United Press International: The steady retreat of glaciers on China’s Qinghai-Tibet plateau during the past 40 years is troubling, scientists in the Asian nation said Wednesday. Xin Yuanhong, senior engineer in charge of a three-year field study, said the glaciers at the headwaters of the Yangtze, China’s longest river, now cover 406 square miles, down from 482 square miles in 1971, Xinhua reported. The scientists said the melting, enough to fill Beijing’s largest reservoir, was occurring at a “worrisome speed,” …