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A range of human activities pose a risk to life in, and the health of, the deep sea. Key among these are deep-sea fishing, the possible start of deep-sea mining, and a range of geoengineering plans proposed as solutions to the climate crisis that could impact deep ocean areas

The principal drivers of threats to the deep sea are the same across all these activities: governments prioritizing exploitation over ocean protection, failure to honor commitments, lack of transparency, and inadequately regulated exploitation and extraction. Many of these problems are rooted in the fundamental flaws of the current global economic model, where short-term gains for the powerful few override longer-term benefits for the many. Both individually and collectively, these failures are allowing and enabling the degradation of vulnerable deep-sea ecosystems.

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The DSCC addresses these drivers by holding governments and industry to account against their commitments, obligations and responsibilities, and by supporting the reform of deep-sea governance and policy frameworks. Our goal is to achieve ambitious, effective deep ocean protection.

Deep-sea mining to source metals including nickel, manganese, cobalt and copper could result in one of the largest impacts of any industrial activity on our planet. There is widespread concern about the potential threats to the ecosystems and habitats of the deep if mining is allowed to go ahead. Increasingly urgent questions are being asked about whether deep-sea mining is necessary, desirable, or economically viable.

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Deep-sea mining is still in the experimental stage and its possible impacts on the deep ocean remain largely unknown. But existing information and observations from exploratory deep-sea mining are leading scientists to warn that biodiversity loss would be inevitable, extensive, and most likely irreversible. Deep-sea mining would also disturb our planet’s largest carbon sink during the global climate emergency.

There is currently no evidence that the marine environment can be effectively protected from the harmful effects of deep-sea mining. Allowing this destructive new industry to go ahead is therefore inconsistent with the international community’s environmental protection obligations under the United Nations Convention on the Law of the Sea (UNCLOS).

Three types of deep-sea mining are currently envisaged. On the abyssal plains, deep-sea mining targeting polymetallic nodules would involve strip-mining the seabed. Depending on the method employed, this process would remove or disturb the top 6-20 centimeters of the seafloor sediment, leading to the potential extinction of species living on or within it. The nodules themselves support complex ecosystems that would be entirely lost, causing species to go extinct. Each mining operation would effectively devastate 8,000–9,000 square kilometers of deep ocean seabed over a 30-year license period. 

Similarly, stripping seamounts of their outer layer of crusts – to extract cobalt and other metals – would destroy critical deep-sea habitat and all life that depends on it, such as deep-sea sponge and cold-water coral ecosystems that can take thousands of years to grow.

Finally, mining hydrothermal vents would destroy habitats and kill the organisms that live there before we have had the chance to study the biodiversity of these unique and fragile ecosystems.

Beyond the immediate direct impacts on mined ecosystems, there would also likely be wider consequences:

  • As collector vehicles mine the seafloor, sediments would be resuspended, creating plumes which could disperse over tens to hundreds of kilometers beyond mining sites. These sediment plumes would smother suspension feeders such as cold-water corals and sponges on the seafloor adjacent to mining areas – however, the full potential extent of impacts is unknown as there is limited scientific data on the effect of plumes on individual species and ecosystems. 
  • The discharge of wastewaters containing seawater, sediment and mine tailings (or mining “fines”) back into the ocean would form mid-water plumes that could travel hundreds of kilometers. These plumes would cloud the water column, would affect filter-feeding organisms, and could introduce toxic concentrations of metals to marine food webs.
  • Noise, light pollution and sediment plumes could seriously impact species – including whales – that use sound, echolocation or bioluminescence to communicate, find prey and escape predators.
  • Marine sediments are a huge and globally important carbon store, with much of this carbon locked away in the deep sea where it can remain for millenia. Deep-sea mining could disrupt the natural processes that transport carbon from the surface to the seafloor, and disturb carbon-rich sediments, impacting the deep sea’s role in ocean carbon cycling and storage.




Deep-sea mining is also expensive. Although it may one day be profitable to individual companies (all currently registered in the Global North), questions are being raised about deep-sea mining’s wider economic benefits and to whom they would accrue. The International Seabed Authority (ISA) is required under UNCLOS to ensure that the exploration and exploitation of international areas of the ocean “be carried out for the benefit of (hu)mankind as a whole.” That means the ISA should only license mining in areas of the seabed beyond national jurisdiction if it will benefit humankind. However, recent calculations suggest that the annual royalties that would be collected by the ISA for each mining license would only amount to a few hundred thousand US dollars for each ISA Member State. Much of the wealth would go into the pockets of mining companies. Deep-sea mining is a risky business. Some analysts are warning that it is also a bad investment based on dubious economics. Papua New Guinea lost over US$ 100 million of its investment in deep-sea mining in its national waters. The government of Papua New Guinea is now concerned about the environmental implications of deep-sea mining, and in 2019 it called for a moratorium on deep-sea mining in its own waters. 

Due to the risk of irreversible ecosystem loss and the destruction of invaluable carbon storage, in June 2022 the UN Environment Programme’s Finance Initiative (UNEP-FI) published a briefing paper stating that the financing of deep-sea mining activities is not consistent with the Sustainable Blue Economy Finance Principles. Mounting concerns about the environmental and financial risks associated with deep-sea mining have led to a growing number of businesses, banks and financial institutions to opt out of investing in the industry, and instead joining the call for a moratorium.



Deep-sea mining poses a threat to communities who rely on a healthy ocean, not only for their livelihoods and immediate survival, but also due to a deep spiritual and cultural connection. Indigenous Peoples across the Pacific Ocean, for example, sustain a different relationship with the natural world from that of the West and see the deep sea as a sacred place for creation. The deep sea illustrates and explains the histories and cultures of those before us. The potential destruction of tangible and intangible cultural heritage by deep-sea mining continues an ongoing legacy of colonialism, through cultural erasure and the continuous drive for profit from imperial powers.  

To find out more about the governments and other stakeholders calling for a moratorium, click here.

The 2015  United Nations World Ocean Assessment found that bottom trawling has caused widespread, long-term destruction to deep-sea environments globally. The damage caused by deep-water trawl fisheries has led to pervasive concern about the conservation of fragile seabed habitats.


The World Ocean Assessment stated that it may take “centuries to millennia” for deep-sea ecosystems to recover from the impact of bottom trawling. It also reported that the “vast majority of deep-water fisheries have been carried out unsustainably … This has led to the serial depletion of dozens of stocks.” Notable species targeted by deep-sea fisheries include orange roughy and roundnose grenadier, which grow and reproduce extremely slowly, making them especially vulnerable.

The threat posed to deep-sea biodiversity by destructive deep-sea fishing is comparable to the devastation of tropical rainforests on land. Thousands of species are at risk, most of them still unknown to science and many not existing anywhere else on Earth.

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Fragile deep-sea ecosystems such as seamounts, oceanic ridge systems, and ecosystems where cold-water corals and deep-sea sponges provide a rich habitat for many other species are especially at risk from deep-sea fishing.

These ecosystems stand no chance against the ruthlessly effective “bulldozers” dragged by bottom trawlers, and they can also be impacted by deep-sea longline fisheries. Deep-sea bottom trawling is an especially indiscriminate fishing method, with high bycatch and discard rates compared to other types of fishing gear. Many species, including some that are highly endangered, are accidentally caught and thrown back into the sea dead. After heavy trawling, coral ecosystems on seamounts are reduced to bare rock and coral rubble.

The extensive and well-documented impacts of deep-sea fishing include:

  • Indiscriminate physical damage to deep-sea habitats and the species that live there, including many that are fragile, long-lived, and endemic to specific deep ocean areas. This loss/damage of biogenic habitat extends far beyond the areas actually being trawled.
  • The removal of benthic fauna, significantly reducing deep-sea biodiversity and abundance.
  • High levels of bycatch, including sensitive VME-indicator species like corals and sponges which have very slow rates of recovery. Populations of deep-sea species may take decades to centuries to recover even after fishing has ceased.
  • Disturbance, erosion and degradation of carbon-rich seabed sediments. Bottom trawling may emit some 1.5 billion tons of aqueous carbon dioxide (CO2) annually, according to a recent study; however, these rates are debated, and further research will provide more precise figures.
  • Damage to deep-water communities has been recorded across the global ocean, including off both coasts of North America; off Europe from Scandinavia to northern Spain; on seamounts in the Northwest Pacific to the north and west of Hawaii; around New Zealand and Australia; and across the Southwest Pacific and Southern Indian Ocean.

As the search for solutions to the climate crisis intensifies, governments, industry and scientists are looking increasingly to the ocean. As a result, several “ocean-based climate interventions” are currently being developed that propose deploying geoengineering manipulations and technologies to remove and store CO2, manage solar radiation, or generate renewable energy. 

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Many of the geoengineering solutions being considered would involve the large-scale transfer of particles, organic matter or CO2 into the deep ocean. Even the proposed interventions that focus on the surface layers, such as raising ocean albedo to reflect more heat, would impact the deep sea due to connectivity through the water column. Scientists are concerned that manipulating the ocean to mitigate climate change could present new and currently unknown biogeochemical threats to deep-sea ecosystems. The proposed geoengineering climate solutions also raise serious unresolved questions related to governance, cost, effectiveness, and social license. 

Carbon capture and storage technologies are among the geoengineering solutions being cited as essential tools for addressing the climate emergency. The Synthesis Report released by the Intergovernmental Panel on Climate Change (IPCC) in March 2023 asserts that carbon capture and storage will need to be deployed at a large scale well before 2050 to achieve the global 1.5 °C target. G7 leaders also called for the “deployment of carbon dioxide removal (CDR) processes with robust social and environmental safeguards” in their May 2023 Summit Communiqué. However, the potential for ocean-based carbon capture and storage technologies to make a meaningful contribution to the long-term storage of CO2 is unknown.  

Two methods of carbon capture and storage currently under development are the injection of CO2 into deep-sea sediments and the injection of CO2 into the water column of the deep sea. Scientists are already warning us about the risks associated with deep-sea carbon capture and storage technologies, and the large gaps in our knowledge about the potential environmental, social and economic consequences. 

Questions being raised about the desirability, efficacy and risks of deep-sea carbon capture and storage include:

  • How would deep-sea species and ecosystems be affected by the changes to seawater chemistry caused by CO2 injection? Scientists warn that elevated CO2 levels could lead to lower pH levels, reduced rates of calcification, growth and reproduction impairment, reduced circulation of oxygen supply and mobility, and increased mortality. 
  • How would deep-sea species react or adapt to the changes? Deep-sea CO2 injection in particular has been found to have lethal effects on the microscopic life of marine sediments. Even small changes in environmental conditions are expected to cause long-term damage, as deep-sea organisms have adapted to live in highly stable conditions. We do not currently know enough to fully predict what the impact on deep-sea life could be.
  • Is CO2 sequestration in the deep ocean a viable method of long-term carbon removal?  CO2 stored in the water column of the deep-sea risks being brought back to the surface via ocean circulation over the course of hundreds of years, meaning it is unlikely to remove carbon on a millennial time scale. Seabed storage is believed to be a more stable option, but there is a risk that CO2 could escape through faults or fractures in the sediment or due to excessive injection. This could also pose a threat to seabed ecosystems.
  • What are the cost, equity and justice implications? The cost of deep ocean carbon capture and storage is predicted to be comparable to or greater than geological storage. When the full life-cycle costs are factored in, these technologies may be found to have a limited value as a tool for achieving net zero. Environmental justice advocates have long opposed technology-based carbon capture and storage solutions, as they are unlikely to benefit – and may pose risks to – communities.
  • Conversations about carbon capture and storage and other geoengineering climate solutions are growing louder, but so are public concerns about their uncertainties and risks. There is currently no social license for embarking on ocean geoengineering technologies. In June 2023, Hoesung Lee, chair of the IPCC, warned that using technologies that capture CO2 or remove it from the atmosphere was “no free lunch” and that countries should be wary. Furthermore, he noted that over-reliance on carbon capture and storage technology could mean the world misses the 1.5 °C target.


The DSCC is calling for a precautionary approach to geoengineering climate solutions until the environmental, social and economic risks are comprehensively understood.

Find out more about the work the DSCC is doing to advance solutions that remove or mitigate key threats to the deep sea and protect its precious living resources.