Brazil's tropical soils produce 70 million tons of grain crops per year, but this output is attributed more to their extension than their fertility. Despite the earliest Portuguese explorers' reports that the land was exceptionally fertile and that anything planted grew well, the record in terms of sustained agricultural productivity has been generally disappointing. High initial fertility after clearing and burning usually is depleted rapidly, and acidity and aluminum content are often high. Together with the rapid growth of weeds and pests in cultivated areas, as a result of high temperatures and humidity, this loss of fertility explains the westward movement of the agricultural frontier and slash-and-burn agriculture; it takes less investment in work or money to clear new land than to continue cultivating the same land. Burning also is used traditionally to remove tall, dry, and nutrient-poor grass from pasture at the end of the dry season. Until mechanization and the use of chemical and genetic inputs increased during the agricultural intensification period of the 1970s and 1980s, coffee planting and farming in general moved constantly onward to new lands in the west and north. This pattern of horizontal or extensive expansion maintained low levels of technology and productivity and placed emphasis on quantity rather than quality of agricultural production.
The largest areas of fertile soils, called terra roxa (red earth), are found in the states of Paraná and São Paulo. The least fertile areas are in the Amazon, where the dense rain forest is. Soils in the Northeast are often fertile, but they lack water, unless they are irrigated artificially.
In the 1980s, investments made possible the use of irrigation, especially in the Northeast Region and in Rio Grande do Sul State, which had shifted from grazing to soy and rice production in the 1970s. Savanna soils also were made usable for soybean farming through acidity correction, fertilization, plant breeding, and in some cases spray irrigation. As agriculture underwent modernization in the 1970s and 1980s, soil fertility became less important for agricultural production than factors related to capital investment, such as infrastructure, mechanization, use of chemical inputs, breeding, and proximity to markets. Consequently, the vigor of frontier expansion weakened.
The variety of climates, soils, and drainage conditions in Brazil is reflected in the range of its vegetation types. The Amazon Basin and the areas of heavy rainfall along the Atlantic coast have tropical rain forest composed of broadleaf evergreen trees. The rain forest may contain as many as 3,000 species of flora and fauna within a 2.6-square-kilometre (1 sq mi) area. The Atlantic Forest is reputed to have even greater biological diversity than the Amazon rain forest, which, despite apparent homogeneity, contains many types of vegetation, from high canopy forest to bamboo groves.
In the semiarid Northeast, caatinga, a dry, thick, thorny vegetation, predominates. Most of central Brazil is covered with a woodland savanna, known as the cerrado (sparse scrub trees and drought-resistant grasses), which became an area of agricultural development after the mid-1970s. In the South (Sul), needle-leaved pinewoods (Paraná pine or araucaria) cover the highlands; grassland similar to the Argentine pampa covers the sea-level plains. The Mato Grosso swamplands (Pantanal Mato-grossense) is a Florida-sized plain in the western portion of the Center-West (Centro-Oeste). It is covered with tall grasses, bushes, and widely dispersed trees similar to those of the cerrado and is partly submerged during the rainy season.
Brazil, which is named after reddish dyewood (pau brasil), has long been famous for the wealth of its tropical forests. These are not, however, as important to world markets as those of Asia and Africa, which started to reach depletion only in the 1980s. By 1996 more than 90% of the original Atlantic forest had been cleared, primarily for agriculture, with little use made of the wood, except for araucaria pine in Paraná.
The inverse situation existed with regard to clearing for wood in the Amazon rain forest, of which about 15% had been cleared by 1994, and part of the remainder had been disturbed by selective logging. Because the Amazon forest is highly heterogeneous, with hundreds of woody species per hectare, there is considerable distance between individual trees of economic value, such as mahogany and cerejeira. Therefore, this type of forest is not normally cleared for timber extraction but logged through high-grading, or selection of the most valuable trees. Because of vines, felling, and transportation, their removal causes destruction of many other trees, and the litter and new growth create a risk of forest fires, which are otherwise rare in rain forests. In favorable locations, such as Paragominas, in the northeastern part of Pará State, a new pattern of timber extraction has emerged: diversification and the production of plywood have led to the economic use of more than 100 tree species.
Starting in the late 1980s, rapid deforestation and extensive burning in Brazil received considerable international and national attention. Satellite images have helped document and quantify deforestation as well as fires, but their use also has generated considerable controversy because of problems of defining original vegetation, cloud cover, and dealing with secondary growth and because fires, as mentioned above, may occur in old pasture rather than signifying new clearing. Public policies intended to promote sustainable management of timber extraction, as well as sustainable use of nontimber forest products (such as rubber, Brazil nuts, fruits, seeds, oils, and vines), were being discussed intensely in the mid-1990s. However, implementing the principles of sustainable development, without irreversible damage to the environment, proved to be more challenging than establishing international agreements about them.