This article was updated on July 31, 2023 to reflect the current status of the International Seabed Authority's ongoing deep-sea mining negotiations.

In the race to cut greenhouse gas emissions and rein in climate change, demand for critical minerals is booming. Materials such as lithium, cobalt and graphite are essential components of EV batteries, wind turbines, solar panels and other low-carbon technologies increasingly powering the world’s energy systems. Mining for these materials on land is already underway, but with demand surging, some are now looking to tap the seafloor for its millions of square kilometers of metal ores.

Indeed, some nations are already applying to the UN’s International Seabed Authority (ISA) for deep-sea mining exploration permits. But despite years of research, little is still known about the deep ocean, and many fear that extracting minerals from it could pose grave consequences for both marine life and planetary health.

After failing to reach an agreement in July 2023, the ISA now has until 2025 to finalize regulations that will dictate whether and how countries could pursue deep-sea mining in international waters. Formal discussions about its potential environmental impacts will kick off in 2024 and could help inform ISA’s decision. What will happen in the meantime remains unclear.

With the future of deep-sea mining still under debate, here’s what we know so far about the proposed practice and its impacts — and what we don’t:

1. What Is Deep-sea Mining and How Would It Be Done?

Deep-sea mining aims to retrieve valuable mineral deposits found on the ocean’s floor, hundreds or even thousands of meters below its surface. Alongside a diverse array of marine life at these depths are significant reserves of copper, cobalt, nickel, zinc, silver, gold and rare earth elements — materials that are essential to building zero-carbon energy components and other technologies but can be difficult to source.

In the deep sea, these minerals are contained within slow-forming, potato-sized polymetallic nodules, as well as in polymetallic sulphides (large deposits made up of sulphur compounds and other metals that form around hydrothermal vents) and metal-rich crusts on underwater mountains (seamounts). While there has been commercial interest in these minerals for decades, recent advancements in technology have made it possible to mine these areas by sending vehicles down to harvest mineral deposits from the seafloor.

Polymetallic nodules that look like small rocks on the floor of the deep sea.
Mineral nodules on the seafloor in the Clarion-Clipperton Zone, a key area of interest for deep-sea mining. Photo by ROV KIEL 6000/GEOMAR

In the case of polymetallic nodules — which are currently the primary focus for deep-sea mining — mining vehicles would collect mineral deposits from the surface of the seabed, not unlike a tractor plowing a field, along with the top layers of sediment. The materials collected would then be piped up to a surface vessel for processing and any waste, such as sediments and other organic materials, would be pumped back into the water column.

2. What’s the Current Status of Deep-sea Mining?

While exploratory mining to test equipment has occurred at a small scale, deep-sea mining has not yet been undertaken commercially. But some national governments and mining companies plan to begin as soon as possible, which could be in the next few years. What happens next will hinge on the ISA and how it decides to regulate deep-sea mining.

In 2021, the Pacific Island nation of Nauru notified the ISA of its plans to begin mining in international waters, triggering a contentious provision in the UN Convention on the Law of the Sea (UNCLOS) known as the “two-year rule.” The rule requires that, starting two years after the date of this notification, the ISA must "consider" and "provisionally approve" applications to mine — regardless of whether a final set of regulations has been agreed on. The two-year period elapsed in July 2023 and ISA’s ensuing meeting ended with no final rule in place. Now, its Council is working with a view to adopt regulations by 2025.

Members of the ISA Assembly (comprised of all 168 members) will also meet in 2024 and will likely discuss the potential impacts of seabed mining on the marine environment for the first time. Some hope these discussions will lead to a “precautionary pause” on mining activities while further research is conducted, although whether this will occur — and what could happen in the meantime — remains unclear.

While the ISA has two more years to establish a code for international waters, countries could still go ahead with mining projects in their own domestically controlled waters, known as “exclusive economic zones” (EEZs). In practice, though, many will be constrained by a lack of available funding and technical ability. There is also a great diversity of opinion on deep-sea mining among nation states with some, such as Nauru, leading the charge for exploration and extraction while others, such as Germany and Canada, have called for national and regional moratoria.

Countries may also be deterred from mining in their own EEZs because the bulk of the most attractive mineral deposits are found on vast seafloor abyssal plains in international waters. One area of particular interest is the Clarion-Clipperton Zone in the Pacific Ocean. This mineral-rich region already hosts exploration contracts for 17 deep-sea mining contractors, with their combined exploration areas covering approximately 1 million square kilometers (about the same size as Ethiopia).

Map showing where large reserves of critical minerals are located in the deep ocean, primarily in the Pacific.

3. What Are the Potential Benefits of Deep-sea Mining?

Proponents of deep-sea mining argue that it can help meet the world’s pressing need for critical minerals, which will likely only continue to grow as countries scale their decarbonization efforts. Estimates suggest that global demand for some such minerals could rise by as much as 400%-600% in the coming decades as the world increases its reliance on wind and solar power, electric vehicles, batteries and other zero-carbon technologies. Several studies have concluded that there is no shortage of mineral resources on land, but the world still faces significant hurdles in locating viable reserves and quickly scaling up mining and processing operations.

Some also view deep-sea mining as an alternative pathway that can circumvent certain risks associated with mining activities on land. Since extraction activities would occur exclusively at sea, deep-sea mining is unlikely to be associated with environmental hazards such as deforestation and freshwater pollution that can impact communities neighboring mines on land.

Similarly, the difficulty in accessing deep-sea mineral deposits for exploitation means that artisanal (small-scale) mining operations would be impossible and strong regulation of labor conditions may be feasible. This could potentially avoid the human rights abuses associated with some terrestrial mining operations. However, experiences of labor abuse in distant-water fishing operations show this outcome is not guaranteed.

4. What Are the Risks of Deep-sea Mining?

While the deep sea was once thought to be devoid of life — too dark, cold and starved of food for anything to survive — we now know that it is the largest habitable space on the planet and home to a dazzling array of life. To date, tens of thousands of species have been found in the deep ocean, with estimates that there could be millions more. In the Clarion-Clipperton Zone alone, a key area of interest for deep-sea mining, researchers have recently discovered over 5,000 species that were entirely new to science.

A bright pink starfish on the floor of the deep ocean among small, potato-shaped mineral nodules.
A starfish in a field of manganese nodules on the seafloor in the Clarion-Clipperton Zone. Thousands of previously unknown deep-sea species have already been discovered in this area, which some seek to mine for its mineral resources. Photo by ROV-Team/GEOMAR

With exploration and testing still in the early stages, further research is required to determine the possible ecological impacts of deep-sea mining. But the science to date paints a concerning picture.

  • Direct harm to marine life: There is a high likelihood that less mobile deep-sea organisms would be killed through direct contact with heavy mining equipment deployed on the seabed, and that organisms would be smothered and suffocated by the sediment plumes these machines are likely to create. Warm mining wastewater could also kill marine life through overheating and poisoning.
  • Long-term species and ecosystem disruption: Mining activities could impair the feeding and reproduction of deep-sea species through the creation of intense noise and light pollution in a naturally dark and silent environment. For example, the sound pollution from these activities could negatively impact large mega-fauna like whales, posing further risk to populations already strained by climate change and other human activities. Because many deep-sea species are rare, long-lived and slow to reproduce, and because polymetallic nodules (which may take millions of years to develop to a harvestable size) are an important habitat for deep-sea species, scientists are fairly certain that some species would face extinction from habitat removal due to mining, and that these ecosystems would require extremely long time periods to recover, if ever.
  • Possible impacts on fishing and food security: It’s not just the seafloor that’s at risk. Under current designs, waste discharge from mining vessels could spread over large distances, potentially kilometers away from the areas being mined. This may pose a threat to open ocean fish and invertebrates which are crucial to international fisheries — such as tuna stocks that help drive the economies of many small island developing states in the Pacific, including Kiribati, Vanuatu and the Marshall Islands. Effects of this mining waste could include suffocation, damaged respiratory and feeding structures, and disrupted visual communication within and amongst species, alongside changes in the oxygen content, pH, temperature and toxicity of seawater. However, more research is needed on the characteristics of the discharge plumes themselves and the tolerance of ocean species to fully understand these impacts.
  • Economic and social risks: While extraction would occur offshore, the deep-sea mining industry would still need shoreline facilities, whether for processing or transshipment of material. This would require land acquisition and development, which has historically driven habitat loss affecting coastal communities dependent on marine resources the most. And, though the UN has designated high-seas minerals “the common heritage of [hu]mankind” and declared that any mineral extraction should benefit all nations, the current regulatory regime of the ISA appears to promote the flow of mining profits to developed states, or to shareholders of mining companies, rather than being inclusive of developing nations.
  • Potential climate impacts: The ocean is the world’s largest carbon sink, absorbing around 25% of all carbon dioxide emissions. Microscopic organisms play a critical role in this climate-regulating system, helping to sequester carbon in the deep sea and reduce emissions of other planet-warming gases, such as methane, from seabed sediments. The loss of deep-sea biodiversity following mining activity may impact the ocean’s carbon cycle and reduce its ability to help mitigate global temperature rise.

5. Is Deep-sea Mining Necessary?

The global supply of critical minerals and rare earth elements must grow in the coming years, and quickly. But there is no easy answer to meeting this need, given the immature state and potential dangers of deep-sea mining and the well-understood harms associated with terrestrial mining. While mineral reserves on land appear sufficient to meet global needs, the world must address how to responsibly scale up mining and processing operations in a way that minimizes environmental and social risks.

Within the next 15-20 years, mineral recycling could become a viable alternative to mining for a large portion of material requirements. The World Bank estimates that if recycling rates for end-of-life batteries increase significantly by 2050, it could decrease the need for newly mined minerals by around one-quarter for copper, nickel and lithium and by about 15% for cobalt. However, in the short term (by 2030), there will not be enough of these minerals in circulation to make recycling a feasible approach.

Better recycling practices in established waste streams, such as from electronics and electrical equipment, can help alleviate some short-term supply pressure while preparing the secondary supply chain to handle a large volume of end-of-life zero-carbon energy products in the future. There is also a range of research efforts underway to obtain the necessary minerals without mining virgin land, including recovery from coal waste or hard rock mine tailings.

Finally, as battery technologies continue to evolve, it is possible that deep-sea mineral deposits will lose their attraction as alternative technologies not reliant on such minerals become more common. For instance, there is a growing shift away from nickel manganese cobalt oxides (NMC) batteries towards lithium iron phosphate (LFP) batteries, with LFP batteries gaining significant market share from 2015 to 2022; their key materials, lithium and iron, are not targets of deep-sea mining. Emerging technologies such as sodium-ion batteries also have the potential to alter the EV battery market by replacing lithium and cobalt with cheaper and more abundant options.

With Serious Questions Still Unanswered, What Comes Next?

In developing regulations for deep-sea mining, the ISA and other stakeholders have a rare opportunity to take a breath before taking the plunge. Rather than extracting resources first and addressing the consequences later, this is a chance to step back and consider the environmental and social implications of deep-sea mining before any activity gets underway. Any decision made should be rooted in evidence robust enough to ensure that no serious harm is done to people, nature or the climate.

In order to continue with the possibility of deep-sea mining, key questions and knowledge gaps should be addressed by the ISA, the mining industry, scientists and national governments:

  • What is the potential magnitude and extent (both in space and time) of deep-sea mining impacts on marine species and environments, and what are the likely ecological consequences?
  • What are the potential social and economic impacts of deep-sea mining? Is it possible for the industry to be advanced in a way that meets the UNCLOS goal of fostering sustainable economic development, international cooperation and equitable trade growth for all countries?
  • How can a circular mineral economy be further developed to lessen the need for environmentally intrusive practices? More research must be conducted into land-based and urban mining practices to improve their efficiency, as well as into improving product design to reduce demand for and increase recycling of critical minerals.
  • What are the possible positive and negative implications of deep-sea mining in achieving the UN Sustainable Development Goals, as well as for furthering research into deep-sea environments?
  • What regulations could be developed to ensure that the financial benefits from deep-sea mining operations, should they occur, are equitably distributed among nations?

Finally, for the exploration of deep-sea mineral resources to continue, regulations should be drafted in full and in transparent collaboration with interested parties and key stakeholders, including ISA members, mining corporations and scientists. These regulations should be backed by science and other forms of knowledge, be enforceable, and offer effective protection for delicate marine environments from the impacts of mining.