Altitudinal Zonation Applied primarily in Latin America, this term refers to the differentiation of distinct environmental regions characterized by specialized agricultural production, based on elevation. Each elevation layer or “zone” is marked by a unique, or nearly unique, set of agricultural products suited to the growing conditions at that particular altitude.
This structure is most pronounced in countries in the Caribbean, Central America, and tropical South America where the local topography is characterized by coastal lowlands that rise abruptly into mountainous regions in the interior. The various zones of production are typically referred to by the Spanish terms Tierra Caliente (hot land), Tierra template (temperate land), Tierra Fria (cold land), and, if the elevation reaches above 12,000 feet, terra helada (frozen land). Some scholars identify yet another zone in Andean South America, the Tierra Nevada, which stretches from roughly 15,000 feet to higher elevations, and which is generally unoccupied by humans.
The Tierra Caliente is located between sea level and approximately 3,000 feet in elevation. It experiences warm, humid temperatures year-round, and frequently receives abundant rainfall, in some places exceeding 60 inches a year. Naturally occurring vegetation in this region is typically tropical rainforest, or in somewhat drier areas, tropical savanna. Population densities here are typically high where the land is being cultivated. The climate provides an ideal setting for the commercial production of tropical specialty crops, many of which are exported northward to the large North American market. Bananas, sugar cane, tobacco, and various tropical fruits, including mangoes, papaya, plantains, and others are raised on large plantations, as well as various staple crops such as wetland rice and corn. Within the zone there is some altitudinal layering as well: bananas, rice, and sugar are raised in the lower elevations, while tobacco, corn, and sometimes coffee are planted on the higher reaches of the slopes. In areas where the soils are less productive or there is insufficient rainfall to support the plantation crops, commercial livestock, primarily cattle, and pigs, are raised. The Tierra Caliente is a region of intensive cultivation in most instances, and for some countries, especially Caribbean islands that lie at lower elevations and that depend largely on the production of a single crop (sugar cane in Haiti, for example), represents the only commercial agricultural region.
A different set of crops characterizes the Tierra template. This zone occupies roughly the elevations between 2,500 feet and 6,000 feet. It is considered temperate because the average temperatures are usually much cooler than those of the tierra caliente, and there is typically less rainfall at these altitudes. As in the tierra caliente, human population densities are relatively high, due to the more comfortable climate, and the intensive cultivation in many places of the central specialty crop of the templada, coffee. Coffee may be cultivated only in the higher reaches of the tierra caliente, due to the coffee plant’s sensitivity to high temperatures and humidity, but the tierra templada offers an ideal climate for coffee production. Moreover, the well-drained, volcanic soils found in many sections of the tierra templada make the location perfect for coffee. Coffee cultivation is supported by the enormous demand of the North American and European markets, and coffee bean production is the single most important component of the agricultural economy for many Latin American countries. Brazil and Colombia together account for more than 40 percent of global production in an average year. Tobacco is a secondary cash crop produced in the tierra templada, and corn is also grown there, mostly for local consumption. A relatively new product of this zone is cut flowers, also focused toward the North American export market. Latin American growers supply much of the U.S. floral market during the winter months.
The region known as the tierra fria is found approximately from 6,000 feet to 12,000 feet and represents the highest zone of significant human habitation. Population densities here are much lower than in the two lower zones, due to the lack of large-scale commercial agriculture, as well as the frigid temperatures, encountered especially at the upper reaches of the fria. Frosts are common in this region, and the growing season is much shorter than at lower elevations. The natural vegetation at this level consists mostly of hardy evergreens at the lower elevations, and brush, grasses, and stunted trees at the top of the tierra fria. The growing season at the lower end of the fria is frequently long enough to allow for the cultivation of wheat or barley, and highland pastures at this elevation often support sheep, or indigenous livestock such as llamas or alpacas. In the Andean countries of South America, indigenous peoples make up a high percentage of the population of the tierra fria.
Lying between 12,000 and 15,000 feet, the tierra helada represents a harsh environment of sparse settlement and restricted activity. This is the highest level of permanent human occupation, with the majority of villages clustered along the lower margin of the zone. Few crops can be grown at these extreme elevations, and animal husbandry is limited almost exclusively to hardy indigenous animals adapted to the cold temperatures and thin atmospheres, like the llama, alpaca and vicuna, although sheep can be raised in some locations in the lower part of the helada. Crops are restricted to those that may be grown underground such as tubers, or in some instances fast-maturing varieties of grains at the lower end of the zone. Only subsistence agriculture is found at this elevation, as the climate is too cold to support any commercial crops.
The highest zone is the tierra nevada, found only in the Andean region of South America. Located above 15,000 feet, the nevada is an environment dominated by snow pack and glaciers and does not support any permanent human settlement. Agriculture is nonexistent, and even animals adapted to high altitudes do not survive for extended periods in the extreme conditions of the tierra nevada. Although of no direct economic importance to the countries of South America, the nevada plays a vital role as a supplier of water to the rivers and streams of the Andean region, providing a crucial resource to agricultural production downslope.