Improving environmental management practices in deep-sea mining

As the business of deep-sea mining develops, greater attention is being paid to the ways in which the impacts from mining on the environment might be minimised and controlled. The management of environmental impacts is highly complex encompassing a wide variety of topics including physical oceanography, sediment characteristics, particle sinking velocities, particle aggregation, sediment geochemistry, toxic discharges, chemical contamination, biological studies from microbes to mammals and from the sea surface to the subseabed, studies of biodiversity, genetic connectivity, ecosystem functioning, the value of ecosystem services, hydrodynamic plume modelling and noise and light hazards. Owing to the history of how contractors in deep-sea mining have developed, there are a wide variety of approaches to environmental management. This chapter seeks to assist contractors in achieving a more consistent approach by making some key recommendations and highlighting some outstanding issues. It covers why environmental baseline studies are necessary and how various levels of environmental assessment will help contractors achieve a suitable standard when submitting Environmental Impact Assessments. In particular it highlights the use of the ‘mitigation hierarchy’ as a suitable way to consider environmental management issues. Apart from detailing ways in which environmental impacts might be minimised and avoided altogether, at the local and regional scales, the chapter calls for greater consideration of ways to assist ecosystems to recover more quickly through enhancing natural ecosystem processes. The restoration of marine ecosystems, as occurs after a mine has been closed on land, should be included in environmental planning but requires experimental research to be undertaken during the exploration phase and before an Environmental Impact Statement is submitted to gain an environmental and social licence to exploit deep-sea minerals