innumerable individual decisions that are rational on a small scale (e.g., subsistence farming, ranching, or lumbering for profit) but that have consequences that are irrational on the large scale (e.g., alteration of hydrological patterns, effects on global climate, or reduction of biodiversity). The basic problem of tropical deforestation is seen in the fact that habitat destruction in the tropical rain forests is proceeding at an average annual rate of 100,000 200,000 square kilometers, an area the size of England. Precisely what is disappearing is a matter of argument, and that is part of the problem. The tropics contain a disproportionate share of the world's species of plants and animals, many of them endemic to tiny habitats. Above and beyond the species they comprise, tropical forest habitats offer several classes of local and global values: hydrological, in preventing soil erosion and downstream siltation, and climatological, in maintaining local precipitation and the atmospheric balance of gases (Katz
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