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SOUTH AMERICA
Overgrazing, cultivation of unsuitable land, land degradation by woodcutting--and the associated water erosion--are
long-standing problems in the arid regions of South America. Wind erosion is a major threat in the semiarid pampas in
Argentina, where moving sand dunes have ruined much land. Salinity and waterlogging have adversely affected irrigated regions
in western Argentina, particularly along the Rio Salado, and in the numerous narrow irrigated valleys crossing the coastal plain of
Peru. The very large salinas and salarea (salt lakes) found in western Argentina, northern Chile, and the altiplano of Bolivia and
Chile are of natural origin rather than being due to man's activities. There is little evidence of land improvement, and conditions
are either worsening, or at least not improving, nearly everywhere.
Desertification Characteristics
Heavy woodcutting for mine timbers and fuel accompanied the settling of western South America by the Spaniards in the 16th
and 17th centuries. Along with that went localized overgrazing of livestock and the cultivation of the nearby slopes, with the
inevitable accelerated erosion, It was not until the 19th and 20th centuries, however, that land degradation on the slopes of the
Andes Mountains and the coastal ranges become widespread. Population increases and land tenure systems in effect in most
countries of South America have combined to put further pressure on the arid regions in recent years (Figure 6).
Desertification has been held to a moderate level in semiarid northeastern Brazil by the erratic character of the rainfall there. Land
destruction probably would have been much worse if the rainfall were more reliable and if severe droughts did not occur so
frequently. The original caatinga vegetation is xerophytic and is adapted to the long dry periods that occur each year (Banco do
Nordeste do Brasil, 1964).
The coast of Peru is crossed by a large number of short rivers flowing from the Andes to the Pacific Ocean. Many of the irrigated
valleys are affected to some degree by salinization and waterlogging. The valleys constitute only a small part of the coast desert
of Peru and even less of the Chilean desert. Most of the desert has experienced little development or desertification.
Farther south, in the semiarid coastal mountains of Chile, land degradation due to overgrazing and cultivation of sloping lands
has been severe around population centers. Indiscriminate woodcutting has also been an important negative factor in the
development of the region.
In Argentina, which has more arid land than any other South American country, overgrazing has led to the degradation of range
vegetation from the high plateaus in the north to the cold Patagonian desert in the south. Wind erosion plagues both range and
cultivated lands, especially in the southern half of the nation.
Magnitude of Desertification
Overgrazing of rangelands has been the most destructive aspect of desertification in all the arid regions of South America. There
has been a progressive elimination of palatable species by cattle, sheep, and goats over many decades. Along with this has
gone the cutting of trees for timber, firewood, and charcoal. In the Gran Chaco of Argentina it is difficult to find good stands of the
valuable red and white quebracho trees that once grew everywhere.
Water erosion has followed overgrazing through the continent, and wind erosion has become an acute problem in parts of
Argentina (Prego et al., 1971). The most serious wind damage has been done in the dry-farmed areas of central Argentina where
cultivation has led to the formation of mobile dunes. In 1963 an estimated 16,000,000 hectares of land were affected to varying
degrees by wind erosion, and the situation has become worse since then. Soil fertility has declined and runoff has increased.
Salinization and waterlogging affect about 20 percent of the irrigated land in the coastal valley of Peru (Comite Peruano de Zonas
Aridas, 1963) and large sections of the semiarid Gran Chaco, in and around the province of Santiago del Estero. The same
problem, to a lesser degree, appears in the irrigated regions in arid western Argentina and in northeastern Brazil.
Although only about 22 percent of the arid regions of South America are severely or very severely affected by desertification the
problem is critical because the best lands have been degraded and the degradation is continuing. Virtually no improvement of
grazing lands has occurred anywhere, nor have soil salinization and water-logging been controlled. Some progress has been
made in stabilizing sand dunes in the dry farming areas of Argentina but much remains to be done. Water erosion in the Andes
and the semiarid western coastal ranges continues to present problems and may be getting worse. A fast-growing population
virtually assures greater desertification in the years ahead unless governments become determined to cope with the problem.
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