File photo shows the Caohai National Nature Reserve around sunset in the Yi, Hui and Miao Autonomous County of Weining, southwest China's Guizhou Provincem Dec. 31, 2016. There was a time when the Caohai National Nature Reserve was threatened by water body recession and pollution, but in recent years its ecological system has greatly improved after a series of control measures were implemented here. (Xinhua/Yang Wenbin)
