More joint efforts are needed in the protection of estuaries as they come under the increasing threats of climate change, loss of biodiversity and pollution, according to experts at an international conference in Dongying, Shandong province, on Thursday.

Estuaries are vital channels performing both social and economic functions, and their protection, restoration and sustainable management are crucial in achieving sustainable development goals, said Susan Gardner, director of the ecosystems division of the United Nations Environment Programme, in a video message to the World Estuarine Cities Conference for Cooperation and Development.

"It is easy to see why 60 percent of the global population lives near an estuary, and of the 32 largest cities in the world, 22 are located beside estuaries, that includes New York and Shanghai," she said.

Despite their importance, estuaries are being affected by climate change and growing urbanization in coastal areas, causing serious losses, many experts warned.

Estuarine cities closely link the diversified ecosystems of rivers, land and oceans with human social and economic activities, meaning they play an important role in the sustainable and high-quality development of estuaries, said Chen Mingxing, professor at the Institute of Geographic Sciences and Natural Resources Research of the Chinese Academy of Sciences.

The institute released the Report on the Development of World Estuarine Cities at the conference, which includes the overall situations of the world's estuarine cities and some specific development models such as Rotterdam in the Netherlands and Quebec City in Canada, as well as Shanghai and Dongying.

Dongying, where the Yellow River flows into the Bohai Sea, has made great efforts in ecological protection, which were praised in the report.

In early winter, the city's Yellow River Delta National Nature Reserve welcomes flocks of widgeons and spot-billed ducks. Egrets twitter in the woods and swans rest on the lake in elegance.

Home to one of China's best wetlands, the delta is often dubbed a paradise for diversified groups of birds. The wetland area in the delta stretches 1,130 square kilometers and is 20 percent bigger than it was many years ago, according to the local government.

The number of bird species observed in the delta has doubled to reach 371 from 187 in 1992, making it the largest breeding ground in China for oriental storks.

"The environment in the urban areas of our city is also improving, attracting more birds to build nests. Oriental storks and egrets are frequently seen in the urban areas," said Liu Zhifeng, a resident of Dongying.

Ecological protection has brought benefits to the city's high-quality economic development. The city registered an average annual growth of GDP of 6.8 percent during the past decade.

Liu Chuan contributed to this story.