South America referat

South America, the fourth largest of the earth's seven continents (after Asia, Africa, and North America), occupying about 17,819,100 sq km (about 6,880,000 sq mi), or about 12 percent of the earth's land surface. It lies astride the equator and tropic of Capricorn and is joined by the Isthmus of Panama, on the north, to Central and North America. The continent extends about 7400 km (about 4600 mi) from the Caribbean Sea on the north to Cape Horn on the south, and its maximum width, between Ponta do Seixas, on Brazil's Atlantic coast, and Punta Pariñas, on Peru's Pacific coast, is about 5160 km (about 3210 mi).

Drainage and Water Resources The greater part of South America is drained to the Atlantic Ocean by three river systems: the Amazon, Orinoco, and Paraguay-Paraná. Each of these large rivers also provides access to the interior. The smaller Sao Francisco River drains northeastern Brazil. Numerous lesser rivers drain the Caribbean and Pacific flanks of the Andes. The most important of these is the Magdalena River and its tributary, the Cauca River. This system, which drains north through Andean valleys in western Colombia to empty into the Caribbean Sea, has also provided a traditional access route to the interior. Scores of short Andean streams have sustained agriculture for centuries in Ecuador, Peru, Chile, and northwestern Argentina. Considerable hydroelectric power potential exists in the streams of the Andes and in those of the Guiana and Brazilian Highlands. The Mantaro Valley hydroelectric scheme in the Andes of Peru provides most of Lima's electricity. South America has few large lakes. Many of the large permanent lakes are situated at relatively high elevations in the Andes. Among the largest are Lake Titicaca and Lake Poopó in Bolivia; Buenos Aires, Argentino and Nahuel Huapí lakes in Argentina; and Lake Valencia in Venezuela.

Vegetation The vegetation zones of South America correspond closely with the climatic zones. The areas of wet tropical climate have a dense cover of rain forest, or selva. The largest forest area in the world, this rain forest covers much of equatorial South America, including the Brazilian coast and the lower slopes of the Andes, and contains tropical hardwoods, palms, tree ferns, bamboos, and lianas. Open forests and brushlands are found in the areas of winter drought chiefly on the Venezuelan coast, in northeastern Brazil, and on the Gran Chaco. Between these drier areas and the rain forest are zones of tall grass (savannas, or campos) and of scrub and grass (campos cerrados). Mixed (containing both deciduous and evergreen trees) and deciduous forests occur in southern Brazil and along the slopes of the Andes. In Brazil the forest grades, to the south, into areas of rolling prairie interrupted by wooded hills. The Gran Chaco is characterized by grassy plains and open thorn scrub forest. The flat Pampas of east central Argentina is the largest midlatitude grassland of South America. To the south a zone of scrub steppe (monte) marks the transition to the low brush and bunch grass that cover the drier and cooler Patagonia region. Along the Pacific coast, the vegetation grades northward from forest to open woodland, to shrubs and grass in central Chile, and eventually to the scrub and desert vegetation that prevails into northern Peru and up to the mountain flanks.

Animals South America, Central America, the lowlands of Mexico, and the West Indies may be classified as a single zoogeographic region usually called the Neotropical Region. Fauna is characterized by variety and a singular lack of affinity with the fauna of other continents, including North America north of the Mexican Plateau. Found throughout are families of mammals absolutely confined to the region, including two unique species of monkey, bloodsucking bats, and many unusual rodents. The region has only one kind of bear, the spectacled bear; no horses or related animals, aside from one species of tapir; and no ruminants, except lamoids (members of the camel family), which include alpacas, llamas, and vicuñas. Also characteristic of the continent are jaguar, peccary, giant anteater, and coati. Birds display still greater isolation and singularity. About 23 families and about 600 genera of exclusively Neotropical birds occur, as well as the greater part of other important families, such as those of the hummingbirds (500 species), tanagers, and macaws, together with a great variety of sea fowl. The largest birds include the rhea, condor, and flamingo. Reptiles include boas and anacondas; iguanas, caimans, and crocodiles are found in many areas. Freshwater fish are varied and abundant. Regional exclusiveness also characterizes insects and other invertebrates. On the whole, South American fauna is more local and distinct than that of any continent other than Australia; probably more than four-fifths of its species are restricted to its zoogeographic boundaries. The Galápagos Islands are the habitat of reptiles and birds that are unknown elsewhere, including the Galápagos giant tortoise, Darwin's finches, and the Galápagos penguin.

Mineral Resources South America has diverse mineral resources, many of which have not been extensively exploited. Mineral deposits are widely distributed, but certain areas of the continent are particularly renowned for their wealth. In the Andes placer gold has been worked in various areas since before the colonial era. The mountains between central Peru and southern Bolivia produced silver and mercury in the colonial era, and such industrial minerals as copper, tin, lead, and zinc today. Copper is worked at large deposits in northern and central Chile and in central and southern Peru. A highly mineralized area containing bauxite, iron ore, and gold lies between Ciudad Bolívar and northern Suriname, near the northern margin of the Guiana Highlands. In east central Brazil rich gold and diamond strikes occurred in the colonial era, some of these mines are still producing. Although South America is a major producer of rare metals, the large reserves of high-grade iron ore and smaller reserves of bauxite are more important to the emerging industrial power of the continent.

South America is lacking in large coal reserves. Coal is found in scattered and relatively small deposits in the Andes and in southern Brazil. Coal has been an important fuel for industry and transportation primarily in Chile, Colombia, and Brazil. Petroleum, however, is widely distributed. Most of the continent's reserves of petroleum and natural gas lie in structural basins located mostly along the eastern margins of and in the Andes, from Venezuela to Tierra del Fuego. The largest known fields are in the Lake Maracaibo area of Venezuela. Other deposits occur in northern Colombia, Ecuador and Peru, south of the Andes in eastern and central Venezuela, and just east of the mountains in Colombia, Ecuador, Peru, Bolivia, Argentina, and Chile.

Agriculture Most crop and livestock production in South America is for home consumption and domestic markets. Nevertheless, revenues from agricultural exports are very important in many South American countries. The processing, internal marketing, and exporting of agricultural products account for a substantial part of commercial and manufacturing activity. Although agriculture, together with hunting, fishing, and forestry, accounts for about 12 percent of the gross domestic product (GDP) within the continent, it accounts for more than 30 percent of the labor force in Bolivia, Paraguay, Peru, and Ecuador, between 20 percent and 30 percent in Colombia, Brazil, and Guyana, and less than 20 percent in Suriname, Chile, Uruguay, Venezuela, Argentina, and French Guiana. The most intensive forms of commercial agriculture are concentrated near cities. Perishables, such as vegetables, fruits, and dairy items, are the principal products here. The production of such staples as root crops, beans, and corn is more dispersed. In many areas these crops are raised by subsistence farmers under unfavorable climatic or soil conditions. Wheat and rice tend to be produced wherever conditions are most suitable. The nonexport beef-cattle industry is dispersed widely; the raising of beef cattle for export is of particular importance in Argentina, Uruguay, Paraguay, and Colombia. Export-oriented agriculture is pursued in the tropical areas and midlatitudes, where arable land and access to ports are optimal. Among the tropical crops, coffee is the most important. It is produced in the highlands, chiefly in southeastern Brazil and in west central Colombia. Cacao is important in eastern Brazil and west central Ecuador. Bananas and sugarcane are produced throughout the Tropics, mostly for domestic markets. Bananas are grown for export in Colombia and western Ecuador; sugar is produced for export in coastal Peru, Guyana, and Suriname. Cotton has been produced for export for many decades in coastal Peru. Cotton and sugarcane are also raised (both for export and domestic markets) in northeastern and southeastern Brazil. In southeastern Brazil soybeans have, since the 1970s, become an important export crop. Soybeans are less important in Argentina, where fertile prairie soils have long supported grain and livestock industries of worldwide importance. Argentine wheat, corn, linseed, beef, mutton, hides, and wool are important items of international trade. Uruguay has a long-standing export trade dominated by wool and hides.

Forestry and Fishing Although the continent is 50 percent forested and is surrounded by seas rich in marine life, the forestry and fishing industries in most South American nations are small and oriented toward domestic markets. Some tropical hardwoods and softwoods are exported, however, much of the wood coming from the Amazon Basin, where large tracts of forest are being cleared for conversion into range and cropland. Also exported is pine lumber from southern Brazil and south central Chile, together with some pulpwood. Significant areas of commercial forest have been planted in Chile and Brazil. The widespread planting of eucalyptus trees for firewood, for timbering, and for use in rough construction has historically been important.

South America's most important commercial fisheries are the Pacific coastal waters. Large amounts of anchovies for fish meal are caught off the Peruvian and Chilean coasts, though overfishing has depleted recent harvests. Tuna are taken off the Ecuadorian and Peruvian coasts. Crustaceans are an important catch in Chilean, Brazilian, and Guianese waters.

Mining Most mining for export is on a large scale. The long history of foreign corporate control of South American mining operations is waning because of national political pressures. Petroleum, copper, bauxite, and iron ore are the principal commodities in value and volume, but mineral exports are greatly diversified. South America is an important world producer of lead, zinc, manganese, and tin. Although all South American countries have some mineral production, Venezuela's oil and gas account for more than half the total value of the continent's output. Mineral production is of great importance to several national economies. Venezuela's exports are dominated by crude and refined petroleum, and derivatives; while the dependence on mineral exports is somewhat less in Suriname, Bolivia, and Chile. Peru and, in recent years, Ecuador, have relied heavily on the sale of minerals. Such exports generate government revenue, but mining contributes little to continental GDP and employment. Nevertheless, mineral commodities are important to the continent's growing industrial diversification.

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