Going Deep: Cautious Steps toward Seabed Mining

The deep ocean was once assumed to be lifeless and barren. Today we know that even the deepest waters teem with living creatures, some of them thought to be little changed from when life itself first appeared on the planet. The deep ocean is also essential to the earth’s biosphere—it regulates global temperatures, stores carbon, provides habitat for countless species, and cycles nutrients for marine food webs.1 Currently stressed by pollution, industrial fishing, and oil and gas development, these cold, dark waters now face another challenge: mining. With land-based mineral sources in decline, seabeds offer a new and largely untapped frontier for mineral extraction, and companies are gearing up to mine a treasure trove of copper, zinc, gold, manganese, and other minerals from the ocean floor.2,3 The ocean floor is home to a wealth of species, some of which—such as this bamboo coral (Isidella tentaculum)—have only recently been discovered. Proponents of seabed mining claim it causes less ecological damage than terrestrial extraction. ... Scientists, regulators, and mining companies are now collaborating on frameworks and strategies for mining the seabed responsibly. Cindy Van Dover, director of the Duke University Marine Laboratory and chair of the school’s Division of Marine Science and Conservation, says that’s encouraging, given that seabed mining appears to be inevitable. “There’s been a lot of engagement on the environmental side,” Van Dover says. “A hundred years from now, people will look back and ask if we got this right. We need to be sure that we do.” Copper grades, or the percentage of copper per unit of mined substrate, have declined with steadily rising extraction, from a high of 10–20% during the late nineteenth century to less than 1% today.4 By contrast, copper grades in seabeds slated for exploitation in 2018 by the Canadian mining company Nautilus Minerals, lying under 1,600 m of water off Papua New Guinea, average 7.2%.5 It’s estimated that 500 billion metric tons of polymetallic nodules—mineral clumps loaded with varying levels of manganese, cobalt, nickel, and copper—lie scattered under waters up to 6,000 m deep in the Pacific, Atlantic, and Indian oceans.6 Proponents of seabed mining assert that extracting minerals from the deep ocean will inflict less environmental damage than mining on land, which displaces communities, removes entire ecosystems, exacerbates erosion, and pollutes groundwater, rivers, and streams. But according to Craig Smith, a professor of biological oceanography at the University of Hawai‘i at Mānoa, seabed mining will also stir up vast plumes of sediments, some of which could resettle over areas much larger than the mine sites themselves. Scientists worry the plumes could cause widespread ecological damage and kill off deep-sea fauna that they know little about. Without appropriate regulations, they say, seabed mining will further erode the ocean’s capacity to provide essential ecological services, adding to what are already acute concerns for the ocean’s overall health. “Deep-ocean ecosystems can be incredibly fragile,” Smith says. “And it’s possible that after the mining starts, huge areas could be impacted before any one of them has a chance to bounce back.”