Mining

Shallow-water mining not a ‘silver bullet’ to resolve growing global need for metals: Study

Shallow-water mining involves removing sediment-bearing minerals, which offer refuge to seafloor organisms; this could trigger local extinctions  

 
By Rohini Krishnamurthy
Published: Wednesday 14 September 2022
Photo: iStock
Photo: iStock Photo: iStock

Mining metals such as gold, cobalt and copper from depths of 200 metres (m) below the sea, also known as ‘shallow-water mining’, could trigger local extinctions of marine species, a new study has highlighted.

Such mining was not a sustainable substitute for deep-sea mining, where valuable minerals needed to build batteries critical for clean energy transition are mined from ocean depths greater than 200 m, the paper noted.

Deep-sea mining has not been implemented yet due to concerns over the environmental impacts of mining activities.

Meanwhile, there is interest in shallow-water mining as it is considered a relatively low-risk and low-cost option to satisfy the demand for metals and minerals. Also, technology for shallow-water mining already exists.

Laura Kaikkonen, visiting researcher from the University of Helsinki, Finland and the lead author of the study, told Down To Earth:

Although several shallow-water mining projects have either been considered or are being developed across the globe, most of these projects and even the existence of shallow-water minerals are unfamiliar to most people.

Namibia has been mining diamonds off its coast in depths of up to 130 m. Indonesia has been extracting placer deposits — sediments containing gold, silver, tin, and platinum.

Mexico, New Zealand and Sweden have proposed shallow-water mining, the report highlighted. Mexico is considering mining marine phosphorites, phosphate-rich nodules used in fertiliser and industrial chemicals, in water depths of 50-100 m.

Sweden is interested in exploring the shallow waters (60-150 m) of the Bothnian Sea for polymetallic nodules, mineral deposits containing nickel, cobalt, copper, titanium and rare earth elements.

New Zealand, however, pulled the plug on the project due to environmental concerns, according to the report.

Despite these developments, the researchers said, the impacts of shallow-water mining haven’t been thoroughly investigated. This could be because “shallow-water mining has been on many occasions compared directly to sand and gravel extraction,” Kaikkonen noted.  

“Further environmental impact studies have not been conducted as they have been thought to be similar to the impacts of sand and gravel mining,” the expert added.

Still, several claims, she said, have been made about shallow-water mining being an environmentally and socially sustainable alternative to land mining without evidence.

Impacts on marine life

Shallow-water mining involves removing sediment-bearing minerals, which offer refuge to seafloor organisms. This could trigger local extinctions and changes in species composition, the researchers warned.

Also, ploughing the seafloor releases plumes, which could impact water quality. Other issues could be the release of harmful substances from the sediment and disturbance from noise and light, the paper added.

“As shallow-water ecosystems are already under stress due to pollution, and the impacts of climate change, even seemingly small-scale mining activities can drastically affect marine ecosystems, especially at local scales,” Kaikkonen said.

Therefore, the researchers said shallow-water mining activities should not be considered the “silver bullet to resolve the growing global need for metals” until the environmental and socioeconomic impacts are thoroughly investigated.

Meanwhile, nations have not agreed on whether deep-sea mining should be permitted amid environmental concerns at the recently concluded 27th session of the Assembly of the International Seabed Authority.

“There is not enough rigorous scientific information available concerning the biology, ecology and connectivity of deep-sea species and ecosystems, or all the ecosystem services they provide,” Jessica Battle, an expert on global ocean governance and policy at The World Wide Fund for Nature had previously told DTE.

Without this information, she added, one could not understand the potential risks of the mining activity for deep-ocean biodiversity, ecosystems and human well-being.

The current paper was published in the journal Trends in Ecology & Evolution.

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