Accelerating mining of critical minerals is central to the clean energy transition. In order to avoid the worst impacts of climate change and keep temperatures well below 2 degrees Celsius, production of clean energy technologies that require critical minerals—solar panels, wind turbines, transmission lines, electric vehicles, batteries—will need to scale several times over. By 2040, demand for the minerals that these technologies depend on will be as much as six times more in total tonnage than in 2020. Battery and critical material recycling—if rapidly scaled—can meet a fraction of this demand, but not all of it, so more mining will be needed. 

That an industry with a less than stellar environmental track record is so critical to protecting the environment in the coming decades is not without irony. To ensure mining expansion is a net good, it must be done judiciously, responsibly, and with focused effort to avoid the land degradation, watershed contamination, and ecosystem devastation that can come from poorly managed projects. In the effort to identify new, readily mineable resources that might avoid some of these environmental risks, scientists and entrepreneurs are increasingly eyeing the abyssal plains of the deep sea. 

Although they lie at least 10 thousand feet below the ocean’s surface, abyssal plains have much in common with the deserts we see above land. They are sparsely populated, but host a diversity of unique creatures that are specially adapted to the extreme conditions of their habitat. In many of these deep-sea deserts, potato-sized polymetallic nodules—concretions of manganese and a host of other unusual metals—serve as foundational ecosystem features, acting as a substrate for stationary organisms that in turn sustain thousands of starfish, crustacean, sea cucumber, and other animal species. The nodules also have enormous economic value, containing a veritable mother lode of nickel, copper, cobalt, and other rare metals collectively known as rare earth elements (or REEs)—all metals that are essential for building the batteries, wires, turbines, solar panels, and electric vehicles that will power the clean energy economy. 

The novelty, fragility, and pristine nature of deep sea ecosystems have led many environmental organizations—and several countries—to call for a ban or moratorium on deep sea mining, arguing that too little is known about the local environmental impacts that mining activity may cause. Certainly, caution and continuous investigation into the impacts of deep sea mining and ways to minimize them is warranted, but it is equally important to weigh the environmental impacts of not mining such regions, in assessing what the most responsible path forward may be. 

If exploiting abyssal plains for critical minerals is prohibited, then terrestrial mining would need to expand. Considering just cobalt, nickel, and copper, a collective 25 million tons of these three metals were mined from onshore metal deposits in 2023, and their demand is anticipated to grow 1.5- to 2-fold over the next quarter century. Currently, over 80 percent of cobalt is mined in the rainforest-rich regions of the Democratic Republic of Congo (DRC) and Indonesia, and over two-thirds of nickel is mined from Indonesia and the Philippines, meaning that mining does not just have local environmental impact, it compounds the climate crisis through the destruction of carbon absorbing rainforests. Copper production is more evenly distributed globally, but still has mines in rainforest-rich regions like Peru, Indonesia, the DRC, and parts of China. None of these countries have a strong track record on environmental protections or robust labor standards.  

With responsible management and pro-active mitigation, the impacts of terrestrial mining can be minimized, and ecosystems can mostly recover after operations cease. In the case of tropical forests, above ground biomass density can fully recover in two or three decades, and species diversity can recover in a few decades more. However, poor management of terrestrial mines can lead to the accumulation of large tailings piles of mine waste that can leach heavy metals and acidify local ground water supplies. Degraded soils and exposed mining scars can prevent revegetation, and metal-rich dusts can cause health risks to nearby communities. 

From this perspective, deep sea mining has some first-order advantages over terrestrial mining. It largely avoids the risks associated with the production of large tailings piles and other mine waste. Lifecycle analyses suggest that polymetallic nodule mining and processing produces significantly less greenhouse gas emissions than terrestrial mining. And, given the biomass density and biodiversity of the tropical forest regions in which so many cobalt, copper, and nickel mines are concentrated, the number of individual organisms and diversity of species directly impacted by deep sea mining activity is much lower per metric ton of metal than terrestrial mines. 

But unlike terrestrial mining, where ecosystems can be re-established if mining is properly managed, it is reasonable to expect that on human timescales, sections of the abyssal plain that are mined will not recover. Polymetallic nodules take millions of years to form. Given the role they serve as an anchor to the immobile animals that represent the bottom of the deep sea abyssal plain food web, once the nodules are gone, the ecosystem disappears. 

Does that mean we should enact a permanent moratorium on deep-sea mining, as some organizations and countries have suggested? Not necessarily. While it certainly makes sense to proceed cautiously, and with a priority on assessing and minimizing impact, reaching global decarbonization goals as quickly as possible is a paramount priority that requires a 50 percent or more increase in cobalt, copper, and nickel production over the next six years, and a doubling by 2050. Given the average 23 year discovery-to-production timeline for opening new terrestrial mines, even if we establish that the environmental impact of terrestrial mining is less than deep sea mining, there is not a clear pathway for meeting near-term demand with onshore mining alone.  

For cobalt and nickel, the additional production capacity needed between now and 2050 (above a 2023 baseline) could be met by mining about 10 percent of the Clarion Clipperton Zone (i.e., the 5 million square kilometer region in the North Pacific Ocean—to the south and east of Hawaii—that is the best studied nodule-bearing abyssal plain to date), or 0.2 percent of all abyssal plain ecosystems, globally.4 That cost—while not insignificant—might be what buys the world time to grow and improve our onshore practices: creating environmentally responsible terrestrial mining capacity and robust recycling programs, while helping us achieve the climate goals that are critical to all ecosystems, including the remaining 99.8 percent of the ocean’s abyssal plains. 

In weighing the potential value and risks of opening the deep sea to mining, the American southwest provides a useful corollary. Cryptobiotic soil crusts—a microscopic community of organisms that stabilize desert sands so that plants can take root—take hundreds of years to form, but a single footprint to destroy. And yet, we have sacrificed some cryptobiotic soil to build roads, trails, visitor centers, and informational signs in national parks across the southwest. There is a cost: stretches of an ecosystem that took hundreds of years to build, lost for the purpose of people’s vacations. But the benefits outweigh the costs: by providing localized venues for people to experience the beauty and understand the value of these landscapes, sacrificed stretches of desert prevent the potential devastation of the entire ecosystem.  

Humans—like all animals—cannot survive without extracting resources from the world around us, whether water, food, shelter, or energy. A responsible mining future is not one in which we stop extracting resources. It is one in which we carefully balance the tradeoffs of different approaches in order to minimize impacts, maximize nature preservation, and triage climate change as quickly as possible, whether that means mining on land, or in the sea.