Shallow water extraction at sea: hardly foreseeable consequences for people and the environment

Environmentalists have huge concerns about deep-sea mining. Meanwhile, companies are increasingly turning their attention to shallow-sea areas to mine for minerals and metals. The consequences are difficult to predict.

At the end of 2021, the Scandinavian Ocean Minerals (SOM) company turned to the Swedish environmental authorities. The mining company has applied for permission to drill test holes in Bottensee, a part of the Baltic Sea between Sweden and Finland. The ultimate goal is to extract manganese nodules at a depth of between 60 and 150 meters, i.e. in a relatively shallow area of ​​the sea. To do this, the company would also need an exemption from Sweden’s general ban on dumping mined bottom sediments back into the sea.

Manganese nodules contain manganese and iron, but also the economically interesting elements copper, nickel and cobalt.

(Photo: Picture Alliance / team ROV, GEOMAR-Helmholtz-Z.)

A decision has not yet been made in Sweden, but the case illustrates two things: the world is thirsty for raw materials. And the extraction of mineral resources from the seabed is increasingly the center of attention.

So far, public attention has mainly focused on deep-sea mining, which is only developing gradually, i.e. the extraction of raw materials such as manganese nodules or massive sulfides from water up to 5000 meters deep. The International Seabed Authority (ISA), headquartered in Kingston, Jamaica, had already issued exploration licenses to Germany at the turn of the millennium for an area of ​​the central Pacific – the Clarion Clipperton Zone (CCZ) – to Germany. But deep-sea mining still seems a long way off: technically complex, expensive and extremely risky for the still partially unknown environment.

With rising commodity prices and deepening geopolitical conflicts, this form of mining may be closer. ISA is currently preparing an international framework for the exploitation of deep-sea mineral resources in international waters.

Little explored effects

It would be easier to extract mineral resources from the continental shelf, that is, those sea areas that are located in front of the coasts. With water depths of mostly up to 200 meters, the raw materials are not only much easier to extract than in the deep sea, but they also have to be transported less far. Furthermore, up to a maximum distance of 200 nautical miles – 370 kilometers – from the coast, the areas are considered exclusive economic zones, so the national authorities decide on the mining activity.

However, according to some experts, this shallow-water extraction – also known as shelf extraction – is ecologically even more questionable than deep-sea extraction, which has only been partially studied in terms of environmental consequences. “Unlike deep-sea extraction, the biomass of organisms is much higher in this area,” says Annemiek Vink of the Federal Institute of Geosciences and Natural Resources (BGR) in Hanover. “Also, phytoplankton, which is very important for storing carbon dioxide from the atmosphere, will be affected.”

Raw materials have been mined on continental shelves for more than 100 years: on the one hand, there are oil and gas platforms all over the world. The two fossil fuels are also mined in German territorial waters: in the North Sea at the Mittelplate oil field off the coast of Dithmarschen and in the Doggerbank natural gas field. Added to this is the global extraction of sand and gravel for construction purposes, including in the German North Sea and the Baltic Sea.

But now other mineral resources in shallow waters are attracting the attention of mining companies: minerals and metals. This is what the researchers Laura Kaikkonen and Elina Virtanen from Helsinki write in the journal “Trends in Ecology and Evolution”. Since 2002, diamonds have been mined off the coast of Namibia at a depth of around 130 meters. The authors locate the world’s largest metal extraction in the sea off the coast of Indonesia: tin is mined there on a large scale.

And off the Mexican coast of the Pacific, phosphorites – that is, sediments containing phosphorus, for example for the production of fertilizers – must be raised from a depth of 50 to 100 meters. The Mexican environmental authorities are currently examining a corresponding application.

Large-scale mining

“The offshore industry started with oil and gas,” says BGR expert Carsten Rühlemann. However, this would attract oil or gas fields under the sea floor. “When mineral raw materials are extracted, on the other hand, vast areas are excavated extensively.”

Such large-scale mining not only puts companies in conflict with local residents and environmental organizations, but also with other potential users of a marine area, such as fishing, tourism and shipping.

As early as 2017, researchers from the Geomar Helmholtz Center for Ocean Research Kiel wrote that the search for raw materials in the sea was moving closer to the coast Mark Hannington, Sven pointed out that a large area of ​​about a third of the entire land mass lies below sea level on the Petersen continental shelf and Anna Kratschell in “Nature Geoscience”.

As these vast platform areas are largely geological extensions of the rocks on the mainland, the mineral resources mined on the mainland could also be developed in the offshore platform, they said. “When you consider the number of known mineral deposits on the mainland near the coast, the potential of the offshore continental shelf is astounding.”

Death Sentence for Ecosystems?

But an example from New Zealand shows how sensitive the public in industrialized countries can be to marine mining. There, an application to promote iron-rich sands off the North Island was recently rejected. For 20 years, Trans-Tasman Resources Limited (TTR) has wanted to extract up to 50 million tons of this sand every year off the west coast of the island, against opposition from fishermen’s associations, conservationists and organizations of the indigenous Maori.

The environmental agency EPA had already approved the license, but the Supreme Court canceled it in October 2021. The Supreme Court returned the request to the EPA on the condition that it respects historical treaties with indigenous peoples.

TTR continues to fight for a license. The mining business offers New Zealand an unprecedented economic opportunity, the company funds scientific research and the damage to the environment is however only short-term and manageable, TTR CEO Alan Eggers wrote in the newspaper ” New Zealand Herald “in August.

Tim Packeiser of the environmental organization WWF doubts that: “If sediments are removed over a large area, the habitat disappears, along with the organisms that live there.” Furthermore, the marine ecologist points out that the excess substrate will likely be dumped into the sea. This is a “death sentence” for sensitive ecosystems, especially coral reefs.

Or is it a green offshore industry?

“Since shallow water mining has not been considered in many places, environmental regulation is not sufficiently addressed in many national legislations,” write Kaikkonen and Virtanen. This gray area creates the opportunity to circumvent the rules and poses significant risks to the environment.

The two write that mining removes sediment and thus the basis of life for the inhabitants of the seabed, meaning the species could become locally extinct. Additionally, sediment clouds raised during dredging or vacuuming would cloud the water and suffocate the organisms. “In addition, there is a possible release of dangerous substances from the sediments and disturbance of marine life through the noise, light and vibrations of the work.”

The Swedish company Scandinavian Ocean Minerals mentioned at the beginning takes a different view: in essence, the mining of manganese nodules in the Baltic Sea offers the possibility of a “transition to a fossil-free society,” according to the website. After all, the minerals it mined could be used for batteries, solar cells and semiconductors, for example.

The consequences of mining on the Baltic Sea are also limited: the ecosystem is relatively poor in species and since the light does not reach the seabed anyway, there is no photosynthesis there. “Therefore, a local sediment plume on the bottom does not affect the primary production of algae”, points out the company, which speaks of “green offshore industry”.

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