biological impoverishment

Nowhere on earth is the threat of biological impoverishment because of deforestation greater than in the Amazon Basin of South America. The Amazon supports approximately 300 million hectares of tropical forest, the largest single area of tropical forest communities in the world (Fig. 2). Estimates of global biodiversity point to the tropics as the source of 50 to 90% of all species on Earth (Wilson 1992); the richest forests often support over 300 tree species per hectare, approximately the same number of tree species in all of North America. Recent estimates of deforestation suggest that between 1 to 3 million hectares are being cleared annually in the Amazon Basin (Lawrence 1997; Fig. 3). Based on estimates of 1% annual tropical forest loss, the Amazon may be losing as many as 11 to 16 species per day (Wilson 1989), and the resulting ecosystems are often highly degraded (Buschbacher 1986). The deforestation of Amazonia presents a challenging study of the interactions among people, their values, and the environment. Is deforestation in the Amazon any different than what occurred in industrialized Europe and North America centuries past? Should Amazonians develop their lands as they see fit? Do peasant farmers actively clearing forests value their environment any differently than world conservation organizations, you, or I? What does the world stand to lose by watching the destruction of tropical forests? These are some of the most hotly debated environmental questions today, leading to several international conventions like the recent United Nations Convention on Biodiversity at the Rio de Janeiro "Earth Summit" in 1992. Factors leading to rapid tropical deforestation Why are tropical forests being cleared in the Amazon Basin at such an alarming rate? Historically, deforestation has been caused by the interaction of many factors, seven of which are presented here for simplici...