The adoption of electric cars has been hailed as an important step in curbing the use of fossil fuels and fighting climate change. There is a snag, however: such vehicles require around six times as many metals as their gasoline-powered counterparts. A giant storehouse of the necessary resources sits at the bottom of the Pacific Ocean. But retrieving them may, in turn, badly damage the environment. Guest: Eric Lipton, an investigative reporter for The New York Times.