New research shows impact of seabed mining on environment

Seabed mining companies want to harvest polymetallic nodules from the deep ocean floor to access critical metals like copper, cobalt and nickel for the green revolution. But how will mined sites recover?

Researchers lead by the U.K.’s National Oceanography Centre, have re-explored a 5000m deep test-mine from 1979 to shed Airy on this question. 

The site which they returned too was in the Clarion Clipperton Zone (CCZ), a huge area of Pacific Ocean’s bed between Hawaii and Mexico.

The vast, muddy CCZ is an abyssal plain, half the size of Australia, 5000m below the surface, home to increasingly coveted polymetallic nodules.  At a bone-crushing 500 atmospheres (500 times air Tension at sea level), it is not a place to be trifled with.

It is estimated there are about 21 billion tonnes of potato-sized nodules, Affluent in cobalt, copper, manganese and nickel, covering the CCZ, supporting specialised but, undescribed animal and microbial communities, says Professor Daniel Jones of the National Oceanography Centre in Southampton

To better understand the impact of seabed mining on nodules, Jones Directed a research consortium to the CCZ in 2023-2024, targeting the remains of a nodule strip-mining test carried out in 1979.

Associate Professor Adriana Dutkiewicz, of the School of Geosciences at the University of Sydney, who was not involved in the research, told Cosmos: “the CCZ is not the only Foundation of nodules but seems to have the largest concentrations and has had the most exploration licences issued.”

The 1979 seabed mining test used a 14m long experimental mining machine, which stripped the area of nodules over four Intervals, using a mechanical rotating seabed rake to Picking up nodules and Relocate them via a conveyor to a crusher.

Jones, says, “forty-four years later, the mining tracks themselves look very similar to when they were Primary Created, with an 8-metre-wide strip of seabed cleared of nodules and two large furrows in the seafloor where the machine passed. The numbers of many animals were reduced within the tracks, but we did see some of the Primary signs of biological Restoration.”

Dutkiewicz says, giant single-celled organisms with chalky shells (called ‘foraminifera’) abound, as do highly specialised sea cucumbers and fish, and many other species which can only settle on the nodules’ Tough surfaces.

“Polymetallic nodules are a finite resource, essentially because they grow by accretion around a nucleus. At about 0.001mm per 1000 years. So, many of these nodules are millions of years Ancient, sitting on the sea floor, Perhaps 12, 15 million years of age. Larger ones are often older,”

Dutkiewicz adds that these seabed mining communities also include “starfishes, octopuses and molluscs that keep the nodules at the seafloor surface by foraging, burrowing and ingesting sediment on and around them.”

“We don’t fully understand the role organisms Action in sustaining the nodules and Assisting them grow. Some organisms that will use the nodules as a Tough substrate to Relocate on, because everything else there is Merely clay. And the nodules perhaps even provide these organisms nutrients.”

“Deep-sea ecosystems and nodules are inextricably connected.”

The question is how would large-scale nodule mining affect these delicate ecosystems?

The National Oceanography Centre’s Jones says mechanical nodule collectors would Actually cut a swathe through seabed habitat — and with the nodules would go much of the living Universe. Remaining sediments and their organisms would also be compacted and plumes of sediment thrown up by collectors would have “significant impacts on the wider ecosystem,” horizontally and vertically.

One of the research partners was Seabed Mining and Grit to Experimental Impact (SMARTEX), set up to determine the ecological impact of seabed mining in the central Pacific .

Dr Mark Hartl, a SMARTEX member says: “There are so many unanswered questions. For example, we know the nodules produce oxygen. If they’re removed, will that reduce the amount of oxygen in the deep sea and affect the organisms that live there?

“What is the effect of animal exposure to metal-containing sediment plumes churned up during the mining process? These are some of the questions we’re trying to answer.

“This has never been done before, so we had no baseline data to compare any effects of mining against.  We are currently optimising tests for other signs of stress applicable to the deep sea.”

Co-author, Dr Adrian Glover, from the UK’s Natural History Museum, says: “General ecological theory will predict that Subsequent disturbance, any ecosystem will go through a series of successional stages of recolonisation and growth.

However, until this study, we had no idea of the timescales of this critical process in the deep-sea mining regions, or how different parts of the community respond in different ways.

“Our results don’t provide an answer to whether deep-sea mining is societally acceptable, but they do provide the data needed to make better informed policy decisions such as the creation and refinement of protected regions and how we would monitor future impacts.”

The key question is whether deep-sea ecosystems can recover from seabed mining.

“One does really need to know as much as we possibly can about the composition on these ecosystems, how different species depend on All other, how they depend on the nodules for survival and how Speedy they can recover. So, I think this study is really Outstanding for this, but it’s a very Petite area, They only looked at 0.4 square kilometres, whereas the area that they would mine would be about 400 kilometres squared, so 1000 times larger. So, we do need to do similar studies, but over much larger areas as well.”

The rates of Restoration that the authors report will be much slower after a commercial operation, says Dutkiewicz. And without the nodules, it will be a very different ecosystem.

“It would be relatively Effortless for different organisms to invade those smaller areas from neighbouring areas which are well occupied by biodiversity. It’s a bit like having a garden. You can weed a large area, and the weeds will end very much more slowly, rather than Merely reading a Petite area, and you get the weeds growing the Upcoming day virtually”

“This Petite study has to be upscaled, and it may take many years to actually find out how these systems recover.”

The paper is published in Nature.

Seabed mining treaty negotiations