It's no wonder so many environmentalists sound like downers. Forests are being wiped out at the rate of one a year. Cities such as Beijing and New Delhi choke on . Global temperatures and tides continue an .Don't despair! Forty years after the environmental movement peaked, the world has some historic success stories that reduce pollution and save lives every day. This week marks the 25th anniversary of the Montreal Protocol, a model international agreement that reduced pollution-inflicted damage to the Earth's protective ozone layer.Environmental issues follow certain patterns -- the questioning of science, the questioning of proposed solutions and sometimes, the quiet disappearance of the problem when collective action works. "Despite denials at the time, they all proved economically feasible and have resulted in tangible improvements for people," said David Goldston, director of the government affairs program at the Natural Resources Defense Council.Click through to see 13 of the world's top environmental success stories.Read more news.