Noise pollution from suspected 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 noise from just one mine can travel 500 km (more than 300 miles) in mild weather conditions.
Seventeen contractors with exploration licenses are looking at mining the Clarion-Clipperton Zone (CCZ), an area spanning 4.5 million square kilometers between Mexico and Hawaii that has mineral-rich nodules known as polymetallic nodules.
The scientists estimated the noise impact if each of these mining companies started 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 to marine mammals.
Marine mammal species known to be sensitive to noise occur in the CCZ, including endangered migrating baleen whales and deep-sea toothed whales. Many deep-sea species – about which very little is known – are believed to use sound and vibration 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 potentially hosts millions of species that have yet to be identified, and the processes there enable life on Earth to exist,” said Travis Washburn, a 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 it before it occurs.
The impact of noise pollution from deep-sea mining is “understudied and neglected”, according to the report, whose findings have implications for mining regulations, by the International Seabed Authority (ISA).
The Pacific island of Nauru has said it plans to start deep-sea mining and has invoked a UN rule two years ago that could force the ISA to finalize regulations allowing deep-sea mining by next July. The scientific study follows widespread concerns from governments, corporations and environmental organizations that the science and management of deep-sea mining remains inadequate to continue exploration.
Moving forward without strict and transparent standards in place “would represent the start of a large-scale, uncontrolled experiment,” the report said. The authors called on the ISA to use the “precautionary principle” and, in the case of deep-ocean mining, to ensure that only one or two mines operate at a time until the impact of noise pollution is fully understood.
Beached whale on the Pacific coast of Mexico. Many marine mammals known to be sensitive to noise are found in the main mining area. Photo: Guillermo Arias/AFP/Getty
Their analysis used noise levels produced by existing industrial processes, such as dredging, oil and gas exploration, as proxies for deepwater mining. The findings show that if all 17 contractors operated one mine each, it would lead to increased noise levels over an area covering 5.5 million square kilometers – much larger than the European Union.
Craig Smith, co-author and professor emeritus of oceanography at the University of Hawai’i, said, “If our modeling is correct, environmental regulations, including the number of mining operations allowed in the Clarion-Clipperton area, may need to be reconsidered.”
Currently, companies are required to survey areas where mining is proposed and compare them to control areas at their sites where no mining will occur. These are known as ‘conservation reference areas’. Each contractor has up to 75,000 sq. km.
“Our models suggest that nowhere in … the entire 75,000 sq km is free of noise impact,” Smith said. “The regulations may need to be changed so that the control zones are further away.
“We haven’t been able to do the studies, but if the mining operations continue at the same time, it could have a big impact on a whole bunch of organisms.”
The authors, who were unable to find peer-reviewed data on the noise levels of 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 seabed mining components in a timely manner,” they wrote in the report.
Their findings are likely to underestimate noise levels, the scientists suggest, because the machines they modeled operate in shallower waters. They are also likely to have missed acoustic energy generated by heavier deep-sea machinery, as well as auxiliary ship pumps and other sound sources.
The ISA is tasked with protecting the marine environment from “serious damage” from seabed mining. While there are recommendations for noise impact assessment, it has yet to define what constitutes serious harm, including unacceptable noise levels, according to the report.
In a statement, the ISA said: “Effective protection of the marine environment is ensured through requirements for baseline environmental studies and environmental impact assessments and monitoring as set out in the Exploration and Future Exploitation Regulations.”
Test mining and testing of mining components require an environmental impact assessment that includes noise measurements, the release said, adding that the testing will provide “a better understanding of the potential impact of noise” on the deep-sea bed and deep-sea biodiversity.
Add Comment