Noise pollution from deep-sea mining could radiate across the ocean

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Scientists have found another reason why companies and governments should not mine the seabed – an area rich in mineral resources, from manganese to cobalt, but also important from a biodiversity point of view and highly vulnerable to human intervention. Noise pollution from activity could stretch across the ocean for hundreds of miles, creating a “cylinder of sound” from the surface to the sea floor that could affect ocean creatures.

A humpback whale. Image credit: Wikipedia Commons.

Researchers from the University of Hawaii, the Oceans Initiative, Curtin University and the National Institute of Advanced Industrial Science and Technology have found that the sound of a single deep sea mine can travel 500 kilometers (more 300 miles) in mild weather – with cumulative impacts adding up from multiple mines.

Seventeen companies are currently exploring the possibility of operating the Clarion-Clipperton Zone (CCZ), an area that covers 4.5 million square kilometers (1.7 million square miles) between Mexico and Hawaii. The area has many mineral-rich heaps known as polymetallic nodules, which are said to be carved out by gigantic machines.

If each company launches just one mine, an area of ​​5.5 million square kilometers (2.1 million square miles) would have high noise levels, the researchers estimated. This could have incalculable impacts on noise-sensitive species, such as whales, and undermine efforts to preserve mining-free zones to be used for scientific comparisons.

“What surprised me the most was how easy it would be for the sound of one or two mines to impact nearby areas that have been set aside as experimental controls,” said Rob Williams, co-founder of Oceans Initiative, in a statement. “With so many unknowns, we need a careful comparison of these preservation benchmark areas with the sites where mining is taking place.”

The issues of noise pollution

While mining companies are already testing smaller-scale prototypes of deep-sea mining systems, they have yet to share their underwater noise pollution data. This means that the researchers had to use the noise levels of other better-studied industrial activities, such as coastal dredges and vessels in the oil and gas industry, as placeholders.

Andrew Friedman, project manager of the Pew Seabed Mining Project, said actual noise levels from deep-sea mining are likely to be different once actual data becomes available, but they are more likely to be higher than the proxy data. Indeed, the seabed mining equipment is much larger and more powerful than the proxies used for the study. So this is a conservative estimate that will likely be much worse in real life if deep sea mining gets the green light.

But even this conservative estimate is concerning. The researchers found that noise levels within a four to six kilometer radius of each mine could exceed thresholds set by the US National Marine Fisheries Service, above which there is risk of impacts to marine mammals. Marine mammal species, known to be sensitive to noise, can be found throughout the Clarion-Clipperton area.

This includes endangered migrating baleen whales (Mysticetes) and deep-toothed whales (Odontocetes), for example, but the list goes on much longer. Deep-sea species, which we don’t know much about, are thought to use sound and vibration to communicate, navigate, and detect predators in the absence of sunlight. The noise would likely disrupt their ecosystems, the researchers said, in ways we don’t even understand yet.

This is why so many people are adamant that deep sea mining should not even begin until we can understand the environmental risks associated with it.

The island nation of Nauru invoked a UN rule in 2019 that could force the International Seabed Authority, the organization that regulates mining in areas beyond national jurisdiction, to complete the regulations that would allow mining by 2023. The move came despite concerns from scientists and NGOs, who argue that the science around deep-sea mining is still insufficient.

“The deep sea is potentially home to millions of species that have yet to be identified, and the processes there allow life on Earth to exist,” study author Travis Washburn said in a statement. “With careful study and management, we have a unique opportunity to understand and mitigate human impacts on the environment before they occur.”

Right now, there’s a lot about deep-sea mining we don’t understand, and the pleas of environmentalists are sure to clash with those of would-be miners. What kind of result will this lead to? Again, we’re not sure yet.

The study was published in the journal Science.

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