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Deep-sea mining has long-lasting impact on marine ecosystems, research shows

A deep-sea mining test that lasted only two hours might have decreased fish and shrimp populations in the surrounding vicinity significantly even after a year, research in Japan showed.

Deep-sea mining is the extraction of valuable minerals from the ocean below 200 meters (650 feet), potentially impacting fragile ecosystems. 

Lately, it has become a contentious issue, as several countries and companies have joined the global race to mine resources including cobalt, copper, and manganese amid increasing demand for renewable energy and consumer electronics.

The research was based on an investigation into the environmental impact of Japan’s first successful test in 2020 to extract cobalt crusts from the top of Takuyo-Daigo deep-sea mountains, in the northwest Pacific Ocean, to mine cobalt, a vital mineral in electric vehicle batteries.

The data, examined by the researchers one month before and after, as well as a year following the experiment conducted at the site, showed that the mined areas became less habitable for ocean animals and created a plume of sediment that spread through the surrounding water, according to the study published Friday in the Current Biology journal.

One year after the mining test, researchers observed a 43% drop in fish and shrimp density in the areas directly impacted by sediment pollution, a statement accompanying the study said.

They also noted a 56% drop in the fish and shrimp density of surrounding areas, adding the research team thinks it could be due to the mining test contaminating fish food sources.

“’Enough to shift things’

Even a brief two-hour test could have long-lasting consequences on the marine life in a particular area, the research said, adding further study is needed.

“I had assumed we wouldn’t see any changes because the mining test was so small,” said the study’s first author Travis Washburn, a marine ecologist who works closely with the Geological Survey of Japan. 

“They drove the machine for two hours, and the sediment plume only traveled a few hundred meters. But it was actually enough to shift things.”

A Greenpeace activist holds a sign as he confronts the deep sea mining vessel Hidden Gem, commissioned by Canadian miner The Metals Company, as it returned to port from eight weeks of test mining, off the coast of Manzanillo, Mexico, Nov. 16, 2022. Credit: Reuters.

The study concluded that “although highly mobile swimmers likely simply leave the area, resulting in little loss of biodiversity, this may not be possible if multiple mining operations occur at similar times resulting in a very large, cumulative deep-sea mining areal footprint.” 

Experts say seabed ecosystems are not yet fully explored, so the impact of deep-sea mining on marine ecosystems is unknown.

Friday’s research authors said they would need to repeat the study several times to understand better how deep-sea mining impacts the ocean floor. 

They said that multiple years of data should be collected before a mining test occurs to account for any natural variation in ocean animal communities.

“These data are really important to get out,” Washburn said in the statement. “A set of regulations is supposed to be finalized soon, so a lot of these decisions are happening now.”

“We’ll have to look at this issue on a wider scale, because these results suggest the impact of deep-sea mining could be even bigger than we think.”

Lasting impact

James J. Bell, a professor at the Victoria University of Wellington in New Zealand who was not involved in the study, said the “results demonstrate just how susceptible the marine communities associated with seamounts might be to the impacts of mining and that these impacts could be long-lasting.”

“Importantly, this study also shows that even very small-scale mining activity can have lasting impacts. Until we have a full understanding of what the impact of mining is on these ecosystems, we should take a very cautious approach,” Bell said, especially given that seabed mining is being considered by many states worldwide.

Commercial deep-sea mining has not yet begun, though exploratory licenses have already been granted by the United-Nations-backed regulator International Seabed Authority, or the ISA, which has authority over seafloor resources outside a given country’s jurisdiction.

It has yet to finalize a set of deep-sea mining regulations. The ISA started global discussions in Jamaica on Monday to possibly adopt mining regulations, with talks expected to continue until the end of July.

Many countries, the seafood industry, marine conservancy groups, and scientists have called for a “pause” to proceed in developing regulations and complete them before granting any licenses to mine seabed thousands of feet under the ocean’s surface. 

Kat Bolstad, an associate professor at the Auckland University of Technology, said deep-sea mining could be “catastrophically destructive to the immediate seafloor, and producing noise, vibrations, clouds of sediment, and other impacts that we cannot yet fully predict.”

“The effects of large-scale deep-sea mining are likely to be substantial, longer lasting, and more complex than we can anticipate,” she said.

“There is widespread scientific agreement: We need a far greater understanding of deep-sea ecosystems before we can make responsible decisions.”

Edited by Malcolm Foster.