An aerial view of sprawling Yundang Lake that connects to the sea in Xiamen. ZENG DEMENG/FOR CHINA DAILY

Mangroves restored

So far, the renovation of Yundang Lake has cost about 1.99 billion yuan ($277 million).

"We are not only engaged in environmental restoration, but also preserving our city's culture," Pan said.

"For example, our sailing sports lead the way in China. People in Xiamen no longer just observe the sea from the shore. They can now sail and see dolphins in the sea. It has changed our lifestyle."

To restore wetlands, the city's forestry bureau and Xiamen University planted mangroves along lakefronts and seashores.

The mangrove restoration projects were done in "forest-friendly" areas including Yundang Lake and Tong'an Bay. The area of mangrove forests in Xiamen increased from around 33 hectares in 2000 to 174 hectares in 2023, the ministry said.

As mangrove plantations expanded, marine ecosystems flourished, with water birds returning to nest and frolic.

In the past, coastal waters in Xiamen suffered from severe eutrophication — an overabundance of nutrients such as nitrogen and phosphorus in water caused by excessive aquaculture and haphazard development.

As a result, the native mangrove forests, known for their crucial role in protecting coastlines and mitigating the impact of waves, disappeared.

Yang Shengchang, an associate professor of environmental studies at Xiamen University, said: "Replanting mangroves by the sea posed challenges. The elevation of the plant above mud flats had to be carefully considered to avoid long submersion that could hinder sapling growth.

"Selecting suitable species required extensive experimentation to ensure adaptability to the local environment. Moreover, the planting density had to be the best to withstand tidal forces without being washed away."