Large areas of the warm, humid tropics in Southeast Asia, the Pacific, Latin America, the Caribbean, and Africa are hilly or mountainous. Jackson and Scherr (1995) estimate that these tropical hillside areas are inhabited by 500 million people, or one-tenth of the current world population, many of whom practice subsistence agriculture. The region most affected is Asia which has the lowest area of arable land per capita. Aside from limited areas of irrigated terraces, most of the sloping land, which constitutes 60% to 90% of the land resources in many Southeast Asian countries, has been by-passed in the economic development of the region (Maglinao and Hashim, 1993). Poverty in these areas is often high, in contrast to the relative wealth of irri­ gated rice farms in lowland areas that benefited from the green revolution. Rapid population growth in some countries is also exacerbating the problems of hillside areas. Increasingly, people are migrating from high-potential lowland areas where land is scarce to more remote hillside areas. Such migra­ tion, together with inherent high population growth, is forcing a transforma­ tion in land use from subsistence to permanent agriculture on fragile slopes, and is creating a new suite of social, economic, and environmental problems (Garrity, 1993; Maglinao and Hashim, 1993).