Aquatic life suffers under coal mining
Current US regulations are found to be insufficient to protect fish, salamanders, and invertebrates from the impacts of mining waste. Kathryn Allen reports.
Coal mining in the USA is having a detrimental impact on stream biodiversity, despite current federal statutes designed to prevent this – the 1972 Clean Water Act and the 1977 Surface Mining Control and Reclamation Act – say researchers from the University of Tennessee, USA.
Detailing their results in the study, Impact of coal mining on stream biodiversity in the US and its regulatory implications, the researchers claim that the abundance and variety of aquatic life, including fish, invertebrates, and salamanders, has reduced as a result of coal mining. Affected streams averaged 32% lower taxonomic richness and 53% lower total abundance than streams unaffected by mining, indicating that regulations are insufficient.
The study recommends tightening US regulations, including the reinstatement of the Steam Protection Rule – designed to reduce coal mining’s impact on water quality and biodiversity, and revoked by President Trump in February 2017. It also suggests prohibiting the dumping of any mining waste in all streams, improving the standards of reclamation outcomes, and refusing permits for mountaintop mining valley fill – a form of surface mining in which excess rocks are dumped in valleys – once the total mined area exceeds 6.3% of the watershed.
Assessing the taxonomic richness and abundance in streams affected by mining once the current regulatory statues were in place, the team compared data to unmined streams. It found that affected waterways were downstream of valley fills created by mountaintop mining operations. All but one of the studies surveying streams were in the vicinity of mountaintop coal mining in central Appalachia, while the other examined underground coal mining in Pennsylvania.
Xingli Giam, Assistant Professor in the Department of Ecology and Evolutionary Biology, University of Tennessee, told Materials World, ‘As rainwater seeps through these valley fills, it comes in contact with previously unweathered rock surfaces. Ions [including calcium, magnesium, and sulphate] and minerals contained in rocks dissolve in the water, resulting in higher concentrations of them, as well as metals and non-metals entering the stream downhill of the valley fill.’ These ions can be toxic to aquatic life.
‘In the study that examined the impact of an underground coalmine, treated discharge also increased the conductivity of the water,’ said Giam. This increase in conductivity can disrupt osmoregulation – the maintenance of osmotic pressure in an organism’s fluids.
Giam added, ‘Besides these impacts, the direct dumping of overburden into valleys also buries ephemeral, intermittent, and, in some cases, small perennial streams, leading to the direct destruction of valuable habitats.’
Taking into consideration projections from the US Energy Information Administration regarding coal production in the USA, which forecasts an increase from just over 671 million tonnes in 2016 to 781 million tonnes by 2040, without the Clean Power Plan – an Obama-era administration policy aimed at tackling carbon emissions – the team identified watersheds at the greatest risk of biodiversity loss from continued and expanding coal mining.
These included the Elk in West Virginia, Upper Clinch and Powell in Tennessee and Virginia, Upper Cumberland in Tennessee and Kentucky, and Locust and Upper Black Warrior in Alabama. They were identified to be at greatest risk due to the current high level of coal production and large number of endemic fish within them.
Limitations of these findings include the focus on mountaintop mining valley fill, as it is concentrated in Appalachia, meaning estimated effect sizes can only be generalised for this region. The team therefore calls for urgent studies assessing mining impacts in other regions.
The results also compare control sites with those impacted by mining, rather than comparing data from the same stream pre- and post-mining. While this is a limitation, the team points out that it highlights the need for mining companies to collect data before mining begins in order to monitor impact more closely. This was a feature of the revoked Stream Protection Rule, which, while believing its reinstatement would be beneficiary, Giam thinks is unlikely under the current administration.
Mining companies are required under the Surface Mining Control and Reclamation Act to complete reclamation. This varies between states, but, according to Giam, ‘In general, mining companies are required to restore the mining area to approximate original contour and ensure that the backfilling, compacting, and grading of overburden results in a physically stable structure and prevents landslides, erosion, and water pollution.’ Drainage should also be built in valley fills, directing water away from dumped material.
However, the effectiveness of reclamation in improving aquatic biodiversity is uncertain, with the researchers finding that even when reclamation is carried out, mined sites had on average only 66% of the richness and 32% of the abundance of unmined sites. The reclaimed sites studied had experienced reclamation between 4 and 33 years before assessment.
To read the study, visit go.nature.com/2JJMr2P