The world needs more metals for batteries to fight climate change. Should it come at the cost of these animals?

If you were to dive to the bottom of the ocean somewhere between Hawaii and Mexico, you might see a field of sunken treasure. Here, in what’s called the Clarion-Clipperton Zone (CCZ), much of the seafloor is covered with fist-sized rocks that contain valuable metals like cobalt, manganese, and nickel.

These dull-looking rocks formed over millions of years, as metal that was dissolved in seawater grew around a bit of matter, such as a shark tooth (similar to how a pearl grows around a grain of sand). Known as polymetallic nodules, they are abundant in the CCZ, though you can find them in several regions of the ocean. And you don’t have to dig to reach them; they sit on or near the ocean floor, looking plump for the picking.

For years now, a handful of companies and foreign governments have been pushing to mine nodules in the CCZ and elsewhere. These rocks contain metals needed to build batteries for electric cars and other clean-energy technologies for which demand is surging. (Worldwide, consumers bought 6.6 million electric vehicles last year, and analysts expect sales to triple by 2025.)

Those metals — particularly cobalt — are currently mined from the ground, and have been linked to environmental destruction and human rights abuses. That’s why proponents of deep-sea mining see harvesting nodules as a good thing; they claim it can be less harmful than stripping metals from the Earth.

But by mining the ocean floor, the industry could just be swapping one form of environmental destruction for another.

Scientists still don’t know much about the impacts of deep-sea mining, and what they do know suggests that it could be incredibly destructive, underscoring a core tension in the race to reduce greenhouse gas emissions: Some technologies come at the expense of biodiversity and it’s often not clear how to weigh the trade-offs.

What is certain is that the CCZ is full of life, and much of it remains undiscovered. The images below, which come from research expeditions in the CCZ, reveal some of its most mind-bending creatures, from sponges that look like light fixtures to worms that shimmer as they swim. Mining could put many of them at risk.

Reaching depths of 18,000 feet and spanning 1.7 million square miles, the seabed of the CCZ is unmatched in species diversity, compared to other regions of the ocean known as abyssal zones that have depths between roughly 10,000 and 20,000 feet.

“The CCZ has the highest biodiversity of any abyssal area that’s been sampled in the ocean,” said Craig Smith, a professor emeritus at the University of Hawaiʻi at Mānoa, who’s been studying fauna in the CCZ for more than three decades. “That’s significant because abyssal habitats cover more than half of the solid surface area of the Earth.”

Some of the most spectacular creatures in nodule fields are sea cucumbers, wormlike creatures related to sea stars and urchins. Exhibit A: Psychropotes dyscrita, a.k.a. the gummy squirrel.

Resembling a squirrel-shaped gummy candy, this deep-sea organism — which comes in different colors — may use its “tail” as a sail, Smith said. “We think that it may move around the bottom by putting this tail up and catching very weak currents that move it along the bottom.”

To dive the CCZ is to experience a foreign planet, where many creatures appear “otherworldly,” Smith said.

With 10 tentacle-like appendages protruding from its head, this dazzling, free-swimming worm — which was first described in 2010 — looks part-worm and part-squid and 100 percent alien.

“When you start getting down to deeper depths, you’re involving biology that is alien to humans,” the deep-sea explorer and investor Victor Vescovo, who has raised doubts about the business case for seabed mining, told me. “You feel like an astronaut. It’s like going to another planet.”

Equally strange are the sponges that look nothing like … sponges.

Consider Chondrocladia lampadiglobus, the ping pong tree sponge (or what I would call the mid-century-modern-light-fixture sponge). A carnivore, it uses these gelatinous balls to trap and eat little critters floating by.

Other sponges form stalks out of glass-like particles called spicules. “They literally look like glass fibers in a fiber optic cable,” Smith said of the glass-like stalks. The stalks make useful foundations for sea anemones, like the white one on top of the sponge below.

Some animals in the abyssal zone resemble those in shallower waters but are just a bit extra. This urchin in the CCZ, for example, has incredibly long spines, many inches long.

When an urchin has longer spines, they are more easily moved by currents, and more easily damaged, Smith said. But down in the CCZ, the currents are mellow, and so sprawling spines are less of a hazard, he suspects. Long spines may only be able to evolve where the current is weak.

Importantly, many critters also attach themselves directly to the polymetallic nodules, and appear to rely on them for survival, Smith said.

In 2016, Smith and marine biologist Diva Amon, among other researchers, published a study documenting about 170 species of megafauna (i.e. large animals) in a 30-square-kilometer area in the eastern CCZ. Half the animals were found only on nodules.

What’s more, the vast majority of species that researchers have collected in the CCZ are new to science, according to a recent review led by Amon. Estimates suggest that anywhere between 25 percent and 75 percent of species remain unaccounted for in areas that scientists have already studied, the review found. So there’s much more to discover, even in areas that scientists have already explored.

To harvest polymetallic nodules, companies will likely drop large tractor-like devices into the water that have caterpillar treads (like those you might see at a construction site). They’ll drive around the seafloor, vacuuming up nodules and pumping them back up to a ship on the surface through what’s called a riser pipe.

Beyond killing life on the nodules, the operation will likely release plumes of sediment from the collection device and from a discharge pipe, and it will make a lot of noise. Together, these disruptions are likely to be a big problem for marine life, Smith said.

Ecosystems in the abyssal zone are incredibly sensitive to disturbance, he said. Creatures here grow very slowly — meaning, they take a long time to recover after injury or repopulate an ecosystem. They’re perfectly adapted to an environment that’s more or less pristine: The water is usually completely clear. There’s no fishing and little human-caused noise.

Sediment plumes could make it harder for animals to feed or communicate with each other, according to Amon’s review. “This could ultimately result in significant changes in entire ecosystems and the services they support,” she and her co-authors write. Meanwhile, noise from the machines could impair animals’ ability to detect prey, avoid predators, and find mates.

“We don’t really know how sensitive these communities are to noise, but we expect they are likely very sensitive because this is a quiet environment,” Smith said.

The effect of noise on life in the abyssal zone is among the many potential impacts that researchers still don’t understand. Even a lot of baseline information is missing, such as how rare the CCZ’s species might be.

“If we want to apply the precautionary principle, we have to assume that most of the species are not very broadly distributed and are potentially susceptible to extinction from large-scale disturbances,” Smith said. “It’s reasonable to say that if all the mining license areas are mined there would be a pretty high risk of species extinctions for a number of species.”

Climate change damages the environment, too, and the world will need a lot more batteries to fight it. But experts point out that there are other ways to develop clean technologies that don’t involve harvesting the seabed, such as cobalt-free batteries, which some major EV manufacturers have started to embrace.

More than 650 marine and policy experts have now signed a letter calling for a pause on deep-sea mining until there’s more science to back up the case for it. Major car manufacturers including BMW and Volvo, as well as tech giants Google and Samsung, have also backed a moratorium on seabed mining.

“I’m neither for nor against mining,” Smith said. “I’m a scientist, and I’m for making our knowledge and data available. We need to have people that can talk about the science that don’t have an agenda.” But, Smith says, “we do know that mining will cause massive damage.”

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