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Mining operation in Peru. (Photo by R. Butler)
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Environmental impact of mining in the rainforest
Gold, copper, diamonds, and other precious metals and gemstones are important resources that are found in rainforests around the world. Extracting these natural resources is frequently a destructive activity that damages the rainforest ecosystem and causes problems for people living nearby and downstream from mining operations.
In the Amazon rainforest most mining today revolves around alluvial gold deposits. Due to the meandering nature of Amazon rivers, gold is found both in river channels and on the floodplains where rivers once ran. These deposits are actively mined by large-scale operators and informal, small-scale miners. Both operators rely heavily on hydraulic mining techniques, blasting away at river banks, clearing floodplain forests, and using heavy machinery to expose potential gold-yielding gravel deposits. Gold is usually extracted from this gravel using a sluice box to separate heavier sediment and mercury for amalgamating the precious metal. While most of the mercury is removed for reuse or burned off, some may end up in rivers. Studies have found that small-scale miners are less efficient with their use of mercury than industrial miners, releasing an estimated 2.91 pounds (1.32 kg) of mercury into waterways for every 2.2 pounds (1 kg) of gold produced.
While there is no scientific consensus on mercury contamination in the Amazon, according to biologist Michael Goulding, there is evidence of mercury causing problems in other ecosystems. Elemental or inorganic mercury can be transformed (methylated) into organic forms by biological systems and enter food chains. Not only are methylated mercury compounds toxic, but highly bioaccumulative, meaning that mercury concentrations increase up the food chain. Top predators, including otters, birds of prey, and humans, will have the highest levels of mercury in their systems. Those who eat large amounts of fish are at the greatest risk.
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Location of the Grasberg mine.
A Giant Mess on New Guinea
Freeport-McMoRan, based in New Orleans, has operated the Mount Ertsberg gold, silver, and copper mine in Irian Jaya, Indonesia, for over 20 years and has converted the mountain into a 600-meter hole. As documented by the New York Times and dozens of environmental groups, the mining company has dumped appalling amounts of waste into local streams, rendering downstream waterways and wetlands "unsuitable for aquatic life." Relying on large payments to military officials, the mining operation is protected by a virtual private army that has been implicated in the deaths of an estimated 160 people between 1975 and 1997 in the mine area.
Freeport estimates that it generates 700,000 tons of waste a day and that the waste rock stored in the highlands—900 feet deep in places—now covers about three square miles. Government surveys have found that tailings from the mines have produced levels of copper and sediment so high that almost all fish have disappeared from nearly 90 square miles of wetlands downstream from the operation.
Cracking down on the Freeport's environmental abuses and questionable human-rights practices has proved a challenge since the mine is one of the largest sources of revenue for the Indonesian government. An Indonesian government scientist wrote that "the mine's production was so huge, and regulatory tools so weak, that it was like 'painting on clouds' to persuade Freeport to comply with the ministry's requests to reduce environmental damage," according to a December 27, 2005, article in the New York Times.
For more take a look at "Below a Mountain of Wealth, a River of Waste" in the New York Times. The article was written by JANE PERLEZ and RAYMOND BONNER.
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Other toxic compounds are used and generated in the mining process as well. Mining exposes previously buried metal sulfides to atmospheric oxygen causing their conversion to strong sulfuric acid and metal oxides, which run off into local waterways. Oxides tend to more soluble in water and contaminate local rivers with heavy metals.
Cyanide, a highly toxic compound, is also often used to separate gold from sediment and rock. While cyanide is supposed to be carefully monitored to prevent its escape into the surround environment, spills do occur—especially when there's no one around to enforce mining regulations. The effects of poisoning can be widespread, especially when a waste-holding pool overflows or breaks, as it did in Guyana in August 1995.
The Guyana spill made international headlines for its magnitude—over one billion gallons (four billion liters) of cyanide-laced waste water was released into a tributary of the Essequibo— and its effects, causing widespread die-offs of aquatic and terrestrial plant and animal life, poisoning floodplain soils used for agriculture, polluting the main source of drinking water for thousands of people, and striking a major blow to the nascent eco-tourism industry on the river. The mine, run by Golden Star Resources of Denver and Cambior of Montreal, at first tried to cover up the spill by burying fish carcasses. Six days after the spill, after locals found dead wildlife, the mine reported the accident to the Guyana government. Despite the damage inflicted by the spill, the government granted additional mining concessions on the New River shortly thereafter.
Large-scale mining operations, especially those using open-pit mining techniques, can result in significant deforestation through forest clearing and the construction of roads which open remote forest areas to transient settlers, land speculators, and small-scale miners. These settlers and miners are probably a greater threat to the tropical rainforest environment than industrial mining operations. Wildcat miners enter regions rumored to have gold deposits and clear forest in search of riches. They hunt wildlife, cut trees for building material and fuelwood, and trigger erosion by clearing hillsides and detonating explosives. Miners can also bring diseases to local indigenous populations (where they still exist) and battles over land rights. One well-documented example is the conflict between the Yanomani Indians of Northern Brazil and Venezuela and garimpeiros—illegal Brazilian miners. Reports indicated that Yanomani populations have fallen significantly since the first incursion of miners in the 1980s.
While deforestation and chemical pollution from mining can impact the rainforest environment, downstream aquatic habitats fare worse. Increased sediment loads and reduced water flows can seriously affect local fish populations.
Photos of a mining operation in the Peruvian Amazon
Review questions:
- How does mining affect the rainforest and local rivers?
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Continued: Fires
Unless otherwise specified, this article was written by Rhett A. Butler [Bibliographic citation for this page]
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Recent news
Scientists call for mining ban, new protected areas in Suriname
(6/20/2008) In a resolution set forth at their annual meeting in Paramaribo, Suriname, the largest group of tropical biologists called upon the Surinamese government to evict informal gold miners from three ecologically important areas in the South American country. Miners have been blamed for a number of environmental problems including over-hunting of wildlife, deforestation and destruction of riparian habitats, erosion, and mercury pollution in waterways.
Geology, climate links make Guiana Shield region particularly sensitive to change
(6/14/2008) Soil and climate patterns in the Guiana Shield make the region particularly sensitive to environmental change, said a scientist speaking at a biology conference in Paramaribo, Suriname.
Venezuela bans gold-mining in forest reserve, will not issue new open-pit permits
(5/21/2008) Venezuela banned gold mining in its Imataca Forest Reserve and said it will not issue new permits for open-pit mines anywhere in the country, according to Reuters.
Malaysia rejects coal project in Borneo rainforest
(4/14/2008) Malaysia has rejected a $408 million coal-fired power plant near a protected rainforest area in Sabah, on the island of Borneo.
Lungless frog discovered in Borneo
(4/11/2008) A lungless frog has been discovered on the island of Borneo. Scientists say the species may shed light on the process of evolution in some organisms.
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