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Deep-sea mining: An environmental solution or impending catastrophe?

The nodules seen here and strewn across the seafloor are phosphorites with ferromanganese crusts. They were deposited here millions of years ago and grow about 2 millimeters every million years. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2019 Southeastern U.S. Deep-sea Exploration.

  • A new report by the Deep Sea Mining Campaign and MiningWatch Canada examines the potential risks of seabed mining operations targeting polymetallic nodules: rock concretions that harbor minerals like manganese, nickel, cobalt and copper.
  • While deep-sea mining has not started in any part of the world, 16 international mining companies have contracts to explore the seabed for minerals within the Clarion Clipperton Zone (CCZ) in the Eastern Pacific Ocean, and other companies have contracts to explore for nodules in the Indian Ocean and Western Pacific Ocean.
  • The report suggests that polymetallic nodule mining would negatively impact ecosystems, biodiversity, fisheries, and the social and economic dimensions of Pacific island nations, and that this mining requires a precautionary approach. Mining companies, on the other hand, say nodule mining is less destructive than land mining, and that mining operations can benefit Pacific island nations socially and economically.
  • Mining companies also say polymetallic nodule mining is necessary to provide the minerals needed for renewable energy technologies, while opponents say these minerals can be extracted from land sources, including recycled electronics.

In 2007, a submersible with a large drill descended 1,600 meters (5,250 feet) into the sea off the coast of Papua New Guinea (PNG), landing near a network of hydrothermal vents that host an array of rare and unique sea life. The machine operators, working for Canadian mining company Nautilus Minerals, Inc., began drilling into the seabed, searching for copper, gold, zinc and silver. In the years that followed, the company drilled again and again.

By 2019, Nautilus, the first company to ever receive a deep-sea mining license, had gone bankrupt before extracting any minerals, and the PNG government, which had invested in the project, was left with millions of dollars in debt.

Jonathan Mesulam and his son campaigning to ban deep-sea mining in PNG. Image by Jonathan Mesulam / MiningWatch Canada.

The marine environment didn’t fare much better. Jonathan Mesulam, a resident of New Ireland province in PNG, located near a Nautilus project site, said his community experienced “serious impacts” when the company began exploring the seabed.

“We were worried because the mining is experimental, there are no examples anywhere in the world, and Papua New Guinea has no regulatory framework,” Mesulam said in a presentation he gave at a MiningWatch Canada conference in 2019. “Also, we knew that there is an active undersea volcano at that site, could it cause a tsunami?

“It also affected our unique shark calling culture that is our identity,” he added. “We can call sharks to our canoes. They are a major source of food for our people. When Nautilus started its exploration activities the sharks left our waters.”

Polymetallic nodule mining


What happened in PNG is referenced as a cautionary tale in a new report published in May by the Deep Sea Mining Campaign, a program run by The Ocean Foundation, and MiningWatch Canada. While the operation in PNG targeted hydrothermal vents, the report examines a different form of deep-sea mining aimed at polymetallic nodules: potato-sized rock accretions on the seafloor that harbor commercially valuable metals like manganese, nickel, cobalt and copper.

A polymetallic nodule. Image by the DeepCCZ expedition / NOAA.

Polymetallic nodules are found in many parts of the world’s oceans, but a large accumulation occurs in the Clarion Clipperton Zone (CCZ), an abyssal plain that stretches across 4.5 million square kilometers (1.7 million square miles) between Hawaii and Mexico in the Eastern Pacific Ocean. Since the CCZ lies within international waters, any mining in this region would be regulated by the International Seabed Authority (ISA), an intergovernmental body set up to oversee and control mining beyond any country’s jurisdiction. Companies wishing to mine in the CCZ also need to be sponsored by at least one nation in order to get a permit. Currently 16 international companies have contracts to explore the CCZ for nodules, and two companies have permits to do so in the Indian Ocean and the West Pacific Ocean, according to the report.

The report, written by a group of researchers from James Cook University in Australia and the University of the South Pacific, with a main campus in Fiji, reviews 250 scientific articles, reports and industry sources. It analyzes current mining interests in the Pacific Ocean and various mining processes, and assesses the potential impacts on local ecosystems, biodiversity, fisheries, and social and economic dimensions. The report also highlights many gaps in knowledge about deep-sea habitats and species, and how very little is known or understood about the risks of deep-sea mining.

Deep-sea mining has not yet begun anywhere in the world, but many companies are already prospecting the seabed for nodules and other forms of minerals to assess their size, composition, distribution, and economic value.

A map of the Clarion Clipperton Zone in the central Pacific Ocean. Colored areas are those licensed for mining and shaded squares are areas currently protected from mining. Image adapted from the International Seabed Authority, 2018, courtesy of NOAA.

“The reason we decided it was really urgent to put this report out is because … the International Seabed Authority is under a lot of pressure to get the regulations finalized that would allow the mining to start,” Catherine Coumans, one of the report’s editors and the Asia-Pacific program coordinator for MiningWatch Canada, told Mongabay. “The mining could literally start within the next couple of years.”

What’s in the deep sea?


The environmental impacts of nodule mining are manifold, according to the report. Polymetallic nodules, which take millions of years to form, provide a critical habitat for an array of unique and largely understudied species, including deep-sea corals, sponges, sea urchins, starfish, jellyfish, squid, octopus, shrimp, and sea cucumbers. Deep-sea habitats and species are slow-growing, so a full recovery after mining could take thousands, if not millions, of years — if a recovery is possible at all, the report says.

The report suggests that sediment plumes and waste discharge from mining could upset phytoplankton blooms at the sea’s surface, and introduce toxic metals into marine food chains. This mining waste could also travel through the ocean and damage nearby seamounts and coral reef systems, which many fish and marine mammal species depend upon for shelter and food, and put entire fisheries at risk. The report also calls attention to the potential impacts of light pollution, which could disrupt a multitude of species attuned to living in the dark, and noise pollution that could change the swimming and schooling behavior of tuna, and cause dolphins and whales to strand.

A new species (Relicanthus sp.) from a new order of Cnidaria collected at 4,100 meters in the Clarion-Clipperton Fracture Zone (CCZ) that lives on sponge stalks attached to nodules. Image by Craig Smith and Diva Amon, ABYSSLINE Project / NOAA.

Coumans and her colleague, Helen Rosenbaum, at Deep Sea Mining Campaign, said in an email that the scientific studies reviewed by the report’s research team represent a “clear consensus in the scientific community that mining of polymetallic nodules is predicted to lead to a significant loss of biodiversity in the marine environment.”

“Some people who are proponents of mining say, ‘Oh, let’s mine first and then we’ll be able to see what the problems are,’” Coumans told Mongabay. “And we’re saying, ‘Well, we don’t really need to do that.’ We know you’re going to destroy the biodiversity down there and that species are going to be lost. We know that the impacts are going to be long lasting because those nodules take millions of years to form.”

DeepGreen Metals, Inc., a private company based in Vancouver, Canada, was granted a 15-year license to explore minerals in the CCZ through its subsidiary, Nauru Ocean Resources Inc., and has three sponsoring Pacific island states: Nauru, Tonga and Kiribati. When Mongabay reached out to DeepGreen Metals, a spokesperson for the company said that polymetallic nodule mining would be less destructive than land-based mining.

A sea cucumber (Amperima sp.) on the seabed in the eastern region of the Clarion Clipperton Zone. Image by Craig Smith and Diva Amon, ABYSSLINE Project / NOAA.

“We see nodules as an opportunity to compress the disastrous impacts of land-based mining,” the spokesperson told Mongabay in an email. “Whilst nodule collection will impact the seabed where nodules are collected and create sediment plumes, the impacts of which will be studied in-depth over the next three years, our research finds that nodules offer significant environmental and social impact reductions when compared to mining the same metals on land. As it stands, more territory has been set aside in the CCZ under protected ‘areas of particular environmental interest’ than has been licensed out for exploration by the ISA. These protected areas will make sure that the animals in the area have plenty of habitat on the abyssal plain, the largest ecosystem on the planet.

“Mining on land now takes place in some of the most biodiverse places on the planet,” the spokesperson added. “The ocean floor, on the other hand, is a food-poor environment with no plant life and an order of magnitude less biomass living in a larger area. We can’t avoid disturbing wildlife, to be clear, but we will be putting fewer organisms at risk than land-based operations mining the same metals.”

The spokesperson for DeepGreen also said there was a difference between mining polymetallic nodules in the CCZ, which they described as a “deep, dark,” environment, and other forms of deep-sea mining that target cobalt crusts and seafloor vents in shallower waters — the type of activity that Nautilus was conducting off PNG. The former would be much less destructive than the latter, according to DeepGreen. The company also said it would host a research program to better understand the seabed and the organisms living on and around it.

Nodules taken from the Pacific Ocean during an exploratory mission by mining company, DeepGreen Metals. Image by DeepGreen Metals.

“Our program will take in over 100 studies, involving over 100 researchers and scientists who will freely publish their findings over the next three years,” the spokesperson said. “This will make the eastern CCZ one of the most intensely studied regions of the deep ocean. We will generate massive amounts of new knowledge and data which will be shared freely to anyone wishing to analyse it and to extract new information about the deep-ocean.”

‘Who’s going to be the watchdogs?’


To Coumans, another big concern is the lack of supervision of deep-sea mining and the practicalities of addressing any problems. While the ISA is meant to regulate and control deep-sea mining in international waters, Coumans says observation is difficult in the deep ocean.

“On land, you can fly a drone over [a mine], and there’s all kinds of ways to see what’s actually going on,” Coumans said. “But in the deep sea, who’s going to be the watchdogs down there? And if things go wrong, how do you fix it?”

DeepGreen responded to this concern by saying the company had invested in “a suite of technologies” using sensors and underwater drones to enable the company to monitor the mining activity and minimize risk in real-time.

Whale sharks, an endangered species, migrate through the CCZ, so experts believe they could be impacted by discharge of waste from nodule mining. Image by Dudarey Mikhail.

But Coumans says that mining companies don’t have the experience to safely deal with problems several kilometers underwater, even with technology to help them.

“There’s no history of how to actually deal with unpredicted …. impacts,” she said. “On land, we do have that history because we’ve had hundreds of years of mining, and even on land that doesn’t work out very well, so you can just imagine how much more difficult it will be in the deep sea.”

Boom or bust for Pacific island nations?


According to DeepGreen, nodule mining would reap significant economic and social benefits for any Pacific Island nation that partnered with a mining company, especially those countries most at risk from the impacts of climate change.

“It is very easy for privileged activists to say what’s right or wrong for small island developing states,” the spokesperson for DeepGreen said. “It’s probably better to hear what they [Pacific island nations] have to say for themselves on this issue. DeepGreen believes that polymetallic nodules represent an opportunity for these states, which have historically been left behind in global development, to level the playing field, taking advantage of the UN Convention of the Law of the Sea — which has granted them sovereignty over vast tracts of the ocean — to lead in the development of an industry that has the potential to fully supply the critical minerals required for the shift to clean energy with a fraction of the social and environmental cost.”

Sperm whales dive to depths of 1,860 metres to forage, and could reach areas impacted by nodule mining, experts say. Image by Willyam / courtesy of MiningWatch Canada.

While some individuals and groups in Pacific island nations may support polymetallic nodule mining, the report by the Deep Sea Mining Campaign and MiningWatch takes a different view. Deep-sea mining would have many negative repercussions for Pacific islanders, the report says, including adversely affecting local fisheries that provide wealth, employment and food security for many islanders.

“Risks to tuna fisheries and other open ocean species would be greatly increased by mine waste released in surface layers as well as noise and light pollution from DSM [deep-sea mining] infrastructure,” the report says. “Yellowfin and bigeye tuna would be exposed to waste discharges at depths of up to 1,000 metres [3,300 feet] or more, as these species make extended deep dives. Climate change research predicts that tropical tuna stocks will move eastwards in future years, shifting their populations into habitats where nodule deposits occur. If plumes from nodule mining affected seamounts, deep sea snapper fisheries would be at risk.”

The report also says many Pacific islanders are troubled by the potential social, economic and environmental impacts of mining, and that their concerns are validated by a growing “body of knowledge” about the negative impacts of polymetallic nodule mining.

Locals having fun on the boat on the remote Mioko Island, Papua New Guinea, July 2019. Image by Grain Connoisseur Photography / Flickr.

“They [DeepGreen] talk a lot about how this is going to have great windfalls for the Pacific Island countries that would be involved, but the first deep seabed mining project has not had a good outcome for Papua New Guinea,” Coumans said.

Citizens in Tonga are also concerned about their government’s move to sponsor Tonga Offshore Mining Limited, a local subsidiary of DeepGeen Metals. The Civil Society Forum of Tonga, a group of 46 individuals, recently released a statement to try and convince their government to place a moratorium on mining in Tonga’s territorial waters as well as in international waters.

“As the deep sea remains understudied and poorly understood, there are many gaps in our understanding of its biodiversity and ecosystems,” the Civil Society Forum of Tonga said in a statement published on MiningWatch Canada’s website. “This makes it difficult to thoroughly assess the potential impacts of deep-sea mining and to put in place adequate safeguards to protect the marine environment. The livelihood of a billion people in the world is based on the ocean including 90% of the Pacific People. The Ocean is our home and this is the essence of sustainable development.”

A man fishing early morning in Tonga. Image by Asia Development Bank / Flickr.

Is sustainable energy ‘sustainable?’


 Another argument made by companies like DeepGreen is that nodule mining is necessary to obtain the minerals needed for a global transition toward sustainable energy. There is growing demand for certain resources used in the production of wind turbines, solar panels and electric vehicles, according to a report by the World Bank. In fact, the report found that the production of minerals such as graphite, lithium and cobalt would need to increase by nearly 500% by 2050 to meet the growing demand for sustainable energy sources.

Yet Coumans says research shows that the minerals required for renewable energy can be found in existing terrestrial stocks and accumulations of electronic waste, and that the development of circular economies makes deep-sea mining an unnecessary exercise.

“This is not needs-based mining, this is profit based mining, and it’s unnecessary even if you were to believe the argument that we need these metals for the upcoming technology,” Coumans said. “The metals can be mined on land … and we don’t need to extend the harm that we do with mining on land into the deep sea environment.”

Wind turbines. Image by Richard Edmond / Flickr.

‘A precautionary approach’


While companies like DeepGreen say that nodule mining would be far less destructive than land-based mining, the report concludes that “mining of deep sea polymetallic nodules would result in severe and irreversible damage to deep sea ecosystems which include unique and largely unstudied species.” Further research is needed, the authors say, and nodule mining warrants “a precautionary approach.”

The Deep Sea Mining campaign, which is a member of the Deep Sea Conservation Coalition, a group of more than 80 nongovernmental organizations, calls for a moratorium on deep-sea mining, including the issuance of licenses to explore the seabed for minerals, until several objectives have been met. These include acquiring a comprehensive understanding of the environmental, social and economic risks of nodule mining; demonstrating that deep-sea mining can be managed in a way that prevents damage to the marine environment and the loss of biodiversity; ensuring that mining companies receive consent to mine from indigenous peoples in affected communities; conducting exhaustive research into alternative sources of minerals for renewable energy; establishing public consultation mechanisms; and reforming the ISA to ensure transparency and accountability.

A blue sky day over the blue ocean in the western CCZ. Image by Kirsty McQuaid, DeepCCZ expedition / NOAA.

“What people need to understand is what is at risk,” Coumans said. “The risk is to all of the ecosystems that are associated with the deep sea, and that goes right through to the fisheries that a lot of Pacific island nations rely on for food security and also for their livelihood. And the risk is also to the global community. If you destroy these nodules … you are not going to get them back in our lifetime, and you will be destroying the species that are associated with these nodules, as well as the microorganisms, and all the potential that they hold for us going forward.”


Chin, A., & Hari, K. (2020). Predicting the impacts of mining of deep sea polymetallic nodules in the Pacific Ocean: A review of scientific literature. Deep Sea Mining Campaign and MiningWatch Canada.

Banner image caption: Nodules strewn across the seafloor. Image by the NOAA Office of Ocean Exploration and Research, 2019 Southeastern U.S. Deep-sea Exploration.

Elizabeth Claire Alberts is a staff writer for Mongabay. Follow her on Twitter @ECAlberts.

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