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Should we mine the deep sea floor before we discover its true treasures?

  • Written by  Katie Burton
  • Published in Oceans
Polymetallic nodules from 5000m depth of Pacific ocean Polymetallic nodules from 5000m depth of Pacific ocean [Shutterstock/V.Gordeev]
17 Feb
The ocean floor is home to rich deposits of metals and minerals crucial to the transition to net zero. But should we use them?

A hydrothermal vent is an inhospitable place; one of searing temperatures, toxic minerals and, if you’re unlucky enough to get near a black smoker, plumes of dark, sulfurous ‘smoke’. They form at the most volatile fissures of our planet, at the places deep beneath the ocean surface where two tectonic plates pull apart, making way for hot magma to rise, cool and form new crust. This crust isn’t perfect; seawater will find a way to percolate down through tiny cracks to the hot magma below. Here, as pressure builds unbearably, the intrepid seawater warms, dissolving minerals as it does so, before carrying them up again towards the surface. As these hot, mineral-rich waters finally emerge, hitting the cold ocean above, the vent minerals cool and solidify, and finally, a deep-sea hydrothermal vent is born.

It wouldn’t be unreasonable to assume that such places are dead lands, from which any sensible sea creature might flee. But as the scientists who first discovered these habitats, during a 1977 exploration of the Galpagos Rift in the eastern Pacific, found, life is much more extraordinary than we might think. Animals can survive in these places, all thanks to bacteria. In a process called chemosynthesis, these bacteria convert toxic vent minerals into usable forms of energy. In these darks places, devoid of sunlight and photosynthesising plants, you might find deep-sea bathymodiolus mussels, or giant tube worms with red-tipped ends clinging to the rocky vent surface. Crawling across them, you could spot a crustacean, perhaps Kiwa hirsuta, the ‘yeti crab’, so called for the blonde feathery hairs that cover its arms.

These creatures’ tolerance for extremes is remarkable, and upends much of our understanding about the requirements for life. And yet, many of these creatures and their habitats are now deemed officially endangered, and for one reason only: those toxic minerals and metals from which the creatures make their living are useful to a much more powerful animal – us.


Metals and minerals are essential for a net-zero world. Electric vehicle batteries require them, as do wind turbines and photovoltaic panels. Copper, nickel, gold, manganese, cobalt, chromium, molybdenum, zinc, lithium and rare earth metals all have a role to play. Today, we feed our requirements by terrestrial mining; digging into the deep-sea floor has long been considered too expensive to be worth the effort, despite the knowledge that rich deposits exist. However, there are signs that this could soon change.

Hydrothermal vents are one source of interest to prospective deep-sea miners due to their mineral-rich structures. Other potential sources include what are known as polymetallic nodules – loose lumps that can contain high concentrations of several valuable metals and which lie scattered over huge areas of the abyssal ocean floor – and layered, metal-rich chemical deposits known as ferromanganese crusts.

Reaching these deposits remains costly and risky, but states and private actors are, at least, examining the potential to do so. The International Seabed Authority (ISA), the international body responsible for managing the seafloor beyond national jurisdictions, has granted 31 exploratory deep-sea mining contracts, seven of them at hydrothermal vents. Most of the contracts are held by state-backed companies – including those linked to India, South Korea, the UK, China, Singapore, Poland, Russia and Japan as well as some smaller island states. According to an analysis carried out by Unearthed, Greenpeace’s investigative arm, Britain’s partnership with the company UK Seabed Resources holds licences to explore a total of 133,000 square kilometres of the Pacific sea floor, more than any government apart from China.

Bathymodiolus elongatus re4Bathymodiolus elongatus is a large species of deep sea mussel that grows to a length of about 20cm. These specimens were collected from Mussel Valley Hydrothermal Vent Field in the North Fiji Basin. Image: Chong Chen

Some countries are also displaying an interest in exploiting their territorial waters. In 2017, the Japanese government reported that its state-owned mining company had successfully extracted zinc from the seabed off the coast of Okinawa, a first-of-its-kind venture in waters of that depth (1,600 metres).

‘We’re not quite at the point of commercial exploitation, but there’s some indication that some are prepared to maybe take the leap in the next two to three years,’ says Richard Barnes, a professor of international law at the University of Lincoln, who has been closely following developments in this space. He explains that the ISA has, for many years, been developing a deep-seabed mining code that, once agreed, will determine how any mining takes place in the huge swaths of ocean outside state control. ‘The rulebook is in two parts: you’ve basically got the exploration or prospecting aspects of it and then you’ve got the exploitation side, which covers how mining takes place if it’s commercially viable, and subject to what rules. It’s got the first part done.’

The second part remains a work in progress. It was supposed to be finalised by 2020, putting in place a process whereby contractors could apply for 30- year licences to mine assigned ‘claim areas’, but delay followed delay. Now, however, things are on the move. Barnes explains that the ISA has been forced to speed up the drafting process at the behest of a venture being undertaken by a Canadian corporation called the Metals Company and sponsored by the tiny island state of Nauru, off the northeast coast of Australia. The somewhat unlikely partnership would see the company mine manganese nodules in the Pacific’s Clarion- Clipperton Zone.

‘In June 2021, Nauru initiated what’s called the two year rule,’ explains Barnes. ‘Basically, this starts the clock ticking and it requires the ISA to either have completed its mining code within two years, or to consider and decide any licences to exploit on the basis of what it has. So, two years from June, potentially, you’re going to have Nauru and the Metals Company pushing for a licence for deep-seabed mining activities.’

Whether such exploitation actually happens or not is still far from certain, even once the two years are up. The state of the market and the company’s finances will determine viability and, as Barnes notes, ‘it depends whether Nauru is willing to go out there, against probably a bit of a political backlash. Because if there isn’t a mining code in place, you’ve got mining potentially taking place in an even more destructive fashion than it might do under a tightly regulated code.’

Previous attempts may also serve as a warning. Another Canadian company’s mining venture in the waters off Papua New Guinea ran into well-publicised and significant trouble in 2019. As part of its Solwara 1 project, Nautilus Minerals aimed to mine deep-sea vents on the floor of the Bismarck Sea, but by September 2019 it was in administration, leaving sponsor Papua New Guinea down US$157 million. ‘Everyone from the scientific community, through to NGOs, through to other nation states were all urging a precautionary principle; a sense that you don’t know what you’re dealing with, so leave it alone,’ says John Childs, a senior lecturer in international development and natural resources at Lancaster University. ‘Nautilus basically went bust.’ On the Metals Company, he notes that ‘they’re certainly the noisiest of the commercial companies. But I would argue pretty strongly that they’re not particularly close to starting commercial operations.’

Nevertheless, he sees the ISA’s two-year limit to produce a code as ‘a huge shift. Because it’s not just people having a look, trying to map it out, see what’s down there, it’s actually with a view to digging this stuff up.’

NauruMeasuring just eight square miles, Nauru is an island country in Micronesia, northeast of Australia. Through a collaboration with a Canadian mining company it has shown interest in deep-sea mining. Image: Robert Szymanso

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For many marine biologists, the entire notion of deep-sea mining is nothing short of a disaster. The only way to sensibly mine the deep-sea floor, for now at least, is not to do it, they argue. Julia Sigwart is a senior lecturer at Queen’s University Belfast, who specialises in molluscs. She has become particularly well known for her work on one particular mollusc that lives on hydrothermal vents – the sea pangolin – which, in 2019, became the first species to be declared ‘endangered’ by the IUCN explicitly because of the risk of seabed mining.

The sea pangolin is no ordinary snail. From above, it may not look all that unusual, but underneath, its ‘foot’ splays out in a scaly, fringed skirt, constructed from hardened iron sulfides. Its tissues play host to the all-important bacteria that convert minerals into sustenance. It has been observed at just four hydrothermal vents in the Indian Ocean, each around 2.5 kilometres deep but covering a very small area. Even with undiscovered sites, the total habitat area available for the sea pangolin extends up to a potential maximum of 0.27 square kilometres. Today, all sites but one are covered by active mining exploration licenses, and none have any protection from deep-sea mining.

‘I’m not a conservation biologist by training – I fell into working with the Red List because it just seemed to me to be the right thing to do,’ says Sigwart. Her concern, which is echoed by many in the field (more than 622 marine scientists and policy makers recently signed a statement calling for a pause to deep-sea mining) isn’t just that the chimneys themselves could be destroyed, but that any mining activity nearby could impact them. ‘Hydrothermal vents are incredibly small and that’s the entire habitat for the individual animals that live there. If you’ve got mining activity going on even kilometres away, you can kick up a giant sediment plume that just comes along, smothers it completely.’ She isn’t comforted by the lack, or small scale, of commercial operations either. ‘Even under these exploration licences, the contractors are permitted to do test extraction for research and development,’ she says.

Environmental protection rules will form part of the ISA’s final mining code. But, as many people argue, how can you assess environmental impact when we simply don’t know what’s down there yet? ‘There are several huge issues,’ says Sebastian Unger, an ocean governance researcher at the Institute for Advanced Sustainability Studies (IASS) in Potsdam, which is an official observer organisation to the ISA. ‘One is the lack of ecological baselines. If you want to establish whether an activity is harming the environment, you need to establish baseline knowledge on the structure and function of the ecosystem prior to this activity taking place. In comparison to changes occurring after an activity has started, impacts can be determined. So far, environmental baseline studies by mining contractors and criteria for good baselines have not been published. This means accurate and independent scientific assessment is currently not possible. Disturbance experiments, however, have put up warning signs that the impacts to be expected may be large scale and long lasting.’

SEA PANGOLIN 2.psdGBChrysomallon squamiferum, also known as the sea pangolin. This specimen is 43mm long and was collected at a depth of 2,785 at the Longqi vent field, Southwest Indian Ridge in 2015. Image: Chong Chen

Sigwart and her team were able to get the sea pangolin categorised as endangered due to what the IUCN calls the ‘projected future threat’ of mining, and she thinks the importance of this move can’t be overstated. ‘It’s just a red flag to everyone,’ she says. ‘And especially for something that’s being driven by industry, I think that’s really important. Most companies recognise that sustainability is important to their shareholders.’ Her team is now expanding Red List assessments from the Indian Ocean to all species found in deep-sea hydrothermal vent habitats. And yet, while these are positive moves, she still feels that her voice, and those of other biologists, is going unheard. ‘There isn’t enough awareness. And I think part of the problem is that scientists have been caught a little bit on the backfoot. As a scientist working in deep-sea environments, I have a very good understanding of how challenging it is to sample the deep sea. It’s hard, it takes a lot of technology, it’s very expensive. And even a few years ago, my attitude was: this will never happen. But now, it feels much more like the commodities markets are driving in a direction where it’s not just speculation, it’s something that can and will be profitable, if we allow it to be.’

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There’s an obvious counter-argument that mining proponents use when it comes to the environmental impacts of future deep-sea mining: we need these minerals for the clean-tech revolution. The quality of ores on land are dropping, so which would you prefer – cause more destruction to humans and environments on land, or risk losing a few sea creatures?

The Metals Company makes this point in its financial literature and also points to potential supply-chain issues (China dominates supplies of many metals and minerals), as well as human rights and environmental abuses associated with terrestrial mining. Sigwart calls this a ‘false and lazy argument’. The real investment, she says, ‘should be in a circular economy. We need electronic components to be recycled – we do not need more components, we need better use of the components that we already have.’ The Royal Society of Chemistry is pushing for more recycling, pointing out that mobile phones contain at least 30 different naturally occurring elements.

Childs is less convinced that recycling of metals and minerals will ever be enough to meet demand, but he points to the uncertainty of that demand. Researchers and companies around the world are busy testing replacements for some common minerals and metals, or investigating ways to use less of specific metals and minerals without having an impact on performance. We can expect innovation in this field.

Critics in general argue that companies such as the Metals Company are creating a false sense of urgency. A 2020 study published in Nature by an international team of geoscientists noted that some earlier research suggested that primary metal supplies would be exhausted within about 50 years, but went on to state that they ‘will not run out on this timescale’. Some other important elements do exist in much tinier quantities, but, in general, the risk is more to do with extraction becoming prohibitively expensive or prohibitively damaging, rather than a total lack of resources. In short, we can expect to see the quality of already known ores decline as they are exploited, so extracting them may become more difficult. However, very few companies or governments are rushing to the ocean in a panic. Instead, most will, and already are, digging deeper and using new technology to find and extract more. Tellingly, some automobile manufacturers, including the BMW Group, Volvo and Google, have joined the call for a moratorium on deep-sea mining.

‘I see it as a mainly interest-driven argument,’ says Unger, in reference to the notion that we need deep-sea resources to reduce pressure from land-based mining. ‘At the end of the day, if the minerals get rare, let’s say in 20, 30, 40 years time, the next generation could still consider deep-sea mining. Starting mining now should not be on the table when the unequivocal demand has not been determined in view of the developing circular economy; the potential devastating effects of deep-sea mining on the marine environment cannot yet be evaluated; and the developing regulations and procedures of the ISA do not provide the precautionary approach needed to prevent harmful effects.’

shutterstock 1450763351A terrestrial mine in Huelva, Spain. This area along the Rio Tinto, in Andalusia has been mined for copper, silver, gold, and other minerals. Image: Luis Becerra


The ISA has a great deal on its plate. Aside from environmental concerns there is another huge aspect of the mining code yet to be concluded. The UN Convention of the Law of the Sea, under which the ISA operates, holds that the mineral resources of the deep seafloor are the ‘common heritage of mankind’ and the ISA is obliged to put in place rules to implement this principle for the benefit of humankind. For example, it is required to develop a payment mechanism in which revenues from commercial mining are partly shared with developing countries, even including landlocked countries. ‘That’s complicated to develop,’ says Unger. ‘There are many remaining issues, legal, economic and ethical. The question also remains whether there will be any substantial financial benefits left to be distributed after miners have taken their share, after the ISA has deduced its costs, and after the current land-based producers are compensated for eventual losses due to reduced market prices.’

Some observers are also worried that developing countries and small island states which have shown great interest in deep-sea mining, such as Nauru, are already taking on huge and disproportionate risks. ‘Any operator will probably have to provide some security and financial bonds as part of any licence, and if there is anything which goes wrong, it’s generally the operator who has to provide compensation,’ explains Richard Barnes. ‘But if the operator can’t, because it’s not financially solvent, then the fall-back position is that the state itself will have residual liability. Now, that works quite well when the host state has the potential to pay compensation. But what we’re seeing is operations being sponsored by Vanuatu, Tuvalu, Nauru and very poor states which might not have the resources to compensate when things go wrong. If you’ve got pollution or an oil leak in the deep seabed, the restoration costs of that might not be fully compensated for.’

‘At the moment, most concern relates to the deep sea environment, and rightly so,’ adds Unger. ‘But we also have to ask: What is the benefit for humankind? How is it being distributed?’


There’s a paradox at play when speaking to many observers of this field. On the one hand, there’s a great deal of scepticism about the commercial viability of prospective deep-sea mining operations. Many people say that existing proposals are unlikely to work. Most large investors remain unconvinced. And yet, the same people remain deeply concerned. Why? Because if it does happen, they fear disaster. ‘Really once this activity starts I think it will be very difficult for the ISA to intervene, as proponents may sign long-term contracts,’ says Unger. ‘I’m more concerned than optimistic at the moment, I have to say.’

When it comes to terrestrial mining, humanity has got many things very wrong. Environmental destruction, deforestation and child labour plague the sector. As we eye up the ocean floor, the last untouched wilderness on our planet, will things be different?

Subscribe to Geographical today for just £38 a year. Our monthly print magazine is packed full of cutting-edge stories and stunning photography, perfect for anyone fascinated by the world, its landscapes, people and cultures. From climate change and the environment, to scientific developments and global health, we cover a huge range of topics that span the globe. Plus, every issue includes book recommendations, infographics, maps and more!

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