6.5: Deep-Sea Mining

While plastics and their impacts on marine life have captured the public’s attention in recent years, another potentially destructive human activity is gaining momentum. Ocean mining, the extraction of mineral resources from the seafloor, raises the potential for serious impacts on ocean habitats, marine organisms, and even people. The possible harmful consequences of ocean mining deserve our attention.

Deep-Sea Metals

Though we rarely think about it, the manufacture of smartphones, green technologies, batteries, and many other devices requires minerals. At least 14 different minerals go into a smartphone. While many are present in tiny quantities, each is required for a smartphone to function properly (USGS 2017). Some 1.43 billion smartphones were sold globally in 2021 (Statista 2022). The rapidly increasing demand for renewable energy technologies (e.g., solar panels, wind turbines) and battery technologies (e.g., electric cars, electrical storage) has led to concerns about shortages in the supply of minerals. Making matters worse, the supply chain for minerals involves countries around the world, raising issues of security, diplomacy, regulation, ecology, and human welfare (Ali et al. 2017).

Worried about global shortages, governments and industries have increasingly looked toward the seafloor as a source of minerals. The deep seafloor exceeds land deposits in terms of abundance for nearly all minerals (e.g., Hein et al. 2013). Four types of deep-sea mineral deposits have received the most attention:

• marine phosphorites, phosphate-rich sedimentary rocks formed in oceanic upwelling regions with high biological productivity, mostly continental margins, but also some oceanic seamounts (Filippelli 2011)
• polymetallic nodules, also known as manganese nodules, tennis-ball-sized globes of different metals that precipitate slowly around a nucleus (a shell or bone fragment, for example) on the seafloor (Cuyvers et al. 2018)
• polymetallic crusts, similar to nodules in composition, forming as a coating on rocks along the flanks and summits of seamounts (Cuyvers et al. 2018)
• seafloor massive sulfide deposits, essentially, the sulfur-rich chimneys and deposits of hydrothermal vents (Cuyvers et al. 2018)

As reported by Mining-Technology.com (Davies 2019), “The deep sea could contain more cobalt, nickel and rare earth minerals than all land-based reserves combined forecast . . . to account for 15% of global supply by 2050.”

Status of Deep-Sea Mining

Until now, deep-sea mining has remained in a testing phase. But pressure is mounting to allow commercial deep-sea mining to begin (e.g., Lyons 2021). In June 2021, the Micronesian island nation of Nauru (the third-smallest nation in the world next to Vatican City and Monaco) invoked a United Nations Law of the Sea rule known as the two-year rule, which would require a decision on seafloor exploitation by mid-2023 (Reid and Lewis 2021). As Blanchard et al. (2023) describe it, “A lot of work has yet to be done to evaluate how environmental considerations will be embedded into the DR , if deep-sea mining does indeed go ahead.”

There seems little doubt mining can be carried out successfully. In 2017 Japan became the first country to excavate polymetallic sulfides from an inactive hydrothermal vent in the Okinawa Trough (Okamoto 2018). And in 2020 Japan was able to retrieve more than 1,400 pounds (649 kilograms) of copper and nickel-enriched crust from the seabed near Minami-Tori-shima Island (JOGMEC 2020). A number of countries and companies have obtained leases and manufactured equipment for deep-sea mining.

At the same time, efforts are underway to address potential environmental concerns. The International Seabed Authority, which works under the UN Law of the Sea treaty, continues to work on adoption of environmental regulations that would reduce environmental impacts. But uncertainty remains, particularly with regard to scientific understanding of deep-sea ecosystems and their response to disturbances from mining (Beaulieu et al. 2017). The European Union Parliament recently called for a moratorium on deep-sea mining “until its effects on the environment are better understood and can be managed” (Lewis 2021).

Impacts of Deep-Sea Mining

Oceanographers have reasons for concern. A 1989 seafloor “plowing” experiment in the Peru Basin so damaged the habitat that it had still not recovered 26 years later (Lledo et al. 2019). Track marks remained visible and microbial activity was severely reduced (Vonnahme et al. 2020). In some places, the sediments had become so compacted that animals could no longer inhabit them (Ackerman 2020). Though scientists acknowledge the limitations of extrapolating results from one region to another, their experiments underscore the need to proceed with caution.

Oceanographers have barely begun to explore the diversity of organisms inhabiting these regions. A 2016 study using remotely operated vehicles (Chapter 4) within the Clarion-Clipperton Zone—an abyssal plain southeast of Hawaii targeted for collection of polymetallic nodules—found seven species “new to science” and higher than average biodiversity (Amon et al. 2020). Such discoveries underscore how little scientists know about these regions of the ocean.

Seafloor impacts are not the only ones that concern scientists. A group of oceanographers recently expressed concerns about the impacts of deep-sea mining on organisms living within the water column. Plumes of sediments kicked up by mining operations may threaten midwater ecosystems, which “represent more than 90% of the biosphere contain fish biomass 100 times the annual fish catch” (Drazen et al. 2019). Sediments may impair the breathing of organisms, bury organisms directly, and impair the ability of organisms to find food or communicate (Christiansen et al. 2020). Locations targeted for mining boast some of the clearest waters in the world ocean and the impacts of increased sedimentation may be high (Smith et al. 2020). Increased ocean noise has also been cited as a concern (Christiansen et al. 2020).

Should We Mine the Deep Seafloor?

While some ask, “Should we mine the deep seafloor?” (Beaulieu et al. 2017), others respond, “Seabed mining is coming—bringing mineral riches and fears of epic extinctions” (Heffernan 2019). Indeed, deep-seafloor mining appears inevitable (e.g., Hein et al. 2010).

Whether inevitable or not, some people believe that deep-sea mining could be carried out in a manner that minimizes its impacts to organisms and the marine environment. At least one company—DeepGreen Metals—has partnered with research institutions to address scientific concerns (Moore 2020). Underscoring the need for this type of research, Smith et al. (2020) write:

The deep sea contains many of the most pristine, poorly studied, and evolutionarily remarkable ecosystems on our planet—in situ scientific knowledge addressing the full scales and intensities of seabed mining should be obtained and properly applied to sustain biodiversity and ecosystem functions in the deep sea if mining is to proceed.

Deep-sea mining—dubbed the “new gold rush” by one author (Tasoff 2017)—appears on the brink of rapid expansion once regulations and investments in technologies take hold. When it does, the riches will be there for those with the money and technology to find and extract them.

On the other hand, some argue that the need for deep-sea mining has been overhyped (Miller et al., 2021; Earle and Kammen 2022). Green energy and other metal needs can be met without deep-sea metals. They point to the fact that even some automakers support a moratorium on deep-sea mining. As Earle and Kammen state in the opening of their article, “Seldom do we have an opportunity to stop an environmental crisis before it begins. This is one of those opportunities.”