Aerial photo taken on July 31, 2018 shows the scenery of the Awancang Wetland in Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. (Xinhua/Chen Bin)

Photo taken on May 26, 2017 shows an aerial view of the Puzhehei state wetland park in Qiubei County, southwest China's Yunnan Province. (Xinhua/Hu Chao)

Photo taken on May 26, 2017 shows an aerial view of the Puzhehei state wetland park in Qiubei County, southwest China's Yunnan Province. (Xinhua/Hu Chao)

Tourists visit the Dajiuhu wetland in Shennongjia, central China's Hubei Province, May 18, 2018. (Xinhua/Du Huaju)

Cattle graze in Dajiuhu wetland in Shennongjia, central China's Hubei Province, May 18, 2018. (Xinhua/Du Huaju)