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What a new study found about the long-term impact of deep sea mining

The findings have come at a time when there has been a growing demand for establishing a moratorium on all deep sea mining activity

Greenpeace activists from New Zealand and Mexico confront the deep sea mining vessel Hidden Gem in 2022. (Photo: Reuters)

A strip of the Pacific Ocean seabed that was mined for metals more than 40 years ago has still not recovered, according to a new study. It said that the mining had led to long-term sediment changes and reduced the populations of many of the larger organisms living there.

The study, ‘Long-term impact and biological recovery in a deep-sea mining track’, was published in the journal Nature on March 26. It was carried out by a team of scientists led by Britain’s National Oceanography Centre.

The findings have come at a time when there has been a growing demand for establishing a moratorium on all deep sea mining activity. In fact, last week, 36 countries attended a council meeting of the United Nations’ International Seabed Authority in Kingston, Jamaica, to discuss if mining companies should be allowed to extract metals from the ocean floor.

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What is deep sea mining?

Deep sea mining involves removing mineral deposits and metals from the ocean’s seabed. There are three types of such mining: taking deposit-rich polymetallic nodules off the ocean floor, mining massive seafloor sulphide deposits, and stripping cobalt crusts from rock.

These nodules, deposits and crusts contain materials, such as nickel, rare earths, cobalt and more, that are needed for batteries and other materials used in tapping renewable energy and also for everyday technology like cellphones and computers.

Engineering and technology used for deep sea mining are still evolving. Some companies are looking to vacuum materials from the seafloor using massive pumps. Others are developing artificial intelligence-based technology that would teach deep sea robots how to pluck nodules from the floor. Some are looking to use advanced machines that could mine materials offside of huge underwater mountains and volcanoes.

Companies and governments view these as strategically important resources that will be needed as onshore reserves are depleted and demand continues to rise.

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What are the findings of the study?

The study examined the impact of a small-scale mining experiment on a part of the Pacific Ocean’s seafloor. Carried out in 1979, the experiment involved removing polymetallic nodules off the seabed. The scientists analysed the 8-metre strip during an expedition in 2023.

They found that the experiment had led to long-term changes in the sediment of the area, and a dip in the population of the organisms living there.

“The evidence provided by this study is critical for understanding potential long-term impacts… Although we saw some areas with little or no recovery, some animal groups were showing the first signs of recolonisation and repopulation,” NOC expedition leader Daniel Jones told Reuters.

This is not the first time that scientists have raised concerns about deep sea mining. Previous studies have shown that mining below 200 metres can lead to harmful noise, vibration, sediment plumes, and light pollution. A 2023 study published in the journal Current Biology found that animal populations decrease where deep sea mining occurs and it leaves a wider footprint than previously thought.

(WITH INPUTS FROM AP)