The potentially imminent start of deep-sea mining in international waters could impact whales, dolphins and porpoises, particularly in terms of noise pollution, according to experts who say there needs to be urgent research into the issue.
In a new perspective piece published in Frontiers in Marine Science, scientists from the University of Exeter, Greenpeace Research Laboratories, and Oregon State University say proposed deep-sea mining activities would likely produce a range of noises with frequencies that overlap with those used by cetaceans for communication purposes, potentially leading to behavioural changes in these animals.
The authors say most assessments of deep-sea mining’s potential impact on biodiversity have focused on “species associated with the seabed and not mobile marine megafauna” like whales and dolphins. This is partly due to a paucity of data on cetaceans in proposed mining areas, says lead author Kirsten Thompson, a marine scientist at the University of Exeter in the UK
“Cetaceans are a very diverse group of animals and most of what we know about them comes from studies closer to the coast and offshore islands,” Thompson tells Mongabay in an email. “Research in the open ocean is challenging and the fact that they have largely been overlooked in mining impact assessments is really a reflection of how little we know about the species that live there.”
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The impact on cetaceans could also be profound, because the species that routinely dive this deep (which include beaked whales) have already shown themselves to be highly susceptible to acoustic disturbance when at depth.
Naomi Rose, marine mammal scientist, Animal Welfare Institute
Deep-sea mining could begin in the near future
Deep-sea mining in international waters has not yet begun, but members of the International Seabed Authority (ISA), the UN-affiliated regulator, are working to finalise rules that would enable it to start in the near future — possibly as soon as this year. One proposed form of seabed mining would target polymetallic nodules, metal-rich rocks containing nickel, cobalt, copper, titanium and rare earth elements found on deep sea underwater plains. There’s increased demand for these materials for use in renewable energy technologies like wind turbines, solar panels and electric car batteries as countries strive to lower greenhouse gas emissions. These minerals are currently mined on land, but there’s a shortage of them required to meet the energy transition, according to a 2021 report by the International Energy Agency.
Supporters of deep-sea mining say this activity will generate a substantial and necessary supply of metals for the shift toward climate-friendly energy sources. They add that mining the seabed will be far less destructive than mining on land.
Yet critics say too little is known about deep-sea environments and species to properly assess the impact of deep-sea mining on the ocean. Moreover, they say what is known suggests that deep-sea mining would cause irreparable damage to ancient marine ecosystems that help support all life on Earth.
In June 2021, the Pacific island nation of Nauru, which sponsors a subsidiary of Canadian firm The Metals Company (TMC), triggered a “two-year rule” found in the United Nations Convention on the Law of the Sea (UNCLOS), to urge the ISA to allow its deep-sea mining operation to begin in two years under whatever rules are in place by then. Experts say this approval would set TMC’s operations into motion and pave the way for other companies and their sponsoring states to start operations across the world’s oceans.
In response to Nauru’s move, the ISA scheduled a series of meetings to finalise its mining rules within two years so that exploitation could begin. While some member states of the ISA have been supportive of moving forward, others, including France, Chile, New Zealand and Palau, have called for a moratorium, a “precautionary pause,” or even an outright ban on deep-sea mining. Many scientists, conservation experts and companies like Renault, Rivian, BMW and Samsung SDI also oppose deep-sea mining.
‘Sensitive to noise’
Cetaceans “produce and detect sounds within a number of specific frequency bands” for communication purposes related to foraging, social interactions, and breeding, according to the new perspective piece. But the authors say that deep-sea mining operations could interrupt these behaviours by transmitting various anthropogenic sounds at different frequencies — from equipment used for extracting, pumping and overseeing mining — through a process called “auditory masking.” Low-frequency sounds, such as the noise produced by surface vessels, could travel hundreds of kilometres through the ocean, potentially affecting cetaceans over an extensive area. The authors say it’s a “reasonable expectation” for commercial-scale mining to operate 24 hours a day.
The paper calls particular attention to the Clarion-Clipperton Zone, a 4.5-million-square-kilometre (1.7-million-square-mile) area in the Pacific Ocean earmarked for deep-sea mining, which provides habitat for up to 30 cetacean species, including threatened blue whales (Balaenoptera musculus), sperm whales (Physeter macrocephalus) and fin whales (Balaenoptera physalus). Beaked whale species, known to be highly sensitive to anthropogenic sounds such as military sonar, also inhabit the area.
“These elusive [beaked] whales really are the extreme deep divers of the whale family and likely forage at the depths where mining could occur,” Thompson says.
In September 2022, TMC and its operating partner, AllSeas, conducted a mining test in the CCZ to collect about 14 metric tons of nodules. The operation was hit by controversy after scientists tasked with monitoring the tests leaked a video showing sediment discharge being dumped onto the ocean surface, raising questions about the environmental impact of mining operations. A 2020 paper suggested that discharge could be environmentally destructive by dispersing sediment and dissolved metals. In a response published on its website, TMC called the incident a “minor event” that “did not have the potential to cause harm to the marine environment.”
The CEO of TMC, Gerard Barron, also tells Mongabay that the company is assessing its noise output and the potential impacts on cetaceans through the development of a “validated underwater sound model,” generated in collaboration with experts at HR Wallingford, an engineering and environmental hydraulics group, and the Scottish Association of Marine Science. The company gathered acoustic data during its recent mining test in the CCZ, which it will combine with three years of environmental baseline data to inform the environmental impact statement (EIS) that TMC is required to submit to the ISA when applying for a commercial mining license, he tells Mongabay in an emailed statement.
“The data gathered during the pilot collection system trials will allow us to understand any potential impacts on marine mammals and if required, how we can optimise our system to mitigate this impacts,” Barron says. He adds the company is working to ensure its operations “remain within environmental thresholds.”
TMC’s EIS would be made public if the company eventually makes an application to begin mining, the company said.
Thompson of the University of Exeter says it’s important for there to be scientific, peer-reviewed assessments of mining-related noise and its impact on cetaceans — but that such an assessment has yet to be published.
“We know noise pollution in the ocean is already a problem for cetaceans and introducing another industry that is expected to operate 24/7 would inevitably add to existing anthropogenic noise were deep seabed mining to go ahead,” Thompson said in a statement. “Despite this lack of information, it appears industrial-scale mining could soon begin in one of the planet’s few remaining undisturbed environments.”
Noise isn’t the only thing that could negatively affect cetaceans, according to the paper. Cetaceans might also be impacted by sediment plumes produced by mining vehicles on the seabed, as well as sediment discharge that could “increase turbidity in the water column and could mobilise contaminants.” The authors also raise concerns about future deep-sea mining operations that may target seamounts, which are rich in metals needed for renewable energy technology.
“Seamounts are now known as important offshore habitats for some cetacean populations that forage or regroup around them but we still lack basic knowledge of these fragile ecosystems,” Solène Derville, a co-author of the paper and marine mammal scientist at Oregon State University, said in a statement. “In this context, it is very hard to assess the magnitude of the impacts of seamount seabed mining on the animals that live and feed around these structures.”
The authors add that more research is needed to understand the possible impacts of mining plumes and seamount degradation on cetaceans.
Assessments ‘urgently required’
Naomi Rose, a marine mammal scientist for the Animal Welfare Institute, who was not involved in this study, says it would be “absolutely foolish” for deep-sea mining to go ahead.
“The impact on cetaceans could also be profound, because the species that routinely dive this deep (which include beaked whales) have already shown themselves to be highly susceptible to acoustic disturbance when at depth,” Rose tells Mongabay in an email. “But really — the impact on cetaceans is the deep sea’s least worry. The entire assemblage of species that make up benthic [seabed] ecosystems will be damaged and destroyed by deep-sea mining.”
Rose says that at the very least, “major environmental assessments should be made” before mining is permitted. “This is generally true, of course, for any human activity in pristine habitat, but in this case, it is urgently required,” she adds.
Thompson says such assessments, which would require thorough surveys of cetaceans in mining areas, would be “logistically challenging and therefore expensive,” but feasible.
“We can use acoustics, molecular methods, visual surveys and potentially remote sensing to identify which species are present in the deep ocean areas targeted for mining,” she says. “These surveys will take time, but we need this detailed information before any commercial mining goes ahead.”
Without sufficient knowledge of how deep-sea mining could impact cetaceans, mining shouldn’t go forward, Thompson says.
“Once mining has started,” she says, “it will be difficult to stop.”
This story was published with permission from Mongabay.com.
