Machines designed to harvest minerals from the deep ocean are causing substantial damage to life on the seafloor, according to the most extensive research yet carried out on test mining activity. Scientists found a 37% drop in animal abundance along machine tracks compared with untouched areas, alongside a 32% reduction in species diversity.
The study examined one of the most remote and least understood environments on Earth, a section of the Clarion–Clipperton Zone (CCZ) in the Pacific Ocean, an area rich in polymetallic nodules containing nickel, cobalt and copper. These minerals are vital for renewable energy technologies, and demand is expected to at least double by 2040.
Thousands of Species at Risk Many New to Science
Researchers documented more than 4,000 seafloor animals, an estimated 90% of them previously unknown to science. They focused on small organisms between 0.3 mm and 2 cm, including worms, sea spiders, snails and clams species that form the foundation of deep-sea ecosystems.
Mining vehicles scrape away the top five centimetres of sediment, which is where most of these animals live. “If you’re removing the sediment, you’re removing the animals in it too,” said lead author Eva Stewart of the Natural History Museum and the University of Southampton. Even those not directly killed by machinery may be harmed by polluted sediment plumes released during extraction.
While some animals may escape the immediate disturbance, it is unclear whether they can recolonise the mined areas or how long that might take.
Impacts Extend Beyond the Tracks, but Not as Far as Feared
Sediment clouds generated by the machinery spread into nearby zones, but scientists did not observe a reduction in the number of animals in those areas. Instead, they detected shifts in which species were most dominant. “We were expecting a bit more impact,” said Dr Adrian Glover of the Natural History Museum, “but we didn’t see much beyond changes in species composition.”
However, many experts argue that even limited damage could have profound consequences given the fragility and slow-growing nature of deep-sea ecosystems.
Reaction Divides Experts
The work was commissioned by The Metals Company, a mining firm seeking commercial approval to harvest CCZ nodules. Although the company saw the results before publication, scientists emphasised that their analysis was independent and could not be altered.
The Metals Company said the findings were “encouraging,” arguing that impacts appeared confined to the directly mined zone rather than spreading “thousands of kilometres” as some activists had feared.
But others saw the results very differently. Dr Patrick Schröder, of Chatham House, said current technologies are “too damaging to permit large-scale commercial exploration,” warning that the effects would scale dramatically if applied across vast mining concessions.
Future of Deep-Sea Mining
Deep-sea mining is one of the most contentious environmental debates of the decade. The International Seabed Authority (ISA) has issued 31 exploration licences but has not yet approved commercial extraction in international waters. Thirty-seven countries, including the UK and France, now support a temporary ban until risks are better understood. Norway has recently postponed its own mining plans, while the United States has called for accelerated development to secure mineral supply chains.
Scientists warn that ecosystems in the deep ocean evolve slowly, making them highly vulnerable. Some fear major damage could occur before humanity even discovers the full diversity of species living there. Oceans already face pressures from warming, acidification and pollution and large-scale mining could add a new layer of stress to an essential planetary system.
The research has been published in Nature Ecology & Evolution. If current methods prove too destructive, companies may need to design less invasive techniques for retrieving seafloor nodules.
References:
https://www.bbc.co.uk/news/articles/cedx2p8gnx9o
