ABSTRACT
Human occupation of a watershed need not result in degradation of soil and water resources, even under the extremes of tropical climates. A modern advance in the design of rural roads is the replacement of the deep narrow roadside drainage trenches, wherever space permits, by broad shallow grassed waterways, which are less susceptible to erosion. The rapid population growth in tropical developing countries has spilled very large numbers of subsistence cultivators into the remaining forests. At high levels of investment, as in large plantations of oil palm, rubber, or cocoa, the long-term stability of soils and water resources is required as the basis for future dividends. Despite their luxurious natural vegetation, many tropical soils have low levels of plant nutrients. Remote sensing by satellite imagery, aerial photography, and side-looking radar is providing increasing evidence of the scale and gravity of the impact of human populations on their environment.
