The Amazon basin

The Amazon basin, covering 6.157 million square kilometres, is one of the largest river basins in the world. It is shared by seven countries: about two-thirds of the basin (4 million square kilometres) is in Brazil, nearly 1 million square kilometres lies in Peru, 825 thousand square kilometres in Bolivia, and the rest in Venezuela, Ecuador, Colombia, and Guyana.

The region is characterized by a high annual rainfall — averaging over 2 thousand millimetres — falling during two rainy seasons separated by drier periods. The vegetation is mainly dense rain forest, including extensive wetlands (almost 600 thousand square kilometres). The Amazon region is also home to some of the world’s largest and most diverse ecosystems.

Because the basin is sparsely populated (25 million people, mainly living in the highlands and on the slopes of the Andes, with a density of only four people per square kilometre) and there is plenty of water available throughout, there have been few contentious issues related to the management of its resources. With the growing drive to build dams and the encroachment of mining operations, this situation is expected to change.

The population density of the rain forest itself is very small, as most settlements are situated along the rivers. The major cities of the basin are Manaus and Belém, with about 1.5 and 2 million people respectively; others include Iquitos in Peru and Santarém in Brazil. The river plays an important role in both transportation and fishing. Travel  between communities of the basin has traditionally been by boat, although lately air travel has also become important.

Land routes are few and, in the heart of the forest, almost nonexistent. Fishing has been one of the main subsistence activities of the population. Thus, contamination of the aquatic bioresources may represent not only a health hazard but also elimination of a source of food and income.

The region is also home to numerous indigenous micronations, which are well adapted to using the forest ecosystems.

Although the destiny of these groups is closely linked with that of the water systems, decisions on basin management are usually made without any consideration of their point of view or interests.

Land policies in Brazil have traditionally favoured the newly arrived occupant, who can prove possession by burning or logging the forest, rather

than native groups who have lived on the land for many generations.

These policies have not changad much, during the last year the elected president Jair Bolsonaro, has imposed new restriction to the delimitation of indigenous areas and new forest fires have erupted reducing the area of the rainforest at the highest historic rate.

An important drive to occupy the region has been promoted by the building of dams, particularly by Brazil, which is the largest country in the area and has defined hydroelectric dam construction as a national strategy. There are plans to build dams at 43 sites on 13 rivers; they will have a generating capacity in excess of 70 thousand megawatts (Mougeot 1988). This “hydro-development” drive is to be concentrated in three river systems: the Xingu (32%), the Tocantins (20%), and the Madeira (15%). A number of dams have already been built, both on the Amazon and in neighbouring basins (such as the Paraná) with similar characteristics. In some cases, disastrous environmental and social effects have been observed (such as in the Tucurui impoundment on the lower Tocantins).

As a result of deforestation, hydrological regimes are already changing throughout the basin. Droughts and floods, formerly unknown, are taking place along many tributaries, and water quality is being affected by the increasing amount of effluent wastewaters entering the rivers from cities and mining operations.

Contamination from mining is related to the establishment of gold mines. Gold is extracted from ore using mercury or cyanide solutions. (In Brazil, the mercury technique is more common.) Both procedures damage the environment.

Cyanide is highly poisonous and mercury becomes concentrated as it moves through the trophic chains and may reach toxic levels in some aquatic organisms that are consumed by the local people. In Japan, mercury poisoning affected the villagers of Minamata Bay in the 1950s, killing 1 382 people (Serril 1994). In the Amazon, mercury pollution is particularly serious in the upper basins of the Madeira, Tapajós, and Xingu rivers, and

there are indications that widespread poisoning may be taking place in some of the most polluted areas. In the fishing community of Rainha, upstream of Itaituba on the Tapajós, tests on the population showed mercury levels far in

excess of the 6 ppm maximum accepted by the World Health Organization. Similar data were obtained in several other locations. In the Madeira River basin, hazardous levels were found in the fish-eating Kayapo communities.

Continuing mining operations are expected to increase the environmental and human health effects of mercury contamination further.

With deforestation and indiscriminate occupation, the apparently invulnerable Amazon ecosystem is deteriorating, and this is not only affecting its inhabitants but also the population of the world at large. It will not be easy to address the many issues that are producing these changes in the Amazon basin. New policies will be required in many areas. Land

allocation rules and recognition of the land rights of indigenous peoples should be reviewed. Migration to the region must also be checked through adequate policies. The environmental and social impact of hydro projects should be strictly and independently evaluated to ensure that no further ecological destruction takes place. Finally, any strategy will have to take into account not only the interests of the distant industrial metropolises but also the views of the people who live in and suffer most from pollution of the Amazon: the indigenous nations who have managed their

land in a sustainable way for innumerable generations.