Mining affects the environment and associated biota through the removal of vegetation and topsoil, the displacement of fauna, the release of pollutants and the production of mine overburden. Mining pollution is caused by land excavation; the discharge of mine pit water or waste water; the dumping of waste rock, tailings or slag; and the discharge of metallic smoke and dust into the atmosphere.
Coastal and offshore mining activities that can have an impact on the marine and estuarine environments include: sand and gravel mining for minerals, beach replenishment or industrial uses; oil and gas exploration and production; coral (limestone) mining; and diamond dredging. Terrestrial mining may also cause the release of metals and sediments to estuaries and the sea. The effects can be measured in the destruction of seafloor habitats and the alteration of the marine species diversity and productivity of an area, including commercial fish species.
Extraction of metallic mineral ores, and the refining and disposal of wastes from metallurgical industries, cause significant local environmental problems, such as acid drainage. Air pollution during these processes includes dust from mining and acidic gases, carbon dioxide and other greenhouse gas emissions from smelting, refining and other kiln operations.
Mining and quarrying are noisy, and may use blasting techniques causing noise pollution and driving off wildlife.
Abandoned hard rock mine sites may affect public health and the environment due to releases of hazardous substances from waste materials and acid drainage. Many streams and ground water reserves have been seriously affected by acid runoff and releases from abandoned coal mines. In many areas, entire watersheds are unable to support aquatic life and present hazards to the public.
Both active and abandoned coal mines sometimes fill with water, which becomes highly acidic, thus mobilizing heavy metals. During heavy rains, the water may overflow, and downstream water courses may become seriously polluted.
In the USA for example, some 10,500 miles of stream have been affected by acid mine drainage. About half a million acres of land remain unrestored from coal mining operations alone. In Australia, mining threatens two bird species (confirmed) and is speculated to threaten another four birds and six reptiles.
More than 60 North American, European, Japanese and South African mining companies joined the gold rush in the Guiana Highlands of Brazil and Venezuela, where as much as 10% of the planet's gold reserves may lie. Since 1991, the Corporacion Venezolana de Guayana, the agency of Venezuelan state that oversees the forest, has handed out more than 1.4 million hectares in mining concessions.
Lawyers in the Venezuelan attorney general's office called the Corporacion Venezolana de Guayana an illegal, carpet-bagging entity that violated Venezuelan mining and environmental laws. The state's governor also condemned the corporation, and it was under congressional investigation.