Proposed deep-sea mining would kill animals not yet discovered

It could begin as early as 2024. The ecological harm would be vast—but scientists can't say yet whether it would be permanent or excessive.

When a 27-ton mining robot called Patania II began vacuuming up metal ores from the bottom of the Pacific Ocean in April 2021, it was not alone. Global Sea Mineral Resources (GSR), the Belgian company that developed the robot, had a group of scientists watching its every move—or rather, an array of remotely-controlled vehicles equipped with cameras and other sensors.

GSR is one of several companies that hopes to begin mining the seabed on an industrial scale in the coming years, perhaps as early as 2024. Some are touting the seabed as a sustainable source of the metals needed to produce batteries for electric vehicles or smartphones. Meanwhile, scientists are trying to figure out just how much ecological damage deep-sea mining would do.

The short answer is a lot, according to the European consortium of scientists who’ve been monitoring GSR’s efforts and reported preliminary results recently at a virtual meeting. But it is too soon to tell how much of the damage would be permanent or whether it should be considered excessive.

Each mining operation like GSR’s in the eastern Pacific would remove the “biologically active” surface layer from about 200 to 300 square kilometers (77 to 166 square miles) of seafloor each year, said Matthias Haeckel, a marine biochemist at GEOMAR Helmholtz Center for Ocean Research in Kiel, Germany. Haeckel oversees “MiningImpact”, a research project funded by European governments.

“If mining takes place, it should be done without loss of biodiversity and ecosystem functions,” said Ann Vanreusel, a marine biologist at Ghent University in Belgium and another member of the consortium.

That’s a hard standard to define, however, let alone enforce, because so little is known about deep-sea ecology. On two expeditions to the Pacific region targeted by GSR and other companies, the researchers identified thousands of species—70 to 90 percent of which were new to science.

“That in itself is a great example to show that, ‘Hey, we do not have a good understanding of how this ecosystem operates’,” says Diva Amon, a marine biologist and National Geographic explorer who did not participate in MiningImpact. In a review published this month in Marine PolicyAmon and her colleagues argued that at least a decade should be spent filling the gaps in scientific understanding before commercial deep-sea mining could begin.

The industry is operating on a faster time frame.

"A battery in a rock"

The region that GSR is exploring, called the Clarion-Clipperton Zone (CCZ), is a vast abyssal plain that lies between Hawaii and Mexico, at depths ranging from 13,000 to 20,000 feet. The seafloor mud there is littered with “polymetallic nodules”: potato-size rocks that form when dissolved metals precipitate out of seawater and build up on fragments of rock or marine debris, such as shells or shark teeth. The nodules are particularly rich in cobalt, nickel, copper, manganese, and rare earth elements—they’re like “a battery in a rock”, as one mining company, a Canadian startup called The Metals Company (TMC), puts it.

But the abyssal plain is also home to life not seen elsewhere—from sea cucumbers to crustaceans crawling on the surface of to tiny creatures that live in the sediment itself. During the trials the Patania II removed all that, along with the nodules, down to a depth of three inches or so.

Vanreusel, Haeckel, and dozens of other scientists are investigating what lives around the nodules and whether those animals can recover from mining activity. Amon, who has visited the CCZ since 2013, says that removing nodules will inevitably lead to a reduction in the abundance and diversity of species. 

“Nodules take millions of years to form, and they are a central part of this ecosystem. So by removing them, you are irreversibly damaging this ecosystem,” she says. Octopuses, for instance, lay their eggs on the dead stalks of sea sponges that grow on the nodules.

Deep-sea mining poses other risks, too. Collector vehicles will emit noise and light in an environment that is otherwise in perpetual darkness. As they plow up the seabed, they will also stir up plumes of sediment. A major concern is how far deep-sea currents will disperse those plumes. As the sediment settles back onto the seabed, it could smother living creatures far from the mining operation itself.


The MiningImpact researchers flew a torpedo-shaped robot with a camera and acoustic sensors through the water to track the plumes kicked up by the Patania II at a depth of 15,000 feet. Preliminary photos show that sediment blanketed the seabed some 1,600 feet on either side of  the mining tracks. It appeared to spread as far as several kilometers, albeit in smaller concentrations. The Patania II, named after the world’s fastest caterpillar, was an early prototype. For its commercial mining GSR plans to build a collector four times as big.

In a statement on its web site, GSR says it “will only apply for a mining contract if the science shows that, from an environmental and social perspective, the seabed can be a responsible source of the primary metals needed for population growth, urbanization and clean energy transition.”

It is still too early to say whether the organisms living on and around the nodules collected by Patania II survived the disturbance or not—another expedition to the trial sites in late 2022 will investigate this. But a similar site off the coast of Peru offers some clues. In 1989, German researchers dragged a specially designed plow-harrow across the seabed, cutting and working the sediment. The tracks from the machine are still clearly visible nearly 30 years later, while populations of sponges, soft corals and sea anemones have yet to return.

A big push from a small country

The seabed mining industry has been struggling to get underway for half a century. The International Seabed Authority (ISA)the UN-affiliated agency that promotes and governs mining in international waters under the Law of the Sea, has been developing regulations and a permitting process since 2014. It is supposed to ensure that any mining will be for “the benefit of mankind as a whole.” So far it allows mining companies only to explore deep-sea resources, not exploit them commercially.

But the dawn of industrial deep-sea mining may come soon, thanks in part to the demand for minerals to supply the green energy transition. On June 25, 2021, the tiny Pacific nation of Nauru exercised its right as a member of the ISA to trigger a countdown, essentially forcing the agency to complete the necessary regulations within two years. Nauru’s contractor, TMC, recently went public and is telling potential investors that it expects to start harvesting nodules as early as 2024. The startup also holds exploration licenses through Tonga and Kiribati, two other Pacific island states. It estimates that its three contract areas host enough nodules to electrify 280 million vehicles.

Nauru’s push to fast-track mining rules has environmentalists and scientists sounding the alarm even louder. More than 620 marine scientists and policy experts from 44 countries have since signed a statement calling for a halt to all mining efforts until the ecological consequences are better understood. Dozens of government agencies and the European Parliament support a moratorium, and several manufacturing companies, including Ford, Samsung and Google, have said they won’t source minerals from the deep sea.

A moratorium on deep-sea mining could, however, also slow or halt crucial research. The MiningImpact project had a budget of nearly $11 million (9.7 million euros), funded by European governments, to carry out independent baseline studies and to monitor GSR’s collector tests in the Clarion-Clipperton Zone. Mining companies are also investing millions of dollars in their own environmental surveys.

“My fear is that the funding will not continue at the level of the last few years. So the question then is how much we will learn during a moratorium phase,” says Haeckel. 

The MiningImpact researchers are still busy evaluating their data and the thousands of samples collected. But it will be years, if not decades, before they can ascertain the threshold at which industrial mining would cause “serious harm” —which the ISA is required to prevent—especially beyond the mining sites.

In December 2021, Pradeep Singh, a legal researcher at the University of Bremen, Germany, published an article in the journal Marine Policy, stressing that the ISA and its 168 member states have reached no consensus on what the terms “effective protection” and “harmful effects” mean. And yet, when the countdown ends in July 2023, the ISA will have to start approving or disapproving applications for exploitation licenses. All countries, even those without access to the ocean, have the right to apply.

One approach the ISA might take, Haeckel suggests, would be to allow only a small number of operations initially, rather than 10 at a time. The regulations could then be adapted as more scientific evidence becomes available. But such an approach would be difficult to implement legally.

“There are quite a lot of concerns that industry might push forward,” says Singh, who supports a moratorium. “One mining activity might not be so harmful, but if you allow one, you're going to have to allow others, and then cumulatively, the impacts are going to be disastrous.”

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