The extent and consequences of deforestation and related environmental degradation in the developing world have become the subject of considerable debate and concern. There is disagreement about how rapidly tree-covered land near the equator is being cleared or otherwise disturbed. Likewise, tropical deforestation's impacts have proven difficult to identify and to evaluate. By contrast, the contribution small farmers make to deforestation is universally understood. Land clearing has been more rapid in Rondonia, for example, than anywhere else in the Brazilian Amazon and more than half the deforested land in that state is divided among small agricultural holdings (Browder 1988; Mahar 1989). Throughout the developing world, small farmers are primary agents of deforestation. Small farmers migrate to the third world's forested hinterlands for several reasons. In Indonesia, Brazil, and elsewhere, many colonists have participated in settlement projects organized and directed by the public sector (Repetto and Gillis 1988). Most colonization, however, is spontaneous, stimulated by a variety of push and pull factors. Blaikie (1985) argues that the pursuit of socially disruptive rural development strategies as well as land exhaustion cause small farmers to emigrate from areas they have long cultivated. In southern Brazil, they have been selling off their parcels, taking advantage of prices inflated by tax and other policies favorable to those with large land holdings (Binswanger 1989). Moving to agriculture's extensive margin is promoted by infrastructure development, which reduces the cost of marketing commodities grown in remote areas. Agricultural colonists in many countries also benefit from grace periods for development credit and other subsidies (Pearce and Myers 1988). In addition to being induced to migrate to frontier areas, agricultural colonists in the third world face tenure regimes that promote deforestation. Quite often, removing trees and other vegetation is a prerequisite for establishing formal property rights. In Sudan, for example, the parastatal Mechanised Farming Corporation awards fifteen-year leases only to individuals who clear 85 percent of their holdings in three years. Alternatively, formal property law may make no mention of deforestation's being required for tenure. But since developing country governments usually take years to adjudicate claims for formal property rights-particularly claims made by small farmers settling in hinterlandscolonists tend to safeguard pending land rights by using their parcels continuously for crop or livestock production. In addition, agricultural use rights are the only form of land tenure available to private agents in many countries. The government of Ecuador, for example, terminated all private timber concessions in the country's forest patrimony in 1982. Agricultural colonization of tree-covered land is still permitted, however. Although the factors causing small farm-