Deep-sea mining risks for sharks, rays, and chimaeras

Deep-sea mining is expected to cause disturbances of sufficient scale and intensity to pose a risk to biodiversity and ecosystem function.¹^,²^,³ We assess the potential impact of deep-sea mining on sharks, rays, and chimaeras in Areas Beyond National Jurisdiction (ABNJ) and identify 30 species (of the total 1,223 marine chondrichthyan species) that overlap spatially with the anticipated mining footprint, specifically through 2 pathways: benthic impacts from physical disturbance and the collector vehicle plume² and midwater impacts from the discharge plume.⁴ Most species' depth ranges (83%, 25/30, range: 3%-80%) overlapped vertically with the benthic mining footprint, while all species overlapped with discharge plume scenarios. Further, 17 of these species had >50% depth overlap with benthic impacts of at least one of the mineral types. Seven species were egg-laying, benthic, or benthopelagic, which increases their susceptibility to seabed impacts. Filter-feeding species also had high depth overlap with potential midwater discharge plumes. Nearly two-thirds (60%, 18/30) are already threatened with an elevated risk of extinction, and 64.3% are predicted to be threatened. Our analysis raises concerns that deep-sea mining would compound and worsen their extinction risk. We recommend updated risk assessments of significant adverse impacts to chondrichthyans; robust baseline monitoring prior to, during, and after mining; spatial protections near crust and sulfide mining; and that the discharge plume be set at a minimum depth below 2,000 m or at the seabed to minimize overlap with midwater species.