Noise from deep-sea mining may stretch hundreds of miles

As the world starts to wean itself off fossil fuels and turn to “greener” alternatives, the focus will turn to wind farms, solar energy, electric cars and improved batteries. All these technologies will require a high volume and wide range of metallic resources, many of which are in short supply – except in deposits under the sea bed. 

There is currently no deep-sea mining taking place, but the International Seabed Authority has granted 19 exploratory licenses in the Clarion Clipperton Zone (CCZ), an area of the Pacific Ocean between Mexico and Hawaii. Mining of the sea bed would involve mining platforms at the surface, a range of robotic mining machines and hydraulic pumps, as well as surface ships, all of which would generate underwater noise. 

A new study published in the journal Science examines the potential for underwater noise pollution from seabed mining operations, and concludes that the noise from one mine alone could travel approximately 500 km (about 311 miles) from the source and could potentially affect deep-sea species that are relatively unknown and unstudied. 

For the investigation, an international team of scientists modeled the potential noise pollution effects using known noise levels from oil and gas industry ships and coastal dredges. Although mining companies are already testing smaller-scale prototypes of deep-sea mining systems, they have yet to share their data on underwater noise pollution, so the researchers had to use noise levels from these better-studied industrial activities. 

True noise levels from deep-sea mining may be different from the proxies used in this study, but are likely to be higher, rather than lower, because seabed mining equipment is much larger and more powerful than the machinery used in the proxy activities. “These are probably conservative estimates,” noted Andrew Friedman, director of Pew’s seabed mining project. 

In addition, if there are several mining operations in an area, the sounds generated will overlap and interfere, potentially creating complex noise patterns in the underwater environment. The deep sea is the largest environment on Earth, and is home to organisms found nowhere else, many of which are likely to use sound to communicate, find food, navigate and avoid predators, given the absence of light at these depths.

Overall, 17 contractors are currently exploring the possibility of mining in the CCZ, an area that spans 4.5 million square kilometers (1.7 million square miles). The authors of the study estimate that, if each of the contractors were to launch just one mine, an estimated 5.5 million square kilometers (2.1 million square miles) – an area larger than the European Union – would have elevated noise levels. Not only could this level of mining activity have untold impacts on noise-sensitive species, but the noise generated would carry into areas known as “preservation reference areas” where no mining will take place. These areas have been set aside as controls to monitor the impacts of the mining activity and to use for scientific comparisons. 

“What surprised me most was how easy it would be for noise from just one or two mines to impact nearby areas that have been set aside as experimental controls,” said Rob Williams, co-founder of Oceans Initiative. “With so many unknowns, we need a careful comparison of these preservation reference areas to sites where mining is taking place in order to understand mining’s impacts. But noise will cross the boundaries between preservation zones and mining sites.”

Craig R. Smith is a professor emeritus at the University of Hawaii at Manoa. “Our modeling suggests that mining noise could impact areas far beyond the actual mining sites, including preservation reference zones, which are required under draft mining regulations to be unaffected by mining.” Professor Smith said this finding “could require rethinking of environmental regulations, including the number of mining operations allowed within the CCZ.”

“Estimating the noise of future equipment and installations is a challenge, but we don’t have to wait until the first mines are operational to discover the noise they make,” said Professor Christine Erbe of Curtin University. “By identifying the level of noise in the engineering design phase, we can better prepare for how this might impact marine life.”

The island nation of Nauru invoked a United Nations rule two years ago that could force the International Seabed Authority, to complete regulations that would allow large-scale seabed mining by July 2023. This deadline makes it unlikely that sufficient research will have been done to accurately assess the ecological risks from underwater noise pollution. Because of this, an increasing number of countries, experts, corporations, and environmental organizations are calling for a halt to any seabed mining until scientists can confirm that the mining will not cause harm to the marine environment.

Friedman said that the current study highlights how much remains unknown about mining’s potential impacts, not just on the deep ocean, but throughout the water column. At the moment, the science and governance surrounding deep-sea mining remain woefully inadequate. 

“The deep sea houses potentially millions of species that have yet to be identified, and processes there allow life on Earth to exist,” said Travis Washburn, a deep-sea ecologist at AIST. “While much work is still needed to determine the extent and magnitude of environmental impacts from deep-sea mining, with careful study and management we have a unique opportunity to understand and mitigate human impacts to the environment before they occur.”

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By Alison Bosman, Earth.com Staff Writer