Deep Sea Mining, Part 2: The Next Frontier, or the Ultimate Suicide Mission?

In our in-depth 4-part series, we explore the implications of deep-sea mining: where the drive to mine our ocean depths is coming from, what those effects are, what areas of the ocean are being explored, and where to go from here.

(See list of all articles below.)

Mining Effects on Ecosystems and the Earth

In the first part of our series, we saw that deep-sea mining businesses are planning to explore further, pushing for full-powered extraction to commence on mining’s ‘final frontier’. In this second installment, we look at the effects on oceans, and consequently the planet, of deep-sea rare metal and mineral extraction.

“To the best of our knowledge, life originated in hydrothermal vents…” 

(Van Dover et al., 2018)

Profuse venting at the Beebe Vent Field, approximately 5000m below the surface. Extremely high temperatures (nearly 400 degrees Celsius) mean that many metals are present in the plume, which gives it a distinctive black-smoker appearance. Image credit: Wünderbrot – Own work, CC BY-SA 4.0

Deep-sea mining is seabed mining at depths lower than 200 metres to extract rare metals and minerals such as copper, nickel, aluminium, manganese, zinc, lithium, cobalt, gold, and silver. Different types of pollution resulting from this type of extraction—including sound, light, vibratory, and physical, as well as muddying, fuel leaks and toxic spills—negatively affect species and habitats on many different levels. We can therefore safely assume that while there may not be toxic tailings dams as are present on land mining operations, there will be offloading of huge amounts of toxic waste materials into the surrounding oceans, wreaking destruction and poisoning waters.

People with protection suits analysing seawater on the beach
People with protection suits analysing seawater on the beach

Scientists are only now realising what rich life forms and ecosystems exist at the deepest levels of our oceans, and that potentially much of deep-sea marine life isn’t yet discovered. Seabeds at these depths have been largely (and wrongly) assumed to be formless, muddy plains. Mining and extraction of minerals at these levels would not only disrupt these ecosystems, but likely destroy the evolutionary origins of life itself.

Interconnections between different water levels would also obviously be disrupted. We haven’t been able to realistically appreciate what the destruction of these ecosystems would mean. Research is only just starting to explore the likely consequences of human interference with these natural cycles.

Polymetallic Nodules

Of major interest to mining companies are polymetallic nodules. Polymetallic sulphides and cobalt-rich ferromanganese crusts, which can be found in all oceans, are also in demand. Polymetallic nodules are small rocky clusters rich in these sought-after metals and elements, formed over millions of years on the seafloor. These minerals are used for production of many ‘eco-friendly’ low carbon energy technologies like electric vehicle batteries and solar panels, as well as electronic devices. They are also utilised in the defence industries.

Polymetallic nodules on the sea floor
Photo credit

The formation processes of polymetallic nodules are not yet fully understood. They’re found on abyssal seabed plains, at depths of 3,500–6,500 metres (approximately 11,500 to over 21,000 feet). These vast, flat areas are covered in sediment from hydrothermal vents formed in seamounts.

Seamounts are underwater mountains rising more than 300 metres (1,000 feet) from the seafloor. Home to enormous deep-sea biodiversity including coral reefs, forests, sponge beds, and hydrothermal vents, they provide habitats to millions of interdependent species.

Seamounts - underwater mountains
Photo credit

Hydrothermal vents are like hot springs created by underwater volcanoes located on the edge of converging tectonic plates, deep in the ocean. Cold seawater is heated by the hot magma released by the underwater volcanoes, which then emerges to form the vents, reaching temperatures over 370° Celsius (700° Fahrenheit).

Hydrothermal vent on ocean floor
Hydrothermal Vent. Photo credit:

Deep-sea mining equipment grinds these potato-shaped polymetallic nodules into a slurry (dense liquid) that gets pumped to ships on the surface via long flexible pipes. Materials are then transported onshore for fine processing. This process creates sediment plumes. These disperse widely, adversely affecting ecosystems, and basically suffocating animals. It’s already understood that sediment plumes will likely destroy more wildlife in the future due to thermal pollution, with eventual changes in temperature and in light not being able to penetrate the water.

Image credit Some forms of deep-sea mining will stir up fine sediments on the seafloor consisting of silt, clay and the remains of microorganisms, creating plumes of suspended particles. It is unclear how far these particles may disperse beyond the mining area, how long it would take for them to resettle on the seafloor, and to what extent they may affect ecosystems and species, for instance by smothering animals or harming filter-feeding species that depend on clear, clean water to feed, such as krill and whale sharks.
Sediment plumes seen from space
Example of sediment plumes over the Yangtze Bank in the Yellow and East China Seas. Photo credit

Additionally, seabed erosion caused by disruptive upheaval of the deep-sea ecosystems could also change thermohaline circulation (general oceanic circulation of important deep-water global currents, controlled by differences in temperature and salinity). These currents affect the Earth’s climate by distributing heat and cold around the world. Simultaneously, the process of thermohaline circulation absorbs carbon dioxide from the poles, storing it in the deepest levels of the oceans for hundreds of years. If these worldwide currents were to be affected by deep-sea mining, we can imagine an effective speeding-up of climate disruption and ocean global warming (with all the devastation this would produce).

Thermohaline currents are an important feature of the hydrosphere and play a key role in the global water cycle, moderating temperature and revitalizing water around the globe. Flowing like huge underwater rivers, they transport heat, salts, dissolved gases from the atmosphere (such as carbon dioxide), as well as nutrients vital to phytoplankton and other marine life. 

Thermohaline circulation around the earth's oceans
Image credit Jessica McCollum

We don’t yet know how this is going to affect fish spawn and reproduction of the species which have adapted to life at a deep-sea level. They are generally slow-growing, mature later, live longer and have fewer offspring.

Deep-sea mining companies are fond of boasting that their operations will produce no tailings – the waste materials from mining which are a key environmental impact of mining on land. However, the marine mining equivalent will be 24/7 discharge of wastewater laden with sediment after preliminary processing by a surface support vessel. This would contain unknown quantities of heavy metals that could contaminate marine food webs and commercially valuable fisheries.

Glow-in-the-dark sharks. In February 2021, scientists observed bioluminescence in three species of deep sea sharks, including Dalatias licha (pictured), the largest known luminous vertebrate. Image: Mallefet, Stevens and Duchatelet, 2021 / CC BY 4.0.
Disruption Spells Destruction

Joe Brewer of Earth Regenerators, referring to the work of Will Steffen of the Stockholm Resilience Centre, writes that 6 of the 9 planetary boundaries have (likely) already been crossed, the last 2 of which include ocean acidification (from absorption of about 25% of the increasing emissions of carbon dioxide), and freshwater use (increasing across the planet). This is not only a flashing red warning light for the continued existence of life forms on planet Earth in general, but an especially ominous reminder that any form of mining the ocean, its survival already highly stressed by human intervention, is a knife-edge tipping point, the other side of which is an abyssal point-of-no-return.

Satellite-Based Assessment of Ocean Acidification
Satellite-based assessment of ocean acidification. Image credit

Equally important, there are non-living treasures under threat of destruction through the practice of deep-sea mining, including fossil beds of 16 million-year-old whale skulls thought to belong to 6 extinct species.

While it’s referred to as the ‘final frontier’ in mining circles, and it’s smothered in green-speak promises of sustainable practices, there’s no doubt that allowing full-throttle deep-sea mining would result in the devastation of marine life and the ultimate destruction of our planet.

In our next installment, Deep Sea Mining, Part 3: Awash in Sustainability-Speak, we explore which areas of the oceans are on the radar for exploration and further mining, and why mining companies are pushing for full-force extraction to commence.

*  *  *

The Miner Network is Changing the Face of Mining

With the clear intention to improve existing land mining practices – via regenerative processes, chemical-free processing, and fair labour contracts and working conditions, Miner is changing the face of mining.

Learn about The Miner Pledge here.

We invite leaders across the global mining industry to join us in proactively taking mature steps towards planet preservation.

Collaborate with us to begin a mining narrative that transcends the exploitative thinking that brought us to this teetering precipice. Let’s find our way together to a new (and ancient) paradigm—what author and activist John Perkins calls “moving away from a Death Economy to a Life Economy.” It can be done.

JOIN The Miner Network mailing list and stay informed of the upcoming launch of MINER token.

~ Abheeti Kathryn Pass


Here are the other installments in the series:

Deep-Sea Mining, Part 1: A Shining Example of Misguided Human Ingenuity

Metal-Minded Humans’ Drive for More


Deep Sea Mining, Part 3: Awash in Sustainability-Speak 

The Where, The Who, The Why


Deep Sea Mining, Part 4: The Eco-centric Response

Where To From Here? (to be published next week)