Saleem Ali, an environmental systems scientist at the University of Delaware who also provides research and advice on critical metals to the United Nations, says deep-sea mining should be part of discussions about the green transition. He was co-author of a analysis 2022funded by The Metals Company, which compared mining waste from onshore deposits to that from seabed resources. (Ali says he has never received direct funding from The Metals Company.) For example, the analysis looked at the impact of landmine tailings on water pollution and local biodiversity, and on expected pollution from nodule mining, such as seafloor sediments dumped into the water column by harvesting machines. It suggests that both types of mining will have effects on biodiversity, but deep-sea mining could generate less waste and fewer risks to communities than land-based mining. The study warns, however, that its conclusions are limited by “substantial uncertainty” about the impacts of the sediment plumes.
Ali adds that the International Seabed Authority has been collecting data for at least 30 years, which should be enough to develop rules and regulations regulating seabed mining, even if it is not clear what the long-term impacts are and whether the environmental impacts are likely to be better or worse than mining on land.
“I’m not saying we should move forward with this. What I’m saying is that it deserves to be considered in this broad context of very difficult decisions that we have to make,” he says.
But opponents calling for moratoriums or bans point out that the same study The Metals Company refers to as evidence of a rapid recovery ultimately reached more pessimistic conclusions from its data as a whole. “The effects of polymetallic nodule mining are likely to be long-term,” the authors wrote, and analyzes “show considerable negative biological effects of seafloor nodule mining, even at the small scale of test mining experiments.” Scientists are concerned that deep-sea organisms, which are adapted to living in a dark, quiet, sparsely populated environment, may not be able to cope well with the noise and light disturbances of mining. The organisms will also be exposed to toxic metals and sediment plumes that can interfere with feeding and breathing. The Metals Company did not respond to several requests for comment.
The seafloor of the Clarion-Clipperton zone is home to many creatures, some of which are shown here: anemone (top left), sea cucumber, Psychropotes longicauda (top right), sea urchin plesiodiadema sp. (bottom right) and starfish (bottom left). The biology and ecology of these depths remains poorly understood, making it difficult to know what the ecological impacts of deep-sea mining would be.
Credit: ROV/GEOMAR TEAM (CC-BY 4.0)
The seafloor of the Clarion-Clipperton zone is home to many creatures, some of which are shown here: anemone (top left), sea cucumber, Psychropotes longicauda (top right), sea urchin plesiodiadema sp. (bottom right) and starfish (bottom left). The biology and ecology of these depths remains poorly understood, making it difficult to know what the ecological impacts of deep-sea mining would be.
Credit: ROV/GEOMAR TEAM (CC-BY 4.0)
Because of these unknowns, mining rules should not be rushed, says Anna Metaxas, a deep-sea ecologist at Dalhousie University in Canada who co-authored a 2025 overview of the Potential impacts of mining on the deep ocean ecosystem. in it Annual environmental and resources review. Metaxas participates in the Deep-Ocean Stewardship Initiative, an international nonprofit network of experts to inform seabed policy and governance. She says she previously led a project with land and deep sea mining experts to develop a framework for environmental comparisons of land and seabed mining. But in 2024, She and her coauthors concluded that the data is currently too scarce to do so.
“Our knowledge gaps are really big,” agrees Matthias Haeckel, a marine biogeochemist at the GEOMAR Helmholtz Center for Ocean Research in Kiel, Germany. He is part of a group of 30 researchers and technical experts commissioned by the International Seabed Authority in 2024 to develop the values needed to monitor and evaluate the impacts of mining. The group analyzed toxicity, such as heavy metals, the turbidity of sediments raised by harvesting machines, and underwater noise and light pollution. They are expected to present a first draft of standards and guidelines sometime this year.
Looking for answers… and soon
The Council of the International Seabed Authority (its executive body) met in Jamaica in early March and will do so again in July to debate, and perhaps adopt, mining regulations. The Metals Company is still waiting for approval from the United States to begin commercial mining in the Clarion-Clipperton area. But he says he hopes to have a permit by the end of this year and start mining soon after.
Meanwhile, scientists like Haeckel are scrambling to launch additional research cruises to provide critical data that will inform decisions about the future of seabed mining and the mining code. Haeckel leads a European project called MiningImpact that will return at the end of this year to the research sites where, in 2021, it monitored part of the mining tests carried out by Global Sea Mineral Resources, a subsidiary of the Belgian company DEME. The third phase of MiningImpact aims to see how the ecosystem has fared five years later and promote greater understanding of the ecology of life in the deep abyss.
“The Clarion-Clipperton Zone is a large area and there are still many, many open questions,” Haeckel says. He wonders how mining in the area could be properly regulated when scientists still don’t know what creatures live there or how they interact.
