The Clinton administration yesterday proposed new protections for one-fifth of America’s coral reefs, including bans on fishing and other activities. Less than 3 percent of the 8,600 square miles of reefs in the nation’s waters are currently protected, though environmentalists say that two-thirds of them are at risk from pollution, overfishing, and other commercial activities. The new plan, developed by a government task force, would create “no-take zones” by 2010 where boating and diving are allowed but fishing is not. Some enviros praised the effort, but said more funding is needed and the no-take zones should be extended beyond the 20 percent goal. Coral reefs, which are rich in biodiversity, are under threat around the world. According to a report by the task force, 10 percent of the world’s reefs have already been lost and 70 percent could be lost by 2050.