The mining of the deep sea, at depths of 2,000 metres and greater, is increasingly being considered as a potential solution to the expected global shortage of so-called transition-critical’ raw materials needed for the manufacture of batteries and other technologies that will be key to meeting targets to reduce greenhouse gas emissions. Minerals like lithium, nickel, cobalt, manganese and graphite are essential components of most batteries used today. Rare earth elements (REEs) are needed for a range of technologies, including the engines of wind turbines. Demand for these minerals is increasing and will continue to do so in the race to meet net zero targets. The construction of an onshore wind farm, for example, requires nine times more mineral resources than a gas-fired power plant.

The mineral deposits of transition-critical materials on land are highly concentrated in just a few countries, making their global availability dependent on trade relationships and vulnerable to supply chain disruptions that may result from export restrictions, political instability or natural disasters. The need to diversify supply sources represents a strategic priority for many governments. A number of industry representativesresearch institutesspecialised companies and some governments have highlighted the opportunities that deep-sea mining could offer in the provision of transition-critical materials.

What mineral sources are there in the deep sea and how can they be accessed?

Supporters of deep-sea mining are particularly interested in ‘polymetallic nodules’, which can be found across vast areas of the abyssal plain (the deepest and flattest part of the ocean floor) at depths of 4,000 to 6,000 metres. Unlike terrestrial mineral deposits, one single deposit of nodules can provide access to multiple commodities. For example, one of four key regions, the Clarion–Clipperton Zone (CCZ), a 6 million square-kilometre stretch in the Pacific Ocean between Hawaii and the west coast of Mexico, is estimated to hold 21.1 billion dry tons of nodules containing manganese, nickel, copper and cobalt. Other sources of mineral deposits include seafloor massive sulphides, which can be mined around hydrothermal vents on the ocean floor; and the cobalt-rich ferromanganese crust which is rich in cobalt and found on underwater mountain ranges (see more in Table A2 of this report).

Nodules are loosely scattered on the seafloor, making them relatively easy to collect with dredging machines that are driven along the ocean floor and extract the nodules by sucking them up through a tube and pipe them to a vessel on the ocean surface.

What are the environmental impacts of seabed mining?

The deep sea is known to be the largest habitat for life on the planet, home to a vast variety of unique species and ecosystems and thus a wealth of biodiversity. Compared with on-land ecosystems, the deep sea is still poorly understood, with its high pressure, darkness and perpetual cold temperatures making this a challenging environment to access and study. As such it has been referred to as Earth’s ‘final frontier’. However, projects are underway to shine a light on deep sea ecosystems. For example, a 2024 study shows that nodules in the CCZ produce oxygen in the depths of the ocean, where photosynthesis cannot occur. This finding highlights the crucial role of nodules in creating oxygen that sustains life on the seafloor. Other studies suggest that the nodules and sediment contribute to a high habitat heterogeneity, which is the driving force of the CCZ’s megafaunal diversity (megafauna being organisms measuring more 1–4 cm and visible in photographs of the ocean floor). Research published in 2023 identified over 5,000 species not previously known to science in this region. 

The impacts of deep-sea mining are anticipated to extend beyond the mining area and have major and long-lasting consequences for animal life on the seabed and within the sediment. While the full extent of the impacts of deep-sea mining on this highly biodiverse environment is still uncertain, the following key impact drivers are already known:

Habitat removal: Probably the most obvious environmental impact of deep-sea mining is the removal of the nodules themselves, which likely changes the sediment’s geochemistry and causes many organisms to lose their habitat. As nodules grow only a few millimetres every million years, it is unlikely that certain species, especially sessile animals (those which attach themselves to rocks) would be able to recover from their removal.  

Sediment and plume disturbances: The extent to which plumes of fine sediment materials impact species abundance and diversity is not clear, despite much research and modelling, and largely depends on sediment resettlement patterns. However, it is known that the dispersion of fine sediments creates similar effects to air pollution on land, such as barriers to mobility and visualisation for organisms, likely decreasing their reproduction rates.

Water discharges and toxic compounds: Discharged dredging spoils, marine litter and cooling or ballast waters carried by marine vessels associated with mining all have impacts on ocean ecosystems. The mining process may also release toxic compounds that naturally occur on the ocean floor. During the extraction of nodules, streams of water are discharged at the seabed which can increase surrounding seawater temperatures and reduce oxygen levels. On the ocean surface, the minerals are separated, and dissolved metals and sediment are released back into the ocean. Midwater ecosystems, which play a key role in connecting the deep sea with shallow ecosystems, and in absorbing carbon from the atmosphere, are negatively affected by these discharges. For example, zooplanktonic species are destroyed and heavy metals are introduced into the ecosystem – which may contaminate seafood. As the ocean ecosystems between 200 and 1,000 metres’ depth are home to the largest stocks of fish, potential disruptions to sources of food for fish may pose a threat to over three billion people that rely on fish as a source of protein.

Noise pollution: Marine vessels generate noise on the ocean surface, while mining vehicles and related equipment generate noise at the deep-sea level. In the ocean environment sound travels faster than through air and across huge distances, providing an effective communication medium for ocean inhabitants, which are highly sensitive to acoustic changes. Noise from these sources and activity can thus interfere with communication between marine mammals.

Light pollution: Only about 1% of sunlight reaches ocean depths of 200 metres. Consequently, many organisms are adapted to the darkness and have reduced visual capacity. The artificial light used to control mining vehicles’ cameras and monitor the sites disturbs organisms with highly sensitive vision.

From environmental to economic impacts

These environmental impacts can lead to economic disruption in sectors that rely on marine ecosystems for important ecosystem services that directly and indirectly facilitate a wide range of economic activities. Small island developing states and other coastal countries can be disproportionately affected as they have a significant number of economic sectors that depend on marine ecosystems, including fisheries, maritime transport and tourism.

Despite these concerns, some governments have been interested in granting mining licences to harness the potential financial benefits from their sale. Discussions around a financial payment scheme have been ongoing for some time with the aim to develop rules for ‘equitable sharing’ of benefits. But it is still uncertain how they would be structured and the direct benefits from such schemes to countries are estimated to be economically insignificant.

The environmental impacts of mining the ocean could also cause serious disruption to those value chains and create conflict between different interest groups (such as tuna fisheries and subsea cable companies) – including at the international level, due to the transboundary nature of marine activities.

Further, it can be expected that competition will arise between companies operating terrestrial mines and those engaged in the mining of the deep sea on the cost, quantity and extraction time of critical minerals. These pressures can lead to diminished environmental and social protection, which is of particular concern given the lack of visibility and accessibility in the deep-sea environment.

What is the current status of deep-sea mining and its governance?

Most deep-sea mining is expected to take place in international waters, i.e. beyond the territorial waters of any country, where governance and enforcement of regulation depend on international agreements – and are currently lacking when it comes to deep-sea mining. Since its formation in 1994, following enforcement of the UN Convention on the Law of the Sea (UNCLOS), the International Seabed Authority (ISA) has had responsibility for developing rules, regulations and procedures associated with seabed minerals and the authority to oversee related developments in international waters. To date, the ISA has granted over 30 contracts allowing the exploration of around 1.5 million km2 of ocean floor for deep-sea mining.

The ISA has been under pressure to finalise and adopt regulations on deep-sea mining since June 2021. In 2023 the Council of the ISA published a roadmap on how it intends to draft exploitation regulations, planning to  adopt them in 2025.

How are different parties responding to the possibility of deep-sea mining?

A growing number of governments have taken a public stance to voice their concerns around deep-sea mining. Since the launch in June 2022 of the Alliance of Countries Calling for a Deep-Sea Mining Moratorium by the Government of Palau, with Fiji, the Federated States of Micronesia and Samoa, several developed and developing countries have joined the Alliance, but with slightly different demands. Some demand a moratorium on deep-sea mining (e.g. Canada and New Zealand); others are calling for a ‘precautionary pause’ to provide more time for scientific research and establish environmental standards (e.g. Chile and Vanuatu).

More than 50 companies (including car manufacturers BMW Group, Volkswagen and Volvo, and tech companies Google, Apple and Samsung SDI) have signed a business statement outlining their support for a moratorium. And a growing number of financial institutions and insurance companies are becoming wary of the reputational, regulatory and operational risks associated with deep-sea mining and the financial risks associated with a volatile metals market.

As concerns about deep-sea mining grow, there is increased attention on the need for recycling programmes and technological innovation for the production of less resource-intensive products.

The growing demand for transition-critical minerals needed to achieve net zero, combined with the environmentalsocialgeopolitical and supply-related challenges associated with further exploitation of terrestrial sources, means that the debate around deep-sea mining will continue for the foreseeable future.

This Explainer was written by Lea Reitmeier with review by Simon Dikau, Darian McBain and Francisco de Melo Viríssimo and editing by Natalie Pearson and Georgina Kyriacou. It was first published in July 2023 and updated by Lea Reitmeier in September 2024.

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