Deep-Sea Mining Test Reveals 788 Previously Unknown Species and Significant Ecological Loss

Major Study in the Clarion-Clipperton Zone Finds Hundreds of Species and Measurable Damage From a Mining Test

Researchers conducting one of the largest environmental impact studies on deep-sea mining discovered thousands of animals on the ocean floor while assessing the effects of a trial excavation. The team collected 4,350 organisms (each at least 0.3 mm long) and identified 788 distinct species of crustaceans, mollusks, marine bristle worms and other invertebrates from the targeted mining area.

The full results are published in Nature Ecology and Evolution. The study concludes that extracting rare earth metals from depths of roughly 13,000 feet (≈2.5 miles) may not match the most catastrophic early projections, but the observed impacts are nonetheless significant and raise urgent ecological concerns.

Much of the commercial interest in the deep ocean is driven by the presence of large deposits of rare earth metals on the seafloor, minerals needed for batteries, wind turbines and other technologies central to the global transition to cleaner energy. A prime target is the Clarion-Clipperton Zone (CCZ), a continent-sized abyssal plain between Hawaii and Mexico that is mineral-rich but still poorly understood biologically. A 2022 expedition to the CCZ catalogued more than 5,000 previously undescribed species, underscoring how much biodiversity remains undocumented.

"Critical metals are needed for our green transition and they are in short supply," said Thomas Dahlgren, a marine biologist at the University of Gothenburg and co-author of the study. "Several of these metals are found in large quantities on the deep-sea floor, but until now, no one has shown how they can be extracted or what environmental impact this would have."

To quantify impacts, Dahlgren and colleagues surveyed nearly a 50-mile stretch of the CCZ two years before a test run by a deep-sea mineral collector and returned two months after the device had passed over the site. The team's fieldwork spanned about 160 days and produced the >4,000 specimens that revealed the 788 distinct species. Because most species lack formal descriptions, researchers relied heavily on molecular (DNA) data to resolve biodiversity and ecological relationships on the seabed.

The mining test produced clear local effects: within the tracks left by the collector, the study measured a 37% drop in total animal abundance and a 32% decline in species diversity. Those reductions were concentrated in the machine’s immediate path on the seafloor, showing that disturbance from extraction equipment can sharply reduce local populations.

"Deep-sea mining within the CCZ is at a critical juncture, as the industry looks to move beyond the exploration phase and into commercial exploitation," the authors wrote. "Consequently, there is a clear need for direct assessment of the impacts of mining on faunal abundance and biodiversity at the seafloor."

Researchers hope this study will serve as a baseline for future impact assessments and monitoring. Roughly 30% of the CCZ is currently subject to environmental protections; the team called for more targeted research to understand what lives in protected and unprotected areas and how long-term recovery might proceed.

"At present, we have virtually no idea what lives there," said Adrian Glover of the Natural History Museum in London, a co-author of the study.