Some of the most remote regions in South America are its fastest-developing areas. The northern interior of Brazil in the Amazon basin is covered with the world's largest tropical rain forest, the size of the forty-eight contiguous United States. Within some areas of this rich habitat, gold and huge iron ore deposits have been discovered. Development programs have encouraged mining, hydroelectric projects, ranching, and farming there. This has produced a need for clearing the forests and caused a large migration of people into this otherwise remote, isolated region. It has been estimated that 30,000 square miles (78,000 square kilometers) of tropical rain forest were destroyed annually in the 1990's.
The rain forest is not a highly productive growing region for crops. Soils there are thin and have few nutrients. To grow crops and grasses for cattle, slash-and-burn agriculture is practiced. Trees and brush on the land are cut down and burned, and the ashes enrich the soils for a time. This allows for limited production of crops such as corn and rice, but after about three years the nutrients are washed out of the soil by the heavy tropical rains. Farmers and ranchers move on and find new forest area to cut, and the cycle goes on. Rain forests cover only about 5 percent of the total land area of the earth but contain more than half the different types of plants and animals on earth. These forests provide lumber products, medicines, and food.
The Orinoco River drains the Guiana Highlands and the llanos region of Venezuela, flowing into the Atlantic Ocean. The llanos form a large, expansive plain of grassland between the Andes in Venezuela and the Guiana Highlands. Soils are flooded in this area during the rainy seasons, providing for rich grass development and the support of large cattle ranches.
The Amazon River drains the north and western region of Brazil. Although more water moves through the Amazon River than any other river in the world, its location in dense tropical forests under a humid tropical climate makes agriculture there a challenge. Amerindians of the region practice subsistence agriculture, growing yams and bananas and raising some small animals. Cassava, or manioc (a root crop from which tapioca is made) and sugarcane are also grown there in slash-and-burn fashion.
The Parana, Paraguay, and Uruguay Rivers, south of the Amazon lowlands, dissect a great grassland region known as the Pampas and a forested region known as the Gran Chaco, which extends to northern Argentina. The Pampas is not unlike the Midwest of North America. It is a huge grassy plain nearly 400 miles (640 kilometers) long in the central part of Argentina. Agriculture is the primary industry in Argentina and encompasses 60 percent of the country's land. Large estancia (cattle ranches) are common in the region. The soils are well suited to wheat and other grains as well as alfalfa, a grass grown for cattle and horse feed. The level character of the land makes it easy to work, but it is difficult to drain and is prone to flooding.
Paraguay's agricultural zones are divided by the Paraguay River. Tobacco, rice, and sugarcane grow to the east of the river in the more humid climates. To the west, in the drier climates and the Chaco region, is the unique growing area of the Quebracho Forest. Quebracho is a hardwood that grows only in the Chaco. The wood contains tannin, which is used to produce tannic acid, a chemical used for tanning leather. This area is suited for cattle, but because of its rocky and steep topography, the population of goats and sheep rises as one moves farther west toward the Andes. Irrigated with mountain streams from the eastern slopes of the Andes, grapes also grow well and are made into wine.
See also: Coastal Lowlands, Tierra Templada, Tierra Fria
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