The Editor says: The deep sea may be the very birthplace of life on Earth, yet our understanding of the ocean remains limited. What creatures still dwell in the deep? We cannot fully confirm that yet. So as the age of deep-sea mining arrives, could it spark a conflict with our ecosystems? Join Blu for a closer look! Originally published in Science Monthly Issue 500, "The Age of Deep-Sea Mining? The Conflict Between Seabed Mineral Extraction and Marine Ecosystems" 2023.08.15
The International Seabed Authority (ISA) — the organization responsible for managing the international seabed, seabed-related resources, and overseeing international deep-sea mining activities — recently held meetings at its headquarters in Kingston, Jamaica, to discuss whether companies may begin excavating minerals and precious metals from the seabed, including cobalt, nickel, and sulfides. Proponents of deep-sea mining argue that research into electric vehicles and renewable energy batteries has been flourishing in recent years, and that developing these fields will drive up demand for precious metals — making deep-sea mining a potential solution for meeting today's demand while supporting a low-carbon economy. However, research has already indicated that the potential ecological impact of deep-sea mining may be far greater than we imagine. A recent study published in Current Biology was the first to examine what effects mining cobalt-rich crusts from the deep sea would have on the deep-sea environment.
What Impact Does Deep-Sea Mining Have on Marine Life?
In the deep sea, hard mineral layers rich in cobalt form part of underwater mountain ranges and represent one of the three types of deep-sea resources that countries have proposed to the ISA as mining targets. In 2020, the marine resource survey vessel Hakurei, operated by the Japan Organization for Metals and Energy Security (JOGMEC), excavated a 120-metre strip of cobalt-rich crust from a deep-sea mountain range in the northwest Pacific during a two-hour dig — marking a pioneering step in deep-sea mining. To determine the impact of the mining activity on the local ecosystem, scientists reviewed seafloor footage collected by remotely operated vehicles (ROVs) and found that within one year of the excavation, the density of active marine life in the area — such as shrimp and fish — had declined by 43%, while neighboring areas saw a decline of 56%.
Travis Washburn, a benthic ecologist at Japan's National Institute of Advanced Industrial Science and Technology (AIST) and co-author of the study, said he had never previously considered what kind of ecological impact this type of small-scale deep-sea mining might have. He suggested that the reason fish and shrimp left the area may be that the mining operations and sediment contamination disrupted their food sources. Beyond the mining zone itself, however, other findings in the study showed that waters outside the mining area were also considerably affected.
Japan's marine resource survey vessel Hakurei. (Ootahara, CC0, Wikimedia Commons)
A separate study by a team from the University of California, Santa Barbara (UCSB), recently published in the journal npj Ocean Sustainability, found that the movements of tuna living near the ocean surface may also be affected by mining activities. The researchers found that climate change will drive large numbers of tuna into the Clarion–Clipperton Zone (CCZ), located between Hawaii and Mexico in the eastern Pacific — an area that is also a major focus of deep-sea mining operations.
photo credit：Irina Iriser
According to the study's projections, before the mid-21st century, the total population of skipjack tuna (Katsuwonus pelamis) in the region will increase by approximately 31%, while yellowfin tuna (Thunnus albacares) will increase by approximately 23%. Although data on whether deep-sea mining affects animals in the surface ocean remain limited, Diva Amon, the study's lead author, noted that deep-sea mining could harm tuna and other species such as the leatherback sea turtle (Dermochelys coriacea). For instance, sediment plumes produced during mining operations could contaminate seawater and damage the gills and filter-feeding organs of fish; the same problem may arise when mining waste is discharged back into the water. In addition, noise generated by mining operations could alter tuna feeding and reproductive behavior. The impact of deep-sea mining may therefore extend from the ocean surface all the way down to the seafloor.
Will Deep-Sea Mining Be More Destructive Than Land-Based Mining?
On the other side of the debate, The Metals Company — a mining start-up based in Vancouver, Canada — is a proponent of deep-sea mining. The company is actively seeking permits to extract minerals from the seabed and argues that deep-sea mining will help advance the green economy. It also contends that the impact of sediment plumes can be minimized, and that current mining contractors are not targeting polymetallic nodules — mineral-rich seafloor sediments found in the deep ocean. Amon, however, believes that deep-sea mining is unlikely to replace land-based mining of precious metals; both will continue and cause dual damage to two very different environments on Earth. Washburn, for his part, argues that while the direct damage from deep-sea mining may be less severe than that from land-based mining, the fact that it would disturb vast stretches of the seabed could seriously disrupt marine carbon sequestration.
At this stage, humanity's understanding of the deep sea — and of deep-sea mining itself — remains far from sufficient. Amon believes that scientists first need to understand what organisms inhabit the deep sea before they can begin to determine how large-scale deep-sea mining would need to be before it causes critical and severe damage to marine ecosystems. Research into deep-sea science is slow and expensive, and scientists need more time and funding to understand the consequences of deep-sea mining.
Editor-in-charge: Jenny Tsai
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