Deforestation in the Amazon

Brazil has approximately 3.5 million square kilometres of moist tropical forests, equivalent to 30 percent of the world total. Most of Brazil's tropical forests are located in the Amazonian Basin, known as Amazonia.

Dense forests (terra firme) occupy nearly 70 percent of the area and 27 percent is occupied by the cerrado (dry scrub savannah), mainly in the states of Mato Grosso, southern Para, Goias and part of east Rondônia (Fearnside, 1986). From 5 to 10 percent of the area is occupied by wetland (varzea, igapos, lakes).

Amazonia has a critical importance for Brazil. It covers more than half the national territory and has a diversity of human groups including more than 140 indigenous tribes. It has been characterised as the "single richest region of the tropical biome." (Myers, 1984). A single hectare of rainforest near Manaus, for example yields 235 tree species over 5 centimetres in diameter and 179 species over 15 centimetres in diameter.

The variety of birds, fish and insects is also great. There are 2,000 known species of fish in the Amazonian rivers, eight times the number of species in the Mississippi river and 10 times the number found in the whole of Europe. Experts estimate that the real number of fish species might reach over 3,000.

There is a great deal of discussion in Brazil about the extent and rate of deforestation in Amazonia. Much depends on the methodology utilized. The first estimates of deforestation were made in the early 1970s by the Radam project using airborne side-looking radar, suggesting that little clearing of forest had taken place. Landsat images of 1975 have shown that only around 0.6 percent of the forest of the Legal Amazon total area had been cleared (around 30,000 square kilometres). However, deforestation increased rapidly after the mid-1970s.

In 1980, according to Fearnside and World Bank estimates, over 125,000 square kilometres of forest had been cleared. Estimates vary considerably concerning the area deforested up to 1989.

The most recent deforestation measurements by the INPE (Space Research Institute of Brazil) show that by 1988, some 251,429 square kilometres of the Legal Amazonia had been deforested. This is equivalent to 5.12 percent but does not include old deforestation in the states of Para and Maranhao. However, the same Institute now recognizes that the area might be larger, reaching by 1989 some 400,000 square kilometres, or 8 percent of the Legal Amazon (Pinto, 1990). According to Fearnside (1989), estimates based on linear projections show that the deforested area reached 7.2 percent of the region during the same period. Up to 1988, Mahar estimated that almost 600,000 square kilometres had been cleared (12 percent), which constitutes an area larger than France.

During 1987 alone, according to INPE, 20,000 square kilometres of forest were burned, 40 percent of which were recently deforested areas (Setzer, 1988). There are other estimates of 80,000 square kilometres of forests burned in the same year. Experts say that around 46,000 square kilometres of forests were burned in 1989. During the burning period, the smoke spread over millions of square kilometres, causing serious health problems and closing down important airports.

One basic characteristic of the Amazonian region is the low fertility of the soils. According to Salati (1989), the largest part of the Amazonian soils have a low potential as far as nutrients for plants are concerned. Sanches et al. (1982) came to the conclusion that 90 percent of the Amazonian soils have a phosphate deficiency, 73 percent are toxic (aluminium), 50 percent present a hydric deficit, and 24 percent of the soils are subject to flooding. For agricultural purposes there remain only 7 percent which are scattered all over the area.

Shifting cultivation, with long fallow periods, was a small factor of deforestation in Amazonia and was practised mainly by indigenous people and the caboclo local population.

Although it may be difficult to estimate the present rate of deforestation in Brazil, it can be said with confidence that it is high and increasing rapidly and dangerously.

Increasing deforestation in Amazonia has already had significant environmental impacts in the region. Its consequences will increase even more dramatically if the deforestation trends continue.

Atmospheric carbon dioxide worldwide has increased exponentially since the mid-nineteenth century. Most of the carbon dioxide increase has resulted from burning fossil fuel. It is now recognised that the burning of forests is also an important contributing factor to the increase of carbon dioxide in the atmosphere. Not enough information exists, at present, on how much the burning of the Amazonian forests contributes to this process. There is accumulating scientific evidence that increased atmospheric carbon dioxide is associated with a warming trend in the global climate because of the greenhouse effect produced by carbon dioxide and some other greenhouse gases in the atmosphere.

Forests play an essential role in the maintenance of the hydrological balance of the Amazonian region and of the Brazilian territory as a whole. They play an important part in maintaining the high rainfall pattern of the region as forests retain the run-off of the water from rainfall. When large tracts of forestland are converted to pasture, the run-off of the waters into the rivers and igarapes (streams) is much higher. The forest plays an essential role in the transportation of water vapour through cloud movements into the agricultural areas of southern Brazil. This phenomenon has been investigated by the Goder Institute of New York (Fearnside, 1988). Less water transported to the agricultural regions in southern Brazil may be already changing the rainfall patterns in that area and damaging harvests.

Other ecological consequences of deforestation are primarily local. With deforestation, erosion starts to become a serious problem as it causes significant soil losses when soils are exposed by cultivation.

After the forest is cleared, the nutrient stock in the soil usually declines unless replaced by fertilizers. The balance of nutrient losses and inputs may have a link also with the proximity of natural stands of vegetation. Nutrients may be transported in the air from forest edges into adjacent areas. If vast areas of forest are cleared, this transportation of nutrients from adjacent areas may not occur. Moreover, forest clearing leads to soil nutrient losses through leaching; the fixation of many of the nutrients originally present, or added from ash when forest is burned, constitutes a serious problem.

The traditional shifting agriculture which has been practised for centuries in the region had little effect on the environmental balance: the cultivated areas were small; the fallow periods were very long, normally between 10 to 15 years; and usually only patches with relatively good soils were cultivated. The whole situation changed when large tracts of forest were cleared and the land was occupied by pasture. Forms of agriculture which require regeneration of second growth, such as shifting cultivation, are likely to be modified when the surrounding forest has been cleared. These changes often involve shortening the fallow period to a point where vegetation and soil quality are degraded, jeopardising the system's sustainability. Uhl (1989) has thoroughly studied the impact of shifting agriculture on the forest. He concluded that in traditional shifting agriculture, cultivated areas were small and surrounded by forest, the transportation of seeds from surrounding trees was high and regeneration of the forest cover started soon after harvesting. This regeneration does not take place in the same way when large tracts of forest are converted into pasture.

The floodplains of Amazonia, which represent some 5 percent of the whole territory, have been traditionally used for cultivation of species such as rice, cassava, and more recently for jute fibre. This kind of agriculture has been practised by indigenous and riverine populations for centuries (Meggers, 1987). Varzea (floodplain) agriculture is likely to become more risky with continued deforestation of watersheds, because it may alter the flooding cycles. Watershed deforestation usually results in faster run-off after rain, as less water is retained by the vegetation and its associated porous soils (Diegues, 1989).

Deforestation eliminates the production of Brazil nuts (Bertholletia excelsa), natural rubber (Hevea brasiliensis), rosewood oil (Aniba dickel) and timber. Areas with concentrations of these potentially renewable resources are, in many cases, deforested and converted to pasture. Brazil nut trees in the state of Para have, since the nineteenth century, been granted to castanhistas (Brazil nut barons), who enjoy legal title to them. This has raised the value of the land for sale to speculators. Clearing the rainforest closes forever different options for sustainable management of forest resources (Fearnside, 1989b). Many pharmaceutical uses of these products have barely begun to be tapped. Loss of the rainforest, for example, is considered a major setback in the effort to find anti-cancer drugs (Myers, 1976).

A high degree of endemism exists among Amazonian species: many species occur in limited ranges. The potential loss of genetic diversity from deforestation in the Amazonia has been a major concern of biologists worldwide. Some reasons for conserving genetic diversity include the potential for discovery of new organisms of economic value, or finding new uses for already known organisms; this includes new crop plants and variety. Ecological diversity, as well as genetic diversity in the strict sense is quickly destroyed by deforestation. Often complex, convolved associations go extinct long before the lost individuals of the species involved disappear.

This essay has highlighted just a few of the many reasons why the destruction of the Amazon Rainforest should not be allowed to proceed at its present rate. Numerous proposals are being made by different agencies, organisations and individuals to stop Amazonian deforestation. Many focus on national policies and development strategies. Others stress the urgency for international action, controls, sanctions and financial support. Still others emphasise local level initiatives and alternatives. I consider these proposals of paramount importance. In my opinion, the Amazonian Rainforest is a precious resource which should not be destroyed through ill-informed exploitation. Not only would the loss of this rainforest be a loss of a beautiful, natural wonder, but on a more practical level, it would be the loss of a whole series of precious resources on a local, national and international level. The extent of these losses is one which we may never measure if deforestation continues to shrink the rainforest, constantly causing the extinction of, potentially precious, endemic species.