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.
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 blow to the emerging 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.
Accounts of the Guyana cyanide spill of 1995 are found in World Rainforest Movement, "Guyana: Logging Freeze Starts to Melt, More Mining," 3/14/96 and Bretton Woods Reform Organization (BWRO), "A Call for Accountability for Poisonous Cyanide Discharge," 8/28/95.
Examples of environmental degradation caused by Freeport mine operations in Indonesia is presented by Chatterjee, P., "Human Rights-Indonesia - US mining giant implicated in Indonesia atrocities," 1995; Press, E., "Freeport: Corporate Predator," The Nation. July 31/August 7, 1995; and Walsh, P., "Witnessing 'GP?K' Drama, blood, and tears of Jo-Mun Nerk's Children in the Freeport Concession Area," Australian Council for Overseas Aid, 1995.
The Rainforest Action Network (1993-1995) described the Yanomani situation including malaria and armed conflicts between miners and the Yanomani.
Gold mining in the Amazon rainforest is covered in Nigel J.H. Smith, Emanuel Adilson S. Serro, Paulo T. Alvim, and Italo C. Falesi, Amazonia - Resiliency and Dynamism of the Land and its People, The United Nations University, 1995.
Pfeiffer, W. C. and L. D. de Lacerda. ("Mercury inputs into the Amazon region, Brazil," Environmental Technological Letters 9: 325-330, 1988) found that for every kilogram of gold produced, an estimated 1.32 kg of mercury is dumped into the environment.
The gold find at Serra Pelada in the Brazilian Amazon is reviewed by Schmink, M. ("Social change in the garimpo," in John Hemming (ed.), Change in the Amazon basin, Vol. 2: The frontier after a decade of colonisation, Manchester:Manchester University Press, 1985) and Mallas, J. and N. Benedicto ("Mercury and gold mining in the Brazilian Amazon," Ambio 15(4): 248-249, 1986).
The forest fires of Southeast Asia during the 1997-98 ENSO event received unprecedented coverage for an environmental event.
Estimates for area affected: McCall, C. "Asia's unique species go up in smoke. Reuters. 6/17/98; and Kinnaird, M.F. and O'Brien,
T.G., "Ecological effects of wildfire on lowland rainforest in Sumatra," Conservation Biology Vol. 12 No. 5 (954-956), October 1995; Stolle, F. and Tomich, T.P., "The 1997-1998 fire event in Indonesia," Nature and Resources Vol. 5, No. 3, July-Sep 1999;
Pollution and health impacts: Balowski, J., "Suharto Fiddles While Indonesia Burns" Greenleft Weekly, October 15, 1997; Edwards, N., "Public Anger Could Heat up Over Southeast Asia Smog," Reuters, 22-SEP-97; and Gilbert, C., "Indonesia's Peat Smoulders Underground," Environment News Service, 11/13/97; Stolle, F. and Tomich, T.P., "The 1997-1998 fire event in Indonesia," Nature and Resources Vol. 5, No. 3, July-Sep 1999.
Economic costs: AP, "Acid Rain and Other Problems Coming Soon for Southeast Asia." 11/10/97; AP, "Malaysia orders experts to keep quiet on haze" 11/7/97; AP, "Drought Cuts Indonesia's Harvests; Haze Worsens in some Parts" 10/24/97; Johnson, C., "Indonesia's Fires Could Cost 5-6 B, experts say," Reuters, 3/17/98; Rajendran, R., "Southeast Asia Fire Damage Estimated at around $4.4 billion," Reuters, 5/29/98; Stolle, F. and Tomich, T.P., "The 1997-1998 fire event in Indonesia," Nature and Resources Vol. 5, No. 3, July-Sep 1999; and Xinhua, "Forest Fires in Indonesia Cause Huge Economic Losses," 10/23/97.
Ecological impact: Abramovitz, J.N., Agence France-Presse, "Indonesia counts the cost of forest fires" 10/6/97;McCall, C. "Asia's unique species go up in smoke. Reuters. 6/17/98; Agence France-Presse, "Fires multiplying in Indonesian disaster: World Wide Fund for Nature" 9/29/97; AP (AP:3), "Wildlife in Indonesia under Even Bigger Siege Due to Drought, Fires" 10/6/97; Estrade, B., "Heat from Indonesian fires to be felt at climate meet," Agence France-Presse, 11/28/97; Gilbert, C., "Indonesia's Peat Smoulders Underground," Environment News Service, 11/13/97; Pardomuan, L., "Green Group Warns of Crises after Indonesian Fires," Reuters, 15-OCT-97; Raven, G., "Indonesia Fires Hit National Parks--Pressure Group," Reuters, 10/9/97; Rosenfeld, D., "Dense smoke turns off normal tropical rainfall," Geophysical Research Letters, Vol. 26 (3105) 1999; Williams, L. and Baker, M., "South Asia's Year of Reckoning." Sydney Morning Herald, 10/6/97; and Xinhua, "Fires reduce insects in East Kalimantan, Indonesia," 4/20/98;
Political culpability in Indonesia: Abramovitz, J.N., Agence France-Presse, "Indonesia counts the cost of forest fires" 10/6/97; Aditjondro, G.J., "Palm Oil Nepotism Adds Fuel to Disaster" Australian Financial Review, 10/13/97; Agence France-Presse, "Jakarta Reinstates 45 Permits Revoked for Forest Burning Violations" 12/2/97; Balowski, J., "Suharto Fiddles While Indonesia Burns" Greenleft Weekly, October 15, 1997; Della-Giacoma, J., "Fires burn unchecked in Indonesia's South Sumatra," Reuters. 10-SEP-97; Edwards, N., "Public Anger Could Heat up Over Southeast Asia Smog," Reuters, 22-SEP-97; Gilbert, C., "Indonesia's Peat Smoulders Underground," Environment News Service, 11/13/97; Gopalakrishnan, R., "Indonesia Timber King Denies Responsible for Fires," Reuters, 10/3/97; Johnson, C., "Indonesia's Fires Could Cost 5-6 B, experts say," Reuters, 3/17/98; Lamb, D., "Fires Again Ravage Indonesia's Forests," Los Angeles Times, 3/23/98; Reuters, "Indonesian Fires No Accident, Singapore Paper Say" 10/2/97; Richardson, M., "Indonesian Crisis Prompts Fears of New Smoke Pollution." International Herald Tribune. 2/13/98; Thoenes, S., "In Asia's Big Haze, Man Battles Man-Made Disaster," The Christian Science Monitor, 10/28/97; and Williams, L. and Baker, M., "South Asia's Year of Reckoning." Sydney Morning Herald, 10/6/97;
Transmigration program: Gilbert, C., "Indonesia's Peat Smoulders Underground," Environment News Service, 11/13/97; MacKenzie, I., "Fire Ribbons Send Smog from Indonesian Peat Bogs," Reuters. 11/11/97; and Thoenes, S., "In Asia's Big Haze, Man Battles Man-Made Disaster," The Christian Science Monitor, 10/28/97.
History of fires in Southeast Asia: Balowski, J., "Suharto Fiddles While Indonesia Burns" Greenleft Weekly, October 15, 1997; Leighton, M. and Wirawan, N., "Catastrophic Drought and Fire in Borneo Rain Forests Associated with the 1982-83 El Nino Southern Oscillation Event," in G.T. Prance, ed. Tropical Rain Forests and the World Atmosphere, Westview: Boulder, Colorado 1986; and Nathan, D., "Can you really hope that the haze will go," Singapore Straights Times, 10/5/97.
Climactic Impact: Williams, L. and Baker, M., "South Asia's Year of Reckoning." Sydney Morning Herald, 10/6/97; Pardomuan, L., "Green Group Warns of Crises after Indonesian Fires," Reuters, 15-OCT-97;
Rosenfeld, D. ("Dense smoke turns off normal tropical rainfall," Geophysical Research Letters, Vol. 26 (3105) 1999) found that dense smoke from the Borneo fires of 1997-1998 completely turned off normal tropical rainfall in some places because moisture was divided among so many droplets that they were too small to fall as precipitation.