Sparing the Land by Collecting Minerals at Sea

An ocean scientist argues for open-mindedness toward seafloor mining

Sparing the Land by Collecting Minerals at Sea

If a screenwriter were writing a new film with an anti-environment villain, one of the easiest ways to establish the moral bankruptcy of the antagonist would be to make the character a corporate industrialist hell-bent on mining the deep ocean.

The average audience, after all, does not require even a single frame of film to imagine that deep sea mining might involve any number of ecological horrors. Most opponents of deep sea mining lean into such favorable preconceptions, vividly characterizing deep sea mining as a catastrophic act of ocean ecosystem vandalism, which any responsible citizen ought to categorically oppose with do-or-die fervor.

Thus it may come as a surprise that none other than James Cameron, passionate deep ocean explorer and director of the ocean-themed “Avatar: The Way of Water,” recently expressed feeling open-minded toward deep-sea mining as a “less wrong” alternative to conventional land-based mining.

A challenge is that seafloor mining immediately starts off at a reputational disadvantage, a product of what Cameron calls society’s “weird habit of blowing the wrong thing out of proportion.” This instinctive reaction leads many to overlook the potential for deep sea mining to offer a more just, lower-impact, and lower-carbon way to mine metals than conventional terrestrial mining – a proposition that evidence so far seems to suggest has real promise.

As an oceanographer by training, I endorse Cameron’s suggestion, as heretical as that may seem. Collecting metals from the seabed may well be a “more right” way for humanity to source some of its needs for new metals.

This opportunity to pioneer a new dramatically lower-impact form of mining highlights how important it is for environmentalists and ocean scientists to critically reexamine the automatic instinct to oppose any further alteration of our seas. In the face of forces like climate change and far more extensive human activities that have and will continue to keep changing the oceans, such aspirations are already futile. Equally futile are superficial attempts to reject new mining both on land and at sea with impossible recycling math, thereby avoiding having to wrestle with the energy transition’s implacable trade-offs. With these factors in mind, it is well worth asking whether we ought to continue concentrating the impact of our metals production on land in service of a shining ideal of ocean conservation that is already unattainable.

What is deep sea mining, really?

While some have speculated about mining other potential ocean-based resources for many decades, collecting seafloor nodules is closest to commercial operations and at the focus of most of the ongoing debate. Other marine resources remain far more speculative, and would be subject to their own unique environmental assessments and regulatory restrictions. Indeed, no commercial-scale harvesting of seafloor metals has occurred yet, as governments and industry await the finalization of international regulations and environmental standards.

In certain regions of the abyssal seafloor between 3.5 and 6 kilometers in depth, natural chemical processes have formed vast fields of potato-sized concretions rich in manganese, nickel, copper, and cobalt. As coincidence would have it, manganese, nickel, and cobalt are the exact metals used to manufacture the nickel-manganese-cobalt lithium-ion battery packs found in many electric vehicle batteries and other electronic devices. Nickel and manganese are also used extensively in many standard steel and aluminum alloys as well as in other clean energy technologies like hydrogen electrolysis cells, while copper is a crucial component for countless power grid infrastructure elements. Finally, supply chains for these metals exhibit a concerning degree of overconcentration, with around 70% of cobalt and nickel processing and 44% of copper refining currently based in China. Consequently, deep-sea nodules pose implications for the metal requirements of not just electric car batteries, but for the clean energy transition as a whole.

Prospectors propose using remotely-operated robots to simply vacuum up these nodules and pump them to motherships at the ocean’s surface. In contrast, mining these same metals on land would typically require clear-cutting forest and vegetation, then blasting and digging surface excavations or deep mine shafts to extract buried ore, exhuming the soil layer and many layers of rock in the process.

No form of mining is without environmental impacts, and the same is certainly true for seafloor nodule collection. Most of the robotic collector vehicles currently in testing use hydraulic jets to dislodge the nodules, sucking up the metal-rich rocks along with the top 5-10 centimeters of sediment. This will likely kill the majority of bottom-dwelling organisms caught in the collector’s path. The sediment ingested by the collector vehicle is subsequently ejected, creating a plume near the seafloor in the vehicle’s wake that could harm or bury seafloor life. While being transported to the mothership at the ocean’s surface via pipe, the nodules may rattle within the pipe, generating loud underwater noise. Finally, return water and sediment carried to the mothership through these pipes must be brought back to the ocean floor which may affect local carbon and nutrient cycling and generate a relatively dilute, light sediment plume.

Let there be no doubt that harvesting deep-sea nodules would deteriorate local seafloor ecosystems to some extent. But the direct and more long-lasting seabed disturbance is limited to the path of the collector vehicles. The effects of the sediment plume near the seafloor depend on how much the sediment cloud rises and travels horizontally, and how much plumes affect bottom-dwelling organisms. The impact of noise from piping nodules to the surface depends on the equipment used and the sensitivity of nearby animals to that noise. Furthermore, impacts like noise and ejected sediment could cease immediately should mining companies pause or end operations.

Meanwhile, the one-third of Earth’s surface covered by land contains all of our paved concrete cities, all of our land-based mines, and all of our vast expanses of cropland and livestock pasture. To date, the burden of nearly the entirety of society’s current and historic demand for metals has fallen upon this minority of the planet’s surface area that we happen to live in closest proximity to. Nor should we forget that society also already carries out numerous ocean-based economic activities—fishing and whaling, marine shipping, the dredging of shipping channels, sand harvesting, offshore oil and gas drilling, and the construction of offshore wind turbines, undersea pipelines, and cable networks. Many of these operations produce similar impacts in terms of noise and local seafloor disturbance.

Sourcing metals from nodules could be preferable to conventional mining on land from a human perspective as well. Extracting metals from remote locations at sea that are literally uninhabitable may avoid many of the risks to human communities and sociopolitical conflicts that terrestrial mining can pose. The production of metals from nodules would also rely primarily on skilled labor in sectors with traditionally strong union representation like shorefront workers and metalworkers, avoiding risks like mine worker exploitation and poor safety standards that confront many global mineral supply chains today.

Humanity may also share the benefits of deep sea metals more broadly than has historically been the case in mining. The United Nations Convention on the Law of the Sea (UNCLOS) tasks the International Seabed Authority (ISA) with not only regulating seabed economic activities, but with collecting royalties on mining and redistributing them as benefits to countries globally, prioritizing developing countries in particular. The claims-based nature of seabed exploration under the ISA has also encouraged companies to partner with sponsor nations including small island developing states with few other economic opportunities that could themselves benefit from revenue and administrative fees associated with such agreements. As such, one wonders whether seafloor nodules might offer not just technical and environmental advantages relative to traditional mining, but also produce better social outcomes as well.

An incoherent debate

Ultimately, it is critical to distinguish between accurate claims about deep sea nodule collection and misleading assertions without basis.

Seafloor mining opponents claim nodule collection will pose an existential threat to marine life, driving rare seafloor species to extinction, or threatening fisheries at the scale of entire ocean basins. Activists have lobbied governments and potential industry customers like automakers to support moratoria on deep-sea mining, arguing that nodule collection is too dangerous to allow or consider—at least until scientists learn more about the risks.

But opponents of nodule collection are engaging in exaggeration, cherry-picking, and misleading messaging that clearly call into question their rhetorical commitments to let the science speak. Cases abound where activists have cited scientific research to claim catastrophic impacts of nodule harvesting that far exceed the actual findings in question.

For example, recent Greenpeace campaigns have widely smeared polymetallic nodules as “radioactive” and potentially harmful to workers, a claim that some reporting has uncritically repeated. Yet the actual scientific study that activists are citing concludes that nodules emit low amounts of relatively harmless alpha radiation, which cannot even penetrate human skin, and proposes that simply requiring workers to wear an N95 mask would provide effective protection.

Or there’s the case of exaggerated claims about the future of tuna. A recent study examining the overlap between Pacific tuna population patterns and the nodule-rich seafloor areas has motivated activists, journalists, and fishing industry representatives to label nodule collection as a threat to Pacific tuna on an ocean-wide scale. But it once again appears that nobody has read the underlying paper. The study only investigated the potential for tuna populations to migrate into one nodule-containing seafloor region in response to future climate change, and did not directly study the influence of nodule harvesting operations on tuna. This is a clear case of activists and reporters spawning scientific conclusions from their imagination to fit a desired narrative.

A broader look at activist campaigns against seafloor nodule collection suggests that opponents simply aren’t interested in scientific impact assessments to begin with. Anti-mining advocates represent environmental risks from nodule harvesting as though they are inherent and fundamental, ignoring the potential for regulations or technology to reduce impacts. Scientific findings with any industry connection are dismissed on principle rather than refuted on their research methods or merits. Direct action activists call for decade-long bans on nodule exploration until scientific understanding improves, while obstructing small-scale expeditions intended to conduct some of that very science. And empty lip service in more formal proceedings notwithstanding, opponents’ public messaging remains noticeably disinterested in advancing any solutions to the risks they loudly emphasize.

On the other hand, it is true that deep sea nodules are not, strictly speaking, absolutely necessary for the energy transition. The quantities of metals required to manufacture electric vehicles at global scale over the next few decades would not come close to exhausting either land-based or seafloor nodule deposits. As Table 1 shows, humanity could—without so much as touching deep-sea metals—produce nickel-manganese-cobalt (NMC) batteries for between 1.5 to 5 billion electric vehicles before encountering cobalt supply limitations. More importantly, with a rapidly-growing share of electric vehicles utilizing lithium-iron-phosphate (LFP) batteries that do not consume cobalt, nickel, or manganese, it appears increasingly likely that the future global electric vehicle fleet may not require as much of these three metals.

In pure quantitative resource terms, deep-sea metals are thus optional for net-zero pathways. But given how society is presently grappling with how to best expand and diversify battery metal production today, the insistence that ocean resources are off-limits risks ruling out a promising approach for accomplishing this more efficiently and sustainably.

Table 1: Comparison of seafloor nodule and land-based resources for the chief metals contained in polymetallic nodules, contrasted against requirements for large-scale electric vehicle deployment.

In response, activists challenge the very idea that society requires any significant new mining at all, often by calling instead for improved recycling and a crusade against private automobile ownership. This car-hating recycling-based circular economy platform rather elegantly upholds traditional conservationist principles while dodging most acknowledgement that the global shift towards more sustainable societies might involve ecological tradeoffs. However, it is both incoherent and incorrect. Specific proposals for reducing car ownership are often unrealistically overoptimistic, while cold, hard math suggests that even a vastly smaller global car fleet would still require electric vehicle replacements on the order of at least several hundred million electric cars, relative to the 30 million or so that exist today. The quantitative case for new battery metal mining is unshakeable.

As such, climate hawks would do well to consider the environmental case for deep-sea metals. One particular advantage is adaptive management. Unlike a surface mine on land, where many significant ecological impacts occur all at once during the mine’s initial construction, the fingerprint of nodule collection on the seafloor is incremental with every unit of rocks collected. If scientists conclude that it is important for collector vehicles to leave more nodules behind, operators can adjust accordingly even midway through harvesting an area. If regulators determine that underwater noise from nodule collection is more harmful than anticipated, they can require technology improvements that reduce impacts from that point forward. If collector vehicle technology improves in ways that further minimize environmental risks, regulators can compel all operators to adopt that technology.

At the most basic level, we can imagine forms of seafloor nodule collection that tread extremely lightly upon the seafloor. Regulators are working with scientists and aspiring operators to define initial precautionary thresholds for dissolved metals, noise, light, and turbidity that nodule collectors will in turn commit to meet. Across the conceivable spectrum of approaches one can envision robots that only disturb sediment to half the depth, that use dimmer onboard lights, or that eject sediment in a controlled manner to greatly reduce the size of the plume in their wake. Advocacy by many opponents for seafloor mining bans that would foreclose any of these possibilities hints at a narrow-minded aversion that fixates more on the idea of collecting seabed metals than it does on the actual impacts.

Gatekeepers of the ocean

That ocean conservation activists and ocean researchers opposed to seafloor nodule collection should not be surprising. The average oceanographer chooses the field more out of a genuine love of the ocean and belief in the intrinsic value of oceanic knowledge, than out of any desire to invent world-changing technology or win a Nobel Prize. The same is true for many ocean advocates.

In such loving eyes, the ocean is at once pristine and untouchable, but also fragile and increasingly tainted. Yet such a worldview winds up paradoxically invoking humanity’s longstanding, deep interactions with the ocean to declare the oceans off-limits to new activities.

The idea that the ocean is better off the less humans interact with it too often neglects to consider how treating the seas as sacrosanct can itself come at societal and environmental costs. Fishing well in excess of fish population replenishment serves neither food security nor ocean life, but the seas can support even extensive fishing that spares large areas of land from farming. Cargo ships and the concrete wharfs and dredged channels to support them impose harms on ecosystems, but enable global trade and link continents that would otherwise have to sustain themselves in isolation. Similarly, arguments opposing deep sea nodule harvesting cannot weigh only the costs or benefits to the ocean alone.

A common line of argument declares that humans clearly have not shown any ability to steward the environment on land, and therefore cannot by any means be trusted to extract resources from the ocean. But with nearly all human activities leaving some mark upon the land environment, would environmentalists ever really concede, at any point present or future, that humans have achieved sufficient redemption in their eyes to collect nodules at sea? Indeed environmentalists too often express similar fatalism towards seemingly any kind of human activity. Utopias do not exist, and demanding that humankind achieve utopia before attempting anything new is to effectively insist that society remain in an eternal purgatory of stasis.

The alternative, ecomodernist view is that sourcing metals from the ocean represents a part of the process itself of demonstrating better stewardship of our land ecosystems. The ocean certainly faces its share of problems, and turning to seabed nodules in order to reduce the known problem of mining impacts on land may create new problems—which humans can and will solve in turn. But humanity is already asking enough of the one-third of Earth’s land surface that it is well worth seeking an optimal balance by leveraging the watery two-thirds of the globe a little more. Arguments over the ecological diversity of seafloor nodule regions notwithstanding, it is patently obvious that the richness of biomass per unit area of land cleared for conventional mining is many orders of magnitude greater.

In the end, the better question to ask is not whether humanity should collect deep-sea metals, but rather how. Before claiming that the cost of collecting nodules from the ocean floor is too high, researchers, activists, regulators, and companies should explore the degree to which operators can reduce impacts and define what obligations to hold industry accountable to. As such, calling for immediate moratoriums on deep-sea mining is not only premature, but a circumvention of constructive dialogue and negotiation.

Much will depend on the final form of international seabed regulations, not to mention the formulation of promised mechanisms for collecting and distributing benefits globally from deep-sea activities in international territory. And given the precariousness of global supply chains for key metals, dragging such discussions out for many years would impose its own risks and costs. But fundamentally, the debate over seabed mining would benefit from more open-minded curiosity and willingness to imagine the policy frameworks and technologies that could produce a new and better form of mining—one rooted from the very start in a more progressive vision of shared management of a global commons, for the collective benefit of all humanity.