BEIJING, March 22 (Xinhua) -- Walk into Wild Duck Lake Wetland in suburban Beijing as spring approaches, and you will see birds such as herons, grey cranes and swans skimming through the golden reeds. However, this scene could not be seen a few years ago.

On the occasion of the 27th World Wetlands Day early this year, Beijing Wild Duck Lake Wetland became one of the 18 new sites in China designated as Wetlands of International Importance under the Ramsar Convention on Wetlands.

Following this expansion, the number of Wetlands of International Importance hit 82 in China, covering a surface area of 7.647 million hectares, the fourth largest in the world, according to the National Forestry and Grassland Administration.

"Wetland parks prioritize the harmonious co-existence between humans and nature, in which a favorable water environment plays a vital role in enhancing the biodiversity," said Wang Xiaoxu, director of the natural reserve administration in Yanqing District in Beijing.

At the Wenyu River park, known as the "lung of the capital city," more than 80 mandarin ducks and other water birds including smew, ruddy shelduck and mallard were spotted last winter.

"Waterfowls require a high-standard habitat," introduced Wu Lan, an ecological inspector. "The Wenyu River park is located at the intersection of two rivers with abundant water resources. Its water system has been further improved, thereby turning the park into a popular destination for water birds."

About a decade ago, natural landscapes filled with waterfowls and clean rivers were rare to see in Beijing. Due to urban expansion and population growth, the surface and underground water in the city had been over-exploited, leading to river cutoff and the loss of biodiversity.

Since 2014, Beijing has benefited a lot from the country's South-to-North Water Diversion Project and strived to coordinate the use of local water resources, including rainwater and reclaimed water, to ensure water security.

According to the Beijing Water Authority, as of 2022, the South-to-North Water Diversion Project had transferred over 8.4 billion cubic meters of water from major rivers in the southern parts of the country to the nation's capital.

In addition, Beijing has launched three pollution control initiatives since 2013 to increase the sewage treatment rate to 97 percent and cleaned up over 140 polluted stretches of water.

"The proportion of healthy waters in Beijing reached 87.2 percent in 2022. About 105 species of birds were seen in the rivers, lakes and reservoirs of the capital, including some under national first-class protection," said Huang Zhenfang, deputy director of the water quality and ecology monitoring center at the Beijing Water Authority.

The monitoring result indicates that Beijing has become one of the most biodiversity-rich metropolises in the world, Huang added.

"Beijing's water ecology will continue to be restored and protected, offering a comfortable habitat to fish, birds and amphibians, in an endeavor to contribute to its biodiversity in the long run," Huang said.