This aerial photo taken on October 23, 2017 shows a forest in Daocheng County of the Tibetan Autonomous Prefecture of Garze in southwest China's Sichuan Province. In recent years, authorities in Sichuan have carried out a series of ecological projects to protect eco-systems in the upper reaches of the Yangtze River. (Xinhua/Xue Yubin)

　　This aerial photo taken on August 18, 2017 shows forests in Wolong National Nature Reserve in southwest China's Sichuan Province. In recent years, authorities in Sichuan have carried out a series of ecological projects to protect eco-systems in the upper reaches of the Yangtze River. (Xinhua/Xue Yubin)

　　This aerial photo taken on April 17, 2018 shows trees in Qingchuan County of Guangyuan, southwest China's Sichuan Province. In recent years, authorities in Sichuan have carried out a series of ecological projects to protect eco-systems in the upper reaches of the Yangtze River. (Xinhua/Xue Yubin)

　　This aerial photo taken on October 23, 2017 shows a forest in Daocheng County of the Tibetan Autonomous Prefecture of Garze in southwest China's Sichuan Province. In recent years, authorities in Sichuan have carried out a series of ecological projects to protect eco-systems in the upper reaches of the Yangtze River. (Xinhua/Xue Yubin)

　　This aerial photo taken on July 5, 2017 shows a wetland park in Suining, southwest China's Sichuan Province. In recent years, authorities in Sichuan have carried out a series of ecological projects to protect eco-systems in the upper reaches of the Yangtze River. (Xinhua/Xue Yubin)

　　This aerial photo taken on July 30, 2017 shows a wetland in Daofu County of the Tibetan Autonomous Prefecture of Garze in southwest China's Sichuan Province. In recent years, authorities in Sichuan have carried out a series of ecological projects to protect eco-systems in the upper reaches of the Yangtze River. (Xinhua/Xue Yubin)