The Ocean Column: Mining the Treasures of the Deep Sea

Polymetallic nodules on the deep seabed hold metals needed for clean energy. But as the world debates mining them, scientists warn of irreversible damage to fragile ecosystems which are still barely understood.

The World Beneath the Waves

The deep sea might look like a desolate, muddy wasteland, but in reality, it’s one of the richest and alien ecosystems on Earth. Stretching from 200 metres down to nearly 11,000 metres at its deepest point, this cold, dark realm could host as many as 10 million species, most of them still undiscovered.

 

Alongside this hidden biodiversity lie vast mineral riches. Over millions of years, metals such as nickel, copper, cobalt and manganese have slowly accumulated on the seabed in potato-sized lumps called polymetallic nodules. These were first discovered during the 1870s Challenger Expedition, the first major deep-sea voyage, but it wasn’t until the 1960’s when interest in using the nodules as a resource was considered.

The 19th Century Challenger Expedition revealed life in the deep sea and details of undiscovered seafloor geology, revolutionising oceanography forever. Image Credit: State Library Victoria on Wikimedia Commons.

The biggest concentration of the polymetallic nodules is found in the Clarion-Clipperton Zone (CCZ) of the Pacific Ocean, an area larger than the entire Amazon rainforest. Here, it is estimated that more than 21 billion tonnes of manganese, nickel and cobalt is scattered across the seafloor.

The Clarion-Clipperton Zone is an area rich in polymetallic nodules on the seafloor. Image Credit: US Geological Survey (Public Domain)

The nodules are now referred to as ‘battery rocks’ because the metals inside them are critical for modern technologies, from electric vehicles and renewable energy infrastructure to everyday electronic devices. Nodules can be extracted from the seafloor by deep sea mining, but since their discovery, there has been global debate about what to do with the CCZ and who can use it.

Polymetallic nodules, slow growing lumps of nickel, cobalt, manganese and copper found on the seafloor. Image Credit: Geomar Biddatenbank on Wikimedia Commons

Who Owns the Seabed?

 

Our oceans cover 71% of the Earth: this means that the seabed beneath it is larger than all land combined. So, how can an area of this size be managed? The United Nations attempted to answer this in 1982, when 169 states and the EU signed the UN Convention on the Law of the Sea (UNCLOS), which set rules for the use of the oceans.  The treaty agreed that the seabed in international waters belongs to everyone and not one individual country.

 

The International Seabed Authority (ISA) was created under UNCLOS to regulate and authorise all deep-sea mining activity. In 2000, the ISA and its member states began developing a set of rules for deep sea mining, with the CCZ at the heart of the conversation. More than two decades later, the negotiations are still ongoing and as of this year, no deep-sea mining regulations have been agreed.

 

Amid this indecision, the United States has never ratified UNCLOS. In March, The Metals Company announced plans to apply for mining rights in the CCZ under US law. A month later, President Trump signed an executive order in support of deep-sea mining in international waters, widely criticised as a violation of international law. Because the US is outside UNCLOS, this move risks undermining international governance of the seabed and raises concerns of a scramble for resources in the deep.

 

The Deep Sea Under Threat

This political uncertainty only sharpens the question: if mining does go ahead, what would it mean for the deep sea?

 

Nodules are found across abyssal plains, about 4,000 metres below the surface. These are the largest habitats on Earth, covering more than half the planet’s surface, and are home to diverse marine life. Far from being barren, they are alive with sea cucumbers, urchins, worms, and shrimp, which together form seafloor communities.

Life on the abyssal plains: diverse and highly adapted species thrive in one of the most extreme habitats on Earth. Image Credit: Greg Rouse (Scripps Oceanography), Nerida Wilson (Chief Scientist), FK200308 team / Schmidt Ocean Institute.

The nodules themselves also play an important ecological role. They provide microhabitats across the abyssal plain, with deep-sea corals and sponges using them to anchor and grow. Without nodules, these animals would lose their homes.

 

Deep-sea ecosystems are highly sensitive to disturbance, and mining could have devastating consequences. Heavy machinery would crush habitats, create plumes of sediment that smother life, and introduce light and noise pollution into an ecosystem evolved for silence and dark. Scientists warn that biodiversity loss would be inevitable and largely invisible to us at the surface.

 

438 species have been formally identified in the CCZ, and it’s thought that up to 90% of the animals living there are still unknown to science. This area is already a focus for the ISA’s environmental studies, but it is also one of the most targeted zones for potential mining.

 

Despite this, more than 20 exploration contracts have been granted to states and companies from China, Japan, India, the UK and Germany to name a few. These contracts allow exploration and environmental studies but not commercial mining, at least, not yet.

 

A Race to the Abyss?

 

The ISA’s 30th session, held in Kingston, Jamaica in March and July 2025, again failed to finalise the mining code. No exploitation licences have been approved. Instead, calls for a moratorium, a global pause on deep sea mining until the science is clearer, are growing louder. So far, 37 countries, including the UK, support this proposal.

 

The debate over deep sea mining captures a central tension of the 21st century: how do we power a green transition without sacrificing fragile ecosystems? Proponents argue the nodules are essential for decarbonisation and less destructive than land-based mining. Opponents, particularly organisations such as Greenpeace, argue that the ecological cost of mining the abyss would be catastrophic.

 

As the world awaits a decision, the deep sea remains silent, but the choices we make at the surface may echo there for millennia.

 

About the Author:

Millie is currently studying a MSc in Science Communications at UCL, she is inspired to educate others about relevant scientific concepts, from global issues to everyday life. Millie expresses a strong interest in ocean conservation, environmental sustainability and improving research awareness to connect people with science through informative writing. Find her on LinkedIn here: www.linkedin.com/in/millie-webb-513a45274.