deforestation has not been assessed. Douglas Morton and Ruth DeFries of the Department of Geography led a recent study published in the Proceedings of the National Academy of Sciences that reports an increasing amount of cleared forest is being used for cropland instead of pasture, contrary to claims that cropland expansion happens only on areas previously cleared for ranching. Morton et al. studied forest changes in the state of Mato Grosso in the southern Brazilian Amazon with satellite images and field surveys. Clearings for cropland were found to be twice the size of clearings for pasture, and preparation for crop production happened rapidly, with >90% of lands cleared for cropland planted within one year. Approximately 17% of deforested area in Mato Grosso was converted directly to large-scale mechanized production in 2001–2004. The authors say the increasing forest conversion to cropland is changing deforestation’s environmental impacts, resulting in greater carbon loss per area and fewer forest fragments than forest clearing for pasture.

‘‘Cropland expansion changes deforestation dynamics in the southern Brazilian Amazon’’ by Douglas C. Morton, Ruth S. DeFries, Yosio E. Shimabukuro, Liana O. Anderson, Egidio Arai, Fernando del Bon Espirito-Santo, Ramon Freitas, and Jeff Morisette. Proceedings of the National Academy of Sciences, 103: 14637–14641.