Deep sea mining – the process of extracting minerals from the deep sea floor – has reached a critical turning point. Despite international outcry, Norway has approved future deep sea mining in its territory, becoming one of the first countries to do so. This could trigger a ‘race to the bottom’ between nations. Some consider deep sea mining necessary for the green transition, as certain areas of the ocean floor are abundant in metals used in electric vehicle batteries, wind farms, and solar panels. But mining these metals could destroy one of the Earth’s last pristine habitats and cause far-reaching impacts within and beyond the ocean.
Why mine the deep sea?
Building enough batteries and renewable power sources to meet global energy needs will require a huge amount of metal. Up to 6.5 billion tonnes of materials could be needed between 2022 and 2050 to enable a transition that limits global warming to 1.5°C. Shortages of critical metals like copper, lithium, cobalt and nickel may cause delays. While the Energy Transitions Commission has reported that all the materials needed are contained in land-based reserves, the terrestrial mining process used to extract these materials is often associated with environmental and human rights abuses. For example, nickel mining for electric vehicle (EV) batteries has been driving deforestation in Indonesia. Concentration of supply adds to this issue: for example, China accounted for nearly 70% of global rare earth element production in 2023. This makes the green transition more vulnerable, as concentrated supply chains are less resilient and can be used as geopolitical leverage by supplier nations.
Deep sea mining is being positioned as the silver bullet. Potato-sized lumps of minerals called polymetallic nodules that lie nestled in the deep sea sediment contain the valuable metals needed for the green transition, including nickel, cobalt and copper. The nodules are abundant in certain places: the Clarion-Clipperton Zone (CCZ), a six million km2 plain between Mexico and Hawaii, is thought to hold 21 billion tonnes of them. Mining operations plan to dredge up nodules with a tractor-like vehicle and pump them to the surface. But at what cost?
The arguments for and against
The deep sea is a pristine habitat we are only just beginning to understand. It has been unchanged for millennia. Its slow-growing, long-lived, and specialised inhabitants are unlikely to easily adapt to disturbance caused by mining, and many may be pushed to extinction. The nodules are habitats: half the visible creatures found in the CCZ by researchers in a 2016 study only occurred on nodules. Removing the nodules puts the species that rely on them at risk. Restoration, for example by replacing the nodules with artificial clay ones, may not be financially feasible – one report found that achieving successful restoration is not only unlikely, but would cost more than the revenue generated by the whole mining operation.
One of the key arguments for deep sea mining is the suggestion that it’s the lesser evil when compared to terrestrial mining in rainforests. Copper, manganese, nickel and cobalt together make up 12% of terrestrial mining (the largest category after gold and coal) and drove 997 km2 of deforestation between 2001 and 2019. Deep sea mining advocates argue that although a much larger area would be mined for the same amount of metal, deep sea mining would still remove less biomass per unit metal compared to terrestrial mining. Yet mining’s impacts on marine and terrestrial habitats are not easily comparable. Not only do deep sea and terrestrial mining require different methods, air and water affect the magnitude of the impacts differently. For example, sound can travel far further in water than in air. Marine and terrestrial lifeforms would likely respond to impacts differently, being adapted for very different environments. We don’t currently know how severely the ocean would be impacted by deep sea mining, but given that ocean ecosystems are highly interlinked, damage to deep sea ecosystems may impact those within the broader ocean.
In addition, direct impacts of deep sea mining could also go far beyond the mining area. One of the most talked-about issues is the waste sediment that would be pumped back into the sea, potentially spreading hundreds of thousands of kilometres. Again, the effects are currently unknown, but scientists fear this sediment could choke filter-feeding organisms, introduce toxic metals and radioactive particles into marine food chains, block animals’ vision and sunlight, and smother fisheries.
The sound of mining could also impact marine life. One analysis found that noise from one mine could travel over 500 kilometres. Marine life is very sound-dependant – just two hours of artificial noise was found to impair the energy storage and gravity detection abilities of seagrass, a widespread plant that stores 10-18% of the ocean’s CO2. Deep sea mining operations are required to conduct baseline studies before beginning work, and The Metals Company —a key player in the push for deep sea mining — reports that it is investigating noise pollution. However, acknowledging potential impacts will not necessarily stop them from occurring.
If mining causes mass extinctions, as one study predicts, we could lose species that would have yielded important medical discoveries. Take marine sponges – 2,700 new chemical compounds have been identified from sponges in the last decade alone, and around half are potentially useful for medicine. With the vast majority of deep sea species still unknown (a recent study found that 92% of nearly 5,600 species it documented in the CCZ were unnamed), we don’t know what valuable compounds would be lost.
The mining process’ impact on climate change is also unknown. Nodules may require less energy to process than terrestrial metal as they are generally more concentrated, and so may produce fewer greenhouse gas emissions. But scraping the carbon-rich deep sea floor may release some of the carbon it stores. Deep sea mining could also potentially impact the ocean’s CO2 uptake – sunlight-blocking sediment may reduce photosynthesis, and biodiversity loss may disrupt the ocean’s carbon cycle.
The lesser of two evils?
Terrestrial mining also has severe side effects, with evidence suggesting it may produce up to 65 billion tonnes of waste each year, and could expose 23 million people around the world to unsafe metal concentrations as a result. For example, the 2019 dam collapse in Brumadinho, Brazil, released toxic mining sludge that killed 272 people, destroyed 125 hectares of forest and polluted waterways. The waste produced per unit of metal is generally increasing as higher-quality metal deposits are exhausted.
Both types of mining have consequences, and there are other ways of acquiring the minerals needed for the green transition. With only around 17% of electrical waste currently recycled, scaling metal recycling would significantly reduce the need for new metal. However, metal recycling can be difficult and costly, especially for EV batteries (the main driver for deep sea mining). The foams, glue, and varied battery designs make reclaiming metal a hugely labour and chemically intensive task — more expensive than buying new metal. For circularity to work, recycling must be considered at the design stage.
The best option may be to remove the need to mine, or even use, these metals at all. Lithium and cobalt, two critical battery metals, can now be extracted via absorption directly from sea water, although the technology is still young. And lithium-free and cobalt-free EV batteries have been invented. Better yet, improved public transport infrastructure and uptake could significantly reduce the need for car batteries.
The impacts of deep sea mining on ocean life are far from clear, but current evidence suggests they could be devastating. As well as potential mass ecosystem destruction, deep sea mining could accelerate climate change by damaging the ocean’s ability to absorb carbon. The green transition must not be delayed, but many are questioning whether it should come at the expense of the ocean, via untested measures with unknown consequences. The risks posed by deep sea mining could instead drive investment in innovation, to reduce our reliance on finite natural resources and support a circular economy.
