Age: The undulating hills of Ningxia have been home for Hai Zhengjun ever since he chiselled out a cave shelter on the side of a ridge with a pickaxe and shovel in the 1970s. The 64-year-old has learned never to take water for granted, having spent all his life rearing sheep and sowing crops of wheat and corn in an area environmentalists identify as among China's driest and most ecologically vulnerable. The central and southern parts of the region, which sprawl across the Loess Plateau and are home...