Seabed mining is coming — bringing mineral riches and fears of epic extinctions

Updated: Jan 19, 2020

Plans are advancing to harvest precious ores from the ocean floor, but scientists say that companies have not tested them enough to avoid devastating damage.

By Olive Heffernan /

A ghostly sponge lives on a Pacific seamount, one of the environments targeted by contractors interested in mining the ocean floor.Credit: Zhang Jiansong/Xinhua/Alamy

In 1972, a young ecologist named Hjalmar Thiel ventured to a remote part of the Pacific Ocean known as the Clarion–Clipperton Zone (CCZ). The sea floor there boasts one of the world’s largest untapped collections of rare-earth elements. Some 4,000 metres below the ocean surface, the abyssal ooze of the CCZ holds trillions of polymetallic nodules — potato-sized deposits loaded with copper, nickel, manganese and other precious ores.

Thiel was interested in the region’s largely unstudied meiofauna — the tiny animals that live on and between the nodules. His travel companions — prospective miners — were more eager to harvest its riches. “We had a lot of fights,” he says. On another voyage, Thiel visited the Red Sea with would-be miners who were keen to extract potentially valuable ores from the region’s metal-rich muds. At one point, he cautioned them that if they went ahead with their plans and dumped their waste sediment at the sea surface, it could suffocate small swimmers such as plankton. “They were nearly ready to drown me,” Thiel recalls of his companions.

In a later confrontation, Thiel — who was at the University of Hamburg in Germany — questioned how industry planned to test the environmental impacts of sea-bed mining. He was curtly advised to do his own test. So he did, in 1989. Read more