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Deep-Sea Mining’s Environmental Toll Could Last Decades

A study of microbial communities at the site of a 1989 deep-sea mining test suggests the fragile ecosystem may take half a century to fully recover

A deep-sea starfish attached to what is called a polymetallic nodule. These nodules are being targeted by the burgeoning deep-sea mining industry for their mixture of valuable metals including manganese, cobalt, copper and nickel. (OFOS-Team / Alfred Wegener Institute)
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A deep-sea mining rush appears closer than ever to getting underway. Deep-sea mining, which requires extracting minerals and metals from the seafloor, has scientists and environmentalists worried because a growing body of research suggests its environmental damages are likely to be long-lasting and severe. New research published this week underscores these risks, finding that deep-sea microbes may take half a century to recover from the disturbance of mining, reports Ryan Mandelbaum of Gizmodo.

In international waters, a United Nations body called the International Seabed Authority (ISA) has granted 30 exploration contracts for an area of the underwater abyss three-times the size of California. These seabed parcels are split between 22 countries and companies hoping to extract mineral riches, including cobalt, copper, nickel and rare earth elements used in manufacturing cell phones, batteries and electric cars.

Proponents argue that the mineral deposits found in areas of the deep sea are needed to power the technology of the future and help the world transition away from fossil fuels. Some also argue that deep-sea mining might represent a more ethical way to source minerals, like cobalt, that are associated with human rights violations on land.

While no commercial operations are currently underway, a handful of tests have occurred. Japan conducted a successful test in 2017 and plans to begin commercial mining in Papua New Guinea’s exclusive economic zone were moving forward before finally crashing in September of 2019, reported Ben Doherty in the Guardian.

A planned test of a 25-ton machine designed to vacuum up ore from the seafloor was called off in April 2019 due to a mechanical failure, reported Olive Heffernan for Nature. There have been so few experiments to give scientists an idea of what mining might do to the seabed and the surrounding marine environment that the cancellation of the test was met with disappointment even among conservationists.

“This was definitely a significant setback, because it was really the only opportunity to try to even start to see the interaction of these big, heavy machines with the marine environment,” Kristina Gjerde, a high-seas policy adviser with the International Union for Conservation of Nature, tells Nature.

One of the few experiments testing the impacts of ocean mining began in 1989 off the coast of Peru and is the subject of the new paper, published in the journal Science Advances.

The 1989 experiment involved plowing an area of seafloor 13,615 feet below the surface to simulate the disturbance of mining. Since then, scientists have revisited the area to assess its response.

A 2019 study published in the journal Nature found many species had not returned to the plowed area even 26 years after the undersea dust had settled. The authors wrote that if their results were representative of deep-sea mining activities that the industry’s impacts might be “greater than expected, and could potentially lead to an irreversible loss of some ecosystem functions.”

The new study focused on even smaller organisms: the microbes buried in the sediments of the plowed tracks. A combination of photos and samples taken from the site in 2015 revealed that plowing new tracks slashed microbial community by half and that even the 26 year old tracks had still only recovered two-thirds of their microbes. This reduction in overall numbers of microbes also translated to a 75 percent slowdown of various microbial processes. Overall, the team calculated that it would take a full 50 years for the microbes in the simulated mining area to return to normal.

The researchers hope their study can help inform the environmental regulations that the ISA is still in the process of developing by “pointing out the limits of seabed recovery,” says Antje Boetius, a deep-sea ecologist with the Max Planck Institute, in a statement.

“I don’t think there are any easy answers here, but, environmentally speaking, there is no good that comes out of seabed mining,” Jeff Drazen, a deep-sea biologist from the University of Hawaii who was not involved in the study, told me in 2018 in an interview on behalf of the GEOTRACES GP15 oceanographic expedition.

Drazen is one of a select few scientists who have explored the abyssal plain ecosystem of the Clarion-Clipperton Zone (CCZ), where the majority of the ISA’s undersea mining contracts are located. The CCZ covers 1.7 million square miles between Hawaii and Mexico and its seafloor is littered with polymetallic nodules, potato-like lumps of metal that contain cobalt, manganese, nickel and copper.

This new research gives a taste of the potential fallout of sending a mining machine in the deep sea, but the impacts are not limited to compacted seafloor and smothering sediment plume. The very things being mined also appear important for deep-sea life.

“Half of the species we have observed appear to rely on the nodules, even mobile animals seem to prefer them,” Drazen told me of the species in the CCZ. “The nodules are precisely what make this habitat unique.” And the nodules aren’t replaceable in any normal sense of the word: “When you lift them off the seafloor, you’re removing a habitat that took 10 million years to grow,” Drazen tells Wil Hylton of the Atlantic.

The negotiations run by the ISA to hammer out regulations for its underwater mining code have, like everything else, ground to a halt as a result of the novel coronavirus pandemic, reports the DSM Observer. The ISA’s next meeting to hash out the details that would govern this novel industry was scheduled for July, per the DSM Observer, but it seems unlikely to take place in person, rendering the regulation of this potentially environmentally destructive industry uncertain.

“If deep-seabed mining moves forward, it will be on spatial and temporal scales that are orders of magnitude greater than this experiment,” Diva Amon, deep-sea biologist at the Natural History Museum in the United Kingdom who was not involved in the study, tells Gizmodo.

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