China has constructed thousands of square kilometers of "infrastructure" for the world's largest migratory bird passage in recent years, not only returning many fish ponds and industrial areas to wetlands, but also using technologies such as field monitoring systems to accelerate the restoration of wetland ecosystems, according to the nature reserves.

At the mouth of the Yellow River in Dongying, Shandong province, vast expanses of saline-alkali land have turned red in early autumn, which is an indicator that the ecosystem is healthy. Along the water's edge, several oil pumps stand out.

"In recent years, over 300 oil pumps have been shut down, and strict parameters have been imposed on the remaining wells to protect the ecological environment of the Yellow River Delta wetlands and find a balance between production and conservation," said Zhou Licheng, director of the Yellow River Delta National Nature Reserve's planning and construction department.

The Yellow River Delta is rich in oil and gas resources, with the renowned Shengli Oilfield discovered here in 1961. Apart from closing some oil pumps, Dongying has made efforts to control the invasive species of reed sweetgrass.

Zhou explained that with its strong vitality and robust roots, the species can outcompete other plants, including the saline-alkali vegetation, thereby impacting birds and other wildlife.

"Researchers have explored several effective control methods, such as enclosing tidal water during high tide to drown the reed sweetgrass or crushing the roots and clearing them with machines," Zhou said.

Currently, the reserve has cleared out over 8,700 hectares of reed sweetgrass and restored more than 20,000 hectares of wetlands. In January, remote sensing imagery indicated that the total area of the Yellow River Delta bird habitat had increased from around 56,000 hectares several years ago to approximately 88,000 hectares.

On July 26, at the 46th World Heritage Committee meeting in India, the United Nations Educational, Scientific and Cultural Organization World Heritage Committee approved the inclusion of the Migratory Bird Sanctuaries along the Coast of the Yellow Sea-Bohai Gulf of China (Phase II) in the World Heritage List. The Yellow River Delta bird habitat encompasses three-fifths of the expanded heritage site.

Since 2021, the Yellow River Delta has also been designated as a national park. National parks are a major initiative of the National Forestry and Grassland Administration. The Yellow River Delta is among the second batch of national parks under construction.

According to the administration, in 2021, China established the first batch of five national parks, including the Sanjiangyuan and Giant Panda national parks, covering nearly 30 percent of the country's terrestrial key protected wildlife species.

Zhang Zhengwang, a professor at Beijing Normal University and head of the World Heritage application technical team, said that there are thousands of bird species worldwide that migrate along nine major global migration routes each year.

"The East Asia-Australasia Flyway is the largest migratory pathway for birds, spanning 22 countries from the Arctic through Southeast Asia to Oceania. The Yellow Sea-Bohai Gulf migratory bird habitats in China are crucial stopover and breeding grounds for migratory birds," he said.

With the support of more than 30 research institutions, including the Chinese Academy of Sciences, Dongying has established eight field monitoring and research teaching platforms and developed an integrated monitoring system, enabling scientific and systematic monitoring of wetland bird species.

According to bird monitoring data this year, the wintering populations of key species have steadily increased. The breeding population of black-headed gulls has stabilized at around 10,000 individuals, while 526 oriental stork fledglings and 20 crested ibis fledglings have been observed.

Over the past 30 years, the number of bird species in the Yellow River Delta National Nature Reserve has doubled, increasing from 187 to the current 373 species.

Similar to the wetlands in Dongying, the Snake Island-Laotieshan National Nature Reserve in Dalian, Liaoning province; the Yalu River Estuary bird habitat in Dandong, Liaoning; the Chongming Dongtan Birds National Nature Reserve in Shanghai; and the Nandagang Wetland in Cangzhou, Hebei province, are also included in the World Heritage List.

At the southern tip of the Liaodong Peninsula, the Dalian Snake Island-Laotieshan National Nature Reserve is a crucial passage for migratory raptors flying toward the Shandong Peninsula. It is also known as the "first sacred land for raptor observation on the Chinese mainland".

On Sept 23, more than 11,000 raptors were observed taking off for their southward migration, marking the first "10,000 Raptors Day" on the Chinese mainland.

What makes this bird migration site unique is the presence of around 20,000 snakes on the island. These vipers prey on small birds, forming a distinctive food chain in the area. Boasting the various snake and bird species, the Snake Island-Laotieshan Natural Museum welcomes thousands of visitors each year.

Each site of the Migratory Bird Sanctuaries along the Coast of the Yellow Sea-Bohai Gulf of China has its own educational center, which introduces visitors to the diverse wetland ecosystems.

yandongjie@chinadaily.com.cn