How to Mine the Deep Sea: A User’s Guide to Ocean Destruction

Mining the deep sea, once a speculative enterprise confined to theory rather than practice, is now edging closer to reality. The debate usually goes hand in hand with discourse on a sustainable future, yet the relationship between deep-sea mining and sustainability is far from straightforward.

The transition to clean energy is built on a paradox: the technologies necessary for a net-zero future (wind turbines, grid-scale batteries, electric cars, etc.) require large quantities of metals whose mining have environmental consequences. Demand for these metals, such as cobalt, copper, nickel and manganese, is expected to increase by nearly 500% by 2050. Deploying enough solar, wind and geothermal power to avoid surpassing two degrees of global warming will require around three billion tons of such minerals, according to World Bank estimates.

One of the most promising sources of these minerals lies in the deep ocean. Yet exploiting it would mean opening one of the world’s last great untouched wildernesses, raising a central question: is deep-sea mining really the promising solution mining companies claim it to be?

Choosing a mining site

The Clarion-Clipperton Zone (CCZ) is a mining region roughly between Mexico and Hawaii, outside of any national jurisdiction, that has recently taken center stage in the deep-sea mining industry. It covers around 4.5 million square kilometres of abyssal plain, comparable to the size of the EU.

The seabed lies 4,000–6,000 metres below the surface, far beyond the reach of sunlight and any conventional industry. This region, located in international waters, is especially attractive because of its abundance of polymetallic nodules: apple-sized concretions that grow only a few millimeters every million years and are rich in metals such as manganese, nickel, copper and cobalt. The CCZ contains tens of billions of tonnes of these nodules, making it one of the largest deposits on planet Earth.

Getting to know your regulators

Fortunately for (aspiring) political scientists like myself who enjoy writing about technical subjects, and unfortunately for you as a mining company, successful deep-sea mining involves a good understanding of international law. The most relevant document here is the United Nations Convention on the Law of the Sea (UNCLOS). Adopted in 1982, UNCLOS defines the seabed outside of a state’s national jurisdiction simply as ‘the Area’, and declares it–and the minerals recovered from it–the ‘common heritage of mankind’ (CHM). 

From a historical point of view, the idea of the CHM resembles the Roman legal principle of res communis, referring to common property that cannot be appropriated because it is already owned by everyone – in contrast to res nullius, which refers to property owned by no one but which could be claimed if someone discovered and occupied it. Interestingly, the same concept also governs outer space, the moon and Antarctica. Put simply, CHM means that the resources found in the deep sea and the corresponding benefits must be managed collectively, and for the good of humanity as a whole.

To implement these rather vague principles, the UN established a specialised international body called the International Seabed Authority (ISA), which regulates the exploration and exploitation of deep-sea minerals. Amongst its responsibilities is the issuance of exploration licenses, which is the best shot for a mining company like you to get the chance to start mining. Notably, the ISA has not officially denied any submitted applications for exploration licenses to date. 

The legal framework is thus composed of a principle meant to ensure that everyone benefits equally from deep-sea mining, and an organisation which oversees mining activities — determining who mines and how — in order to prevent environmental harm. In practice, however, there is a structural tension inherent to this dual-mandate: one organisation simultaneously safeguards oceanic ecosystems we barely understand while facilitating companies to access the minerals.

Finding a sponsor

So, if you actually want to mine on the seabed, you cannot just send a vacuum-like mining machine into the Pacific Ocean and start hoovering up nodules. First, you need a sponsor.

Only states can apply to the ISA, which means that any mining enterprise has to work with at least one country that is a party to UNCLOS and is willing to put its name on the application and take the legal responsibility for your project. The state you've chosen to work with has to do more than just cheer you on from the shore. In theory, it should exert ‘effective control’ over you, which means it must review your technical and financial qualifications, enact domestic legislation to govern your activities and penalise you if you violate ISA regulations.

In practice, ‘effective control’ can sometimes look more like a post-office box and a business registry entry, giving rise to concern about so-called ‘flags of convenience’ on the seabed. To put it simply, a profit-driven company is likely to choose a state that is eager for economic gains and has the least capacity to exercise such ‘effective control’.

Once you have a sponsor, you submit a detailed plan of work to the ISA: first for exploration, and eventually for exploitation. If the Council approves your plan, you gain access to a chunk of the CCZ, your sponsor gets a new role as gatekeeper and enforcer, and the ISA gets one step closer to turning the abstract idea of the ‘common heritage of mankind’ into an actual revenue stream.

The rewards then cascade through different channels. You, the contractor, aim to make money from selling the metals. Your sponsor gets to tax you, take a share of the proceeds or charge fees. In turn, the ISA collects royalties that are supposed to be redistributed to the international community through a yet-to-be-developed global sharing system.

The bad news is that the risks do not cascade through the system in the same way as the rewards. Environmental damage from sediment plumes or habitat loss will be localised to particular parts of the ocean and may impact states or communities that will never see a royalty check. Your sponsor, meanwhile, may well enjoy the political benefits and economic rewards of sponsoring you without ever fully exercising ‘effective control’ over you as a contractor.

Understanding the risks

The mining machines you would deploy would travel along the seabed, vacuuming up nodules and pumping them onto ships. This means that huge areas of the seabed will be disturbed in an ecosystem that has been untouched for millions of years.

The science points to the following risks:

1. Light and noise pollution

One of the first consequences of deep-sea mining would be the introduction of light and sound into the deep sea, where it is otherwise largely absent. These disturbances could interfere with species’ behaviours, many of which scientists are only just beginning to understand.

2. Sediment plumes

As machines disturb the seafloor during mining operations, sediments could travel hundreds of kilometres before settling back down, resembling a slow-motion underwater dust cloud and smothering ecosystems.

3. Loss of undiscovered biodiversity

Much of the deep sea and its creatures remains undiscovered. Mining could lead to the destruction of their habitats and potentially lead to the extinction of species before we even know of their existence.

4. Chemical pollution and food chain impacts

The impact of deep-sea mining would not end at the seabed. Mining could also lead to waste materials, which would be released back into the ocean after processing. In a worst-case scenario, these chemicals could affect commercially important fish populations, thereby entering the human food chain.

5. Disruption of carbon storage

Scientists are perhaps most concerned about the impact of deep-sea mining on the ocean's capacity to store carbon and carbon sequestration. This is especially alarming as the ocean is the planet's largest carbon sink, holding over 50 times more carbon than the atmosphere and absorbing around 25% of human-generated emissions. This includes a significant amount of carbon that is transferred to the deep ocean via sinking organic material, which is then consumed by life in the deep ocean and potentially locked away in marine sediments, though the extent to which mining activities might disrupt this process is still uncertain.

Experiments conducted to assess the environmental impact of deep-sea mining show that it takes a very long time for ecosystems to recover. Some experts believe the seafloor in some areas has yet to recover from disturbances caused by experimental trials decades ago. This is in part because it takes millions of years for polymetallic nodules to take form in the first place.

Getting to know the competition

The geopolitics of deep-sea mining is difficult to ignore. With China currently dominating several stages of the battery materials supply chain, diversifying sources of critical minerals has become a strategic priority for many states. Deep-sea mining is therefore an economic opportunity not only for developing island nations, but also for major powers. 

A turning point came in 2021, when the Pacific island state of Nauru invoked a clause in UNCLOS known as the ‘two-year rule’. Under this clause, if a member state declares its intention to start mining, the ISA must finalise exploitation regulations within two years. If these regulations are not completed within that timeframe, mining applications can proceed under a provisional code of conduct. The two-year deadline expired in July 2023. However, the ISA has yet to finalise a comprehensive mining code. In practice, this has created legal uncertainty: while applications could theoretically proceed under provisional rules, no full-scale commercial mining has been approved so far. Negotiations still remain ongoing.

Nauru invoked this clause on behalf of its sponsored contractor, a Canadian firm called The Metals Company, which already holds exploration rights to tens of thousands of square kilometres of the CCZ. Similarly to other firms, The Metals Company argues that deep-sea mining is necessary to speed up the clean energy transition. On the other hand, institutions like the Institute for Sustainable Futures suggest that it may be possible to transition to 100% renewable energy without relying on deep-sea mining. 

Final takeaways: should you mine the deep sea?

Although deep-sea mining is often presented as a way to avoid the negative impacts of conventional land-based mining, it carries its own ethical challenges. While terrestrial mining has been linked to child labour and social harm, particularly in countries like the DRC, it remains unclear whether deep-sea mining would reduce these issues or simply introduce new ones.

Our understanding of the environmental impacts of deep-sea mining is still evolving. However, there is growing evidence that recovery in deep-sea ecosystems is extremely slow. While some land-based environments may recover within decades, disturbances in the deep ocean could persist for much longer – centuries or more. The question is no longer whether we can mine the deep sea, but whether we should.

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Aneta Migátová is a Political Science graduate from Leiden University, currently working at the Centre for Digital Governance, and a student of International Affairs at the Hertie School. She has practical sustainability policy experience from conferences in the United States and Italy, and is particularly interested in the intersection of climate, technology, and security.