The South Asian kingdom of Bhutan has become a champion of environmental protection. Its forests are protected by the constitution, environment classes are taught in school and its electricity is 100 percent hydroelectric. All of this has contributed to making Bhutan the first carbon-negative country in the world. However, that doesn't mean it's immune to the effects of climate change. Because of global warming, Bhutan's glaciers are melting and threatening to flood the villages down below. Our regional correspondents report.