The threat of deep sea mining to marine mammals

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Noise pollution from proposed deep-sea mining could radiate across the ocean for hundreds of kilometers, scientists predict, creating a “cylinder of sound” from the surface to the seafloor.

An analysis by scientists from the Oceans Initiative in the US, the National Institute of Advanced Industrial Science and Technology (AIST) in Japan, Curtin University in Australia, and the University of Hawaii, published in the journal Science, found that the noise from a single mine could travel 500 km (over 300 miles) in mild weather conditions.

Seventeen contractors with exploration licenses are exploring the possibility of exploiting the Clarion-Clipperton Zone (CCZ), an area spanning 4.5 million square kilometers between Mexico and Hawaii, which has abundant mineral-rich lumps known as polymetallic nodules.

The scientists estimated the noise impact if each of these mining companies launched a mine in the CCZ. They found that noise levels within a 4-6 km radius of each mine could exceed thresholds set by the US National Marine Fisheries Service, above which there are risks of behavioral impacts on mammals. marine.

Marine mammal species, known to be sensitive to noise, are found throughout the CCZ, including endangered migratory baleen whales and deep-diving toothed whales. Many deep-sea species, about which little is known, are thought to use sound and vibrations to navigate, communicate, and detect predators in the absence of sunlight. Underwater noise is likely to “disrupt ecosystems,” said the authors of the paper, which was funded by the Pew Charitable Trusts.

“The deep sea is home to potentially millions of species that have yet to be identified, and the processes there allow life to exist on Earth,” said Travis Washburn, deep-sea ecologist at AIST. While much work remains to be done on the impact of noise, he said, there is still an opportunity to understand and mitigate them before they occur.

The impact of noise pollution from deep sea mining is “understudied and overlooked”, according to the report, whose findings have implications for mining regulations, prepared by the International Seabed Authority (ISA).

The Pacific island of Nauru has said it plans to start deep-sea mining and invoked a UN rule two years ago that could force the ISA to complete regulations allowing deep-sea mining by next July. The Science study follows widespread concerns from governments, corporations and environmental organizations that the science and governance of deep-sea mining remain inadequate for prospecting to advance.

Moving forward without rigorous and transparent standards “would represent the beginning of a large-scale, uncontrolled experiment,” the report says. The authors urged the ISA to use the “precautionary principle” and, in the event of exploitation of the deep ocean, ensure that only one or two mines are operating at a time until the impact of noise pollution is fully understood.

Their analysis used noise levels produced by existing industrial processes, such as dredging, oil and gas exploration, as proxies for deep-sea mining. The findings suggest that if the 17 contractors each operated one mine, elevated noise levels would be produced in an area of ​​5.5 million square kilometres, much larger than the European Union.

Craig Smith, co-author and emeritus professor of oceanography at the University of Hawaii, said: “If our model is correct, it could require a rethink of environmental regulations, including the number of mining operations allowed within the Clarion-Clipperton Zone.”

Companies are currently required to study the areas where mining is proposed and compare them to control areas within their sites where mining will not take place. These are known as “conservation reference areas”. Each contractor has up to 75,000 km2.

“Our models suggest that nowhere in… the entire 75,000 square km is free from the impact of noise,” said Smith. “It could require changing the regulations, so that the control areas are further away.

“We haven’t been able to do the studies, but if the mining operations are done simultaneously, it could have a huge impact on a large number of organisms.”

The authors, who were unable to find peer-reviewed data on noise levels from the few deep-sea machines that have been tested, also called for transparency. “We urge contractors to publish information on the sound source characteristics of all deep seabed mining components in a timely manner,” they wrote in the report.

Related: The cacophony of human noise is harming all marine life, scientists warn

Their findings likely underestimate noise levels, the scientists suggest, because the machines they modeled operate in shallower water. They also likely missed the acoustic energy generated by heavier deep-sea machines, as well as support vessel pumps and other sources of sound.

The ISA is tasked with protecting the marine environment from “serious damage” from deep sea mining. While it has recommendations for assessing noise impacts, it has yet to define what constitutes serious harm, including unacceptable noise levels, according to the report.

The ISA was contacted for comment but had not responded at the time of publication.

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