AMAZON RIVER

The Central and Northern Andes and the Amazon River basin and drainage network. Portuguese, Rio Amazonas, Spanish Ro Amazonas, the greatest river of South America and the largest drainage system in the world in terms of the volume of its flow and the area of its basin. The total length of the rivermeasured from the headwaters of the Ucayali-Apurmac river system in Peruis about 4,000 miles (6,400 kilometres), which is slightly shorter than the Nile River but still the equivalent of the distance from New York City to Rome. Its westernmost source is high in the Andes Mountains, within 100 miles of the Pacific Ocean, and its mouth is in the Atlantic Ocean. Boat traffic on the Amazon River near Gurup, Par state, Brazil. The vast Amazon basin (Amazonia), the largest lowland in Latin America, has an area of about 2.3 million square miles (6 million square kilometres) and is nearly twice as large as that of the Congo River, the Earth's other great equatorial drainage system. Stretching some 1,725 miles from north to south at its widest point, the basin includes the greater part of Brazil and Peru, significant parts of Colombia, Ecuador, and Bolivia, and a small area of Venezuela; roughly two-thirds of the Amazon's main stream and by far the largest portion of its basin are within Brazil. The Tocantins-Araguaia catchment area in Par state covers another 300,000 square miles. Although considered a part of Amazonia by the Brazilian government and in popular usage, it is technically a separate system. It is estimated that about one-fifth of all the water that runs off the Earth's surface is carried by the Amazon. The flood-stage discharge at the river's mouth is about 6,180,000 cubic feet (175,000 cubic metres) per second, which is four times that of the Congo and more than 10 times the amount carried by the Mississippi River. This immense volume of fresh water dilutes the ocean's saltiness for more than 100 miles from shore. The extensive lowland areas bordering the main river and its tributaries, called vrzeas, are subject to annual flooding, with consequent soil enrichment; however, most of the vast basin consists of upland, well above the inundations and known as terra firme. More than two-thirds of the basin is covered by an immense rain forest, which grades into dry forest and savanna on the higher northern and southern margins and into montane forest in the Andes to the west. The Amazon Rain Forest, which represents about half of the Earth's remaining rain forest, also constitutes its largest reserve of biological resources. In the later decades of the 20th century, the Amazon basin has attracted international attention because human activities have increasingly threatened the equilibrium of the forest's highly complex activities. Deforestation has accelerated, especially south of the Amazon River and on the piedmont outwash of the Andes, as new highways and air transport facilities have opened the basin to a tidal wave of settlers and entrepreneurs. Significant mineral discoveries have brought further influxes of population. The ecological consequences of such developments, potentially reaching well beyond the basin and even gaining worldwide importance, have attracted growing popular and scientific attention. The first European to explore the Amazon, in 1541, was the Spanish soldier Francisco de Orellana, who is said to have given the river its name after reporting pitched battles with tribes of female warriors, whom he likened to the Amazons of Greek mythology. Although the name Amazon is conventionally employed for the entire river, in Peruvian and Brazilian nomenclature it properly is applied only to sections of it. In Peru the upper main stream (fed by numerous tributaries flowing from sources in the Andes) down to Iquitos (Peru) is called Maran (Portuguese: Maranho), and from there to the Atlantic it is called Amazonas. In Brazil the name Solimes is used from Iquitos to the mouth of the Negro River and Amazonas only from the Negro to the sea. Portuguese Rio Amazonas, Spanish Ro Amazonas, greatest river of South America and the largest in the world in volume and area of its drainage basin. Originating within 100 miles (160 km) of the Pacific Ocean at its westernmost source high in the Peruvian Andes, the Amazon flows almost 4,000 miles (6,400 km) across northern Brazil to its mouth in the Atlantic Ocean on the northeastern coast of Brazil. Its length is second only to that of the Nile. It is estimated that about 20 percent of all the water that runs off the Earth's surface is carried by the Amazon. The flood-stage discharge at the river's mouth is about 6,360,000 cubic feet (180,000 cubic m) per second, which is more than 10 times that of North America's Mississippi River and four times that of the Congo River in Africa. The discharge is so great that it turns seawater from salty to brackish for more than 100 miles offshore. There are more than 1,000 known tributaries of the Amazon, rising in the Guiana Highlands, the Brazilian Highlands, and (principally) the Andes. Seven of these are longer than 1,000 miles (1,600 km); one, the Madeira, flowing northeastward from Bolivia, is more than 2,000 miles (3,200 km) long. Navigable throughout the year, the Amazon can accommodate large freighters as far inland as Manaus, 1,000 miles upriver from the Atlantic. The Amazon flows over a gently sloping terrain and is characterized by oxbow lakes, abandoned channels, and other marks of a meandering river. Floods, by depositing fertile silt as they recede, annually rejuvenate an area of some 25,000 square miles (65,000 square km), or nearly double that of The Netherlands, and the river's total drainage basin, about 2,700,000 square miles (7,050,000 square km), is nearly twice as large as the area drained by any other river in the world. The Amazon and its tributaries may be described as a vast sea of freshwater, supporting millions of fish, including catfish, electric eels, and piranhas. Additional reading Introductory overviews of the Amazon River basin include Helen Schreider and Frank Schreider, Exploring the Amazon (1970), a well-illustrated descriptive book; the treatment of the basin in N. Mark Collins (ed.), The Last Rain Forests (1990), pp. 110129; Catherine Caufield, In the Rainforest (1985); and Hilgard O'Reilly Sternberg, The Amazon River of Brazil (1975). The issue of tropical forest conversion and its ecologic impact came to public attention with the appearance of R.J.A. Goodland and H.S. Irwin, Amazon Jungle: Green Hell to Red Desert? (1975). Collections of essays on the basin, often elaborating on this theme, include Harold Sioli (ed.), The Amazon: Limnology and Landscape Ecology of a Mighty Tropical River and Its Basin (1984); Robert E. Dickinson (ed.), The Geophysiology of Amazonia (1987); Marianne Schmink and Charles H. Wood (eds.), Frontier Expansion in Amazonia (1984); and John Hemming (ed.), Change in the Amazon Basin, 2 vol. (1985). Susanna Hecht and Alexander Cockburn, The Fate of the Forest: Developers, Destroyers, and Defenders of the Amazon (1989), is an overarching historical survey, richly documented, with a critical examination of the political, social, and economic background of the escalating degradation of the Amazon environment. Other studies of people and society, mostly with emphasis on Brazil, include Marianne Schmink and Charles H. Wood, Contested Frontiers in Amazonia (1992); Julie Sloan Denslow and Christine Padoch, People of the Tropical Rain Forest (1988); Eugene Philip Parker (ed.), The Amazon Caboclo (1985); John Hemming, Amazon Frontier: The Defeat of the Brazilian Indians (1987); and, for later archaeological discoveries, Anna C. Roosevelt, Secrets of the Forest, The Sciences, 32:2228 (November/December 1992). Works on resources and ecology include Eneas Salati et al., Amazonia, in B.L. Turner II et al., The Earth as Transformed by Human Action (1990), pp. 479493; David Cleary, The Brazilian Rainforest: Politics, Finance, Mining, and the Environment (1991); Kent H. Redford and Christine Padoch (eds.), Conservation of Neotropical Forests (1992); Hilgard O'Reilly Sternberg, Manifest Destiny and the Brazilian Amazon, in Conference of Latin Americanist Geographers, Yearbook, vol. 13 (1987), pp. 2535; Michael Goulding, Amazon: The Flooded Forest (1989); William M. Denevan and Christine Padoch (eds.), Swidden-Fallow Agroforestry in the Peruvian Amazon (1988); Philip M. Fearnside, Human Carrying Capacity of the Brazilian Rainforest (1986); D.A. Posey and W. Bale (eds.), Resource Management in Amazonia (1989); and, on dwindling wildlife, Nigel J.H. Smith, Man, Fishes, and the Amazon (1981); and Kent H. Redford, The Empty Forest, BioScience, 42(6):412422 (June 1992). Broader surveys of the economic development of the basin include Minimum Conflict: Guidelines for Planning the Use of American Humid Tropic Environments (1987), prepared by the United Nations Environment Programme in cooperation with the government of Peru; and Stephen G. Bunker, Underdeveloping the Amazon (1985), with an overview of economic history. Henry Walter Bates, The Naturalist on the River Amazons, 2 vol. (1863, reissued 1989); Alfred Russel Wallace, A Narrative of Travels on the Amazon and Rio Negro, 2nd ed. (1889, reprinted 1972); and Richard Spruce, Notes of a Botanist on the Amazon & Andes, 2 vol. (1908, reissued 1970), are classics of natural history exploration. Wm. Lewis Herndon and Lardner Gibbon, Exploration of the Valley of the Amazon, 2 vol. (185354), is also informative. James J. Parsons