Wetlands-lakes, rivers, marshes and coastal areas-are the country's most fragile ecosystems, and they are also vital feeding and breeding grounds for migratory birds, according to Li Yan, deputy head of the wetland management office at the National Forestry and Grassland Administration.

Wetland coverage in China has expanded steadily over the past five years, growing by 202,600 hectares and making a significant contribution to water quality and environmental protection, the administration said.

On July 31, 1992, China joined the Ramsar Convention on Wetlands of International Importance Especially as Waterfowl Habitat. By the end of last year, the country was home to 899 national wetland parks, and nearly half of China's wetlands are protected by governments at various levels.

Conservation of the nation's wetlands is crucial because China ranks fourth in the world in terms of wetland coverage, and the nation's 65.9 million hectares represent 10 percent of the global total, according to the World Wide Fund for Nature.

China also has some of Asia's most important wetlands, such as Poyang Lake in Jiangxi province, and the continent's longest river, the Yangtze.

It is also the source area of major waterways such as the Lancang River, which is known outside China as the Mekong River.

Last year, the administration published a report that showed coverage in China's 57 key wetlands listed in the convention expanded by 2,479 hectares from 2018 to 2019 as a result of measures such as returning farmland to wetland and the closure of many fish farms.

In July 2019, Phase I of the country's major migratory bird sanctuaries, which lie along the coast of the Yellow Sea and Bohai Gulf, was added to the UNESCO World Heritage List by the World Heritage Committee.

The 186,400 hectares of Phase I, located in Yancheng, Jiangsu province, are important for more than 3 million birds among the East Asian-Australasian Flyway populations.

They provide a critical habitat for 17 endangered wild species on the International Union for Conservation of Nature's Red List of Threatened Species.

Those species include the spoon-billed sandpiper and Nordmann's greenshank, two of the world's rarest migratory birds, which depend heavily on the tidal flats for their survival.

According to the administration, China will apply Phase II this year. It will cover the habitats of many migratory bird species in Tianjin and Shanghai, and the provinces of Liaoning, Hebei and Shandong.

The Phase II area is rich in biodiversity, with about 280 fish species and more than 500 invertebrate species providing a wide range of food sources for millions of migratory birds.

"Having the sanctuaries listed as World Heritage sites has helped raise people's awareness of migratory birds and also contributed to biosecurity and biodiversity globally," Yan Chenggao, deputy director of the administration's nature reserves department, said.