Qiantang district in Hangzhou has demarcated 18.9 square kilometers of land for ecological protection, according to the Hangzhou bureau of planning and resources on Aug 19.

The designated protection area covers lands that are ecologically sensitive and vulnerable, as well as key zones for biodiversity.

The designated area has become a habitat and transfer station for migratory birds, said a staff member of the Hangzhou bureau of planning and resources. Thousands of migratory birds will gather in the area before the start of each winter, according to the official.

A recent survey on biological diversity suggested that more than 140 varieties of birds are found in the area. Among them, 19 varieties are classified as second-level species that are under prioritized protection.

China's central authorities in 2017 issued guidelines for an ecological red line strategy that would enforce strict protection of certain zones.