 Atlantic coast.
Gold mining reached a feverish pitch in the 1980s, stimulated by high world prices of gold. At the height of the Amazon “gold rush,” as many as a half million transient miners (garimpeireos) came equipped with picks, shovels, and sluice boxes to search for the mineral in the alluvial deposits of the Tocantins valley at Serra Pelada. Brazil’s annual production peaked in 1987 but declined thereafter. Large amounts of the mercury used to extract the gold were released into rivers and caused the fish, which are so important in the local diet, to become unsafe to eat. Moreover, since the 1990s mercury contamination has grown among Amazonian peoples, especially those groups that are more isolated and consume large amounts of fish. On the Madeira River, teams operating from rafts pump up from the riverbed auriferous sediments, which have to be subjected to a treatment similar to that used in gold mining. Bauxite mining, both at Carajás and on the Trombetas River north of the Amazon, requires the use of large settling ponds to trap effluents.
The energy requirements of both the Carajás development and the city of Belém are met by the giant Tucuruí hydroelectric plant on the Tocantins River, one of the largest hydroelectric power stations in the world. A more modest hydroelectric facility on a small river north of Manaus supplies that city with power. A growing sensitivity to the harmful consequences for both human beings and the environment due to the construction of large dams has caused several ambitious projects to be placed on hold.
The principal oil developments within Amazonia have taken place in the Oriente regions of the Andean countries. Oil pipelines originate from districts in both Colombia (the upper Putumayo) and Ecuador (Agrio Lake), as well as northeastern Peru, and end at export terminals on the Pacific coast. Within the Brazilian and Bolivian portions of the basin, developments have been of minimal consequence.