The Amazon basin, the region of South America drained by the Amazon River, represents the largest area of tropical rain forest in the world. Extending across nine different countries and covering an area of 2.3 million square mi (6 million sq. km), the Amazon basin contains the greatest abundance and diversity of life anywhere on the earth. Tremendous numbers of plant and animal species that occur there have yet to be discovered or properly named by scientists, as this area has only begun to be explored by competent researchers.
It is estimated that the Amazon basin contains over 20% of all higher plant species on Earth, as well as about 20% of all birdlife and 10% of all mammals. More than 2,000 known species of freshwater fishes live in the Amazon river and represent about 8% of all fishes on the planet, both freshwater and marine. This number of species is about three times the entire ichthyofauna of North America and almost ten times that of Europe. The most astonishing numbers, however, come from the river basin's insects. Every expedition to the Amazon basin yields countless new species of insects, with some individual trees in the tropical forest providing scientists with hundreds of undescribed forms. Insects represent about three-fourths of all animal life on Earth, yet biologists believe the 750,000 species that have already been scientifically named account for less than 10% of all insect life that exists.
However incredible these examples of biodiversity are, they may soon be destroyed as the rampant deforestation in the Amazon basin continues. Much of this destruction is directly attributable to human population growth . The number of people who have settled in the Amazonian uplands of Colombia and Ecuador has increased by 600% over the past 40 years, and this has led to the clearing of over 65% of the region's forests for agriculture.
In Brazil, up to 70% of the deforestation is tied to cattle ranching. In the past large governmental subsidies and tax incentives have encouraged this practice, which had little or no financial success and caused widespread environmental damage. Tropical soils rapidly lose their fertility, and this allows only limited annual meat production. It is often only 300 lb (136 kg) per acre, compared to over 3,000 lb (1,360 kg) per acre in North America.
Further damage to the tropical forests of the Amazon basin is linked to commercial logging . Although only five of the approximately 1,500 tree species of the region are extensively logged, tremendous damage is done to the surrounding forest as these are selectively removed. When loggers build roads move in heavy equipment, they may damage or destroy half of the trees in a given area.
The deforestation taking place in the Amazon basin has a wide range of environmental effects. The clearing and burning of vegetation produces smoke or air pollution , which at times has been so abundant that it is clearly visible from space. Clearing also leads to increased soil erosion after heavy rains, and can result in water pollution through siltation as well as increased water temperatures from increased exposure. Yet the most alarming, and definitely the most irreversible, environmental problem facing the Amazon basin is the loss of biodiversity. Through the irrevocable process of extinction , this may cost humanity more than the loss of species. It may cost us the loss of potential discoveries of medicines and other beneficial products derived from these species.
[Eugene C. Beckham ]
Caufield, C. In the Rainforest: Report From a Strange, Beautiful, Imperiled World. Chicago: University of Chicago Press, 1986.
Cockburn, A., and S. Hecht. The Fate of the Forest: Developers, Destroyers, and Defenders of the Amazon. New York: Harper/Perennial, 1990.
Collins, M. The Last Rain Forests: A World Conservation Atlas. London: Oxford University Press, 1990.
Cowell, A. Decade of Destruction: The Crusade to Save the Amazon Rain Forest. New York: Doubleday, 1991.
Margolis, M. The Last New World: The Conquest of the Amazon Frontier. New York: Norton, 1992.
Wilson, E. O. The Diversity of Life. Cambridge, MA: Belknap Press, 1992.
Holloway, M. "Sustaining the Amazon." Scientific American 269 (July 1993): 90–96+.