Major seafood industry and marine conservancy groups are calling for a “precautionary pause” in the global race to mine deep-sea minerals, pointing to new research that suggests excavating the ocean seabed could cause tuna populations to plummet.

The groups said Tuesday that they will send an appeal to the United Nations-backed International Seabed Authority (ISA), asking it to proceed with extra caution in developing regulations and complete them before granting any licenses to mine seabeds thousands of feet under the ocean’s surface. 

Most of the waters proposed for such development lie beyond national jurisdictions and have become the latest frontiers and flashpoints in the global rush to source rare metals for electric batteries and other technologies that are important for the climate-critical transition away from fossil fuels.

The appeal coincides with research, published Tuesday in the journal Nature npj Ocean Sustainability, finding that tuna—one of the world’s most valuable fisheries, worth $40 billion a year—will migrate away from increasingly acidic and oxygen-starved waters into an area of the Pacific called the Clarion-Clipperton Zone. 

This region, between Hawaii and Mexico, is rich with polymetallic nodules that are embedded with minerals, including nickel, cobalt and copper, and has been targeted by deep-sea mining companies seeking licenses to exploit the resource. 

“This is the first time there’s ever been climate modeling of tuna stocks in relation to deep-sea mining,” said Diva Amon, the lead author of the study and a marine biologist with the Benioff Ocean Science Laboratory at the University of California, Santa Barbara. “And it’s also the first time, more importantly, that seafood industry players, including some pretty major ones, have come out with a statement about needing a moratorium.”

The research suggests that the movement of the tuna populations to the zone will lead to clashes between fishing and mining companies on the high seas—beyond the eye of regulators and with negative ecological and climate consequences. 

“The three most valuable tuna fisheries—bigeye, skipjack and yellowfin—are going to increase in the Clarion-Clipperton Zone and will overlap with mining,” Amon said. “That means there’s going to be increased potential conflict between the deep-sea mining industry and the fisheries industry.”

“By conflict, we mean spatial conflict—the fact that two competing industries will be operating in the same area,” Amon added. “But also the environmental impact conflict: Deep-sea mining will have grave environmental consequences that could impact the fishery. We’re going to see decreased catches and economic consequences for countries that rely on tuna.”

Researchers have previously projected that tuna populations will move eastward as climate change alters the composition of ocean waters. The new research finds that they’ll relocate to the Clarion-Clipperton Zone, potentially putting them into direct contact with mining companies operating there.  

“You have big tankers, with big machinery operating 4,000 or 5,000 meters below the surface, and at the same time you have boats with long lines fishing for tuna,” said Juliano Palacios Abrantes, one of the study’s authors and a researcher at the University of British Columbia. “So you have chances for entanglement and conflict between the industries.”

The mining process could generate sediment plumes that smother prey fish, killing off the tuna’s food supply.  Mining could spread toxic metals into the mesopelagic zone, known as the “Twilight Zone”—the region of the ocean between 650 and 3300 feet under the sea surface that is home to species of fish that underlie the human seafood supply.  Noise and light pollution could alter migration routes.  Researchers worry that this noise could be disorienting for larger species, too, including whales.

Tuna swim thousands of miles every year, often passing through the Clarion-Clipperton Zone, meaning that populations well beyond the area could be impacted.  “We don’t know how tuna behavior will change,” Palacios Abrantes said.

The ocean already is bombarded with pollutants, from plastics to toxic chemicals that accumulate in fish. Mining could add to the brew. Nearly 750 scientists have signed onto a statement warning against deep-sea mining as the ocean environment copes with these pollutants and the compounding effects of climate change. “Deep-sea mining would add to these stressors, resulting in the loss of biodiversity and ecosystem functioning that would be irreversible on multi-generational timescales,” the statement reads.

But the burgeoning mining industry maintains that the only way to produce enough minerals for the clean energy transition is to tap into the ocean. And the industry’s effort is currently playing out at a meeting of ISA, underway in Jamaica.

Two years ago, the tiny island of Nauru, one of the members of ISA, triggered an obscure provision in maritime law that requires the organization to issue a license for deep-sea mining within 24 months. Negotiators at the meeting are currently working on related regulations—and could issue the exploitation license this month. (ISA has already issued 31 exploratory licenses to member countries.  Eighteen of them are for the Clarion-Clipperton Zone.)

Nauru, an island nation of about 12,000 people off the coast of Papua New Guinea, which happens also to be highly dependent on tuna, is leading the charge. According to international rules, a company that applies for an exploratory license has to be linked to a particular country. Nauru has worked in tandem with The Metals Company, a Canadian company that has been the biggest player in deep-sea mining and a major advocate for the industry.

This week, Canada joined the list of nations calling for a moratorium on deep-sea mining. A number of major corporations have also pushed for a moratorium, including some car makers. A major car maker in China has recently said it won’t use cobalt in its batteries.

The United States is not one of ISA’s members because it is not a party to the United Nations Convention on the Law of the Seas (UNCLOS), so it cannot apply for a license. But American companies are getting in on the action: U.S.-based defense contractor, Lockheed Martin, has a wholly owned subsidiary in Singapore that is pursuing a license, Amon said. 

Like most of the deep sea, relatively little is known about the bottom of the Clarion-Clipperton Zone. Researchers are just beginning to discover the biodiversity there. The projections of what could happen to tuna populations if mining operations work in this zone are hypothetical.

“I think uncertainty plays an important part here,” said Palacios Abrantes. “There’s a lot of uncertainty of what climate change will do to tuna stocks, so this is adding a layer of complexity that in the opinion of many of us, we don’t really need.”

The mining industry has maintained that ocean-based mining doesn’t damage as many species as terrestrial operations and has few of the human rights impacts. But marine researchers worry that if mining companies get the green light to operate in a deep ocean environment, they’ll do so in a problematically obscure and distant place.

“At least on the land, you can see the problems,” Palacio Abrantes said. “In the deep sea, you can’t see what you’re destroying.”

The researchers say that hastily granting deep-sea mining licenses will only deliver a small portion of the metals needed to meet demand.

“It’s like smoking to lower stress. We’re causing long-term damage for short-term gain,” Amon said. “The ocean is our greatest ally in the climate crisis. It absorbs heat. It sequesters carbon. Seventy to 90 percent of the species we’re finding there are brand new to science. This is an area that we’re just beginning to understand. The risk is too great.”