BEIJING, April 22 (Xinhua) -- Every spring and autumn, hundreds of thousands of migratory birds stop to rest and feed on a stretch of tidal wetland at the eastern tip of Chongming Island, less than 100 kilometers from downtown Shanghai.
The Shanghai Chongming Dongtan National Nature Reserve, a key stopover on the East Asian-Australasian Flyway, became Shanghai's first world natural heritage site in July 2024.
The recognition followed years of restoration and protection work in the reserve.
Niu Dongliang, director of the reserve's management center, said the reserve faced an ecological crisis in the late 2000s as Spartina alterniflora, an invasive plant species, spread rapidly across the wetland and squeezed bird habitat.
Synchronised waterbird surveys showed that the number of waterbirds in the reserve stood at more than 122,000 in 2006, but dropped to fewer than 40,000 in 2009 as the invasive species spread rapidly.
In 2013, the reserve launched an ecological restoration project covering 24.2 square kilometres, treating more than 25,000 mu of Spartina alterniflora and creating nearly 40,000 mu of quality bird habitat.
Bird numbers have risen steadily ever since. The 2025 synchronised waterbird survey recorded nearly 498,000 individuals, more than twelve times the 2009 low.
The change is also reflected in endangered species populations. The tundra swan, under national second-class protection in China, once wintered at Dongtan in large numbers, with about 3,000 to 3,500 recorded in the 1980s. After the 1990s, the population fell sharply -- from several thousand to just over a dozen by the early 2000s -- due to a combination of factors, including the spread of invasive species.
To help reverse the decline, Niu and his colleagues factored in the ratio of vegetation to open water, water depth and food supply during the design of an ecological restoration project, and introduced habitats specifically suited to wintering geese and ducks.
As conditions improved, tundra swans gradually returned. In 2016, more than 60 were found wintering in the restored area. In March 2026, the count reached 5,216, far exceeding the previous record.
Rising bird numbers have been accompanied by steady improvements in the reserve's monitoring and protection work.
When Niu first started working at the reserve in 2014, he and his colleagues rode bicycles along bumpy dirt roads, carried monocular telescopes and waded through tidal creeks in waterproof trousers to observe and record birds, vegetation and human activity. Today, high-definition cameras and drones have become the main tools for patrol and monitoring.
The reserve's conservation work has also extended into the surrounding community. Dongtan has about 30 square kilometers of reed beds, important habitat for birds such as the reed parrotbill and the Oriental reed warbler. To prevent the degradation of reed communities, the reserve adopts rotational harvesting, cutting part of the reeds each year.
Drawing on the traditional craft of reed-flower shoe-making, the reserve worked with local craftspeople to develop reed-based products such as paintings and lamps. The initiative has turned discarded reeds into a sustainable resource while reviving a traditional skill and creating income for nearby residents, Niu said.
He added that the reserve now faces new challenges like the spread of Canadian goldenrod, the decline of native scirpus mariqueter communities, and insufficient food supply for some bird species. Floating nest platforms built partly from recovered marine debris are also being tested to protect breeding waterbirds from summer storms.
"Seeing the number of rare and endangered birds increase, we know the restoration path we chose was right," Niu said. "All the effort has been worthwhile." ■
