Leave mining waste (tailings) in place following cessation of disposal operations
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
Mine tailings (the ore waste of mines typically in the form of a mud-like material) originate from both coastal and land-based mining activities and can be disposed of in the marine environment. These mine tailings disposals are known as â€śsubmarine tailing disposalâ€ť in shallow waters, and â€śdeep sea tailings disposalâ€ť in deeper waters (Vare et al. 2018). Mine tailings can have negative impacts on subtidal benthic invertebrates through physical disturbances, smothering, chemical contamination (Marinho et al. 2017), and changes in sediment characteristics (Kathman et al. 1983) and submarine tailing disposal has been prohibited in parts of the world (Kline & Stekoll 2001). However, where it occurs, following cessation of activities, removal can incur additional disturbances. As such, leaving mine tailings in place following cessation of activities, and allowing the potential natural recovery of the seabed and its invertebrate community (Kline & Stekoll 2001), can perhaps reduce the risk of additional impacts resulting from their removal. Evidence for related interventions is summarised under â€śThreat: Energy production and mining â€“ Cease or prohibit submarine mining disposalâ€ť.
Kathman R.D., Brinkhurst R.O., Woods R.E. & Jeffries D.C. (1983) Benthic studies in Alice Arm and Hastings Arm, BC in relation to mine tailings dispersal. Institute of Ocean Sciences, Department of Fisheries and Oceans.
Kline E.R. & Stekoll M.S. (2001) Colonization of mine tailings by marine invertebrates. Marine Environmental Research, 51, 301â€“325.
Marinho C.H., Giarratano E., Esteves J.L., Narvarte M.A. & Gil M.N. (2017) Hazardous metal pollution in a protected coastal area from Northern Patagonia (Argentina). Environmental Science and Pollution Research, 24, 6724â€“6735.
Vare L.L., Baker M.C., Howe J.A., Levin L.A., Neira C., Ramirez-Llodra E.Z., Reichelt-Brushett A., Rowden A.A., Shimmield T.M., Simpson S.L. & Soto E.H. (2018). Scientific considerations for the assessment and management of mine tailings disposal in the deep sea. Frontiers in Marine Science, 5, 17.
Supporting evidence from individual studies
A replicated, paired, controlled, pilot study in 1994â€“1996 of 90 plots of soft seabed in Auke Bay, Alaska, USA (Kline & Stekoll 2001) found that leaving mine tailings on the seabed after ceasing disposal operations, or removing them, led to similar changes in invertebrate community composition, abundance, biomass and species richness, but either way remained different to nearby natural communities, after 22 months. After 22 months, invertebrate community compositions were similar in plots with and without tailings but remained different to plots of natural sediment (data presented as graphical analyses). Plots with and without tailings had similar invertebrate abundance (with: 900 vs without: 1,050 individuals/tray), biomass (370 vs 380 mg/tray), and species richness (50 vs 48 species/tray). Plots with and without tailings had similar abundances to the natural plot (natural plot abundance: 920 individuals/tray), but their biomasses were higher (natural plot biomass: 150 mg/tray,) and richness were lower (natural plot species richness: 40 species/tray). In 1994, 48 plastic trays (as experimental plots, 8 cm deep, 15 cm diameter) were filled with either tailings or sediments without invertebrates (to mimic removal of tailings) and deployed in pairs by divers at 21 m depth in a circular arrangement (30 m diameter). After 9, 17, and 22 months, 10 trays/treatment were recovered (in total: 30 of the 48 trays), and 10 plots of nearby natural sediment were sampled using a tray as a corer. Invertebrates (>500 Âµm) were identified, counted, and dry-weighed.Study and other actions tested