The risks of deep-sea mining: Disruption on a massive scale

It’s important that we understand the scale of what mining companies have in store for the central Pacific. Because once we begin mining the seafloor, there’s no turning back.

Polymetallic nodules on the floor of the Clarion-Clipperton Zone of the central Pacific Ocean.

The world is in the midst of a historic transition from fossil fuels to renewable energy from the sun, wind and other sources. With growing scientific alarm about global warming and increasing evidence of the harm it is causing for people and the environment, that transition cannot happen soon enough.

Yet, many of the technologies the world is relying on for the clean energy transition depend on so-called “critical minerals.” Where will they come from?

The answer, at least to some mining companies and their supporters, is “the ocean.” In a few weeks, the International Seabed Authority (ISA) – the entity that regulates mineral extraction in international waters – will continue meetings from March in which they considered whether to allow mining companies to extract mineral-rich nodules from the seafloor in the central Pacific Ocean.

It can be hard to envision the impact of deep-sea mining. After all, the areas currently under exploration are relatively far from major land masses and miles beneath the ocean surface. These are among the most remote and unexplored areas on Earth.

But it’s important that we try to understand the scale of what mining companies have in store for the central Pacific. Because once we begin mining the seafloor for critical minerals, there’s no turning back.

illustration of deep-sea mining techniques

Deep-sea mineral resources and impacts of mining.Photo by U.S. Government Accountability Office | Public Domain

Deep-sea mining explained

To picture the scale of a deep-sea mining operation, start with the nodules. These potato-sized, mineral-rich rock concretions on the seafloor contain a mix of manganese, cobalt, nickel, and trace amounts of lithium and rare earth metals. They grow only a few millimeters every million years.

The nodule collection method that’s been tested most extensively by mining companies is the use of tank-like mining vehicles that roll along the ocean floor on caterpillar tracks and can weigh up to 250 metric tons. Imagine a giant plow tearing through the seafloor, and you’re not far off.

Other technologies have been proposed, from vehicles that blast high-pressure water at the seabed (think a massive pressure washer on the ocean bottom) or use a robotic arm that plucks up individual nodules to limit damage to the seafloor and the creatures that reside there. But there is no guarantee that these alternatives will prove technically feasible.

Severe and lasting damage to ecosystems

Even mining equipment intended to be “lower disturbance” can cause permanent damage to seabed habitats – and the areas of the ocean in the sights of deep-sea mining advocates are rich in such habitats. Research in the Clarion-Clipperton Zone (CCZ), for example, a region of the central Pacific gaining attention from mining companies, has shown that the density of seabed organisms in the region’s nodule-rich abyssal plains can be twice that of nodule-free areas

These wildlife communities can take many years to recover from disturbances. One study involving simulated deep-sea mining operations found that even decades later, the areas of seabed disturbed during the experiment had failed to regain their original species diversity, and had lost over half of their original population density of seabed and mobile fauna. The loss of the hard surfaces provided by nodules depleted some habitats to below the populations of neighboring nodule-free zones.

Whereas the damage caused to land-based ecosystems by terrestrial mining is highly visible, deep-sea mining sites may appear “out of sight, out of mind.” But research on biodiversity loss, noise and light pollution, disruption to carbon storage and the spread of potentially harmful contaminants suggests that mining operations would almost certainly inflict serious harm on deep-ocean ecosystems.

Sizing up deep-sea mining’s impact

Whatever long-term impacts deep-sea mining has on ocean ecosystems, they’ll be taking place on a truly gargantuan scale.

Let’s take a look at the numbers. 

A 2022 report produced for the ISA estimated the amount of various metals that could be produced annually from the Clarion-Clipperton Zone by 2035. The moderate scenario in the study – six mining operations working simultaneously – would produce 18 million metric tons (about 40 billion pounds) of nodules per year. 

To collect this quantity of nodules solely from the most nodule-rich areas of the Pacific under exploration would require the annual disruption of nearly a hundred square miles of ocean floor. But producing that same quantity of nodules from areas with the average nodule concentration of the CCZ (about 15 kilograms per square meter) would require the disruption of about 460 square miles of seabed every year – an area roughly the size of Los Angeles. 

And that’s just the moderate scenario. With a dozen active mining operations, that figure grows to an area of disturbed seabed roughly equivalent to Los Angeles, Denver and New York City combined. Every single year.

The impact of mining would not just be limited to the seafloor at the mining sites themselves. Sediment containing naturally-occurring toxic compounds is kicked up when removing the top layer of seabed. Research suggests that this sediment could be carried a thousand kilometers in every direction over the course of a single 20-year mining operation.

What we’d get from the disruption

What’s all that destruction worth? The answer is: not nearly enough to make it justifiable. Taking out that L.A.-sized piece of seabed habitat every year would get us about 1% of the copper needed to meet the estimated 2035 demand for the energy transition. That’s not trivial, but also not a game-changer.

Deep-sea mining could have a significant impact on cobalt and nickel production. But these are two metals that electric vehicle manufacturers are currently reducing the use of in batteries. A 2020 study estimated that the world would need to mine half as much cobalt and nickel for EV batteries over the period between then and 2050 if manufacturers were to shift from nickel- and cobalt-heavy battery designs to lithium iron phosphate batteries that do not use those metals at all. That transition now seems to be well underway. Add in aggressive recycling and the need for those metals could be reduced by a further 30% (for cobalt) and 25% (for nickel). In short, the massive disruption caused by deep-sea mining is not necessary to solve a problem that appears to be far less of a problem than it was several years ago. 

Building a circular economy

If we want to avoid deep-sea mining, and with land-based critical mineral extraction causing its own suite of environmental and social consequences, how can we be sure to get the materials we need for the clean energy transition?

There are some surprising options. Millions of tons of critical minerals exist within products we have already produced – many of which wind up in the trash. Globally, more copper and cobalt are thrown out each year in e-waste than Pacific deep-sea mining is likely to be able to produce, at least by the middle of the next decade.

Our new report “We Don’t Need Deep-Sea Mining” recommends a circular economy approach built on the “5 Rs” – reducing, reusing, recycling, reimagining and repairing products. Electronics, from smartphones to electric vehicles, can be redesigned to last longer and use materials and energy more efficiently. Other innovations in clean energy technologies may decrease the need for certain minerals altogether.

Combined with effective recycling programs, the International Energy Agency estimates that these strategies could reduce demand for newly mined nickel by 15% in 2040, and twice that for cobalt and copper. This eases the short-term supply challenges in upcoming years while ensuring that future devices need not be replaced as often. Less material, less mining.

The good news is that the global transition to renewable energy is well underway, and it will bring with it tremendous benefits – not least for our beleaguered climate. By getting the most possible use out of the materials we extract from the Earth – and ensuring that they are recycled at the end of their useful lives – we can build a clean energy economy that protects the health of our oceans, rather than putting them at risk.


Caroline Crowley

Intern, Frontier Group

Caroline Crowley is a Frontier Group intern from Medford, Mass. As an undergraduate at the University of California, Berkeley, she studies Environmental Economics and Policy and works with environmental nonprofits including the California Public Interest Research Group (CALPIRG). She focuses her academic and advocacy work on the interactions between renewable energy policy, marine conservation, and local communities.

Tony Dutzik

Associate Director and Senior Policy Analyst, Frontier Group

Tony Dutzik is associate director and senior policy analyst with Frontier Group. His research and ideas on climate, energy and transportation policy have helped shape public policy debates across the U.S., and have earned coverage in media outlets from the New York Times to National Public Radio. A former journalist, Tony lives and works in Boston.

Kelsey Lamp

Director, Protect Our Oceans Campaign, Environment America

Kelsey directs Environment America's national campaigns to protect our oceans. Kelsey lives in Boston, where she enjoys cooking, reading and exploring the city.

Nathan Proctor

Senior Director, Campaign for the Right to Repair, U.S. PIRG Education Fund

Nathan leads U.S. PIRG’s Right to Repair campaign, working to pass legislation that will prevent companies from blocking consumers’ ability to fix their own electronics. Nathan lives in Arlington, Massachusetts, with his wife and two children.