deep sparkly ocean with weird creatures like a blue toned worm and a jellyfish with a scary silver claw reaching into the water
Mining technology could look for resources deep under the water (Image composite: Getty/NOAA with design by Alessandra Banal)

ScienceJune 1, 2023

What is deep sea mining, and how could it alter a vital ecosystem?

deep sparkly ocean with weird creatures like a blue toned worm and a jellyfish with a scary silver claw reaching into the water
Mining technology could look for resources deep under the water (Image composite: Getty/NOAA with design by Alessandra Banal)

Applications to mine in the ocean could begin in July. Why are scientists and activists so concerned?

Far from the light of the surface, animals are pale; some glow in the dense darkness, have translucent shells; grow very big or very small. Even the most comprehensive list of deep ocean life is missing major species – and with the prospect of deep sea mining approaching, that’s a major concern. 

Take this vision of a deep and distant ocean, populated with peculiar life, and add industrial activity. A massive vacuum cleaner snaking across the sea floor, shovelling chunks of mineral into its maw, or an autonomous underwater vehicle reaching its precisely controlled claw for a piece of phosphorus, its engineered treads unconcerned what life forms might get in the way. James Hita, Greenpeace New Zealand’s oceans campaigner, wants people to see the deep sea as a location bustling with enigmatic biodiversity – a place to protect. “It’s not an abyssal plain,” they said. “It’s full of life – and it’s full of character.”

dark water and some weird spiky underwater animals clinging to a rock
A cluster of sea urchins (and a single crinoid), living on an elevated rocky feature, photographed on a 2016 dive. (Image: NOAA under a Creative Commons licence)

The New Zealand government called for a moratorium on deep sea mining last year. Taking place in international waters at depths greater than 200 metres, deep sea mining is a subset of seabed mining – though that term usually refers to extracting resources from the ocean floor in domestic waters. A bill calling for the immediate halt of seabed mining in Aotearoa didn’t pass its first reading in parliament in May.  

Governed by the Jamaica-based International Seabed Authority (ISA), a UN organisation, mining in international waters currently isn’t taking place at scale. However, member state Nauru declared an intention to sponsor a mining application in 2021, triggering a “two year” clause that requires the ISA to determine regulations for deep sea mining by July 2023, when applications can begin. Mining could start as soon as 2024. 

“Our position is that there must not be deep sea mining anywhere in the world, ever,” said Hita. Greenpeace New Zealand is running a global campaign to rally governments and citizens to take action against the practice. 

Scientists are largely on the side of delaying any mining licences until there’s a clearer sense of what the impact could be. “The ocean is vast and deep and difficult to explore,” said Jonathan Gardner, a professor of marine biology who sits on the technical advisory board of a mining company, in comments to the Science Media Centre

a diagram showing seabed mining through a boat extracting resources from the sea floor
Mining for iron sand. Infographic via Kiwis Against Seabed Mining (

Most international work has been done at small scales, while a mining operation would necessarily be big. Nevertheless, Gardner said that some results of mining would be predictable. “Any rock extraction process is going to break up and grind the rock, thereby removing the natural surface on which organisms live. The mining machines themselves are large and heavy and will cause direct impact by crushing animals.” 

As well as removing texture and “structure” that creates habitat on the seafloor – much like bottom trawling does at shallower depths – deep sea mining would likely release sediment into the ocean, impacting how much light is in the water and how the water flows. “Picture a sediment plume that stretches from Taranaki to Wellington,” Hita said. 

Gardner explained the science of sediment: “Sediment plumes may be short-lived or long-lived, depending on the local conditions and currents, but generally these sediment plumes will smother animals or clog their delicate feeding and respiration surfaces.” Additionally, “in some cases, the sediment itself may be toxic because it contains resuspended particles that are associated with naturally-occurring heavy metals.” Some of the mined minerals may also be radioactive. Marine organisms absorb carbon in their bodies, and the ocean is a major carbon sink; it’s possible that mining could disrupt this important function, and instead cause the ocean to release carbon. 

a green circuit board/computer guts with a battery being placed inside. this description is being written by soumeone who could know tell you what a graphics card is even if you put them at gunpoint, so it is not very helpful
Deep sea mining could extract resources used in electronics (Photo: Getty Images).

As deep sea mining would inevitably be extremely resource-intensive and expensive, the minerals that companies would aim for are expensive ones. “Nodules” about the size of tennis balls are found on the seafloor, formed from valuable minerals like manganese and phosphorus. Mining equipment, some of which has already been developed, could guzzle these nodules up like a crumb before a vacuum cleaner. Some of these elements are used in items like electric batteries, but even companies like Volvo, Google and BMW have called for a moratorium until alternatives are exhausted and the impact on marine ecosystems is clearer.

Part of the motivation to exploit the seafloor for resources is geopolitical. Minerals available on the seafloor, like cobalt and phosphorus, are currently mainly produced in conflict zones like the Democratic Republic of Congo, or China, whose trading relationship to Western countries is at times fragile. “It’s worth noting that rare earth elements play a key role in the electronics of highly sophisticated military equipment on land, at sea and in the skies, so new sources of these minerals have been sought to help reduce world reliance on the supply from China,” Gardner told the Science Media Centre.

“[Deep sea mining] might bring the cost of the minerals [the companies] are seeking down, so not a single land-based mine will close because of this,” Hita says. They worry that mining would rely on creating an illusion of scarcity to justify damaging environmental practices far from land, rather than recycling minerals that have already been mined.

The Pacific Ocean, where many mineral deposits have been found (although only a small percentage of the seafloor has been mapped) will likely be the first area where companies want to mine in international waters. “Our ocean has no boundaries so there are potential transboundary issues such as sediment plumes that can travel across borders,” said Alanna Smith, director of Cook Islands-based environmental NGO Te Ipukarea Society. “Pacific Islanders rely on the ocean as a healthy source of food… Recent studies are saying the outer layer of nodules contains highly radioactive material which could potentially enter our food chain.”

Smith is particularly concerned that the costly research to assess the impacts of mining will be carried out by mining companies, which will be looking for information that may support their applications. “Environmental studies are likely to be supplied and funded by mining contractors,” she said. Traditional ways of life could be impacted; for instance locals in Papua New Guinea have said that their traditional practice of “shark calling” would be threatened by sediment plumes that hurt marine life. 

As a UN body, the International Seabed Authority has a complex structure; New Zealand is a member of its general assembly but not its council. Greenpeace’s Hita said that a vote for a moratorium on deep sea mining could be conducted among the ISA assembly, where Greenpeace is an observer. Hita encouraged people who are concerned to sign the Greenpeace petition and express their feelings about the sea to their local MP.

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