 Under his leadership, Greenpeace achieved some of its greatest victories, including a 1991 treaty forbidding oil and gas exploration in Antarctica for half a century; the Montreal Protocol to phase out chemicals that cause ozone depletion; and a treaty banning the dumping of nuclear waste at sea.Greenpeace's persistent small-boat protests eventually forced France to abandon its nuclear testing in Polynesia, and the United States off Alaska.Sawyer later shifted Greenpeace's focus to fighting climate change and promoting renewable energy.