As Rising Ocean Temperatures Break Records, Deep-Sea Mining and Migratory Tuna Veer on Climate Change-Driven Collision Course

Research Follows Unprecedented Seafood Industry Statement on Economic and Environmental Impacts of Deep-Sea Mining on High-Seas Fisheries; New Hawaii Law Targets This Looming Threat

In the wake of record-high global ocean surface temperatures, new research reveals that bigeye, skipjack and yellowfin tuna fisheries in the Eastern Pacific Ocean will increasingly overlap with projected deep-sea mining operations as climate change adjusts the range of these highly migratory species. This points to potential increased conflict over and impacts on some of the world’s most valuable and important fisheries if deep-sea mining moves forward. The study, published in Nature npj Ocean Sustainability today, focuses on the Clarion-Clipperton Zone of the Pacific Ocean, a maritime region southeast of Hawaii containing 1.1 million square kilometers (424,712 square miles) of deep-sea mining exploration contracts.

“The high seas harbor a trove of biodiversity, and there are critical sectors of our economy that depend on this biodiversity,” said study co-author Dr. Juliano Palacios Abrantes from the University of British Columbia. “There is already uncertainty about the impact of climate change on the health and geographic range of tuna. Deep-sea mining will only add to this uncertainty, further threatening tuna species and associated fisheries.”

The new research was released alongside a letter from seafood industry groups — the first of its kind — advocating for a pause in deep-sea mining development until the socioeconomic and environmental impacts could be more thoroughly analyzed. Up to this point, the seafood industry has not taken a stand on deep-sea mining. Among the signers are the Global Tuna Alliance, whose 48 industry partners account for 32% of the global tuna trade, and the Sustainable Seafood Coalition, which represents 45 U.K. seafood organizations.

“In the vast expanse of the high seas, critical for tuna species, we find ourselves sailing into uncharted territory with the unknown risks posed by deep-sea mining,” said Daniel Suddaby, executive director at Global Tuna Alliance. “From threats of prey food shortages due to disrupted midwater ecosystems to the potential upheaval of migration patterns caused by mining disturbances, we must navigate this uncertain landscape with caution. With climate change scenarios further complicating the picture, we cannot underestimate the stakes involved.”

The statement warns that deep-sea mining “poses a threat to the ocean and its inhabiting life. While the extent of deep-sea mining impacts is yet to be determined, it will certainly lead to significant habitat destruction and biodiversity loss, with many potential impacts on fisheries and seafood supply.”

The new research and statement come in advance of a pivotal and much-anticipated meeting of the International Seabed Authority (ISA) — the international body that regulates mineral activities on the high seas — in Kingston, Jamaica (July 10-23). Member countries are expected to debate the design and implementation of deep-sea mining regulations — even as opposition to ocean mining grows. The meeting immediately follows the July 9 expiration of a landmark two-year rule calling for the ISA to set regulations on deep-sea mining, which could set the stage for exploitation to begin immediately.

“We already have the triple crises of climate change, biodiversity extinction and pollution because we have failed to acknowledge and account for the risks of industrial activities,” said study lead author Dr. Diva Amon from the Benioff Ocean Science Laboratory at the University of California, Santa Barbara. “We can’t just hold our breath and hope that adding deep-sea mining, with its potentially significant environmental risks, will be okay. ”

In the new study, researchers identify the potential specific risks of deep-sea mining to the tuna industry. Working with two different projections on how climate change would impact the range of three tuna species, the authors looked at how the future ranges overlapped with the areas targeted for deep-sea mining operations. Due to climate change impacts on fish migration, the number of fish, or biomass, for these species would increase in the areas allocated for deep-sea mining by 10-11% for bigeye, 30-31% for skipjack and 23% for yellowfin by 2050 relative to today’s values.

“These fishing grounds may be distant, but the food they produce is consumed by millions,” said study co-author Dr. Douglas McCauley, professor at the University of California, Santa Barbara and director of the Benioff Ocean Science Laboratory. “We would be horrified at dumping mining waste across our food-producing regions on land. We shouldn’t be rushing into a decision that could significantly harm ocean ecosystems essential to planetary health and global food security.”

The study shows that deep-sea mining operations could harm these fisheries via four distinct pathways if operations are allowed to move forward, although the extent of harm for each pathway has yet to be calculated:

  • Deep-sea mining operations would generate two plumes of discharge, one where sediment is stirred up at the seafloor and a second where wastewater and fragmented material are discharged into the ocean from the surface mining vessel. Depending upon the depth of discharge, both could disrupt the feeding and breathing of tuna and their prey, as well as increase fish stress hormone levels, among other impacts. These plumes could extend the impacts of deep-sea mining horizontally for tens to hundreds of kilometers and vertically for hundreds to thousands of meters, impacting a wide area of tuna habitat.
  • Second, the return-water discharge plume is expected to contain elevated concentrations of toxic metals, which could be incorporated into deep-sea food webs and enter our seafood supply through tuna and other economically important species. Even if there were only low risks from toxic accumulation, this could still provoke a negative consumer reaction.
  • Third, mining noise could also be extensive and cause physiological and behavioral impacts on tuna and their prey, possibly leading them to change their feeding and reproductive migrations, which could potentially increase stress and reduce catch rates in affected areas.
  • Last, an increased density of mining vessels could limit or alter fishing vessel operations and possibly change tuna behavior. These impacts may extend more broadly throughout the ocean environment — for example, possibly impacting seabirds and their complex relationship with migratory tunas.

“The Mining Code currently does not regulate the depth of discharge plumes, while plumes have the potential to spread widely and impact pelagic communities, including fisheries,” said study co-author Dr. Jesse van der Grient from the South Atlantic Environmental Research Institute. “This work shows the need to consider the effects of mining on fisheries and consider mining regulations not just for the current environmental conditions, but also for future climate projections.”

A growing number of ISA member states are advocating for a precautionary pause, moratorium or ban on deep-sea mining until the science is clear on its impacts. More than a dozen ISA member countries have called for a pause or ban on mining operations around the globe, including France, Germany, Spain, New Zealand, Palau, Fiji, Costa Rica and more.

With the statement, the seafood industry signers join this group of countries. Alongside an earlier push from more than 800 marine science and policy experts from over 44 countries worldwide, the European Academies’ Science Advisory Council issued a statement calling for a moratorium. They are joined by banks, manufacturers, the fishing industry, Hollywood activists, civil society organizations and members of the public in calling for a moratorium.

Some countries and even U.S. states have taken legislative action against deep-sea mining. In early June, Hawaii Governor Josh Green signed a new law enabling the state’s Department of Transportation to prevent vessels engaged in deep-sea mining activities from mooring in Hawaii’s harbors. The new law follows a legislative resolution passed earlier this year urging Hawaii’s Department of Land and Natural Resources to prohibit seabed mining in the state’s territorial waters. The bill is the latest in a series of legislation from U.S. states to limit the impact of deep-sea mining activities in state waters, with lawmakers in California, Oregon and Washington already prohibiting the activity.

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