Environmental impact of mining can occur at local, regional, and global scales through direct and indirect mining practices. Mining can cause erosion, sinkholes, loss of biodiversity, or the contamination of soil, groundwater, and surface water by chemicals emitted from mining processes. These processes also affect the atmosphere through carbon emissions which contributes to climate change.
Some mining methods (lithium mining, phosphate mining, coal mining, mountaintop removal mining, and sand mining) may have such significant environmental and public health effects that mining companies in some countries are required to follow strict environmental and rehabilitation codes to ensure that the mined area returns to its original state. Mining can provide various advantages to societies, yet it can also spark conflicts, particularly regarding land use both above and below the surface.
Mining operations remain rigorous and intrusive, often resulting in significant environmental impacts on local ecosystems and broader implications for planetary environmental health. To accommodate mines and associated infrastructure, land is cleared extensively, consuming significant energy and water resources, emitting air pollutants, and producing hazardous waste.
According to The World Counts page "The amount of resources mined from Earth is up from 39.3 billion tons in 2002. A 55 percent increase in less than 20 years. This puts Earth's natural resources under heavy pressure. We are already extracting 75 percent more than Earth can sustain in the long run."
Erosion Erosion of exposed hillsides, mine dumps, tailings dams and resultant siltation of drainages, creeks and rivers can significantly affect the surrounding areas, a prime example being the giant Ok Tedi Mine in Papua New Guinea. Soil erosion can decrease the water availability for plant growth, resulting in a population decline in the plant ecosystem.
Soil erosion occurs from physical disturbances caused by mining activities (e.g. excavation, blasting, etc.) in wilderness areas. This causes disturbances of tree root systems, a crucial component in stabilizing soil and preventing erosion. Eroded materials can be transported by runoff into nearby surface water, leading to a process known as sedimentation. Moreover, altered drainage patterns redirect water flow, intensifying erosion and sedimentation of nearby water bodies. The cumulative impact results in degraded water quality, loss of habitat, and long-lasting ecological damage.
Sinkholes
A sinkhole at or near a mine site is typically caused from the failure of a mine roof from the extraction of resources, weak overburden or geological discontinuities. The overburden at the mine site can develop cavities in the subsoil or rock, which can infill with sand and soil from the overlying strata. These cavities in the overburden have the potential to eventually cave in, forming a sinkhole at the surface. The sudden failure of Earth creates a large depression at the surface without warning, which can be seriously hazardous to life and property. Sinkholes at a mine site can be mitigated with the proper design of infrastructure such as mining supports and better construction of walls to create a barrier around an area prone to sinkholes. Back-filling and grouting can be done to stabilize abandoned underground workings.
Water pollution Mining can have harmful effects on surrounding surface and groundwater. If proper precautions are not taken, unnaturally high concentrations of chemicals, such as arsenic, cyanide, sulphuric acid, and mercury can spread over a significant area of surface or subsurface water. Large amounts of water used for mine drainage, mine cooling, aqueous extraction and other mining processes increases the potential for these chemicals to contaminate ground and surface water. As mining produces copious amounts of waste water, disposal methods are limited due to contaminates within the waste water. Runoff containing these chemicals can lead to the devastation of the surrounding vegetation. The dumping of the runoff in surface waters or in a lot of forests is the worst option. Therefore, submarine tailings disposal are regarded as a better option (if the waste is pumped to great depth). Land storage and refilling of the mine after it has been depleted is even better, if no forests need to be cleared for the storage of debris. The contamination of watersheds resulting from the leakage of chemicals also has an effect on the health of the local population.
In well-regulated mines, hydrologists and geologists take careful measurements of water to take precaution to exclude any type of water contamination that could be caused by the mine's operations. The minimization of environmental degradation is enforced in American mining practices by federal and state law, by restricting operators to meet standards for the protection of surface and groundwater from contamination.The principal federal laws are: Resource Conservation and Recovery Act (solid waste management and groundwater protection). , Clean Water Act (surface water pollution control). , This is best done through the use of non-toxic extraction processes as bioleaching. Furthermore, protection from water contamination should continue after a mine has been decommissioned, as surroundings water systems can still become contaminated years after active use.
Air pollution The mining industry contributes between 4 and 7% of global greenhouse gas emissions. The production of greenhouse gases, such as CO2 and CH4, can occur both directly and indirectly throughout the mining process and can have significant impacts on global climate change.
Air pollutants have a negative impact on plant growth, primarily through interfering with resource accumulation. Once leaves are in close contact with the atmosphere, many air pollutants, such as O3 and NOx, affect the metabolic function of the leaves and interfere with net carbon fixation by the plant canopy. Air pollutants that are first deposited on the soil, such as heavy metals, first affect the functioning of roots and interfere with soil resource capture by the plant. These reductions in resource capture (production of carbohydrate through photosynthesis, mineral nutrient uptake and water uptake from the soil) will affect plant growth through changes in resource allocation to the various plant structures. When air pollution stress co-occurs with other stresses, e.g. water stress, the outcome on growth will depend on a complex interaction of processes within the plant. At the ecosystem level, air pollution can shift the competitive balance among the species present and may lead to changes in the composition of the plant community. The impacts of air pollution can vary depending on the type and concentration of pollutant released. In agroecosystems these changes may be manifest in reduced economic yield.
Adaptation and mitigation techniques to reduce air pollution created by mining are often focused on using cleaner energy sources. Switching from coal and diesel to gasoline can reduce the concentration of greenhouse gases. Furthermore, switching to renewable energy sources, such as solar power and hydropower, may reduce greenhouse gas emissions further. Air pollution may also be reduced by maximizing the efficiency of the mine and conducting a life-cycle assessment to minimize the environmental impacts.
Acid rock drainage
Sub-surface mining progresses below the water table, so water must be constantly pumped out of the mine in order to prevent flooding. When a mine is abandoned, the pumping ceases, and water floods the mine. This introduction of water is the initial step in most acid rock drainage situations. Acid rock drainage occurs naturally within some environments as part of the weathering process but is exacerbated by large-scale earth disturbances characteristic of mining and other large construction activities, usually within rocks containing an abundance of sulfide minerals. Areas where the earth has been disturbed (e.g. construction sites, subdivisions, and transportation corridors) may create acid rock drainage. In many localities, the liquid that drains from coal stocks, coal handling facilities, coal washeries, and coal waste tips can be highly acidic, and in such cases it is treated as acid mine drainage (AMD). The same type of chemical reactions and processes may occur through the disturbance of acid sulfate soils formed under coastal or estuarine conditions after the last major sea level rise, and constitutes a similar environmental hazard.
The five principal technologies used to monitor and control water flow at mine sites are diversion systems, containment ponds, groundwater pumping systems, subsurface drainage systems, and subsurface barriers. In the case of AMD, contaminated water is generally pumped to a treatment facility that neutralizes the contaminants. A 2006 review of environmental impact statements found that "water quality predictions made after considering the effects of mitigation largely underestimated actual impacts to groundwater, seeps, and surface water".
Heavy metals Heavy metals are naturally occurring elements that have a high atomic weight and a density at least 5 times greater than that of water. Heavy metals are not readily degradable and therefore, are subjected to persistence in the environment and bioaccumulation in organisms. Their multiple industrial, domestic, agricultural, medical and technological applications have led to their wide distribution in the environment; raising concerns over their potential effects on human health and the environment.
Naturally occurring heavy metals are displayed in shapes that are not promptly accessible for uptake by plants. They are ordinarily displayed in insoluble shapes, like in mineral structures, or in precipitated or complex shapes that are not promptly accessible for plant take-up. Normally happening heavy metals have a high adsorption capacity in soil and are hence not promptly accessible for living organisms. However, the impacts of heavy metal transformation and interactions with soil organisms is highly dependent on the physicochemical properties of the soil and the organisms present. The holding vitality between normally happening heavy metals and soil is exceptionally high compared to that with anthropogenic sources.
Dissolution and transport of metals and heavy metals by run-off and ground water is another example of environmental problems with mining, such as the Britannia Mine, a former copper mine near Vancouver, British Columbia. Tar Creek, an abandoned mining area in Picher, Oklahoma that is now an Environmental Protection Agency Superfund site, also suffers from heavy metal contamination. Water in the mine containing dissolved heavy metals such as lead and cadmium leaked into local groundwater, contaminating it. Furthermore, the presence of heavy metals in freshwater may also affect the water chemistry. High concentrations of heavy metals can impact pH, buffering capacity, and dissolved oxygen. Long-term storage of tailings and dust can lead to additional problems, as they can be easily blown off site by wind, as occurred at Skouriotissa, an abandoned copper mine in Cyprus. Environmental changes such as global warming and increased mining activity may increase the content of heavy metals in the stream sediments. These impacts may also be enhanced in areas located downstream from the heavy metal source.
Effect on biodiversity