Researchers completing one of the largest impact studies on the potential environmental impacts of deep-sea mining found a bit more than they bargained for on the ocean floor: 4,350 animals, each at least larger than 0.3 millimeters. From these, they ultimately identified 788 separate species of unique crustaceans, mollusks, marine bristle worms, and other creatures living in this sought after mining zone.
While the team found that harvesting rare earth metals from over 13,000 feet below the ocean’s surface may not be quite as destructive as initially theorized, the disruptions are still cause for serious concerns. The team’s findings are published today in the journal Nature Ecology and Evolution.
Despite being one of the most inhospitable environments for humans on the planet, there is a rapidly growing commercial interest in the deepest parts of the ocean. Unfortunately, this fascination is frequently less about conservation and more about profits. That’s because some of the planet’s largest deposits of rare earth metals are located on the seafloor, which makes them an increasingly attractive target for companies.
One of the most attractive targets for deep sea mining advocates is the Clarion-Clipperton Zone (CCZ), a continent-sized abyssal plain located at a depth of around 2.5 miles between Hawaii and Mexico. In addition to being rich in minerals, the CCZ is also one of the world’s least understood habitats. In 2022, marine biologists announced the discovery of over 5,000 new species catalogued during a research excursion to the area.
With so much biodiversity left to explore, conservationists have repeatedly voiced worries about the environmental impacts of deep sea mining on regions like the CCZ. However, there is barely any research into the topic.
“Critical metals are needed for our green transition and they are in short supply,” Thomas Dahlgren, a marine biologist at Sweden’s University of Gothenburg and study coauthor, said in a statement. “Several of these metals are found in large quantities on the deep-sea floor, but until now, no one has shown how they can be extracted or what environmental impact this would have.”
To learn more about the possible effects, Dahlgren and his teammates surveyed a nearly 50-mile stretch of the CCZ two years before it was slated to receive a test run from a deep sea mineral mining vehicle. They then returned two months after the collector for a total of 160 days of fieldwork, having spotted the over 4,000 organisms living there, including those 788 separate species of mollusks, crustaceans, marine bristle worms, and more.
“I have been working in the Clarion-Clipperton Zone for over 13 years, and this is by far the largest study that has been conducted,” Dahlgren explained. “Since most species have not been described previously, molecular (DNA) data was crucial in facilitating studies of biodiversity and ecology on the seabed.”
The mining test’s effects were stark: within the machine’s tracks, the team calculated a 37 percent decrease in total animal population along with 32 percent decrease in diversity.
“Deep-sea mining within the CCZ is at a critical juncture, as the industry looks to move beyond the exploration phase and into commercial exploitation,” the study’s authors wrote. “Consequently, there is a clear need for direct assessment of the impacts of mining on faunal abundance and biodiversity at the seafloor.”
With this first major project completed, marine biologists hope it can serve as a baseline for future analysis of deep sea mining impacts. Moving forward they hope to also investigate the 30 percent of the CCZ currently protected by environmental regulations.
“At present, we have virtually no idea what lives there,” added Natural History Museum of London researcher and study coauthor Adrian Glover.
