Ethny Childs
February 2024

#IESTurningTheTide - Examining the impacts of deep-sea mining

View of the ocean from below with a light source coming from above

As part of our UN Ocean Decade endorsed #IESTurningTheTide project, we have been exploring topical issues related to marine conservation and restoration and the sustainable blue economy through dedicated events and online articles. As part of our blue economy theme, we held a forum focused on understanding the potential impacts of deep-sea mining on marine environments featuring speakers from the iAtlantic Programme: Prof. Murray Roberts, iAtlantic coordinator and Professor of Applied Marine Biology and Ecology at the University of Edinburgh, Dr. Marina Carreiro Silva, Co-lead of the Azores Deep-sea Ecology research group at the Okeanos Institute of the University of the Azores, Portugal, Prof. Andrew K. Sweetman, Leader of the Seafloor Ecology and Biogeochemistry research group at the Scottish Association for Marine Science, and Matthew Gianni, Co-Founder and Policy Advisor of the Deep-Sea Conservation Coalition. This article summarises some of the key discussions from the event.

The current state of marine environments 

The marine environment is experiencing rapid environmental change from a number of human activities, ranging from pollution to destructive fishing practices to climate change. As well as ocean warming, climate change is having, and will have, a number of important knock-on effects such as ocean acidification and deoxygenation, with all these factors driving further changes in how food is produced in the upper ocean and transferred to the deep seabed. There has been increased focus on the need for protecting marine environments from anthropogenic pressures, such as through the dedicated day at COP28 for Nature, Land Use and the Oceans and the Biodiversity Beyond National Jurisdiction “High Seas” Treaty agreed in March 2023

Marine ecosystems are not only experiencing the deleterious impacts of these stressors but are also having to contend with the cumulative impacts of these, affecting their health, resilience, and ability to provide vital ecosystem services. It is therefore important that the potential impact of additional stressors, and their cumulative impact, are considered to ensure that marine flora and fauna are effectively protected. 

What's behind the focus on deep-sea mining? 

The need for a net zero transition to mitigate against the worst impacts of climate change has led to an explosion in demand for certain minerals that are needed for technologies critical for the net zero transition, such as nickel, cobalt and manganese for electric vehicle car batteries. However, terrestrial mining for minerals is seeing declining ore grades, meaning less mineral ore is being extracted from the same amount of rock mined. This is leading to concerns around how the demand for minerals will be met through terrestrial mining alone and has led to increasing interest in mineral-rich clusters in the deep ocean. At the same time, electric vehicle manufacturers are increasingly developing and employing batteries that do not require high cost metals such as cobalt and nickel found in the deep sea.  


Table 1. Types of mineral-rich clusters in the deep ocean
Cluster type Area found Minerals of interest
Polymetallic nodules Deep abyssal plains Mn, Ni, Cu, Co
Polymetallic sulfides Hydrothermal vent fields Au, Ag, Cu, Zn
Cobalt crusts Sides/flanks of seamounts Fe, Mn, Co, Cu


Researchers in the iAtlantic project are undertaking detailed research into the potential effects of deep-sea mining on ecosystems both in the water column (pelagic zone) and at the seafloor (benthic zone). As climate change is a significant factor in today’s changing ocean, their research also takes into account the synergistic and potentially cumulative effects of ocean warming and acidification on ecosystems coming under stress from mining activities. Their research is currently ongoing and further findings will be released when published.

What is iAtlantic?

iAtlantic is a multidisciplinary research programme seeking to assess the health of deep-sea and open-ocean ecosystems across the full span of the Atlantic Ocean. The programme is a large consortium with ~188 scientists working on related projects. iAtlantic has five key objectives

  1. Align and standardise ocean observing in the north and south Atlantic to enable short, medium and long-term assessment of ocean circulation
  2. Build and enhance human and technological capacities for cost-effective cooperation and planning across the Atlantic
  3. Map deep and open-ocean Atlantic ecosystems at local, regional and basic scales
  4. Work with industry, regulatory and governmental stakeholders to use this knowledge in support of a sustainable blue economy
  5. Assess the stability, vulnerability and tipping points of these ecosystems in relation to a range of stressors 

Exploring the environmental impacts of deep-sea mining 

Deep-sea mining will have many impacts on marine ecosystems, ranging from pelagic to benthic habitats. Benthic environments will be affected in two key ways: the physical destruction of the seabed by mining practices and the generation of sediment plumes of fine particulate matter. Effects will not only be localised; modelling studies have shown that deep-sea mining may generate plumes with environmentally significant sediment concentrations covering distances of 150 km2, equivalent to 10,000 football fields. 

Impacts of deep-sea mining on cold-water corals 

Cold-water corals live in deep, dark waters and provide crucial habitats for a multitude of species, including invertebrates and many commercially important fish species.

Mining activities will occur in tandem with ocean warming, acidification, deoxygenation, and likely reduced food supply driven by climate change. Research is being done to explore how these changes will interact with mining activities to influence the resilience and recovery capacity of deep-sea ecosystems and species, like cold-water corals. Initial research is showing that even small concentrations of polymetallic sulfide particles found in sediment plumes from deep-sea mining can have lethal effects on cold-water corals, with particular sensitivity shown at the larval stages. More research is needed to determine thresholds of sediment concentrations and the recovery capacity of organisms after a plume event. 

Impacts of deep-sea mining on pelagic species

Mining activities in the deep sea may result in the production of sediment plumes that travel far through the pelagic zone (water column) of the ocean. This is an area in which many ecologically important marine animals live, feed, and travel through. Research into the impacts of sediment plumes on a robust deep-sea jellyfish have shown that plumes can trigger a stress response and lead to significant health decline. This provides an insight into the potential impacts of deep-sea mining on marine species in the pelagic zone and indicates that mining may have implications for a wide range of species and habitats. 

The Clarion Clipperton Zone (CCZ) is of particular interest for deep-sea mining, with estimates that the total amount of metallic nodules equates to over 21 billion tonnes, meaning that there is enough to fuel societies' demands for critical metals for decades. However, seabed mining activities in this area are governed by the International Seabed Authority (ISA) and there is considerable debate amongst the member countries of the ISA as to how much, if any, seabed mining should be permitted by the ISA in the CCZ, and how the industry could be regulated to ‘ensure the effective protection’ of the marine environment as required under international law given the many gaps in baseline information and scientific knowledge of the species and ecosystems in the area and uncertainties over the potential environmental impacts. 

What is the current state of play for deep sea mining?

The ISA established under the 1982 UN Convention on the Law of the Sea (UNCLOS), governs deep-sea mining in international seabed areas, with no mining allowed without their permission. There are several principles set out around international deep-sea mining, for example all nations must benefit financially from the ISA charging royalty fees for mining licenses, all countries must have equal opportunities to mine, and mining must be managed to ensure effective protection of the marine environment and the prevention of damage to the flora and fauna of the marine environment.

At the time of writing (February 2024), three ISA exploration licenses have been granted for polymetallic sulfides in the Atlantic, for France, Russia and Poland. The majority of the commercial interest in deep-sea mining in international waters currently lies in mining polymetallic nodules in the deep abyssal plains of the Clarion Clipperton Zone (CCZ) in the eastern Pacific, where the ISA has issued 17 exploration contracts to date. 

In addition to concerns over loss of biodiversity and the broader environmental impacts of deep-sea mining, there are concerns around the structure of the ISA, particularly around the transparency of contracts, incentives for deep-sea mining through “use it or lose it” clauses and monopolisation due to the small number of countries/organisations currently holding most of the exploration licenses. Moreover, the concept that all countries should have equal opportunities to seabed mine and benefit financially from deep-sea mining activity licensed by the ISA means that the potential financial benefit for each signatory will be very modest. 

Find out more and view Matthew Gianni's presentation slides

Is deep-sea mining necessary?

Despite the interest in deep-sea mineral clusters, it has been estimated that their potential to contribute to the demand for transition critical minerals is only minor. Over a 30-year license period, it is estimated that each mine in the CCZ producing a projected ~3 million metric tons of nodules mined per year (dry weight) equates to only approximately 0.14% of Cu, 1.1% of Ni and 3.2% Co per year above terrestrially mined supplies in 2022. 

Research has indicated that the net zero transition can be done without deep-sea mining. Alternative technologies, substitute materials, recycling and better management of terrestrial mining could all prevent the need for supplementation of minerals from deep-sea mining. Next generation batteries are already in production/planned that don’t require minerals from the deep-sea. 

The detrimental impacts of mining on ecosystems, fisheries, migratory species, and the biological carbon pump could be severe. It has been estimated that in the CCZ, half of species discovered to date depend on polymetallic nodules to survive and they are likely to take millions of years to recover. 

For this reason, there is growing support for a moratorium on deep-sea mining and the UNEP Sustainable Blue Economy Finance Initiative argued that it is not compatible with a sustainable blue economy.

What next?

Our Turning the Tide project is continuing its final theme of marine conservation and restoration including blogs, roundtables and webinars. Join the dedicated mailing list to keep informed on the project. If you are interested in getting involved please get in touch with Jo Maniscalco (, Communities & Membership Engagement Officer at the IES. 

Ways to get involved