Environmental impacts of deep-sea mining and implications for management

Currently, approximately 2.7 million km² of the deep seafloor are being explored for metal ores, with potentially a few hundred thousand km² that could be mined within the next 20-30 years. At the mined location, the removal of ores will result in the loss of ore-dependent microbes and fauna, such as sponges and corals, and of the ecosystem functions they provide. The loss can last up to millions of years, the length of time that it takes for the ores to form. It is probable that species extinction will occur. The mining plumes will extend beyond the mined seafloor area and reach into the water column, with the geographic scale dependent on the technology used and the location. The noise generated by mining may spread over hundreds of kilometers in the water. There is currently limited knowledge available regarding the impact of mining plumes or noise on deep-sea life, such as mortality, chronic toxic effects, change in behavior or reproduction that may impact subsequent generations.

Scientific knowledge is currently insufficient for effective environmental management of deep-sea mining. Recent scientific findings, such as significant organic carbon production at inactive vents, the discovery of animal life in the earth’s crust below vents, or 5000 new discovered animal species at polymetallic nodule fields, highlight the unknows in deep sea and the importance of implementing the precautionary principle. Major questions that need to be answered to allow for effective management include for example: What species are present? What ecosystem functions are present? Is restoration possible? How much impact can occur before biodiversity is lost and ecosystem functions are disrupted? Importantly, strategic as well as region specific environmental goals and objectives need to be discussed and set. Otherwise, effective protection of the marine environment from harmful effects that may arise from deep-seabed-related activities may not be ensured.