Aerial photo taken on May 30, 2018 shows the Yunlong township in Haikou city, South China's Hainan province. Efforts made by Haikou city to restore ecosystem have improved the water quality of wetlands, which are expected to play a better role in flood prevention, climate regulation and preservation of the local biodiversity.[Photo/Xinhua]

Aerial photo taken on May 30, 2018 shows the Yunlong township in Haikou city, South China's Hainan province. Efforts made by Haikou city to restore ecosystem have improved the water quality of wetlands, which are expected to play a better role in flood prevention, climate regulation and preservation of the local biodiversity.[Photo/Xinhua]

Aerial photo taken on May 30, 2018 shows the Yunlong township in Haikou city, South China's Hainan province. Efforts made by Haikou city to restore ecosystem have improved the water quality of wetlands, which are expected to play a better role in flood prevention, climate regulation and preservation of the local biodiversity.[Photo/Xinhua]

Aerial photo taken on May 30, 2018 shows the Yunlong township in Haikou city, South China's Hainan province. Efforts made by Haikou city to restore ecosystem have improved the water quality of wetlands, which are expected to play a better role in flood prevention, climate regulation and preservation of the local biodiversity.[Photo/Xinhua]