Refining waterbird habitat conservation in high-density urban areas through nature-based solutions

Waterbirds are highly sensitive to ecological changes in coastal cities. Urban development in coastal regions, marked by dense construction and intense human activities, has led to a pronounced artificial transformation with decreasing coastal wetlands. Currently, research and practice on restoring coastal wetlands for waterbirds are increasing. These approaches can significantly enhance local waterbird diversity. However, some focus primarily on the development and management of constructed wetlands with immediate outcomes, rather than on restoring the tidal regulation functions of natural wetlands via natural processes. Nature-based Solution (NbS) has gained prominence as an effective way to address climate change and bolster resilience in recent years. NbS underscores the significance of protecting, managing, or establishing new ecosystems to implement and utilize natural functions, offering cost-effective and adaptable solutions to complex social challenges.

As a highly urbanized bay area bustling with socio-economic activities, Shenzhen Bay is a pivotal stopover and wintering habitat for migratory birds along the East Asian-Australasian Flyway. The Futian Mangrove National Important Wetland, located in the northeast of Shenzhen Bay, is a part of the Guangdong Neilingding–Futian National Nature Reserve. As the smallest national nature reserve in China, the wintering habitat of migratory birds has been significantly impacted by the compacted surrounding built-up environment. It has become an urgent need for refined high-quality ecological restoration for the habitats.

According to the habitat needs of waterbirds above, a suitability analysis was conducted on the dike-ponds of the Futian Mangrove Wetland, assessing water surface area, water depth, hydrodynamic conditions, shoal and islet morphology, the impacts of vegetation, and the disturbance by human activities. It identified six common problems faced by the unrestored fishponds. (1) Small water surface. (2) Deep water level. (3) Weak hydrodynamic conditions. (4) Lack of shoals and islets. (5) Excessive invasive plants. (6) Heavy human activity disturbance.

This project leveraged Nature-based Solutions to develop a refined model for the ecological restoration of coastal wetland waterbird habitats in compact urban areas. By analyzing waterbird behaviors and habitat requirements, this model outlined six strategies: water

surface expansion, water level control, hydrodynamic conditions improvement, shoal transformation, adaptive vegetation management, and disturbance control. To effectively guide the restoration implementation, high-, medium-, and low-adaptive approaches were proposed accordingly. After restoration in 2022, notable increases in target species, such as Platalea minor, were observed. The variety of waterbirds of the reserve in 2022 increased by 33% compared with 2021, while increased by 50.9% compared with 2016, significantly enhancing ecosystem services of the coastal area. As urban renewal in China is shifting towards spatial redevelopment, this model offers valuable insights for ecological restoration aiming at coastal wetland waterbird conservation across the country, and substantially supports establishing the “International Mangrove Center” in Shenzhen.