Background Image 4 - (Waymer, 2013)
Measuring the impact of mining on the biosphere can be difficult. Mining companies have recently begun a program of biodiversity offsetting where ecologically degenerating mining activity in one area is claimed to be made-up for by preserving another area’s biodiversity. While the idea can improve the company’s image, the idea of “additionality” can render the program a moot point since the area they claim to be preserving was likely under no risk in the first place resulting in a net biodiversity loss (Virah-Sawmy, 2014).
Figure 13 - (Morrison, 2016)
Figure 14 - (The Conversation, 2011)
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Terrestrial EcosystemsIf the area being mined was formally rich in forests the mass deforestation resulting from the presence of the mine would destroy habitats and alter ecosystem dynamics, usually reducing biodiversity (Environmental and Social Impacts of Mining, n.d.). On top of this these forests can also be major carbon sinks covering large swathes of land that after disappearing will release their carbon dioxide, adding to the carbon emissions from the mine itself.
In addition to the habitat loss from the mine itself, the infrastructure required to run the mine such as roads and pipelines as well as the definition of boundaries through putting up fences can fragment ecosystems by hampering the movements of native species. These native species and the formally remote habitats they lived in also may be made more accessible to disturbances from humans, putting additional pressure on species that are already losing habitats (Environmental and Social Impacts of Mining, n.d.). Terrestrial ecosystems can also be afflicted with large amounts of dust during operations from an opencast mine, this dust can coat plants and reduce photosynthesis as well as present a health risk to respiring animals (Kuter, 2013). Opencast mines and the cuts for subsurface mine access can also have a lasting legacy after operation due to the removal of topsoil seedbanks (MIT a, n.d.), without which vegetation finds it very hard to re-establish itself in previously mined areas ensuring habitats remain devastated for decades after operations cease. |
Figure 15 - (USGS, 2015)
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Aquatic EcosystemsThe exposed overburden (through deforestation), especially from unregulated mines in China (MIT a, n.d.), is easily eroded by large storms and can lead to the sedimentation of streams and other water bodies, reducing the ability of aquatic plants to photosynthesise and smother small organisms (Environmental and Social Impacts of Mining, n.d.). This can also be followed by the potential transfer of phosphorous to water bodies from land that can provide aquatic biota with too much phosphorous and lead to eutrophication in aquatic ecosystems (Kuter, 2013).
Spills from effluent reservoirs, pipelines and reservoir bypassing can pollute natural waters with high levels of metals and acids, this can seriously affect aquatic life sensitive to pH changes such as fishes that often can’t breed at pH levels lower than five and some may die at levels of six or lower. In addition to pH levels, salmon, can be sensitive to high copper levels, especially the juveniles (Environmental and Social Impacts of Mining, n.d.). An example of this is the waterways around the Blackbird Mine in Idaho, USA where effluents with high levels of Co, As, Cu and Fe spilled into the Blackbird Creek on a regular basis, this creek feed into the Big Deer Creek which also suffered from acid mine drainage, the combined effects of a lowered pH and high metal concentration resulted in no fish being found between 1962 and 1980 downstream of the creeks (Mebane et al., 2015). |
Figure 16 - (BBC, 2013)
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Both Terrestrial and Aquatic Ecosystems A legacy of subsurface mining affecting the surface is subsidence through collapsing mineshafts causing habitat alteration where two or more threatened species are adversely affected or non-threatened species in the area become threated. This may affect terrestrial ecosystems however the impact is most felt in aquatic ecosystems due to changed water flows through jointing of riverbeds (NSW Office of Environment and Heritage, 2013).
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Figure 17 - (Hadfield, 2013)
Figure 18 - (Seven Seas Search & Salvage, 2014)
Figure 19 - (Dodd, 2012)
Figure 20 - (British Antarctic Survey, 2016)
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Oceanic EcosystemsWhile not usually widely affected by terrestrial mining activity except in areas with mines close to the coast, where the effects of sedimentation in rivers meets the ocean and has the potential to kill-off corals in the coastal photic zone through sediments clogging the coral polyps (Environmental and Social Impacts of Mining, n.d.). Oceanic ecosystems could be at threat in the future if seabed mining becomes industrially viable. This method is seen as a way to acquire higher grade ores than on the ground, up to 15g of gold per tonne of ore around Papua New Guinea. However oceanic ecosystems could be extensively damaged through a number of ways if these ecosystems are not carefully monitored during mining operations (Birney et al., n.d.).
Exploration by remotely operated vehicles can directly lead to habitat disturbance or even destruction through collisions or faults if performed on a large enough scale. The primary disturbance from exploration would likely be from core boring that may lead to sediment plumes taking away nutrients from, or smothering the unique life (MIT b, n.d.) inhabiting the areas around the black smokers being explored. Another significant but short term impact could be the potential for the activation of a black smoker at the drilling site, diverting fluid from the original smoker, depriving that region of nutrients (Birney et al., n.d.). The problem of habitat destruction or disturbance arises when extraction takes place since the habitats (sulphide rich sediments) may be being mined or deeper polymetallic nodules being extracted from under the sediment. While habitat alteration is bad enough, many species around black smokers and surrounding sediment are slow movers (such as gastropods) or sessile (such as tubeworms) which means many would die in the excavation process, potentially leaving the area barren after operations cease (Birney et al., n.d.). These ecosystems may also suffer from acoustic impacts through sonar exploration and material excavation, sonar could alter the behaviour of animals in the area and the excavation of smoker chimneys may lead to sediment landslides through the noise of the drilling or disturb the soft tissues of organisms near the site, potentially leading to more deaths of organisms (Birney et al., n.d.). |
Figure 21 - (Pit Watch, 2013)
Figure 22 - (mining-technology.com, n.d.)
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Case Studies for the BiosphereAn important legacy of opencast mines that extended under the water table is the formation of a toxic mine pit lake, one of the most extreme examples of this is the Berkeley Pit in Montana, USA that formed after the underground pumps that kept the pit from being flooded by groundwater were turned off after copper mining ceased in 1982 (NASA, n.d.). This has resulted in the pit lake’s formation and growth towards the surrounding groundwater systems. In 2013, the water level had reached 5,311.89 feet, only 98.11 feet away from the groundwater level at 5,410 feet. The most recent terrestrial ecological disaster caused by the lake was the death of 342 snow geese through corroded esophagi after they landed in the lake to avoid bad weather (Sometimes Interesting, 2013).
An example of an aquatic ecosystem being devastated by the legacy of mining is the 1995 Guyana spill. One billion gallons of cyanide-laced water spilt into an Essequibo tributary when a waste holding pool built by Golden Star Resources and Cambior was filled over its capacity. This spill caused mass die-offs in both aquatic and terrestrial ecosystems and poisoned the floodplain soils used for agriculture (Butler, 2012). An example of an oceanic ecosystem being affected by mining activities can be found around Misima Island (Papua New Guinea) where after the introduction of open cast gold mining in 1989, corals have been smothered in sediment and have been found to accumulate rare-earth elements (REE’s), lead and other metals from contaminated sediments in their skeletons, this could be used in the future to analyse the true extend of oceanic ecosystem damage from the anthrosphere (Fallon, White and McCulloch, 2002). |