Forty years after an initial deep-sea mining experiment was carried out on a strip of the Pacific Ocean sea floor, marine life is still showing very little signs of recovery – giving weight to those demanding a moratorium or outright ban on all deep sea mining activity.

The results – published this week in the scientific journal, Nature – provide critical evidence to the global deep-sea mining debate and discussions taking place this week at the UN-led International Seabed Authority meeting in Kingston, Jamaica.

It all relates to an experiment carried out in the Clarion Clipperton Zone in the Pacific Ocean back in 1979, where mining tests were carried out some 44 years ago. The results have shown the long-term changes to the sediments in the area while highlighting the decades-long recovery time for any signs of life.

The team, led by Professor Daniel Jones at the National Oceanography Centre and co-led by the Natural History Museum, recently visited the mining test site to find that the tracks of the 100-ton machine sent down to the seabed 44 years ago are still clearly visible, while the impact of the mining on some of the wildlife in this region is ongoing, four decades later.

Professor Daniel Jones, said: “To tackle the crucial question of recovery from deep-sea mining, we need first to look to the past and use old mining tests to help understand long-term impacts.

“Forty-four years later, the mining tracks themselves look very similar to when they were first made, with an eight-metre-wide strip of seabed cleared of nodules and two large furrows in the seafloor where the machine passed.

“The numbers of many animals were reduced within the tracks but we did see some of the first signs of biological recovery.”

What was found was “some recovery” of small and mobile animals living on the sediment surface. It was a type of large amoeba-like xenophyophore, a creature “commonly found everywhere in the Clarion Clipperton Zone,” said Dr Jones. 

“However, large-sized animals that are fixed to the seafloor are still very rare in the tracks, showing little signs of recovery.”

The study is the first glimpse of a timescale for which the ecology of the seafloor ecosystem will go through a series of successional stages of recolonisation and growth. In deep-sea mining regions, the study suggests, we could be looking at the span of decades for life to undergo this critical cycle.

“Our results don’t provide an answer to whether deep-sea mining is societally acceptable, but they do provide the data needed to make better informed policy decisions such as the creation and refinement of protected regions and how would monitor future impacts,” said Dr Adrian Glover, deep sea scientist at the Natural History Museum.

Delegations from 36 countries have been in attendance of a council meeting of the United Nation’s International Seabed Authority in Kingston, Jamaica this week to decide whether mining companies should be allowed to extract polymetallic nodules from the sea floor.

Current discussions are being held over the hundreds of proposed amendments to a 256-page draft mining code.

Meanwhile, environmental groups have called for mining activities to be halted, a move that – according to Reuters – is now supported by 32 governments and 63 large companies and financial institutions.

Deep-sea mining is increasingly being considered as a potential solution to supply the crucial metals required for advancing global technology and driving the transition to a net-zero energy future, though this has been heavily contested by environmental campaigners, scientists, and economists.

A key area of interest for mining is the Clarion Clipperton Zone, a vast region in international waters of the Central Pacific Ocean. Spanning over 6 million square kilometres, it is home to unique and biodiverse deep-sea creatures, many yet to be described by science, as well as a rich mineral resource of polymetallic nodules.

The International Seabed Authority, established in 1994 under international law, is deciding whether to allow deep-sea mining in the region and under what conditions. A key question in this decision is whether deep-sea ecosystems can recover from mining disturbances.

The published study offers a first glimpse at the decades-long process it will likely take for any signs of the recovery of life to follow such a disturbance.

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