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Global Environmental Change: Understanding the Human Dimensions
worthy as a quick and decisive reaction to a threat whose impact lies largely in the future. Many now wonder whether this case offers lessons of value for those struggling to come to terms with other global changes, such as climate change and the loss of biological diversity.
Human activities are decreasing biological diversity on land, in fresh waters and the seas, in industrialized and developing nations, from the coldest inhabited lands to the tropics. But because of the huge variety of species confined to the tropical moist forests, their destruction is likely to cause more loss of biological diversity at the species level than any other human activity. Although the scale of this destruction is hard to measure accurately, recent estimates indicate that, on a world scale, an area of tropical moist forest roughly the size of Honduras is deforested or converted annually (Erwin, 1988), resulting in the extinction of species at a rate that has been estimated at 17,500 species per year, assuming 5 million species in the tropical moist forests (Wilson, 1988). The immediate, or proximal, causes of deforestation are easy to identify: the conversion of forest to agricultural use, logging, mining, industrial development (e.g., hydroelectric power), and the search for fuel wood and fodder. But what lies behind these proximal causes? A popular notion associates the destruction of tropical moist forests with population pressure. But the best analyses suggest that in some important forest regions, such as the Amazon, this argument explains, at most, only a small part of deforestation (see Chapter 3).
In fact, a constellation of distinct, though interacting, forces appears to be at work. The destruction of the tropical moist forest of Brazil's Amazon Basin offers an example. One key force manifests itself in the pressure of international markets for mineral and wood products, coupled with the country's interest in encouraging exports for the purpose of reducing its international debt. Public policies intended to promote economic development also contribute to the destruction of Amazonian forests (for example, government-sponsored road construction, hydroelectric power projects, and favorable tax treatment for large ranching operations, though the last has recently been withdrawn). Corporations cut trees to initiate mining and smelting operations, and more trees to fuel the processes. A frontier mentality encourages rapid use of forest resources on the assumption that there will