Fresh water wetlands

Situated in the southern suburbs of Kunming City, Dianchi is one of the largest freshwater lakes in Yunnan and the sixth largest in China (Refs 1, 2). However, due to rapid industrial development, agricultural activities around the lake, land reclamation, and population growth, Dianchi Lake became severely polluted, ranking among the most contaminated lakes in China. This pollution threatened biodiversity and degraded natural habitats (Refs 1, 2, 3). The introduction of exotic species further disrupted the lake’s ecological balance (Ref 1).
In response, the Kunming Institute of Zoology (KIZ), with funding from the Chinese Government, World Bank and the Global Environment Facility (GEF) launched the Lake Dianchi Freshwater Biodiversity Restoration Project. This initiative aimed to restore natural habitats, improve water quality through biological means, and foster community engagement and institutional capacity, creating a sustainable framework for the long-term conservation of Dianchi's unique freshwater biodiversity (Refs 1, 4).
The project was implemented across four key components: Wetland Management and Restoration, Surveys and Monitoring of Species Conservation, Capacity Building and Training, and Public Awareness (ibid.). The project was rated 'Satisfactory' in terms of outcomes, sustainability, and execution under a comprehensive evaluation framework that employed multiple indicators (Refs 4, 5).

The Dog River Watershed Restoration project aims to protect and enhance the chemical, biological, and cultural integrity of the Dog River Watershed in Mobile County, Alabama (Ref 1). Guided by the Dog River Watershed Management Plan (WMP), the project addresses key issues such as pollution, litter, stormwater management, and habitat degradation (Ref 2). Funded by the National Fish and Wildlife Foundation's Gulf Environmental Benefit Fund and completed in partnership with stakeholders, the project focuses on implementing targeted restoration activities to improve water quality, protect critical habitats, and increase public awareness and access to the watershed (Ref 2). The Dog River Watershed faces significant hazards, including pollution, sedimentation, erosion, and the impacts of urban development (Ref 3). These challenges are intensified by the watershed’s role as an urban estuary, where land use heavily influences water quality and habitat conditions (Ref 3). To mitigate these threats, the project incorporates pollution prevention measures, shoreline restoration efforts, and community engagement initiatives (Ref 4). By prioritizing scientifically supported actions and aligning with broader environmental goals, the project seeks to restore ecological balance and ensure the long-term health and resilience of the watershed and its connected ecosystems in Mobile Bay (Ref 4).
The Watershed Management Plan for the Dog River Watershed is a key component of the Mobile Bay Shore Habitat Conservation and Acquisition Initiative, which focuses on acquiring, restoring, and preserving habitats and wildlife species affected by the environmental disasters of the Deepwater Horizon oil spill that occurred in 2010 (Ref 6). The project spans three critical areas: 300 acres in the Dog River Watershed (as detailed in this project profile), 450 acres within the Three Mile Creek Watershed, and 40 acres in the Garrows Bend Watershed (not in focus here) (Ref 7).

The Filter Ecosystem project, completed in 2007, aims to improve water quality and enhance the ecological health of the Molentargius wetland area in Sardinia, Italy, also known as the Molentargius Saline Regional Nature Park. This diverse territory includes freshwater basins such as Bellarosa Minore and Perdalonga, saline water basins like Bellarosa Maggiore and Stagno di Quartu, and the predominantly dry area known as Is Arenas.
The Molentargius ecosystem is a crucial European site for various aquatic birds and features diverse flora, including endemic species and endangered plants on the "Red List." It is one of the few globally recognized wetlands of international importance for aquatic birds located entirely within a large urban center, protected as a biotope by the RAMSAR Convention in Sardinia's major urban area. Since the 1980s, it has suffered environmental degradation due to inadequate infrastructure for wastewater management and human pressures.
Implemented by the city of Cagliari, the project employs a phytoremediation technique to supply water to the ponds. This involved constructing a phytoremediation system between the Bellarosa Maggiore and Bellarosa Minore ponds, functioning as a surface flow filter ecosystem resembling a marsh or wetland.
The system enhances natural self-purification processes, promoting prolonged contact between water, organic matter, and plants. This setup creates microhabitats that support microbial flora crucial for purification. The project's primary goal is to treat wastewater from the Is Arenas treatment plant, ensuring that the treated water meets optimal conditions for sustaining the wetlands' biodiversity. Additionally, the project will expand reed bed areas, vital habitats for avian species, and is designed to purify up to 300 liters of water per second to meet the area's needs (Refs. 1, 2, 3).

In the 1980s, rapid industrialization, urban population growth, and increased water usage led to severe pollution in Dianchi Lake, exceeding its environmental capacity and significantly degrading its water quality (Ref 1). This deterioration had serious effects on nearby ecosystems, including Cuihu Lake (Ref 2). Cuihu Lake (翠湖), also known as Green Lake Park, is a well-known park and body of water in the center of Kunming, Yunnan Province, China. In Cuihu lake the decline in water quality caused a sharp reduction in native species like the golden line barb, which depend on the local ecosystem for survival, pushing them to near extinction and destabilizing the entire ecosystem (ibid.).
To address this, several effective initiatives have been launched to restore Cuihu Lake’s ecosystem in recent years (Ref 2, 3). One of them was started in 2020 when a restoration project was initiated by the site's administration in collaboration with Dr. Li Weiwei’s team from the Kunming Institute of Zoology, Chinese Academy of Sciences. The project focused on creating micro-habitats and restoring the aquatic ecosystem (ibid.). Ecosystem and biodiversity restoration efforts were conducted across a 5,000 m² area on the east side of Green Lake Park, covering approximately 1/27th of the lake (ibid.).
As a result, more than 20 aquatic animal species are now thriving and contributing to water purification, while three submerged plant species cover over 50% of the project area (Ref 2, 3, 4). Bird diversity and numbers are also increasing, with species like white-breasted kingfishers, green-winged teals, and crested guinea-fowls returning to the area (ibid.). Additionally, there has been a significant improvement in water quality (ibid.).

Two new wetlands were established in Dodder Valley Park as part of the Dublin Urban Rivers Life Project (DURL). This project aimed to create integrated constructed wetlands (ICWs) at strategic locations in South Dublin County to purify wastewater and storm-water before it discharged into rivers.
The ICWs consisted of a series of cells resembling shallow ponds, typically 200 to 300 mm deep. Heavily planted with specific vegetation, these cells treated water by removing nutrients and harmful impurities, resulting in cleaner, purer water being discharged. The water flowing into the wetlands came from wastewater of misconnected appliances and storm-water pipes located under public roads, which collected rainwater from roads, footpaths, and the roofs and patios of houses.
These wetlands also provided important benefits, including flood alleviation, bioretention of particulates and nutrients, improved habitat conditions, and enhanced biodiversity. The project aimed to promote the relationship between green infrastructure and public well-being, creating a complex biological system that supports a diverse range of plants, animals, microorganisms, and hopefully attracts frogs, newts, and birds.
To increase native biodiversity, the wetlands were designed with pollinator-friendly plants and trees, making them visually appealing for park users and the public. A Wetland Planting Day took place on September 9, 2022, with over 40 participants, including residents and representatives from local organizations. This phase of the project fulfilled not only the objectives of the LIFE project but also those of the River Basin Masin Management Plan 2022–2027, the Water Framework Directive, the Climate Change Action Plan, the Floods Directive. (1, 2, 5)

At the beginning of the twenty-first century, Kunming’s urban planning faced major challenges, including fragmented development, environmental degradation, and limited green spaces (Ref 1). In response, the municipal government launched a series of strategic plans aimed at promoting high-quality urban development and environmental restoration.
Baisha Lake was identified as a key area in these strategies, with plans for Baisha Lake Park first highlighted in 2017 (Ref 2) and reaffirmed in the "Opinions on Supporting High-Quality Development in Kunming" in 2021 (Ref 2). To implement parts of this broader strategy, the government entered into public-private partnerships. In 2018, land development rights for parts of East Baisha Lake were granted to Dahua Group, on the condition that 40% of the area be reserved as green space and that ecological restoration efforts be undertaken (Ref 3, 4).
The Eastside Baisha Lake Park project, launched by Dahua Group in February 2023 (Ref 3, 5), is thus one component of this larger government-led urban renewal effort. The project follows the city's planning framework of “one lake, six zones, 46 scenic nodes” and includes 55 hectares of green space, with 40% designated as parkland. By the end of 2023, 6.5 hectares had been completed, and the south bank of the park opened to the public in September 2023 (Ref 3, 6).
The broader East Baisha Lake area's development was originally planned by the state-owned Kunming Urban Construction Company, but land rights were later transferred to Dahua Group. Thus, while a private developer is leading the construction, the project remains a part of Kunming’s publicly driven strategy to restore the lake and enhance urban livability.

The Tres Rios Ecosystem Restoration Project is an ambitious initiative aimed at revitalizing a seven-mile stretch of the Salt and Gila Rivers in Phoenix, Arizona. The Tres Rios Environmental Restoration project involves the rehabilitation of nearly 700 acres in and around the Salt River, restoring a vital wetland and riparian habitat. Initially conceived in 1993 to tackle water quality issues and improve flood control, the project gained significant traction in the 2000s through a partnership between the City of Phoenix and the U.S. Army Corps of Engineers (USACE). Funding was structured with 65 percent from the USACE and 35 percent from the City of Phoenix and the Sub-Regional Operating Group Members, including Scottsdale, Tempe, Glendale, and Mesa.
The Tres Rios project encompasses habitat restoration, flood control, and recreational development, with the primary objectives being to restore a degraded ecosystem, enhance water quality, and provide new recreational spaces. Construction involved relocating 1.6 million cubic yards of earth to shape three large wetland zones and two deep-water retention basins. Additionally, 18,000 feet of underground water lines and 600 feet of 84-inch fiberglass effluent pipelines were installed. To establish a thriving wetland habitat, the project coordinated the planting of over 300,000 aquatic and terrestrial plants.
Habitat restoration efforts re-establish native vegetation and create wetland areas that support local biodiversity. The lush and scenic Tres Rios is now home to more than 150 different species of birds and animals like muskrats, raccoons, skunks, coyotes, bobcats, and beavers. By using treated wastewater to sustain the ecosystem, the project reduces dependency on natural water sources, thereby helping to mitigate water scarcity. The Tres Rios Ecosystem Restoration Project serves as a model for sustainable urban ecological initiatives, combining environmental health with community benefits. (1-8, 10-13)

The Dublin Urban Rivers LIFE (DURL) project incorporates two interconnected wetlands in Griffeen Park as part of its broader initiative to improve water quality, natural water management and aquatic biodiversity in urban areas. These wetlands were specifically designed as a natural sewage system to treat wastewater from the surrounding areas, addressing a significant environmental issue known as "domestic misconnection." Domestic misconnection occurs when household appliances, such as washing machines, dishwashers, and kitchen sinks, are incorrectly linked to surface water drains rather than the sewage system. This leads to untreated wastewater being directly discharged into local waterways, contributing to contamination.
In the River Griffeen catchment, which includes approximately 12,000 dwellings and associated infrastructure, domestic misconnections are a considerable threat to water quality. The DURL project focuses on identifying and rectifying these misconnected appliances to ensure that wastewater is properly treated before entering the river. This process will not only improve water quality but will also provide flood alleviation and support healthier aquatic ecosystems in the area.
The project is aligned with broader environmental policies, including the River Basin Management Plan 2022-2027, the Water Framework Directive, the Climate Change Action Plan, the Floods Directive, and the draft Biodiversity Plan. One of the key strategies is to use a Geographic Information System (GIS) to streamline inspections for domestic misconnections, making the process faster and more cost-effective.
The constructed wetlands in Griffeen Park, with a standing water depth of approximately 30 cm, are planted with a variety of native Irish species. These wetlands offer a natural, sustainable solution to wastewater treatment, with the potential for similar applications across Europe. (Ref. 2, 4)

The Rio Salado Habitat Restoration Area is a urban green space that transformed a former 5-mile-long city dump into a thriving riparian corridor (2, 3, 7, 9). The project, spearheaded by the City of Phoenix in collaboration with the U.S. Army Corps of Engineers, Maricopa County Flood Control District, and the Arizona Water Protection Fund, has revitalized a degraded ecosystem (9). Through decades of concerted effort, involving government agencies, non-profits such as the Arizona Sustainability Alliance, and community engagement, the area has been restored to a lush habitat supporting diverse wildlife, including over 200 bird species (1, 2, 7). The project aimed to mitigate the pressing issues of urban heat, air pollution, and habitat loss that Phoenix grappled with (1). By creating green spaces, improving air quality, and offering recreational opportunities, the Rio Salado Habitat Restoration Area stands as a testament to the power of collaborative conservation and community resilience (1, 6, 7, 9). The restoration area now boasts hiking and biking trails, a nature center, and various educational programs, making it a community space (3, 7, 9).