Environmental Impact Assessments for deep-sea mining: Can we improve their future effectiveness?

Environmental Impact Assessment (EIA) is an important process for evaluating the effects of development, and to assist decisions to effectively manage potential deep-sea mining (DSM). However, although EIA is a widely used and accepted approach, there has been considerable debate over its effectiveness. In this paper, we summarise some of the key problems raised by previous EIA reviews, as well as examining several EIAs carried out in recent years for DSM, and highlight issues identified by management agencies. Scientific shortcomings are discussed, and recommendations provided on ways to improve performance. These include inadequate baseline data, insufficient detail of the mining operation, insufficient synthesis of data and the ecosystem approach, poor assessment and consideration of uncertainty, inadequate assessment of indirect impacts, inadequate treatment of cumulative impacts, insufficient risk assessment, and consideration of linkages between EIA and other management plans. The focus of the paper is on scientific limitations, but we also consider some aspects of their application to elements of process and policy. •Shortcomings in environmental impact assessments for deep-sea mining are identified.•Recommendations are made for how to improve the science underpinning EIAs.•Higher quality EIAs will increase their uptake by managers and their effectiveness in decision-making.•Scientific studies are key to the EIA process, but final decision-making is a complex evaluation of environmental, social, economic and political components.