One-fifth of the world’s freshwater could be under threat from heavy-metals pollution if a giant lead and zinc mine opens as planned upstream from Russia’s giant Lake Baikal, the deepest lake in the world. Mine advocates say leaving the world’s third-largest lead and zinc field unmined would be a waste of natural resources regardless of its location, but environmentalists, conservationists, and area business owners are concerned that high doses of heavy metals from the mine could mess with the lake’s unique ecology and also discourage tourism. Lake Baikal is home to hundreds of unique species, many of them endemic to Baikal. In 2006, an oil pipeline slated to be built within just miles of the lake was scuttled at the last minute due to intense international and domestic lobbying on behalf of the lake. This summer, Russia’s Natural Resources Ministry proposed allowing mining of just half of the lead and zinc deposits near Baikal, but despite such pressure, Russian company MBC Resources still retains a license to extract the deposit’s estimated 13.3 million tons of zinc and 2 million tons of lead.