Is deep sea mining worth it?

The energy transition will need more rare metals, but what are the pros and cons of taking them from the sea floor?
Sade Agard
A remotely operated underwater vehicle (ROV) being lowered into the deep sea.
A remotely operated underwater vehicle (ROV) being lowered into the sea.

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  • Deep sea mining is gaining momentum in response to the increasing global demand for minerals.
  • But new investigations indicate that this could be devastating for ocean ecosystems.
  • Will we need to choose between electronics and the ocean ecosystem?

Deep sea mining— the extraction of valuable metals that lay on the ocean floor— has gained momentum in response to the increasing global demand for metals, fueled in part by the ongoing green energy transition. 

Consider the future of electric vehicles (EVs), for example, where the production of metals like nickel, cobalt, and lithium would need to triple in the next decade to meet projected global electric vehicle demand.

These valuable metals could potentially be pulled from regions such as the Clarion-Clipperton Zone (CCZ) in the Pacific Ocean, which is an area equivalent in size to Europe. At a depth of four thousand meters below sea level, the CCZ contains a wealth of polymetallic nodules—peculiar rounded lumps resembling potatoes.

But the allure of deep sea mining is also raising questions about the sustainability of this type of mining and the impact it will have on the ocean environment.

Adding to the uncertainty, recent regulations on deep-sea mining in international waters are in flux, leading to a regulatory void and a potential commercial free-for-all.

That said, the list of countries calling for a pause on deep-sea mining continues to grow.

In light of these developments, Interesting Engineering (IE) dives deeper into the issues surrounding deep sea mining, examining its environmental impacts, economic opportunities, and ethical concerns.

Mineral abundance

Deep-sea mining offers the promising prospect of abundant mineral resources. Among these potential riches are polymetallic nodules, small potato-sized formations containing manganese, nickel, copper, cobalt, and rare earth elements. 

Is deep sea mining worth it?
Polymetallic (manganese) nodules on the sea floor.

Polymetallic nodules form slowly over millions of years as minerals in seawater gradually accumulate around a nucleus, such as a shell fragment or a mineral grain.

It is estimated that a staggering 27 billion metric tons of these nodules could be found in the Clarion-Clipperton Zone (CCZ) — an expansive abyssal plain spanning 4.5 million square kilometers between Hawaii and Mexico. 

Besides nodules, seafloor hydrothermal vents are another potential source of minerals. These form when seawater seeps into the Earth's crust, becomes superheated by magma, and rises with dissolved minerals and metals.

SMS are typically found in tectonically active regions of the sea floor and are a potential source of copper, zinc, gold, silver, and other precious metals.

Ferromanganese crusts, or cobalt-rich crusts, represent yet another mineral resource. These are found on seamounts, and contain valuable metals such as cobalt and nickel. These form very slowly over tens of millions of years as metallic elements in seawater gradually accumulate on hard surfaces. In particular, they have been spotted in regions across the central Pacific Atlantic and the Indian Ocean.

Reducing land-based mining 

Proponents argue deep-sea mining is a viable alternative to land-based mining, which is the fourth largest driver of deforestation, behind agriculture, infrastructure, and urban expansion. 

Land-based mining is plagued by habitat destruction, air, and water pollution, as well as land use conflicts with local communities and indigenous peoples.

Is deep sea mining worth it?
The New Cobar gold mine in Australia has yielded over 3 million ounces of gold and 200,000 tonnes of copper since 1870. It is considered a medium-sized mine.

For instance, Gerard Barron, CEO of The Metals Company, which is leading efforts to scoop up polymetallic nodules, argued in Al Jazeera, "[Deep sea mining] comes with a whole host of lower environmental impacts than the land-based alternatives."

That's not to assume land-based mining would be entirely replaced by deep sea mining, or even replaced at all. While proponents argue it could alleviate pressure on terrestrial mining, there is no evidence for this and many fear it would simply be used in addition to land-based mining.

Another argument for deep-sea mining is that it could be used to weaken the dominance of countries like China and Russia in supplying critical raw materials. These countries hold significant reserves of land-based essential metals, although there is nothing to prevent them from also mining in the oceans. 

One argument, however, is that deep-sea mining could possibly reduce their reliance on minerals from China and Russia, promoting a more balanced distribution of resources.

Economic opportunities

Experts expect the global metals and minerals market to have a compound annual growth rate of more than 8% between now and 2026 as the energy transition accelerates. 

If deep sea mining were to provide some of these resources, it could create new economic opportunities and jobs—particularly in engineering, geology, and manufacturing. 

Although mining would likely be performed remotely by robots such as ROVs (remotely operated underwater vehicles), more manufacturers and operators of these devices would likely be required. 

Additionally, mining will require research and mapping, creating new opportunities for specialists like geologists who perform similar tasks in the oil and gas industry.

Considering how much is at stake in terms of marine ecosystems (we'll get that next), there will likely also be a huge role for environmental experts. 

Deep sea mining proponents argue that ocean mining could positively impact local economies through infrastructure development, supply chain expansion, and increased economic activity in regions where mining operations are established.

Ecosystem devastation

Set against the uncertain benefits are the possibilities of environmental destruction. The European Academies Science Advisory Council has already warned against the "misleading narrative" that deep-sea mining is necessary for low-carbon transition metals, highlighting "dire consequences" for marine ecosystems.

In fact, according to a report by Planet Tracker, deep sea mining poses a significant risk of habitat loss, causing up to 25 times more biodiversity loss than land mining.

Many research papers on deep-sea mining tend to focus on the direct impacts of nodule mining, including reports that the nodules have extremely high radiation levels and are relied on by delicate ocean ecosystems.

Deep sea mining of nodules results in direct habitat destruction and biodiversity loss. Nodules host unique organisms like corals and sponges that cannot grow elsewhere. 

These formations take millions of years to form, making the loss likely a permanent one. More than half of Pacific abyssal plain species depend on nodules. 

Furthermore, mining machinery disturbs sediments, impacting microbes vital for abyssal plain life, with recovery taking centuries due to slow natural sedimentation rates. Mining companies use robot rovers to roam the ocean floor, sucking up nodules and anything else in their path.

According to a paper by Voltz et al., the natural sedimentation rate in the Clarion-Clipperton Zone is less than 1 centimeter per thousand years.

More than 1.5 million km2 of international seabed is allocated for mining, comparable to the size of Mongolia. This vast region could now be exposed to extensive habitat loss and damage to marine ecosystems, far surpassing the footprint of terrestrial mining.

Norway, for example, has awarded 232,000 km2 of seabed concessions for mineral exploration, while terrestrial mining globally occupies just over 57,000 km2 of land.

Planet Tracker also warns that seabed mining won't reduce terrestrial mining-related deforestation, as only a fraction of seabed metals could replace land mining. The organization highlights that 71 percent of terrestrial mining-related deforestation is attributed to just two commodities: gold and coal - neither of which can be mined from the ocean. This means that ocean mining is unlikely to reduce land-based mining.

Indirect impacts

There are also the indirect impacts of deep sea mining to consider. For instance, machinery can generate sediment plumes that travel far beyond the area mined and smother marine life, including filter-feeding species and small species relied on by larger life forms, potentially devastating entire food chains. 

"You can destroy the area you mine, that's bad enough, but you can also destroy huge areas around the mine," said Professor Philip Weaver, of Seascape Consultants, in a Horizon magazine report.

Research reveals that sound from the operation of a single nodule mining site can also travel up to 500 kilometers, even in gentle weather, disrupting marine species and affecting predator-prey relationships throughout a large area. 

Deep sea mining can also release toxic chemicals, like heavy metals and even radiation, posing risks to marine life, including commercially valuable species.

Unknown long-term effects 

The ocean covers more than 70 percent of Earth's surface, but its depths remain largely unexplored, leaving much unknown about the biodiversity and ecosystems that inhabit it and how they interact. This lack of comprehensive understanding adds to the uncertainties surrounding the long-term impacts of deep sea mining. 

Claims that deep sea mining is "environmentally friendly" falsely assume the deep sea is a lifeless region. In reality, the deep sea contains a vast wealth of pristine, biodiverse ecosystems, and their relationship to the ecosystems of the higher zones is not clear. 

In fact, one study found 92 percent of Clarion-Clipperton Zone species were completely new. Another paper suggested the CCZ contained more than 5,000 species new to science. Deep sea organisms also tend to be slow-growing, meaning habitat recovery — if possible— could take hundreds or tens of thousands of years.

A study published this month found that some of the world’s most valuable fisheries may increasingly overlap with deep-sea mining operations in the CCZ, leading major players in the fishing industry to urge caution.

Is deep sea mining worth it?
A Relicanthus cnidarian on a polymetallic nodule in the Clarion-Clipperton Zone.

Biologists argue that mining operations could devastate already stressed oceans, destroy delicate ecosystems and send plumes of sediment and toxic metals spiralling upwards to poison marine food-chains that are relied on by millions of people.

The deep sea also contains huge reservoirs of carbon which could be disrupted by mining, exacerbating the global warming crisis.

Legal considerations

Deep sea mining is currently governed by the United Nations Convention on the Law of the Sea (UNCLOS), and in areas beyond national jurisdiction this is regulated by the International Seabed Authority (ISA). 

While more than a dozen nations have explored small-scale projects, large-scale commercial mining in international waters is currently prohibited.

However, the island nation of Nauru recently decided to accelerate exploitation of the sea bed. In 2021, Nauru notified the ISA of its intention to sponsor an exploitation application for nodule mining in the Pacific.

Doing this triggered the ISAs ‘two-year rule’ . This is a legal provision in the framework which gives ISA two years to adopt exploitation regulations for deep-seabed mining. Discussions among the 167 member states of the ISA are now under way. The fear is that this is essentially the starting gun in the race to allow extensive deep sea mining.

However, growing number of countries, including France, Chile, Costa Rica, Palau and Vanuatu, are urging ISA to press pause on deep sea mining, to allow time to gather more knowledge about the possible implications.

There are also ethical concerns around indigenous rights and ensuring sustainable practices, which are crucial to safeguard marine biodiversity for future generations.

Developing a balanced legal framework for economic interests, environmental protection, and social equity remains a significant challenge.

This may have gotten a boost, however, by a recent ISA meeting in Jamaica to negotiate rules over deep-sea mining that ended with an agreement to hold formal discussions next year on the protection of the marine environment.

At the meeting China, which had previously blocked attempts to discuss regulations on ocean mining, agreed to allow the item on ISAs 2024 agenda.

Alternatives to ocean mining 

There are many alternatives to deep-sea mining, and it is not even clear that the minerals are actually needed. For example, in the electric vehicle (EV) industry, scaling up closed-loop battery recycling and enhancing battery efficiency can decrease the dependency on rare earth minerals. 

In fact, a number of manufacturers, including BMW, Google, Samsung, Volvo and many other companies even support a global moratorium on deep-sea mining. In fact, calls for a global moratorium on deep seabed mining have been growing.

Many of these companies have pledged not to source any minerals from the deep sea, and to refrain from using mineral resources from the deep sea in their supply chains and not to finance deep-sea mining activities. 

Another approach involves investing in more sustainable terrestrial mining practices to meet mineral demands without resorting to deep-sea exploitation. 

Promoting renewable energy technologies that require fewer critical minerals is also essential in alleviating pressure on deep-sea reserves. 

Lastly, focusing on research and development in eco-friendly mining techniques for land-based operations aims to minimize the environmental impact of mineral extraction. Adopting these alternatives presents opportunities for responsible resource management and ecological preservation.


Deep-sea mining presents opportunities for access to diverse metal resources and altering the geopolitical landscape. For example, Nauru, which hopes to offer commercial licenses for deep sea mining, has few other resources.

Proponents also argue that the industry's growth could create jobs and economic prospects, especially amid the accelerating energy transition.

However, deep-sea mining raises significant and unavoidable environmental questions. Its impact on marine ecosystems and on foods chains which humans rely on is uncertain and potentially devastating, and the lack of international agreement creates risks of irresponsible practices. These must be addressed in order to avoid what many researchers claim would be a cataclysmic destruction of the ocean ecosystem. In fact, there is now near universal

It is clear that responsible and sustainable practices, if not an outright ban, are vital to ensuring deep-sea mining has minimal environmental impact and contributes positively to resource demands.

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