One-fifth of all non-frozen fresh water in the world is located in a single Russian lake, and experts say that lake is in crisis, AFP reports. Siberia's Lake Baikal—the world's deepest lake at more than 5,500 feet—is a UNESCO world heritage site, home to more than 3,600 species of plants and animals, and is called of "exceptional value to evolutionary science." It's also an increasingly popular tourist destination, home to growing communities, and the only source of the omul fish, a type of salmon popular with diners. Thanks to those factors, UNESCO last month said "the ecosystem of the lake is reported to be under significant stress," and President Vladimir Putin in August called the preservation of Baikal a "government priority."
Over the past 15 years, the biomass of omul living in Lake Baikal has been cut in half. A biologist blames a combination of climate change and poaching, and this month the Russian government banned commercial fishing of omul out of fear the fish would disappear entirely. While omul populations are disappearing, Spirogyra algae—not native to Lake Baikal—is spreading across the lake. Scientists say the algae, which is threatening crustaceans and mollusks, is a sign Baikal is struggling to absorb human pollution and sewage. "There used to be underwater forests of sponges 15 years ago, now they are all dead," says a biologist who tested 170 types of sponges in Baikal and found just 11% seemed healthy. Russia is committing hundreds of millions of dollars to cleaning up the lake, but an ecologist says the laws protecting it are voluntary and funding gets stolen. (Read more lake stories.)