Machines used to extract minerals from the deep ocean can cause substantial harm to seabed life, according to scientists who conducted the largest study of its kind. Their research shows a 37% drop in the number of animals living within the tracks left by mining vehicles compared with untouched areas.
The team identified more than 4,000 animals in a remote region of the Pacific Ocean — with 90% of them representing previously unknown species.
Massive reserves of key minerals used in green technologies may lie deep beneath the ocean floor. But because the environmental impact remains uncertain, deep-sea mining in international waters is not yet allowed.
Largest study yet on mining impacts
The research was carried out by scientists from the Natural History Museum in London, the UK National Oceanography Centre, and the University of Gothenburg, working at the request of mining firm The Metals Company. The researchers stressed their independence; while the company saw the findings before publication, it had no right to change them.
Scientists compared biodiversity in the region two years before and two months after test mining operations, during which machines travelled 80 km across the seafloor.
Their focus was on small organisms between 0.3 mm and 2 cm in size, including worms, sea spiders, snails, and clams.
Inside the mining tracks:
- Animal abundance dropped 37%
- Species diversity fell 32%
“The machine removes the top five centimetres of sediment — where most animals live,” explained lead author Eva Stewart, a PhD researcher at the Natural History Museum and University of Southampton. “Once the sediment is gone, so are the animals.”
Even species not directly killed by the machinery may be threatened by pollution from the operations, added Dr Guadalupe Bribiesca-Contreras from the National Oceanography Centre.
Some animals could move away, but whether they will ever return remains unknown.
Sediment clouds had limited short-term effects nearby
In areas adjacent to the vehicle tracks, where disturbed sediment settled, the abundance of animals did not decline.
“We expected more impact there,” said Dr Adrian Glover from the Natural History Museum. “We only saw a shift in which species were more dominant.”
A spokesperson for The Metals Company welcomed the findings, saying they suggest that biodiversity impacts remain confined to directly mined zones rather than spreading over long distances, as some activists had feared.
But experts caution this is not good news
Some environmental analysts argue that the study confirms deep-sea mining is too destructive given current technology.
“These were only tests — small-scale tests — and the impacts were already significant,” said Dr Patrick Schröder of Chatham House. “Scaled up, the damage would be much worse.”
The controversy around deep-sea mining persists. Many scientists worry that life in the deep ocean — much of it still undiscovered — could be harmed before it is even studied. Oceans are already under stress from climate change, warming temperatures, and pollution.
Global tension over mining vs. conservation
The International Seabed Authority (ISA), which regulates activity in international waters, has not approved commercial mining but has granted 31 exploration licences.
Thirty-seven countries, including the UK and France, support a temporary ban. Norway this week postponed its own plans to mine in parts of its waters, including the Arctic.
Meanwhile, in April the US — under President Donald Trump — called for mining projects to be accelerated to secure minerals needed for weapons and national security.
If the ISA decides current mining techniques are too harmful, companies may need to develop gentler ways to lift mineral-rich nodules from the seabed.
Mineral demand continues to surge
The study, published in Nature Ecology & Evolution, took place in the Clarion-Clipperton Zone, a vast stretch of the Pacific Ocean containing an estimated 21 billion tonnes of nickel, cobalt, copper, and other critical minerals — all essential for green technologies such as solar panels, electric vehicles, and wind turbines.
The International Energy Agency predicts demand for these minerals will at least double by 2040.
While the world urgently needs these resources to fight climate change, scientists warn that deep-sea mining could cause irreversible damage to ecosystems we barely understand.
