The deep sea gold rush has just got more frenzied. Copious reserves of “rare earth” mineral deposits have turned up in the sediments in the floor of the Pacific Ocean. These metals are vital to many green-energy and electronic technologies, such as hybrid car batteries.

They were thought to be in short supply: a recent US Geological Survey estimate put world reserves at 100 million tonnes. But now Yasuhiro Kato of the University of Tokyo, Japan, and his team have found the minerals in such high density that a single square kilometre of ocean floor could provide one-fifth of the current annual world consumption. Two regions near Hawaii and Tahiti might contain as much as 100 billion tonnes.

Kato was led to the sea floor when it occurred to him that many land-drawn rock samples containing metallic elements were originally laid down as ocean sediments. “It seems very natural to find rare-earth element-rich mud on the sea floor,” Kato says.

China crisis

Though some rare-earth deposits are found in Russia, other former Soviet states and the US, China controls 97 per cent of the world’s supply. Mining from the ocean floor will open up this market, which will be welcomed by many governments and companies. But will it cause environmental destruction?


“It depends on the nature of the habitats that are being mined,” says Jon Copley, an oceanographer based at the University of Southampton, UK. The rare-earth minerals are in sediments that make up large “abyssal plains”, which are relatively easy to access without causing excessive damage.

Manganese is already mined in abyssal plains in the eastern Pacific. But that is no reason for complacency, Copley warns. “We still don’t fully understand patterns of biodiversity in the deep ocean, so any plans to extract these resources must include a full assessment of environmental impact,” he says.

Journal reference: Nature Geoscience, DOI: 10.1038/ngeo1185