Deep-sea mining: beyond the headlines
A decade ago I used to think deep-sea mining was a fairly straightforward issue. But I've come to realise how it is a complex topic, particularly in its wider context, which doesn't lend itself well to media soundbites.
It's the end of another annual meeting of the International Seabed Authority, and consequently a time when deep-sea mining is in the news again.
As my research investigates the ecology of some of the habitats being targeted for potential deep-sea mining (including work specifically to understand some of its likely impacts), I often get asked about it by news outlets.
Perhaps unsurprisingly, I think the reality of deep-sea mining lies somewhere between some of the investor-attracting promises of the industry, and the predictions of certain catastrophe by some NGOs.
So here's an attempt to set out the issues as I see them. It's a long article (more than 8000 words, which is probably ~25 minutes of reading time), as there is a lot to consider for a fuller perspective. I don't apologise for that (it took me a lot longer to write than it will for you to read it), but I hope it is digestible.
Disclaimer
I don't receive, and have never received, any funding from mining companies - and nor do I receive, or have ever received, any funding from NGOs that are opposed to deep-sea mining (my research is publicly funded through grant proposals to the UK's science funding agency).
I have colleagues for whom each of those conditions apply - and in some cases both - and personally I don't think it affects the objectivity of their research at all. But just to be clear here for anyone who does get concerned about such things.
A further caveat: I will turn out to be wrong about some of the things here. In some cases, that's because the details span areas beyond my own particular field of research (though I have tried to include links to sources where relevant - and I will try to correct the text when I become aware of errors).
But even within my field, I expect it too: finding out that your perspective or understanding of something is incomplete or incorrect is how science progresses (and relies on being prepared to change your view based on further evidence). So I'm used to that - and this article is an attempt to summarise my current understanding.
What's at stake?
First of all, what's driving an interest in mining mineral resources on the ocean floor? It's not only capitalist greed, though undoubtedly those involved hope to become wealthier as a result.
We need more metals than we currently have for the "green transition": the replacement of our current energy infrastructure that produces greenhouse gas emissions (from burning oil, gas, coal etc) with zero-emission energy infrastructure based primarily on renewable sources (wind, solar etc).
That's not to say those metals have to come from the deep ocean - I'll come back to that - but first let's consider why we need the green transition.
Without that new energy infrastructure, we won't achieve the "net zero" goal that many countries have committed to reaching by 2050, to try to keep global warming as close to 1.5 degrees C as possible.
Right now we're at about 1.1 degrees C of global warming compared with pre-industrial times, and we're currently on course towards 2.7 degrees C of warming (i.e. hugely overshooting the 1.5-degree target).
Why have countries agreed a goal of trying to limit warming to 1.5 degrees C?
The impacts of 2 degrees C of warming, for example, are proportionally far greater than 1.5 degrees C. Hitting 2 degrees C rather than keeping to 1.5 degrees C would expose 420 million more people to extreme heatwaves, and expose 61 million more people in urban areas to severe droughts. And 2 degrees C of warming also causes much greater impacts on ecosystems and biodiversity, as conditions change in habitats, with knock-on effects for food production.
That's 2 degrees compared with 1.5 degrees (a 0.5 degree difference in warming) - and to reiterate, we're currently on course for 2.7 degrees of warming (i.e. another 0.7 degrees on top of that...).
In short, keeping global warming as close as possible to 1.5 degrees C would prevent the deaths of several million people (the IPCC projects 250 000 excess deaths per year from climate change by 2050). Let that sink in: death on a scale comparable with the worst deliberate genocides in history, but which we could avoid by taking robust action now.
And there's the further impact that has on global society, through migration of people trying to survive, and ensuing geopolitical turmoil. Plus the more severe global impacts on biodiversity - for example, shallow-water coral reefs that provide a home for perhaps a quarter of the species in the ocean are likely to be largely wiped out at 2 degrees C of warming, compared with 1.5 degrees C.
So that's what's at stake, and why we need more metals.
Which metals do we need - and how much of them?
Low-carbon or zero-emission technology depends on lots of different of metals: for example copper (for anything conducting electricity); lithium (for batteries); and some "Rare Earth Elements" (such as neodynium and dysprosium in magnets, needed for electric motors and wind turbines).
Here's a 2022 list of "critical minerals" produced by the US Geological Survey, and here's a report on the need for some Rare Earth Elements in "green tech".
The need/demand for some elements is changing, however, as technology changes. For example, most existing EVs (electric vehicles) have Nickel-Manganese-Cobalt (NMC) batteries, but the new types of EV batteries have different chemistries using less cobalt and nickel where possible (e.g. "Lithium Iron Phosphate", aka LFP, which is now supplying 40 percent of EV battery demand). But some remain in demand regardless (e.g. lithium is still required for those next-gen EV batteries, even if cobalt and nickel are not), and some will see increases in demand. General Motors, for example, is planning to use new Lithium-Manganese-Rich (LMR) batteries for many of its vehicles by 2030, which contain 65% manganese compared with 10% in the older Nickel-Manganese-Cobalt batteries.
Regardless of fluctuations in metals used in EV batteries, let's consider copper as an example of overall metal demand (as "humanity's first and most important future metal"): we need copper in the technology that generates electricity from renewable sources, and we need copper for the infrastructure that carries that electricity to where it is used, and we need copper in all the devices that use the electricity.
Unlike some other metals such as cobalt, the demand for copper isn't going to change with new technology - because of its electricity-conducting properties (a laws-of-physics limitation), it is fundamental to all technology, as far as I'm aware.
Offshore wind, for example, needs ~8 tonnes of copper per megawatt of generating capacity, in the turbines generating the power and the infrastructure delivering it to the grid ashore. Onshore wind needs ~2.9 tonnes per MW, and solar photovoltaics need ~2.8 tonnes per MW. Coal and natural gas power generation, in comparison, need ~1.1 tonnes of copper per MW of generating capacity.
To change all the internal-combustion-engine (ICE) vehicles currently on the UK's roads to battery electric vehicles (BEVs) requires ~2.3 million tonnes of copper (a typical ICE car contains ~23 kg of copper, while a similar-size BEV car contains ~53 kg of copper).
(Those data are from two recent research papers by Richard Herrington at the Natural History Museum, which are utterly recommended reading to understand this topic: "Mining our green future" [2021] and "The raw material challenge of creating a green economy" [2024] - and for any journalists wanting to understand the wider context of deep-sea mining for their audiences, Richard is definitely a good person to talk to).
As a result, the demand for copper (as one example) to achieve the "green transition" is huge. A May 2024 report published by the International Energy Forum predicts that we will need as much copper in the next thirty years as we have mined in all of human history so far, and a 2025 report predicts a shortfall of 30% between the global supply of copper and demand for it by 2030, potentially slowing the transition to low-carbon infrastructure.
It's also worth noting that individual metals often aren't mined in isolation - many of them occur as "companion" metals. Cobalt is a good example - it occurs with copper, and with nickel, and so many "cobalt mines" are actually primarily copper or nickel mines, where cobalt is also being extracted as a companion metal. About 60 percent of the current global supply of cobalt comes from copper mines in the Democratic Republic of Congo.
Why can't we get the metals we need from recycling?
It would be great it we could just recycle the copper and other metals we're currently using to meet that demand, but unfortunately we can't. For copper, recycling can meet about 30 percent of current (not future) demand. There isn't enough currently in circulation, and we would have to wait for whatever is using the copper to come to the end of its operational life before it becomes available. And to hit net zero by 2050 and thereby try to limit warming to 1.5 degrees, we need to be building new energy infrastructure as quickly as possible.
We need to improve the efficiency of recycling, but can't wait for that either. We're getting better at recycling some metals - here's a 2024 report by the International Energy Agency. If we continue to improve, recycling could meet 25 to 40 percent of the metal requirements to achieve the net-zero transition by 2050 - but we still need more mining for that transition.
So the hope is that during a "dash for metals" to achieve the green transition, we also get better at recycling overall, so that recycling can then help to meet demand beyond the transition.
But recycling alone can't get us through the transition - and in the case of copper as an example, we need to mine more of it as a result.
Where do we want to mine?
Staying with copper as an example, the question then is: where do we want to mine the copper that we need for the green transition?
And this is where deep-sea mining becomes part of the discussion. There's copper in the "seafloor massive sulfide" deposits (aka "polymetallic sulfides") formed by hydrothermal vents, and there's copper in the "polymetallic nodules" (aka "manganese nodules") found on some abyssal plains.
There are other metals in those deep-sea deposits too, so the discussion is not just about copper. Polymetallic nodules also contain nickel, cobalt, some Rare Earth Elements, and of course manganese (giving them their popular name "manganese nodules"). And "ferromanganese crusts" - another type of deep-sea mineral deposit that forms on some seamounts - contain cobalt, nickel and Rare Earth Elements, as well as iron and manganese.
So on one hand, the arguments of mining companies that we need metals found in deep-sea deposits for the green transition are correct (certainly for some metals such as copper; though for some other metals, such as cobalt, newer battery compositions may reduce the need for some of them).
But on the other hand, the point made by NGOs that we don't necessarily need to mine the deep sea to meet the demand for those metals is also correct: we could meet the demand for copper and the other metals just through increased mining on land.
In the case of copper, the prediction that "we need as much copper between now and 2050 as we've mined so far in human history" sounds daunting, but meeting that copper demand would involve the equivalent of opening one new large copper mine every year for the next 15 years (which is potentially feasible).
New mines on land don't just instantly spring into existence, however - the average time from discovery of a new copper deposit to mining it is around 23 years. But to get what we need to limit warming to 2 degrees C (not 1.5), we could potentially accelerate mining of all the currently known copper deposits on land.
But mining on land has impacts, of course, on biodiversity and on local communities. And the nature and extent of those impacts depends on where you mine. So we come back to that question: where do we want to mine? (and I use the word "we" because we all use the products of mining, for example in how you are reading this).
Take Escondida, which is one of the world's largest copper mines, in the Atacama Desert of Chile (and contributes about 2.5 percent to Chile's GDP). That desert is home to some remarkable species of animals and plants of course, but it's not a hotspot for biodiversity like a rainforest, and desert life is pretty sparse, typically with widespread populations of species. There weren't existing local communities in the immediate vicinity of the mine, at altitude in the Atacama desert. And the power supplied for mining there is now 100 percent from renewable energy sources (primarily solar). So as copper mining goes, it has a lower environmental and social impact than mines in some other places.
In contrast, there's the Grasberg copper mine in the Indonesian province of West Papua, just upslope of the biodiversity hotspot of a rainforest (and next to the Lorentz National Park). Tailings disposal from the mine has polluted local waterways, and people have been killed in mine-related conflict and workforce protests.
Ideally, if possible, the equivalent of 15 additional copper mines that we need should be more like the Escondida mine in the Atacama Desert in terms of impact; and clearly we don't want 15 more mines like Grasberg.
But it might not be possible for all the additional mines we need to be like Escondida - the mines will be wherever the copper deposits are (and geopolitically it might not be desirable for them all to be under the jurisdiction of one country either).
We know where the copper is in the deep sea, so how would deep-sea mining compare in terms of impacts with mining in the Atacama Desert or mining in a rainforest?
That's the research question we're involved in answering, by investigating what the environmental and ecological impacts of deep-sea mining are likely to be.
A terrible choice
Before moving on to consider that research question, it's worth reiterating the overall context for deep-sea mining: our world faces a terrible choice.
We could resist further mining anywhere because of its impacts, but in doing so fail to curb higher levels of global warming, which will kill millions of people and have planet-wide impacts on habitats and biodiversity.
Or we can mine the additional metals needed for the green transition, which will inevitably result in impacts on some habitats, and possibly local communities, where that mining takes place - but avoid the global impacts of more severe climate heating.
We are now in a situation where there isn't a zero-impact option for the future. Thanks to the path that we (or rather our politicians) have followed in recent decades, we face that terrible choice. It's the kind of choice often used as a crux in stories (the "impossible choice", also known as "the hero's dilemma" - often framed as a "who do you save or sacrifice?" dramatic situation), and also the "trolley problem" in philosophy, but this is our reality, not fiction or a thought-experiment.
I hope you feel damn angry about us being in that situation - I certainly do.
The best we can do is try to choose the lowest impact forms of mining for the metals that we need, while getting better at recycling for the future (and try to fix our political systems that are structurally vulnerable to the influences of wealthy lobby groups, which contributed to getting us into this mess and continue to exacerbate it).
We therefore come back to the need to understand the impacts of the options we have for mining, to inform that terrible choice.
The research question
So the question that our research is answering is "what are the environmental and ecological impacts of deep-sea mining likely to be?" (and then the answer to that question can be compared with the impacts of the options for mining on land, to make an informed choice).
And I cannot emphasise this enough: we are doing the research because we do not yet know the answer to the question (not to find a particular answer).
If we already knew that all types of deep-sea mining would be catastrophic, for example risking extinctions of species or disrupting the global carbon cycle in the deep ocean, we would be making that very clear to politicians and policymakers.
(And for one particular type of deep-sea mining, where we know it would risk species extinction, we are already doing that).
And if we already knew that all types of deep-sea mining would be catastrophic, we wouldn't need a moratorium on the development of deep-sea mining for "further research" to understand its impacts; we could call for a ban on deep-sea mining right now, based on the evidence of our research, if that were the case.
It's possible that the answer to our research question could turn out to be that all types of deep-sea mining pose a risk of species extinctions - in which case we could rule it out as an option to help provide the metals needed for the green transition.
But it's also possible that our research could find that the impacts of some types of deep-sea mining might be similar to mining in the Atacama desert (we can't rule out that possibility, because we haven't completed the research) - in that case, those types of deep-sea mining might end up being considered as an option.
Note that neither of those are answers to the question "should we mine the deep sea?". They are answers to the question "what are the impacts of deep-sea mining likely to be?". Our research will answer that question, which will then need to be compared with the impacts of other forms of mining.
And it's not just the environmental and ecological impacts that need to be compared: there are also the social impacts, economic impacts, geopolitical impacts, and cultural impacts that need to be considered.
Those are the aspects that all need to be weighed up to answer the wider question "should we mine the deep sea?". As marine ecologists, we can only provide evidence on the aspect that is our area of research - and that's what we're doing - but that aspect alone doesn't necessarily provide an answer to the wider question (unless environmental impacts raise a clear red flag).
What ecological impacts could rule out deep-sea mining as an option?
This is a question that the International Seabed Authority continues to grapple with. Its documents talk about the need to avoid "serious harm" to the marine environment - but exactly what "serious harm" means is harder to establish (as illustrated in the quote at the end of this interview with the new Secretary-General of the ISA, Leticia Carvalho: "What is the definition of harm? That's what we have to discuss").
We can take a pragmatic approach, however. Separate from the International Seabed Authority, the United Nations has brokered an international agreement - the Convention on Biological Diversity - to protect biodiversity. So as an absolute minimum, any regulation of deep-sea mining should seek to avoid the risk of reducing biodiversity - in other words, sending any species extinct.
Note that is only a minimum to avoid - but if deep-sea mining cannot be conducted without risk of species extinction, then it should be a non-starter, given the UN Convention on Biological Diversity.
So for now, let's take that as a definition of "serious harm", and look at what we know so far - and what further research will be required - to understand risks of species extinction from deep-sea mining.
There's more than one type of deep-sea mining
Deep-sea mining is not "one thing": there are different types of deep-sea mining being considered, targeting different deep-sea habitats, and those habitats differ in their vulnerability when it comes to considering any potential risk of species extinction.
To recap - the three major types of deep-sea mineral deposit (and the habitats in which they occur) are:
(1) Polymetallic sulfides (aka Seafloor Massive Sulfides), which form at active hydrothermal vents, on mid-ocean ridges, other "seafloor spreading centres" where plates of the Earth's crust are moving apart, and volcanically-active seamounts. There are around 600 active "vent fields" known worldwide, but each is tiny - in total, they cover an area of ~50 km2 yet are home to more than 400 species of animals only known from those vent habitats.
The polymetallic sulfide deposits are of interest to would-be deep-sea miners for the copper that they contain (along with some gold).
Although the sulfide deposits form at active vents, which are a habitat for unique biodiversity, the deposits remain as "inactive sulfides" when venting naturally ceases at a site and the vent animals have moved on. But the ecology of inactive sulfides is less known than that of active vents, and recent research suggests that some species may depend on inactive sulfides as a habitat. If that's so, then the same case for protecting active vents from mining could be extended to inactive sulfides, as another globally rare habitat for species not found elsewhere.
(2) Polymetallic crusts (aka ferromanganese or cobalt crusts), which form on some seamounts. Seamounts provide rocky seafloor habitat for often-slow-growing deep-sea animals such as cold-water corals and glass sponges (which in turn provide a home for lots of other species).
Polymetallic crusts are of interest for the cobalt, nickel, and Rare Earth Elements that they contain.
There are several thousand seamounts worldwide, each typically several hundred km2 in area, but not all have polymetallic crusts on them (or over all of each one's area).
(3) Polymetallic nodules (aka manganese nodules), which form (over millions of years) on some abyssal plains - and the main area of interest for extracting them is the "Clarion-Clipperton Zone" of the eastern Pacific, a ~6 million km2 area stretching between offshore of Central America and south of Hawai'i. The seafloor of the CCZ lies at ~3800-5800 m deep and is sparsely populated compared with other regions, but home to at least 6000 species of animals, of which fewer than 500 have currently been identified.
Polymetallic nodules contain manganese, cobalt, nickel, copper, and Rare Earth Elements (so it's not just about cobalt and nickel in their case).
It really annoys me when a media article about deep-sea mining highlights some of the species that thrive around hydrothermal vents, and then goes straight to discussing the prospect of mining manganese nodules on abyssal plains. That's the same as talking about species that are only found in the Galapagos Islands, and then talking about the prospect of mining in the desert of Western Australia.
The deep sea is not a single habitat: it encompasses lots of different environments, just as "the land" does, and each has its own ecological patterns and dynamics, which make some more vulnerable to mining disturbances than others.
(These things are NOT the same!
Left: hydrothermal vent on an undersea volcanic rift, ~2.4 km deep.
Right: manganese nodules on an abyssal plain, ~4.8 km deep.
Pics: NERC ChEsSo Consortium & NERC SMARTEX project)
Understanding risk of species extinction from deep-sea mining
There is one type of deep-sea mining that already know would risk species extinctions: mining at active hydrothermal vents for the copper-rich "seafloor massive sulfide" deposits that they create.
Biologists, like me, who study the ecology of those habitats have been unanimous in telling policymakers that active hydrothermal vents would be vulnerable to species extinctions from deep-sea mining.
The total global area of active hydrothermal vent habitat is around 50 km2 (less than half the size of Disney World in Florida), and that habitat is home to more than 400 species of animals that are not found in any other habitat on our planet.
If you were mining on land and said you wanted to mine an area of 50 km2 that was home to more than 400 species not found anywhere else on Earth, it would be a complete non-starter under any responsible regulatory regime.
The actual risk to biodiversity in vent habitats is from cumulative impact at a regional level, reducing "mature" vent habitat that the metapopulations of some species require in those successional ecological systems (and I wrote an explainer about that a decade ago).
Mining at active deep-sea hydrothermal vents is incompatible with international commitments to protect biodiversity. No further research is needed to understand that, and I hope we have been clear about it.
The International Seabed Authority has yet to produce the rules for mining of seafloor massive sulfides, and when they do, I expect those rules to protect active hydrothermal vent habitats from deep-sea mining (and frankly, if the ISA doesn't do that, I think it would risk losing the trust of the scientific community).
But if we already knew that other forms of deep-sea mining - in particular, manganese nodules - would similarly risk species extinctions, we would be as clear about it as we have for active hydrothermal vents.
What about nodule mining?
So how does nodule mining differ, as a prospect, from mining sulfides at hydrothermal vents?
For starters, there's the scale of the habitat involved. Manganese nodules form on some of the world's abyssal plains, which are a huge habitat globally (covering more than a quarter of the ocean floor, though not all abyssal plains have manganese nodules on them).
Within the ~6 million km2 particular area of interest for nodule mining in the eastern Pacific (the Clarion-Clipperton Zone, or CCZ), about 1.5 million km2 of the seafloor has manganese nodules in sufficient abundance to be of interest for mining - and that 1.5 million km2 is ~30 000 times larger than all the world's active hydrothermal vents.
So that makes nodule mining a different prospect to mining at vents - it is not targeting a globally rare habitat.
In some ways, the 1.5 million km2 of seafloor being targeted in the Clarion-Clipperton Zone is a huge area (just over six times the area of the UK). But from another perspective, it is 0.5 percent (i.e. half of one percent) of the global deep ocean.
And the projections are that around 30 percent of the 1.5 million km2 area would be actually mined in the next 20-30 years if mining went ahead there. The other areas within it are either unsuitable seafloor terrain for mining (dotted with "abyssal hills" - our planet's most abundant surface feature) or will be required to become "Preservation Reference Zones" (PRZs) for monitoring mining impacts.
So the prospect is for around 450 000 km2 to be involved in actual mining, i.e. around 0.13 percent (i.e. just over one-tenth of one percent) of the deep ocean.
That's not to belittle the scale of the proposition at all - that 450 000 km2 is still a huge area to expose to an industrial activity (just under twice the size of the UK), and the extent to which impacts spread beyond that area is a topic of further research. But when someone claims that mining there will somehow wreck the entire global ecosystem of the deep ocean - all 305 million km2 of it - you can perhaps see how such a claim for global ocean catastrophe is hyperbole.
Understanding risks of species extinction in nodule mining
For the purposes of assessing risks of species extinction in nodule mining, let's assume a worst case scenario that whatever lives at the seafloor will be wiped out in areas that are mined (rather than a few animals potentially surviving in gaps between mining machine tracks etc).
First of all, let's consider what lives on the seafloor of the area of interest in the Clarion-Clipperton Zone. And the short answer - and I think it's important to be honest about this - is "not very much" (very different from the abundant life at hydrothermal vents).
The seafloor in the area of interest is 4000 to 6000 metres deep, and although conditions vary across the 6 million km2 area of the CCZ, in general the surface ocean above has very little algae growing in it, because it's in an area of the ocean where there are relatively few nutrients. So there's very little food sinking from above onto the ocean floor - and consequently not much life down there, compared with other habitats in the deep ocean (or elsewhere on Earth).
If you were to collect everything living on and in a square metre of the seafloor there, and weigh it all together, it would be tiny compared with the "biomass" from doing the same for a square meter of a coral reef, or a seamount, or around a hydrothermal vent - or even the ground in a local park, for example. The seafloor of the CCZ is one of the least inhabited places on our planet.
But although the biomass there is low, the biodiversity (number of different species) is relatively high (much higher than at hydrothermal vents, for example). There are an estimated 6000 to 8000 species of animals living on the seafloor in the Clarion-Clipperton Zone - and that estimate is based on the rate at which we are finding new ones, as so far only a few hundred have been identified as known species or described as new ones.
Some of those species are undoubtedly beautiful, such as "gummy squirrels" and "Barbie pigs", which are colourful popular names given to some of the types of sea cucumbers found in the CCZ. Perhaps because they're new to us, and because they're from the mysterious ocean depths, we can appreciate how weird and wonderful they seem. But if we were to find a dandelion for the first time in the deep ocean, I think we'd regard it as equally weird and wonderful - but familiarity perhaps blinds us to the wonder of nature when it's closer to home.
So we have a situation in the CCZ where there are lots of species, but members of each species are generally few and far between - and their sparse populations are often spread over a very large area (again, unlike hydrothermal vents, where abundant populations are crammed into tiny island-like habitats).
The sponge Plenaster craigi is an example: it's typically a few millimetres in size, and was described as a new species in 2017. It's one of the most abundant animals found on the manganese nodules themselves, and we already know that its population is spread over at least 900 km of seafloor in the CCZ.
When it comes to assessing potential risk of species extinction from nodule mining, what matters is the distribution of a species in comparison with the area being mined.
The ISA has already established large "Areas of Potential Environment Interest" (aka "APEIs") that are effectively marine reserves: thay have been designated as areas of the CCZ that will never be mined. There were originally nine APEIs, increased to thirteen in 2021 following advice from scientists, and together they cover 1.97 million km2 of seafloor (an area more than eight times the size of the UK).
If the ~1.97 million km2 of APEIs contain the same species as the area being targeted for mining, and their populations are not dependent on the populations in the mining area, then they should protect species from any extinction risk arising from mining impacts.
That "if" is one of the big questions: the current APEIs are largely spread around the edge of the CCZ, while the mining claim areas are in its centre. So an important part of research is assessing how representative they are as potential reserves for marine life in the area, whether they are in the right place, and how species disperse and their populations are connected across the ~6 million km2 of the CCZ.
For me, those are the first and foremost questions of the "further research" being called for to assess ecological risk from nodule mining.
The scale of the task ahead
Answering those questions requires regional-scale study, across the whole CCZ. And that's a big task, which we haven't yet completed.
The threat of serious harm, as I've defined and discussed it here, comes from cumulative impact at a regional scale, rather on the scale of individual mining operations. If and when nodule mining starts, I don't think the first few operations are likely to cause that "serious harm" - but they may lay foundations for it, and eventually further individual operations could tip the system into that outcome.
To understand and potentially manage that situation, we need to survey whether the existing APEIs are representative of the mined areas, for example, and determine whether their populations of species are dependent on those in mined areas or vice-versa.
There's a lot that we still don't know about large-scale patterns of life in the CCZ, in both space and time - and we need to understand those patterns and dynamics to assess likely mining impacts and how they could be managed.
As an illustration of that: in the project in which I'm involved, we've found that there's a major change in the types of marine life on the seafloor of the CCZ, roughly half-way across its 6 million km2 area.
That change occurs at a particular depth as the CCZ slopes in depth from east to west, and that depth corresponds with a change in seawater chemistry that favours some types of marine life over others.
Finding that major pattern in the marine life of the CCZ required collating data from around 20 expeditions that spanned the whole region. It wouldn't have come from a survey of an individual mining licence area by a contractor as part of their required "impact assessment". But data collated from some of those surveys in different areas was part of it, along with data from publicly funded research programmes like ours.
Now that we know that large-scale pattern exists, we need to see how the APEIs are representative of the those different domains of marine life in the CCZ - and how things are going to change in the future, as climate change alters that critical depth for seawater chemistry. And we wouldn't have realised that without such a large-scale study.
Tackling the task ahead therefore requires coordination, which the ISA is supporting through initiatives such as its "DeepData" public database of ecological data from contractor surveys.
It also requires additional investment in research. The ISA does not have the resources itself to fund such large-scale research, involving multiple deep-sea fieldwork expeditions. And it's considered unreasonable to expect mining companies to undertake such CCZ-wide research themselves, as part of the "impact assessment" for their individual licences. So that's why we need publicly funded research programmes such as ours, and international coordination of that research, to address those large-scale questions.
An analogy closer to home
As an analogy, understanding the potential risk of species extinction from nodule mining it comes down to whether we're dealing with the equivalent of dandelions or great-crested newts.
Whenever we mine or build on land, we don't worry about any risk of sending dandelions extinct. We know that the population of dandelions spans a much larger area than our disturbance of their habitat, and that dandelions are great at dispersing their seeds on the wind, and also great at growing on any speck of bare earth habitat remaining among whatever we're doing.
But if we were planning a development on land that affected the few ponds with particular conditions that provide a habitat for great-crested newts, and thereby threatened to wipe out the population of that species, that would be a non-starter for regulatory approval (in the UK, risk to great-crested newts is enough to halt development even in the garden of a former Prime Minister).
Some of the species living on the seafloor will be like dandelions (possibly Plenaster craigi among them, based on research so far). But some of the species in the CCZ could turn out to be like great-crested newts, with restricted habitats that might not be protected by reserve areas.
The "further research" we are doing therefore includes investigating the distributions of species populations across the CCZ, between potential mining areas and protected areas, and assessing how good species are at dispersing as larvae (the equivalent of dandelion seeds for underwater animals).
So far, there are no obvious "red flags" for nodule mining in that regard. Again, nodule mining contrasts with vent mining here: more than 60 species of animals living at hydrothermal vents have been listed as "endangered" by potential deep-sea mining on the IUCN "Red List" of threatened species. But no species from the abyssal plain of the CCZ have yet been added to the Red List as threatened by nodule mining.
But we've barely begun assessing the risk from nodule mining for each species in the CCZ. And there are 6000+ of them - if each one needs to be checked in that way for potential risk of species extinction, then that "further research" could take a very long time.
Will we ever have enough data?
That then begs the question: will we ever have enough data to determine whether nodule mining can be carried out without risk of species extinctions?
It's a valid point raised by some would-be miners, because if the answer is "no", then calling for a moratorium to enable further research is tantamount to a ban, if that further research is an intractable task.
But while there are 6000+ animal species in the CCZ, we don't need to check the individual vulnerability of each one to make a determination.
Instead we can investigate examples that span the range of characteristics that we know make species vulnerable - for example, in the ability of their larvae to disperse. If none of them are found to be at risk, and we know the 6000+ species lie within the spectrum that they represent, then we have the answer.
Take Macrostylis metallicola - a species of isopod crustacean (similar to a woodlouse on land) found on nodules. It was described as a new species in 2020 from specimens collected in the CCZ (and named "metallicola" after the thrash metal band Metallica, in reference to its metal-rich habitat).
Macrostylis metallicola broods its offspring (in a pouch called a marsupium) until they are ready to crawl away on their own (and that's a feature of all isopod crustaceans). Its offspring also don't have a "swimming" dispersal stage (and that's a feature of its family of related species).
Consequently it has a lower ability to disperse and spread, and its populations are more poorly connected over distances than species that have larvae the drift on ocean currents, for example. In other words, it's more like a great-crested newt than a dandelion, in our analogy.
So it's one of the more extreme examples of CCZ species that may be vulnerable to mining impacts. If we find that species like Macrostylis metallicola are not at risk of extinction, by investigating their overall distributions and population connectivity between mining areas and protected APEIs, then we can be confident that other species that don't share those more-vulnerable characteristics are also not at risk.
And that research is a feasible proposition, on a reasonable timescale. But it hasn't yet been undertaken - and it requires a dedicated and coordinated effort, with multiple expeditions sampling from locations across the 6 million km2 of the CCZ. The ISA doesn't have the resources to fund such a programme itself, but hopefully the 30+ nations that are calling for a moratorium to enable "further research" will commit some funding to carry out such work.
Why should we seek to avoid species extinction?
If a species is rare, not contributing much to an ecosystem - or if its contribution is matched by other species, thereby providing redundancy in the system - should it matter if it goes extinct? Particularly if the ecosystem itself continues to exist and work in the same way?
Fundamentally, I think it does matter.
Although the definition of a species can get fuzzy around the edges, each species represents a unique biological entity: a life-form whose genetic code is distinct to some degree from others.
That genetic code is the product of natural selection, and contains a unique combination of solutions that nature has arrived at for that life-form to thrive in the particular conditions of its habitat and lifestyle.
As unique biological entities in that regard, I think every species should have a "right to exist", in some ways analogous to the "right to life" we recognise for individual people as unique entities.
We don't make the "right to life" in any way conditional for people, considering some more or less worthy than others; its universal application is a fundamental expression of respect for other human beings.
I think the same should be true for other species in how we view the natural world. Every species is the product of a unique evolutionary history, and has the potential to continue to evolve. How abundant or rare a species is, or what contribution it currently makes to an ecosystem, is irrelevant in that regard. And I'll offer a tangible case for the benefits of preserving species, as a consequence of their individual uniqueness, in the next section.
If you make recognising a "right to exist" conditional in any way, then where do you draw the line? And once you accept any argument for moving that line, where can it stop?
So for me, the risk of extinction of a single species, no matter its rarity or perceived contribution to an ecosystem, is an absolute red flag. If deep-sea mining involves such a risk, then I don't think it should go ahead. And that's why I'm focused on understanding risks of species extinction - and how they can be mitigated - in the "further research" on deep-sea mining.
What's at stake in preventing species extinction?
I'm also involved in other research to illustrate the benefits of protecting species from extinction wherever we can. In that research, we are exploring the biomedical potential of molecules from deep-sea species.
The unique genetic code of each species can include instructions for making molecules with novel structures, which may for example have anti-microbial or anti-tumour properties. Understanding how those novel molecular structures work to produce those properties can lead to insights for developing new treatments.
That research is "biodiscovery": learning from the ingenuity of nature, recorded in the genetic code of different species, so we can design and synthesise useful new molecules ourselves. It is not "bioprospecting" - it does not lead to, or involve, the harvesting of organisms to extract molecules from them to use (e.g. unlike the collection of horseshoe crab blood for use in vaccine safety testing).
Showing that deep-sea species contain novel molecules with useful properties, which we can learn from, illustrates the benefits of preserving species. And every species has a unique genetic code that we may be able to learn from. So that's the argument I try to get across to policymakers.
It's not just biomedical lessons that we can learn from species, but also lessons for technology and engineering. My favourite example is the "scaly-foot snail" (Chrysomallon squamiferum): a species that lives at hydrothermal vents in the Indian Ocean (described as a new species by a PhD researcher whom I co-supervised, from specimens collected on an expedition that I led), which is teaching us how to make better solar panels.
To cope with the conditions at the hydrothermal vents where it lives, the scaly-foot snail produces tiny crystals of pyrite that make up the metal plates that cover its foot - a feature that is unique to that species. The snail produces those tiny mineral crystals at room temperature, which is something that manufacturers would like to do to make cheaper and more efficient solar panels. And now researchers have figured out how the snail does it, and recreated the process in a lab using readily available ingredients (i.e. nothing that needs to come from the snails), paving the way for industry to follow the snail's lead.
In 2019 the scaly-foot snail was the first species to be listed as "Endangered" by potential future deep-sea mining on the IUCN "Red List" of threatened species, because it is only known to live at a handful of hydrothermal vents in the Indian Ocean, most of which are in areas already under "exploration licences" from the ISA for possible future polymetallic sulfide mining.
A phrase that I trot out in media interviews is that "biodiversity is a library of the ingenuity of nature". If we want to be able to keep learning from that library, we need to look after its books, which are the unique genetic codes of each species. Right now we're playing with fire in the library, and risk burning it down - and there is no back-up copy of the information that each book contains.
How long will the seafloor take to recover from nodule mining?
Coming back to the impacts of nodule mining: in the 1980s, a German research programme (DISCOL - DISturbance and reCOLonisation) began investigating the potential impacts of nodule mining by conducting an experiment in the Peru Basin (rather than the Clarion-Clipperton Zone), where they scraped the seafloor with a plough-like device to simulate the tracks of a nodule mining vehicle.
Return visits to those experimental scars over 26 years revealed little signs of recovery (recolonisation of the disturbed areas by the marine life usually found on the seafloor there) over that timescale. This has led, quite understandably, to concern about how long the seafloor will take to recover from nodule mining - and whether the abyssal plain seafloor is particularly vulnerable and slow in that regard.
Earlier in 1979 a consortium of would-be nodule miners, led by the US Lockheed Corporation, tested a nodule-mining machine at ~4700 m deep in the Clarion-Clipperton Zone, successfully collecting nodules from the seafloor.
A 2023 expedition led by Prof Dan Jones of the UK's National Oceanography Centre (and part of publicly funded research - the NERC SMARTEX project - in which I am involved to investigate impacts of nodule mining) managed to find the track of that mining vehicle test on the ocean floor, and survey it 44 years later to investigate long-term impacts of actual nodule mining in the CCZ. Our project published the results of that study in March 2025.
That research shows that some impacts of nodule mining are long-lasting, which is as expected. Nodules themselves form very slowly, typically over millions of years. So mining certainly will have lasting impact where nodules are removed - the hard surfaces that they provide on the otherwise fine mud of the abyssal plain will not regenerate on any human timescale. And some types of marine life favour those hard surfaces, so that reduces habitat for those nodule-dwelling species.
The research also shows that some types of organisms have recolonised the mining vehicle's track after 44 years. In particular, xenophyophores - unicellular deep-sea organisms up to 5 cm across - have colonised the seabed where the nodules were removed. Xenophyophores are common inhabitants of abyssal plains, but had not been found as initial colonists in previous experiments simulating disturbance from nodule mining.
So overall, our study shows some long-lasting impacts from nodule mining as expected, and changes in what lives where as species respond to the disturbance in different ways. But how the insights from surveying that mining test scale up to understand the likely impacts of full-scale nodule mining is an ongoing area for investigation.
What will matter for determining any extinction risk is how widespread the populations of affected species are, compared with the areas being mined and the areas set aside as reserves.
What about other environmental impacts from nodule mining?
So far we've just considered the direct impact of mining machines killing animals in their path, but there are other impacts to consider from mining operations.
The mining machines also stir up seafloor sediments as they trundle along. Our study of the 1979 mining machine track found that plume of sediment left some infilling between nodules immediately next to its track, but otherwise its impact was not visually discernable after 44 years, and the plume area was colonised by more animals such as sea cucumbers than the track and nearby undisturbed areas.
But in the context of understanding risk of species extinction, that additional impact doesn't really change anything: what matters is how widespread the populations of species are compared with the impacted area.
Most proposed nodule mining operations also involve a "mid-water plume" of sediments. Nodules collected by the machines on the seafloor are piped to a surface ship above, where the nodules are removed, and the remaining sediments are discharged down another pipe, released into the ocean at perhaps 1500 metres deep (to disperse high above the seafloor). That mid-water plume also has impacts - not on life on the seabed, but on what lives in the interior of the ocean at those depths.
Research is therefore investigating how far that mid-water plume disperses, what the conditions are inside the plume, and how that could affect mid-water life. For example, many mid-water animals use bioluminescence to hunt for prey and attract mates - if water is sufficiently turbid in the mid-water plume, it might cut down the range over which those bioluminescent signals work. And lots of sediment could even clog up some animals such as deep-sea jellyfish.
But again, when it comes to risk of species extinction, what matters is how widespread the populations of any affected species are, compared with the impacted area (or rather volume, for those mid-water impacts).
Potential impacts on fisheries are one of the social considerations involved in nodule mining, if the mid-water plumes impact any commercially fished species. For the most part the CCZ is not a prime area for fisheries, however, because there is so little algal growth providing food in the surface ocean there - but any impacts do need to be considered. And some migratory species that are fished elsewhere pass through the area, so the impacts on them from the mid-water plumes need to be assessed too.
There is also underwater noise involved in mining operations, and its impacts need to be considered too. But the noise is at a lower level than some other industrial activities in the ocean (particularly seismic surveying for offshore oil and gas), for which ways of regulating the activity already exist (e.g. with independent marine mammal observers aboard vessels, who can halt operations when whales are sighted nearby) that could similarly be used in nodule mining.
An "Impossible" solution?
There is one approach for nodule mining being developed that potentially avoids several of these further environmental impacts. A company called Impossible Metals is developing harvesting machines that hover above the seafloor, rather than trundling across it on tracks, and pick up individual nodules with robotic arms, guided by cameras and AI (technology adapted from the fruit-picking industry). Once the machine's payload is full with picked nodules, it rises back to the surface ship (rather than pumping nodules up a pipe with a slurry of sediment), so there is no mid-water plume discharge.
By picking individual nodules rather than scraping them up, the Impossible Metals machines don't generate the same seafloor sediment plume either. And they can be programmed to avoid picking up nodules with obvious marine life on them, and to leave a certain percentage of nodules behind on the seafloor as habitat along their path, rather than removing everything.
Inevitably, the Impossible Metals machines are smaller in scale than the traditional machines developed by other deep-sea mining companies, but lots of them could be deployed from a vessel (instead of one large machine attached to the ship by the riser pipe).
The company has tested prototypes in shallower waters, and is planning deep-sea tests in the CCZ. Their starting-point was the list of concerns raised by scientists about mining impacts - and their design goal is to engineer a way around them, potentially enabling collection of nodules without those impacts. If they are successful, it will be interesting to see if the regulator (the ISA) might make that technology the requirement for the industry (and whether NGOs would accept that outcome, if it enables low-impact nodule mining).
What about impacts on "ecosystem services"?
One of the "ecosystem services" (things that nature does that benefit us) that the deep ocean provides, as often mentioned in the context of protecting it from deep-sea mining, is carbon sequestration.
When algae bloom in the sunlit waters of the upper ocean, they use up carbon dioxide from the atmosphere to grow. If their remains sink into the deep ocean (without being eaten and turned back into carbon dioxide by the metabolism of whatever eats them), and if those remains eventually get buried on the ocean floor (rather than being eaten by what lives there, and turned back into carbon dioxide by their metabolism), then that removes carbon from the atmosphere.
There are a lot of "ifs" in that process, and consequently only a fraction of the carbon absorbed from the atmosphere by algae at the surface of the ocean ends up buried in the sediments of the seafloor. But overall, this "biological carbon pump" is important in drawing down carbon dioxide from the atmosphere, and locking some of it away on longer timescales, thereby helping to regulate climate.
Some of the more extreme statements of NGOs have implied that deep-sea mining could disrupt this process on a global scale. But the area where nodule mining is being contemplated, in the Clarion-Clipperton Zone of the eastern Pacific, happens to be a part of the world where the "biological carbon pump" of the ocean is particularly weak.
Although conditions do vary across the 6 million km2 of the Clarion-Clipperton Zone, in general there's not much algae growing in the surface waters of the ocean there, largely because of a lack of nutrients in that region. As a result, the natural rate of sedimentation reaching the ocean floor - as "marine snow" - is among the lowest in the world. Very little carbon gets buried in seafloor sediments there over time, which is also one of the reasons why manganese nodules are abundant there. The nodules form very slowly from chemical reactions on the seafloor, often growing around objects such as fossil shark teeth (in some cases, fossil Megalodon teeth that are at least 2.3 million years old). In the CCZ, they don't get buried in that time by sediments falling from above, unlike in other areas.
So even if nodule mining reduced the burial of carbon there, its global impact would be tiny: the area of CCZ being targeted by mining is half of one percent of the global deep ocean, and an area where there is relatively little natural carbon sequestration.
And it's not clear how deep-sea mining would actually disrupt carbon sequestration. If discharge plumes reduce mid-water life, that could perhaps reduce the rate that carbon sinks to the ocean floor: although some carbon dioxide is released when animals eat and use food, some undigested food gets packaged into poop that can sink more swiftly to the seafloor. So fewer mid-water animals might mean less poop, and thereby reduce that rate of carbon flow down through the ocean.
But fewer animals in mid-water also means less chance of sinking carbon being eaten, and some of it turned back into carbon dioxide, during its descent. So even if it sinks more slowly with less mid-water life, perhaps more of it would reach the seabed - it's hard to guess the consequences.
And a decrease in life on the ocean floor itself, as a result of mortality there from mining, could potentially increase the burial of carbon there, if there's less life to eat it when it settles and thereby turn it back into carbon dioxide.
Further research is required, but given the small proportion of the ocean affected, and the low rate of natural carbon sequestration there, it's not a priority for concern - it will not have an impact on that process in the deep ocean at a global scale.
Recently colleagues have proposed a possibly unrealised "ecosystem service" from manganese nodules, hypothesising that they may also produce oxygen at the ocean floor, through a process of electrolysis. This "dark oxygen" might be locally important for marine life, particularly as the deep ocean becomes deoxygenated as a result of climate heating. Extraordinary claims require extraordinary evidence, however, and some profound questions have been raised about the "dark oxygen" paper, requiring independent verification of its findings.
If it is confirmed, further research will be needed to understand how important that process could be for supporting deep-sea life in the region (and its effects are likely to be local, given the relative small size of the global deep ocean involved), and whether any mining impacts would be addressed by the "APEI" areas of the CCZ that are protected from mining, and "Preservation Reference Zones" required in mining areas.
How does deep-sea mining compare with impacts of other human activities in the deep ocean?
This is not "whataboutery", but an attempt to put the potential impacts of deep-sea mining - which seem to grab public and media attention - into some context.
Industrial deep-sea mining has not yet begun. But we are already inflicting impacts on the ecology of the deep ocean, at a global scale, that outstrip the possible worst case scenarios of impacts from deep-sea mining.
These impacts from other human activities are not a reason to ignore the potential effects of deep-sea mining (and it's certainly not a choice between "mine the deep ocean" or "suffer climate heating").
In fact, other impacts on the deep ocean provide a possible argument to oppose deep-sea mining, to avoid adding further stress to its ecosystems on top of damage that we are already causing. But they also underline the urgent need to do the hard work of curbing greenhouse gas emissions as quickly as possible.
Climate heating affects the deep ocean in several different ways, and its impacts are felt not just in the half-a-percent of the deep ocean represented by the nodule mining area in the Clarion-Clipperton Zone, but worldwide, in all regions and across all deep-sea habitats and species.
Our greenhouse gas emissions trap more heat in the atmosphere, but that extra heat doesn't stay there. More than 90 percent of it is absorbed by the ocean - and so is some of the carbon dioxide that we add to the atmosphere from burning fossil fuels. That uptake by the ocean then has several effects:
(1) the ocean is warming, and that includes the deep ocean. By 2100, seawater temperatures at 3000 to 6000 metres deep are set to increase by an average of 1 degree C - and as it's usually pretty chilly (typically about 2 degrees C) at those depths, that change is fairly dramatic for what lives there;
(2) deep ocean waters are becoming less alkaline ("ocean acidification"), which changes what lives where; animals with calcium carbonate skeletons, such as deep-water corals, may be more restricted in the depths at which they can live as a result;
(3) less food is sinking into the deep ocean from surface waters - and the biomass of mid-water life in some regions may reduce by 22 percent by 2100;
(4) the overall amount of oxygen in the ocean, on which all animal life depends, has declined by 2 percent during 1960 to 2010, and is set to decline much further.
That last impact - "ocean deoxygenation" - is one that particularly worries me. It's the result of a triple-whammy of effects: firstly, less oxygen dissolves in warmer water, so the now-warmer ocean contains less oxygen. But on top of that, organisms respire at a greater rate at higher temperatures, using up that oxygen even more quickly. And thirdly, ocean warming is weakening the deep-ocean currents that sink from polar regions through the ocean depths, carrying oxygen from the atmosphere to all the life down there.
That ocean circulation takes centuries to complete its journey, and the weakening that has already happened means that by the year 2400, the deep ocean will end up with 10 percent less oxygen overall than it had in pre-industrial times. That change is already "baked in" from the climate change that has happened so far - it will just take a while to spread through the deep ocean. Every day that we delay from achieving "net zero" in emissions simply makes that impact even worse. And it is a global impact on deep-sea life.
It will change the distributions and fate of species throughout the deep ocean. As some regions will be affected more than others, some species will be forced into new regions, impacting the populations of other species that become their prey or competitors. And some species might expand their distributions - vampire squid, for example, seem well-adapted to low-oxygen conditions - while others could be threatened if they cannot adapt.
Widespread changes in the patterns of deep ocean life are therefore coming as a result of ocean deoxygenation, while we're still trying to understand existing patterns so that we can inform the management of other human activities.
There are also impacts on the deep ocean from litter (including microplastics in the guts of animals in ocean trenches) and pollution (including from accidents in offshore oil and gas operations), and from deep-water fisheries (including the destruction of vulnerable habitats such as deep-water coral mounds and sponge gardens from bottom-trawling), and they are also important. But for context, they are not as widespread in terms of species and habitats affected as the global impacts of climate change in the deep ocean.
I'm encouraged that concern over deep-sea mining prompts people to be interested in and care about the ecology of the deep ocean. I hope that can be extended into concern about the impacts we're already having on that ecology, which are even more widespread than those from mining could be, and the choices we face to do something about them.
Economic questions
Some reservations have also been raised about the economics of nodule mining. If its financial returns are predicated primarily on income from cobalt and nickel, then reduced demand for those metals in next-generation EV batteries could make it a questionable venture for investors (as highlighted in an article by Victor Vescovo and colleagues).
Nodules contain other critical minerals than just cobalt and nickel, however, such as copper and Rare Earth Elements. Back in the 1970s, before there was any demand for a green energy transition, nodule mining was predicated on the need for manganese, used primarily in steel making, and copper (both of which we still need today, with the latter in particular for the green transition). Whether the economics make sense is therefore an open question (and volatility in commodity prices has arguably driven waxing and waning interest in deep-sea mining over the years).
But even if deep-sea mining were less profitable overall as a proposition, if it turns out to have lower overall environmental and social impacts than terrestrial mining (and could be used to offset highest-impact terrestrial mines), then it might still be desirable to consider as an option, beyond consideration of direct returns to private investors.
Terrestrial vs deep-sea: not an "either/or"?
Even if nodule mining turns out to have lower environmental and social impacts that terrestrial mining, there is a view that it will not necessarily reduce terrestrial mining (or even make much of a dent in the projected growth of terrestrial mining to meet increased metal demand).
Consequently, there's certainly a need to improve regulation and reality of terrestrial mining towards more responsible environmental and social practices - and that need is clear and separate from any consideration of deep-sea mining.
But the main lever being considered to drive that improvement in terrestrial mining is consumer pressure for more sustainably sourced materials in products.
If nodule mining turns out to have lower environmental and social impacts than many terrestrial mines, that same driver could also lead manufacturers away from poorer-practice terrestrial mines in their supply chains, in favour of deep-sea sources. So deep-sea mining is perhaps not so separate from the issue of improving practices in terrestrial mining.
And there is perhaps a way that it might become more of an either/or proposition.
The purpose of the International Seabed Authority is to ensure that benefits from deep-sea mining in areas beyond national jurisdictions (which is most of the CCZ) are somehow shared as "common heritage" of humanity.
At the moment, the ISA is considering options such as partnerships with mining companies that generate income to create a "sovereign wealth" fund, which could be invested in projects "for the greater good", for example advancing development of clean energy technology.
But what if the ISA used that "common heritage" fund to buy out terrestrial mining concessions where they cause greatest environmental and social impact? That could potentially use income from deep-sea mining to offset the worst forms of terrestrial mining, making it more of an either/or proposition.
Where are we now?
To recap:
(1) We don't yet fully understand what the environmental impacts of deep-sea mining would be (particularly for nodule mining), which is why "further research" is needed.
(2) We don't yet know how those impacts will compare with other forms of mining needed for the green transition.
(3) We also don't yet know how other impacts beyond environmental - social, economic, cultural, geopolitical - will compare either.
Together, those provide reasons for a precautionary pause at the moment, rather than rushing ahead with it.
At the of writing, 32 countries including the UK have called for a moratorium on deep-sea mining to allow further research to understand its impacts. That's almost 20 percent of the nations who are parties to the UN Convention on the Law of the Sea, and thereby represented at the International Seabed Authority.
A moratorium is a pause, not a ban.
Moratorium vs ban?
The question I have, as a scientist undertaking the "further research" that has been called for on deep-sea mining, is whether all those calling for a moratorium will accept whatever the results of that research turn out to be.
What if, when we have our answers, the environmental impacts of nodule mining turn out to be similar (or better) than the lower-impact mining in the Atacama Desert, and certainly better than high-impact mining in a rainforest? And what if the overall social impacts are lower than terrestrial mining?
If that's what the further research finds, then some forms of deep-sea mining could (and arguably should) end up being considered as part of the mix for getting the resources that are urgently needed for the low-carbon transition.
But I think some of those currently calling for a moratorium might not accept that outcome.
The principle of subjecting the ocean to another form of industrial activity, when there are alternatives for meeting the demand for metals, is enough to be opposed to deep-sea mining for many people. But in that case, understanding what the impacts of deep-sea mining are likely to be doesn't really matter - that principle will still stand, regardless of whatever "further research" finds.
So if you can't imagine ever accepting deep-sea mining being an option to help achieve the green transition, regardless of whatever further research finds out about its impacts, then please consider whether that is compatible with calling for "further research".
If you aren't prepared to make up (or change) your mind on the basis of whatever evidence further research finds, then please don't call for a moratorium to enable further research.
And ditto if you're only interested obtaining results from further research to support your existing view. That's not why we do research.
(2020 movie "Underwater")
We have a cultural tradition of populating the deep sea with monsters of our imagination. Hell is "down" in many mythologies, and "monsters of the deep" have been a popular trope through history, from the medieval Kraken to recent Hollywood movies such as "Underwater".
Has deep-sea nodule mining, when framed as certain to cause global environmental catastrophe, perhaps become a modern deep-sea monster of our imagination? One where the monster is "us" - or rather, representing the destruction of nature by human greed - and therefore opposing that perceived monster has become a way to express our personal values and identity?
Remember that we don't have actual evidence, at this stage, that the impacts of deep-sea nodule mining will be catastrophic (that's why "further research" is being called for).
When research clarifies what the impacts will actually be - and how they compare with other forms of mining - perhaps we'll see a different picture than the one we imagine.
Of course there are reasons to be opposed to deep-sea mining in principle, e.g. not wanting to expand an industrial activity into yet another already-stressed environment. But in that case, I think it's courageous and honest to call for a ban based on principle, not a moratorium to enable further research.
France is one country so far that is calling for a ban on principle for deep-sea mining, rather than a moratorium to enable further research.
Scientists as activists
Personally I think it's admirable and vital for scientists to be "activists", advocating for a particular course of action, when research has answered a question and indicates what needs to be done during an environmental crisis (for example, on the fundamentals of climate change, and the urgent need to reduce emissions).
When we have a result that's relevant to policy choices, we can't afford to stay silent or somehow "neutral", hoping that the evidence will just speak for itself. It's not a level playing-field out there: powerful vested interests are actively lobbying for the status quo that benefits them.
I think it's different, however, when research hasn't yet provided an answer to its question, i.e. scientists advocating for a particular position in advance of evidence.
But precaution - the need for time for research to give answers - is one thing to advocate for in that latter situation.
When it comes to considering deep-sea mining at active hydrothermal vents: we already know it would risk species extinctions because of the the nature of those tiny island-like habitats (and no further research is necessary on that point). So I hope I'm a vociferous advocate/activist against mining at active hydrothermal vents.
But nodule mining is different: we don't yet understand risk of species extinctions, for example, from that activity. Until (and unless) further research shows otherwise, it remains possible that such risks could be avoided by spatial management in that case. Whether it's desirable or necessary is a whole other question.
I've spent thirty years of my life exploring and investigating deep-sea habitats, and working to bring the wonder of their life to global audiences. I wouldn't have done that if I wasn't passionate about that part of our planet and its biodiversity - the deep ocean is my "back yard".
But I've come to question whether my own visceral opposition to deep-sea mining, which defined my view a decade ago, is really a form of NIMBYism ("Not In My Back Yard"). In the wider context that I've tried to set out here, the issue is not so clear to me now - and consequently evidence needs to be my guide.
So if a spokesperson in a media interview says that deep-sea nodule mining would certainly be catastrophic (i.e. causing species extinctions or disrupting the carbon cycle on a global scale): journalists, please ask them to provide the peer-reviewed research paper, based on observational data, that contains the evidence for that statement. Because if that evidence already existed, we wouldn't need a moratorium to enable further research.
And if a spokesperson says they support a moratorium on deep-sea mining to enable further research, please ask if they would ever consider deep-sea mining as a possible option, depending on whatever that "further research" finds. Because if the answer to that question is "no", then further research is irrelevant.
Of course there's nothing wrong with that: there are reasons to oppose deep-sea mining on principle. But let's be clear and honest if doing so, and not call for further research whose findings could be ignored, or even dismissed, if they don't support an existing position. That's not why (or how) we do research.
Thank you for reading if you made it this far!
Jon Copley, originally posted August 2024 (and updated subsequently).
Postscript, 28 March 2025: "Of course there are reasons to be opposed to deep-sea mining in principle" is what I wrote above, while making a case for personally trying to remain "for evidence"...
This week the New York Times has reported that The Metals Company (aka TMC) - the operator closest to starting nodule mining - has approached the Trump administration for support to begin nodule mining in the CCZ under potential US regulation, rather than under the regulation of the International Seabed Authority (ISA).
The US has never ratified UNCLOS (the UN Convention on the Law of the Sea), which is the treaty from which the ISA derives its mandate.
While the US currently observes most aspects of UNCLOS as "customary international law", the "common heritage" principle at the heart of the ISA (that any exploitation of seabed mineral resources beyond national jurisdictions should in some way benefit humanity as a whole) has always been a sticking point for some US politicians (by being perceived as "socialist").
Apparently the US still has some framework for US-based operators to mine in those "high seas" areas (beyond any national jurisdictions), from when they were poised to begin nodule mining back in the late 1970s (i.e. before UNCLOS III and the creation of the ISA).
The Metals Company's manoeuvre may be intended to put pressure on the ISA to finalise its regulations for nodule mining (and TMC was previously involved in the triggering of the "two-year rule" at the ISA to achieve the same goal). Or perhaps they really do want to go ahead outside the multilateral regulation of the ISA, turning the clock back to the potential "wild west" situation of the late 1970s.
Avoiding "serious harm" from nodule mining requires regional-scale research to understand risk of species extinctions and how that can be avoided by spatial management. That scale of study won't be provided by the "impact assessments" of an individual contractor like TMC going it alone. It requires coordination, and regional databases such as the ISA's "DeepData" initiative. So stepping away from the ISA's framework therefore seems irresponsible if you want to avoid risk of serious harm.
And if progress towards deep-sea nodule mining requires allying with an administration that doesn't give a damn about international law - and which is eroding environmental protection for other industries, and demonstrably attacking science - then that's all I need to know to oppose it.
That's not from the basis of any research evidence about its impacts - but as the choice of with whom to stand as a human being.
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