A car drives on the mountain road at Zoumatai Village of Wuqi County in Yan'an City, northwest China's Shaanxi Province, June 5, 2019. Wuqi County has carried out a development policy since 1998 that returned farmland to forest for ecological protection and sustainable development purposes. (Xinhua/Tao Ming)

　　Aerial photo taken on June 8, 2019 shows the scenery of hills covered with green at Guopan Village of Wuqi County in Yan'an City, northwest China's Shaanxi Province. Wuqi County has carried out a development policy since 1998 that returned farmland to forest for ecological protection and sustainable development purposes. (Xinhua/Zong Mingyuan)

　　Photo taken on June 8, 2019 shows the flowing clouds over Shengli Mountain of Wuqi County in Yan'an City, northwest China's Shaanxi Province. Wuqi County has carried out a development policy since 1998 that returned farmland to forest for ecological protection and sustainable development purposes. (Xinhua/Zong Mingyuan)

　　Photo taken on June 6, 2019 shows the flowing clouds over hills at Yangqing area of Wuqi County in Yan'an City, northwest China's Shaanxi Province. Wuqi County has carried out a development policy since 1998 that returned farmland to forest for ecological protection and sustainable development purposes. (Xinhua/Tao Ming)

　　Aerial photo taken on June 5, 2019 shows hills covered with green at Wuqi County in Yan'an City, northwest China's Shaanxi Province. Wuqi County has carried out a development policy since 1998 that returned farmland to forest for ecological protection and sustainable development purposes. (Xinhua/Tao Ming)

　　Aerial photo taken on June 5, 2019 shows the scenery of hills covered with green at Zoumatai Village of Wuqi County in Yan'an City, northwest China's Shaanxi Province. Wuqi County has carried out a development policy since 1998 that returned farmland to forest for ecological protection and sustainable development purposes. (Xinhua/Tao Ming)

　　Aerial photo taken on June 5, 2019 shows a car driving on the mountain road at Jinfoping area of Wuqi County in Yan'an City, northwest China's Shaanxi Province. Wuqi County has carried out a development policy since 1998 that returned farmland to forest for ecological protection and sustainable development purposes. (Xinhua/Tao Ming)

　　Flowers are seen at Mawan Village of Wuqi County in Yan'an City, northwest China's Shaanxi Province, June 7, 2019. Wuqi County has carried out a development policy since 1998 that returned farmland to forest for ecological protection and sustainable development purposes. (Xinhua/Tao Ming)

　　Photo taken on June 7, 2019 shows flowers at Jinfoping area of Wuqi County in Yan'an City, northwest China's Shaanxi Province. Wuqi County has carried out a development policy since 1998 that returned farmland to forest for ecological protection and sustainable development purposes. (Xinhua/Tao Ming)