By Eleni Matheou

Nowadays, there is a growing global demand for rare earth elements and critical minerals such as nickel, manganese and lithium due to their importance in the production of components that support “green” technologies. Notable examples include the manufacturing of batteries, solar panels and even other types of equipment such as military gear.

As a result, more countries are becoming interested in exploring mineral deposits on the ocean floor, with some even aiming to implement commercial mining operations, though it is worth noting that none have been approved so far. Nevertheless, such deep-sea mining remains a controversial and relatively new industry, which understandably raises serious concerns about potentially irreversible impacts on sensitive and high-value marine ecosystems.

What is deep-sea mining?

Deep-sea mining is the process by which a variety of valuable metals and minerals are extracted from the seabed, usually at depths greater than 200 metres. This emerging industry can be classified into three main types of mining, depending on the targeted mineral resources:

  • Mining of polymetallic nodules, which involves collecting metal-rich nodules from flat abyssal plains
  • Mining of seafloor massive sulfide deposits, found near hydrothermal vents
  • Mining of cobalt-rich crusts, located on the slopes of undersea mountains and ridges

Each method presents its unique environmental concerns due to the extreme conditions and fragility of deep-sea ecosystems.

How is deep-sea mining done?

Polymetallic nodules are among the easiest resources to collect, as they lie loosely on the seabed surface. Specialised underwater robotic vehicles are used to collect them, operating at depths of around 4,000 metres. Two types of machines may be employed: robotic arms that pick up the nodules or hydraulic suction systems that vacuum up the nodules along with upper layers of sediment.

This process produces two types of sediment plumes:

  • Collector plumes, caused by the disturbance of the seafloor.
  • Discharge plumes, which contain waste materials returned to the ocean, either in mid-water or back on the seabed.

This process remains in its early experimental phase, as the full environmental impacts are still unknown. Scientists have expressed serious concerns that it could cause irreversible biodiversity loss.

Biodiversity in the deep ocean

The deep ocean is Earth’s largest and oldest biome, hosting extraordinarily rich and unique ecosystems. It is often characterised by its mysteries, as a vast portion remains unexplored due to its extreme conditions, such as low temperatures, total darkness and high pressure. New information and new species of living organisms are constantly being discovered.

This environment includes various habitats such as abyssal plains, hydrothermal vents, cold seeps and ocean trenches. Due to the extreme conditions, the biodiversity of the deep sea consists of organisms with remarkable adaptations, such as bioluminescent jellyfish, unusual octopuses [Dumbo octopus (Grimpoteuthis)], complex microbial communities, etc. Many of these species are endemic; they cannot be found anywhere else on Earth.

It’s also important to note that some of these organisms grow or reproduce at an extremely slow pace (over hundreds or even thousands of years), making them particularly vulnerable to disturbance.

Impact of deep-sea mining

As the potential impact remains uncertain, concerns are mounting. Deep-sea mining activities threaten marine biodiversity in several ways:

One major threat is the destruction of habitats. More specifically, the use of mining equipment causes physical displacement, which can destroy large habitat areas. Furthermore, discharge plumes can travel hundreds of kilometers, clouding the water, disrupting ecological processes, harming filter-feeding organisms and introducing toxic metals into food chains.

Another significant threat is the continuous noise and artificial light produced by mining machinery, which can severely disturb organisms adapted to absolute darkness and silence. For example, some species of whales (which can dive into the depths of the sea to hunt) rely on echolocation for communication, food detection and orientation, and may be seriously affected by noise pollution.

Additionally, since a large portion of marine organisms remain unidentified, there is a new risk of species extinction before we even get a chance to discover them.

Deep-sea organisms are considered vital because they support essential processes such as nutrient cycling, carbon storage and maintaining the chemical balance of the oceans. Disruption to these functions could result in long-term consequences for the health of the seas.

Regulation and measures to reduce impact

The International Seabed Authority (ISA), established in 1994, is the governing body responsible for regulating mining activities in international waters, where the ocean floor is considered to be the ‘common heritage of humankind’ according to the United Nations Convention on the Law of the Sea (UNCLOS). While the necessary requirements for mining approval have been established and regulated by ISA’s mining code, significant pressure is being exerted on the ISA to authorise contracts before adequate environmental safeguards are ensured.

In contrast, many scientists around the world are calling for a moratorium on deep-sea mining until we have a better understanding of its consequences. Notably, to date, 50 countries, including Greece and Cyprus have expressed opposition, saying ‘no’ to deep-sea mining.

Conclusion

Although deep-sea mining promises new sources of critical minerals and potential economic development for participating countries, the environmental cost may outweigh any possible benefit. The deep sea is not a barren wasteland, but a living and fragile web of life that plays a fundamental role in the proper functioning of our planet.

Knowing that biodiversity in such extreme environments is already threatened by climate change, pollution and overfishing, we must conclude that deep-sea mining might become the final blow.

It is time to apply the precautionary principle, showing restraint until we fully understand the consequences. As tempting as it may seem, the loss of irreplaceable species and ecosystems would be an overwhelming cost we may not be able to bear.

The biggest part of the immense wealth hidden beneath the surface may still be unknown to us, but we must never ignore it.

Eleni Matheou is a research & education officer at The Cyprus Environmental Studies Centre