Deep Sea Mining : the nature of the resource, and the threat to ocean integrity

Prof. Richard Steiner writes in The Huffington Post, 20th October 2015: Adding to concerns about the disastrous decline in ocean ecosystems, now there is another emerging threat — deep sea mining.

While shallow water mining for sand, gold, tin, and diamonds has been conducted for decades, commercial deep sea mining has yet to occur anywhere. But that’s about to change.

Extensive deep sea mineral exploration is currently underway in international waters governed by the International Seabed Authority (ISA), under the U.N. Convention on Law of the Sea (UNCLOSUNCLOS The United Nations Convention on the Law of the Sea, also called the Law of the Sea Convention or the Law of the Sea treaty.), and within Exclusive Economic Zones (EEZs) of many coastal nations.

There are currently three main types of deep sea mineral deposits of interest to industry and governments:

1. Polymetallic nodules (also called “manganese nodules”) are potato-sized metal nodules found on the abyssal plain from 4,000m-6,000m deep. These nodules are rich in manganese, nickel, cobalt, copper, lithium, molybdenum, iron, and Rare Earth Elements. Nodules grow slowly over millions of years, to diameters from 5cm-50cm, and host unique invertebrate communities.
Currently, 13 national consortia operate exploration leases on 4.5 million km2 of the Clarion-Clipperton (Fracture) Zone (CCZ), between Baja and Hawaii. The U.S., as a non-party to UNCLOS and ISA, issued exploration leases on its own to Ocean Minerals Company (OMCO), a subsidiary of defence contractor Lockheed Martin, to explore for nodules in the CCZ. The only nodule deposits being seriously considered within a national EEZ at present are in the Cook Islands in South Pacific.

2. Seafloor Massive Sulphide (SMS) deposits are found beneath deep sea hydrothermal vents along the 67,000 km of volcanically active mid-ocean ridges and back arc basins, between 1,500m-5,000m deep. These contain high-grade copper, gold, silver, zinc, and other trace metals.
Deep sea hydrothermal vent ecosystems were first discovered in 1977 at the Galapagos Rift, and stunned the world of science, as these vent systems rely entirely on chemosynthesis rather than photosynthesis — the first ever known. Over 300 deep sea vent systems have been discovered so far, and it is estimated that perhaps only 500-5,000 may exist in the world ocean, making this one of rarest ecosystems in Earth’s biosphere.
China and Korea hold contracts to explore SMS deposits in international waters of the Indian Ocean, and Russia and France hold exploration leases on the Mid-Atlantic Ridge. Other SMS deposits being considered are in waters of Papua New Guinea (PNG), Vanuatu, Palau, Niue, Fiji, Micronesia, Solomon Islands, Tonga, and New Zealand. The Nautilus Minerals “Solwara 1” project in PNG waters is fully permitted, the mining ship and equipment are being built, and mining is scheduled to begin
in 2018. This would be the first commercial deep sea mining project in history.

3. Cobalt-rich ferromanganese crusts are found on summits and flanks of seamountsseamount A mountain rising from the ocean sea floor that does not reach to the water's surface. They are an important habitat for fish, corals and shellfish. at 400m-4,000m depth. There are some 10,000 seamounts in oceans rising at least 1,000m above the seabed (and perhaps another 90,000 smaller seamounts). Many are in EEZs of central Pacific islands (Federated States of Micronesia, Marshall Islands, Hawaii, Johnston Atoll), and in international waters of the tropical Pacific.
Metal crusts form on shoulders of seamounts, rich in cobalt, nickel, copper, iron, manganese; rare metals such as tungsten, platinum, bismuth, tellurium, etc.; and Rare Earth Elements. Crusts grow slowly, 1mm-5mm per million years, and can reach total thickness of up to 260 mm. Seamountseamount A mountain rising from the ocean sea floor that does not reach to the water's surface. They are an important habitat for fish, corals and shellfish. crusts are currently being explored by China and Japan in international waters of the western tropical Pacific, but many feel actual mining of seamount crusts would be by far the most problematic and least feasible.


Marine phosphate (fertilizer) and methane hydrate (energy) resources found in shallower waters, 100m-500m deep, are often discussed in context with deep sea minerals. Marine phosphate mining is in consideration off Namibia (currently under moratorium), New Zealand (the environmental permit was denied earlier this year, but the developer is considering reapplying next year), and off Baja Mexico, where Odyssey Marine has submitted its EIA for mining the Don Diego phosphate deposit in 70m water depth, 12-25 miles offshore. Japan has successfully tested methane hydrate, or “fire ice,” extraction from its offshore waters.

But here’s the problem.

The deep ocean, where mining is proposed, constitutes the largest and least understood biological habitat on Earth.

It’s an Alice-in-Wonderland world of extremes, extraordinary adaptions, bizarre organisms, beauty and mystery. The region is characterized by darkness (infused with sparkling bioluminescence), extreme pressure, cold temperatures, high biodiversitybiodiversity Biological diversity in an environment as indicated by numbers of different species of plants and animals. (perhaps millions of species, most yet to be identified), slow growth and reproductive rates, and high sensitivity to disturbance (low resilience). Given our poor understanding of deep sea ecosystems, growing industrial interest, rudimentary management, and insufficient protected areas, the risk of irreversible environmental damage here is real.

Environmental risks and impacts of deep sea mining would be enormous and unavoidable, including seabed habitat degradation over vast ocean areas, species extinctions, reduced habitat complexity, slow and uncertain recovery, suspended sediment plumes, toxic plumes from surface ore dewatering, pelagicpelagic The ecological area consisting of the open sea away from the coast and the ocean bottom. The pelagic zone contains organisms such as surface seaweeds, many species of fish and sharks and some mammals, such as whales and dolphins. Pelagic animals may remain solely in the pelagic zone or may move among zones. ecosystem impacts, undersea noise, ore and oil spills in transport, and more.

Due to the global rarity of deep sea hydrothermal vent ecosystems, the impact of vent mining would be disproportionately high relative to terrestrial mining.

Full-scale nodule mining on the abyssal plain would affect thousands of square miles of ocean floor, kill attached invertebrate communities, and create huge subsea sediment plumes that would flow and settle over thousands of square miles of seafloor. Such sedimentation would smother seabed habitat, reduce habitat complexity and biodiversity over vast areas, and post-mining recovery would be extremely slow. Mining of cobalt crusts on seamounts would cause enormous, possibly irreversible impacts to unique, productive seamount ecosystems.

Clearly, we need to avoid such ecological damage. Before any deep sea mining moves ahead, we would need much more extensive scientific research — species identification, community ecology, distribution, genetics, life histories, resettlement patterns, resilience to disturbance, and at least a 10-year continuous time series of observations to understand dynamics of proposed mining sites over-time. In addition, we need more robust management regimes at the ISA and in coastal nations, royalty-sharing and liability agreements, stakeholder engagement, and significant advancements in subsea technology.

Until this is achieved, the only wise policy is a global moratorium on all deep sea mining.

Source: Huffington Post, 20th October 2015. For the full text see


Marinet observes: Marinet is only too aware of the serious adverse consequences of mining the seabed. In the UK’s territorial seas and exclusive economic zone this occurs on a routine basis in the form of mining (dredging) the sea bed for sand and gravel (aggregate for the construction industry). The adverse impact on fish spawning and nursery grounds is immense, and all other marine life in the dredged areas is killed.

Marinet campaigns for a cessation of marine aggregate dredging, and is currently putting a proposal to the UK Government for an alternative source of sand to replace marine-sourced sand, click here for further details.

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