Aerial photo taken on Aug. 1, 2019 shows scenery of the tidal flat wetland along the Songhua River running through Harbin, northeast China's Heilongjiang Province. (Xinhua/Wang Jianwei)

Aerial photo taken on Aug. 1, 2019 shows scenery of wetland around the Harbin Grand Theatre in Harbin, northeast China's Heilongjiang Province. (Xinhua/Wang Jianwei)

Aerial photo taken on Aug. 1, 2019 shows scenery of the tidal flat wetland along the Songhua River running through Harbin, northeast China's Heilongjiang Province. (Xinhua/Wang Jianwei)

Aerial photo taken on Aug. 1, 2019 shows scenery of Sun Island wetland in Harbin, northeast China's Heilongjiang Province. (Xinhua/Wang Jianwei)

Aerial photo taken on Aug. 1, 2019 shows scenery of the tidal flat wetland along the Songhua River running through Harbin, northeast China's Heilongjiang Province. (Xinhua/Wang Jianwei)

Aerial photo taken on Aug. 1, 2019 shows scenery of wetland around the Harbin Grand Theatre in Harbin, northeast China's Heilongjiang Province. (Xinhua/Wang Jianwei)