Deep-sea mining
With land resources rapidly depleting, eyes are turning to the seabed as a whole new source of metals. But at what cost to marine wildlife?
Our quest for mineral resources could have negative impacts on all manner of marine life
Giant, electric mining machines, thundering across the deep seabed miles under water, may seem the stuff of science fiction – like the idea of mining asteroids, or the moon – but they could soon become a reality. Plans paving the way towards the first deep-sea mines were delayed by the pandemic but are likely to move ahead in 2021. If they do, this could give the green light to a brand-new way for humans to exploit the planet’s resources.
Interest in deep-sea mining began in the late 1960s, when corporations explored the possibilities of gathering metal-rich rocks scattered across abyssal plains. Resembling lumps of coal, these nodules take millions of years to form as dissolved minerals in seawater settle onto a hard nucleus, such as a fragment of ancient shark tooth or whale ear bone. The mix of metals usually includes about one-third manganese, plus smaller amounts of cobalt, nickel and rare-earth metals. Several tonnes of nodules were brought up in the 1970s, demonstrating that the industry was technically possible. Nevertheless, following a crash in global commodity prices, the first wave of deep-sea mining didn’t take off.
Wind forward several decades and a second wave of mining interest is underway, with some key differences. Abyssal nodules are still in the picture, especially with the anticipated metal demand for electric car batteries and some types of wind turbine. But where previously abyssal plains were thought to be little more than mud and rocks, scientists now know the nodules create unique habitats for all sorts of species, including long-lived corals and sponges. “These are organisms that can only live on hard substrates,” says Sabine Gollner, a deep-sea biologist at the Royal Netherlands Institute for Sea Research. “And of course, if you remove these nodules, they will not grow back for millions of years.”
A diverse array of species directly relies on nodules. Tardigrades and nematode worms live right inside the rocks. Ghostly white octopuses brood egg clutches fixed to the stalks of sponges. Roaming the soft sediments in between nodules are herds of sea cucumbers, sea anemones, starfish
If deep-sea mining goes ahead, this could give the green light to a brand-new way for humans to exploit the planet’s resources.
and brittlestars. How mining will impact these mobile animals is yet to be fully understood, but it will undoubtedly transform their quiet, slow-paced environment. As Gollner points out, organisms living in the abyss are not used to swift change.
Seamounts and smokers
Aspiring deep-sea miners are now setting their sights on two additional deep-sea features – underwater volcanoes (known as seamounts) and hydrothermal vents or ‘black smokers’. Cobalt-rich crusts settle onto seamounts – in a slow process similar to nodule formation – while black-smoker vents contain metals that precipitate from scorching-hot fluids gushing through cracks in the seabed.
Vents and seamounts both form the basis for rich ecosystems. On hydrothermal vents, about eight out of ten species are endemic and live nowhere else. They include such oddities as giant tube worms, hairyarmed yeti crabs and scaly-foot snails, which make their unique shells from iron. Recently, the scaly-foot (which has highly specific habitat across a small range in the Indian Ocean) became the first animal to be added to the IUCN’s Red List of Endangered species due to the threat of deep-sea mining.
Many seamounts are covered in forests of sponges and corals that create habitat for other species. As Astrid Leitner from the Monterey Bay Aquarium Research Institute explains, mining the crusts from seamounts will destroy everything living on them. “It will probably scare away the mobile animals, too,” she says. Fish use seamounts as spawning grounds; while humpback whales, sharks, sea turtles and other migrating animals feed at seamounts and use them as waypoints (see Q&A, p77).
“Mining needs to be very carefully regulated if we’re going to go through with it,” Leitner says. “We need to know specifically how these ecosystems will react, so that we can figure out a way to manage it. I don’t think we know enough about seamount communities
Managing mining
at this point to be able to do that with the least possible harm.”
Deep-sea mining is much more organised than it used to be. The International Seabed Authority (ISA) is an intergovernmental organisation established by the UN in 1994, to oversee activities on the seabed in the high seas (anything further than 200 nautical miles from shore). ISA officials are drawing up regulations for deep-sea mining, which need finalising before commercialscale mines can open. It’s expected that this ‘Mining Code’ will be released this year.
In the meantime, the organisation has granted 30 exploration permits to mining contractors, covering 1.5 million square kilometres of seabed, an area roughly equal to Germany, France, Spain and Portugal combined. Contracts for hydrothermal vents and seamounts are held by countries including France, Poland, Germany, South Korea, China, Russia and India. Eighteen contracts are in the Clarion Clipperton Zone (CCZ), which is an enormous abyssal plain in the central Pacific, with high concentrations of nodules.
Belgium-based Global Sea Mineral Resources (GSR) has some of the most advanced plans for nodule extraction and is developing prototype mining equipment. In 2021, GSR is launching tests in the CCZ of the second version of its nodule collector – Patania II, which resembles a huge combine harvester on caterpillar tracks. It will be operated remotely from a ship at the surface and gather nodules with a suction device.
Of particular concern are sediment plumes that would likely smother animals such as corals and sponges.
A third phase of testing will follow in 2023 or 2024, with a larger device – Patania III, which will dispatch nodules to a ship at the surface using riser pipes.
In order to get a mining permit from the ISA, contractors would have to carry out baseline studies, conduct an environmental impact assessment of the likely effects of mining, and write an environmental management and monitoring plan – all details that will be laid out in the Mining Code. Of particular concern, besides the immediate footprint of the mines, are sediment plumes that would be stirred up and likely smother immobile animals, such as corals and sponges. How big these plumes would be and how far they would spread are questions that need answering. “We have models that predict what will happen,” says GSR’s head of sustainability Samantha Smith. “And now we can do a field trial to demonstrate how well we can make those predictions.”
When the sediment settles
Scientists partnering with GSR, together with an independent consortium of European scientists, will be gauging the effects of Patania II, using current meters, turbidity sensors and underwater cameras, and gathering biological samples. Smith and her team are also working out whether these sediment plumes could be directed back over areas that have already been mined, to limit their impact. “Part of the reason I’m working with GSR is I think they’ll be first,” Smith says. “The hope is that it would be hard for somebody to follow and not to do it as well.”
More plumes would be created as seawater is separated from the mined ore on support ships and returned to the sea, together with sediments and potentially heavy metals released from the crushed ores. These ‘tailings’ could be released back to mined sites or into the open waters of the twilight zone, about 1,000m down, where experts predict the plumes would impact gelatinous animals, including various jellyfish and siphonophores whose feeding surfaces and gills could become clogged.
“We don’t know how they will be affected,” explains Gollner, “but in the crystal-clear waters in the deep sea, the animals may not have the ability to deal with this kind of stress. This is something we need to find out.”
Sediment may block the bioluminescent lights that many twilight zone animals use to communicate and defend themselves. Midwater plumes could also contaminate plankton with heavy metals, then pass through the food-web to larger animals, including tuna, turtles and whale sharks.
Safeguarding the future
Mining plans will incorporate areas that would be designated as non-mining zones. “Set-aside areas are the key, so we can preserve habitat and biota [animals and plants] representative of what could be lost through mining,” says Smith. A big question is where to locate these areas and what size they need to be, to allow ecosystems to continue functioning. Gollner explains that protected areas must be as similar as possible to the mined areas, but that information is not always available. In the CCZ, there are nine protected areas identified by the ISA, but scientists have so far visited only a few. “Typically, we simply don’t know what’s living there,” she says.
Undoubtedly, a great deal is at stake over the issue of deep-sea mining. Many mining companies are claiming that certain metals will be vital for a low-carbon future, such as rare-earth metals for offshore wind turbines and cobalt for electric vehicle batteries. Known land-based reserves of these and other elements are predicted to become scarce and more expensive to extract in the years ahead, making deep-sea mining an attractive prospect. But there are alternatives. Various car companies are already working on cobalt-free batteries, partly due to price volatility and concerns over unethical cobalt from dangerous, hand-dug mines on land.
Rechargeable battery and solar technology currently in use has changed very little over the decades. Next-generation technologies are in development – such as spray-on solar inks and wind turbines with superconductors, which would require far less or even none of the metals available in the deep sea. “Should we take the risk to destroy parts of the ecosystem in the deep to get minerals?” Gollner asks. “Or should we invest more in other technologies that reduce the use of those minerals?”
Deep-sea minefield
Ultimately, it will be up to the delegates representing 168 member states at the ISA to decide on whether deep-sea mining will go ahead, as well as when and how. As Smith says, deep-sea mining would diversify the world’s metal supply options. “We still have some research to do to definitively say ‘yes, this is 100 per cent the way we should go’.”
Many uncertainties surround the likely impacts of seabed mining and there are calls from NGOs, the European Parliament and various Pacific island leaders to introduce a moratorium. A pause in the seabed mining industry would give scientists more time to get a handle on what lives in these remote regions and how important these intact ecosystems are for the health and functioning of the entire planet. The ocean provides food and inspiration for powerful new medicines, it absorbs huge amounts of heat and carbon – including in abyssal sediments that mining could disrupt. “We shouldn’t forget that the ocean is our big buffer,” says Gollner. “The deep sea matters to us all.”
HELEN SCALES is a marine biologist, writer and broadcaster. Her latest book, The Brilliant Abyss (Bloomsbury, £16.99), is out now.
Next-generation technologies are in development that would need far less of the metals available in the deep sea.