The environmental impact of mining includes erosion, formation of sinkholes, loss of biodiversity, and contamination of soil, groundwater, surface water by chemicals from mining processes. In some cases, additional forest logging is done in the vicinity of mines to increase the available room for the storage of the created debris and soil. Besides creating environmental damage, the contamination resulting from leakage of chemicals also affect the health of the local population. Mining companies in some countries are required to follow environmental and rehabilitation codes, ensuring the area mined is returned to close to its original state. Some mining methods may have significant environmental and public health effects. Nuss and Eckelman (2014) provide an overview of the life-cycle wide environmental impacts of metals production associated with 62 metals in year 2008.
Erosion of exposed hillsides, mine dumps, tailings dams and resultant siltation of drainages, creeks and rivers can significantly impact the surrounding areas, a prime example being the giant Ok Tedi Mine in Papua New Guinea. In areas of wilderness mining may cause destruction and disturbance of ecosystems and habitats, and in areas of farming it may disturb or destroy productive grazing and croplands. In urbanised environments mining may produce noise pollution, dust pollution and visual pollution.
The implantation of a mine is a major habitat modification, and smaller perturbations occurs on an larger scale than exploitation site, mine-waste residuals contamination of the environment for example. Adverse effects can be observed long after the end of the mine activity. Destruction or drastic modification of the original site and anthropogenic substances release can have majors impact on biodiversity in the area. Destruction of the habitat is the main component of biodiversity losses, but direct poisoning caused by mine extracted material, and indirect poisoning through food and water can also affects animals, vegetals and microorganisms. Habitat modification such as pH and temperature modification disturb communities in the area. Endemics species are especially sensitive, since they need really specific environmental conditions. Destruction or slight modification of their habitat put them at the risk of extinction. Habitats can be damaged when there is no enough terrestrial as well by non-chemicals products, such as large rocks from the mines that are discarded in the surrounding landscape with no concern for impacts on natural habitat.
Concentration of heavy metals are known to decrease with distance from the mine, and effects on biodiveristy follow the same pattern. Impacts can vary a lot depending on mobility and bioavailability of the contaminant : less mobile molecules will stay inert in the environment while highly mobile molecules will easily move into another compartment or be taken up by organisms. For example, speciation of metals in sediments could modify their bioavailability, and thus their toxicity for aquatic organisms.
Bioaccumulation plays an important role in polluted habitats : mining impacts on biodiversity should be, assuming that concentration levels are not high enough to directly kill exposed organisms, greater on the species on top of the food chain because of this phenomenon.
Adverse mining effects on biodiversity depends on a great extend on the nature of the contaminant, the level of concentration at which it can be found in the environment, and on the nature of the ecosystem itself. Some species are really resistant to anthropogenic disturbances, while some other will completely disappear from the contaminated zone. Time alone does not seem to allow the habitat to recover completely from the contamination. Remediation takes time, and in most of the cases will not enable the recovery of the diversity present before the mining activity.
Juan Gonzalo Angel