Enhanced protection and restoration of freshwater ecosystems

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.).

The Three Mile Creek Hydrological Restoration project is taking place in one historic channel of the Three Mile Creek, located east of Dr. Martin Luther King, Jr. Avenue, and covering approximately 1,800 linear feet (Ref 3). This project, led by the City of Mobile, aims to remove sediment from the stream channel. This segment of the Creek was bypassed with a straight channel in the early 1980s to control flooding in the area, thus accelerating the accumulation of sediments in the historic channel (Ref 1).
The project's goal is to restore and maintain the natural flow to the historic channel and create a connection to the City and County's Blueway initiatives (Ref 3). This will improve habitat conditions and water quality and help to protect the area’s estuarine and marine water resources (Ref 8). It will also contribute to revitalizing the Three Mile Creek Watershed and provide increased recreational opportunities for citizens, like kayaking and canoeing (Ref 6). Construction work occurred in 2022 and 2023 (Ref 3).
The Three Mile Creek Hydrological Restoration is a key component of the Mobile Bay Shore Habitat Conservation and Acquisition Initiative, which focuses on acquiring, restoring, and preserving habitats, including riparian, wetland, and upland areas that support various fish and wildlife species affected by the environmental disasters of the Deepwater Horizon oil spill that occurred in 2010 (Ref 1). The project spans three critical areas: 450 acres within the Three Mile Creek Watershed (as detailed in this project profile), 300 acres in the Dog River Watershed, and 40 acres of bay shore property in the Garrows Bend Watershed (with the latter two areas being part of separate initiatives) (Ref 4).

The "Recuperación del Laguito" project aims to restore El Laguito, a coastal water body in Cartagena, Colombia, severely affected by sedimentation that blocks natural water exchange with the Caribbean Sea. This blockage has led to stagnant, low-oxygen water, degrading water quality and aquatic ecosystems (ref 1). The project seeks to restore El Laguito’s environmental and social functions by reestablishing seawater flow, reducing sediment impact, improving water quality, and reviving the ecosystem. Additionally, it aims to provide data to guide long-term solutions for sustainably managing this community resource (ref 1).
The project is a response to recurring ecological crises, such as frequent fish die-offs due to low oxygen levels. Local residents initially took matters into their own hands, manually attempting to reopen the channel. The formal intervention started following a 2019 directive from the Ministry of Environment and Sustainable Development, outlining a phased strategy: short-term installation of an axial pump for water exchange, medium-term studies for a permanent fix, and long-term construction plans (ref 3). Currently, the project involves using heavy machinery to clear sediment and allow seawater inflow, supported by the Gobernación de Bolívar, Cardique, and the Cartagena Mayor's Office. This phase serves as a transitional step towards a more sustainable, permanent solution (ref 2). The project’s impacts focus on ecological restoration. Short-term benefits include better oxygenation, reduced harmful algal blooms, and revived marine life. Long-term goals encompass sustainable water management, ecosystem stabilization, tourism enhancement, and the development of recreational and sports facilities in harmony with environmental conservation (ref 4).

Berlin has faced severe water shortages in recent years, with ponds, small lakes, and pools suffering significantly. Many have dried out or disappeared, causing habitats for countless animals and plants to vanish. Urbanization exacerbates the issue, as more areas become sealed, preventing rainwater from replenishing soil and water bodies. Recognizing the urgency, Berlin introduced the Eco-Account, a strategic reserve of areas and initiatives to mitigate the effects of urban development on nature and landscapes. Central to this is the Blue Pearls for Berlin program, focusing on revitalizing small water bodies to restore biodiversity and ecological balance.
The project identified approximately 30 ponds, pools, lakes, and ditches from over 100 candidates to be transformed into "blue pearls." These revitalized areas will support local ecosystems and improve Berlin’s water cycle. The Berlin Rainwater Agency, alongside departments responsible for nature, climate protection, and water management, is spearheading the initiative in collaboration with the Berlin Nature Conservation Foundation.
Two pilot sites—the Schleipfuhl/Feldweiher water complex in Marzahn-Hellersdorf and the Lankegrabenteich in Steglitz-Zehlendorf—were prioritized for restoration in 2024. These efforts include improving water quality and creating diverse habitats for wildlife. Enhancing small water bodies not only provides a refuge for animals and plants but also contributes to climate adaptation. Restored ponds and lakes can cool surrounding areas and improve the urban microclimate by utilizing locally accumulated rainwater. Blue Pearls for Berlin, approved by the Senate in 2022, aligns with the city’s Eco-Account framework, ensuring that these restored blue spaces offset ecological damage caused by infrastructure and urban projects. The initiative offers Berliners new ways to experience nature, fostering a balance between development and environmental preservation. (Ref. 1, 2, 4, 6, 7)

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 Upper Detroit Riverfront Habitat and Parks Restoration Project aims to restore and enhance vital fish and wildlife habitats along the Detroit River. This initiative seeks to rehabilitate approximately 30 acres of upland and shoreline habitats within Riverfront-Lakewood East Park, A.B. Ford Park, and Mariners Park (all located alongside the river), covering nearly one mile of the Detroit River and its shorelines.
Key outcomes include improving approximately 1,000 linear feet of existing shoreline along the Detroit River by incorporating native wetland edges and fish spawning shelves into the restoration efforts. The project also plans to enhance around 2,000 linear feet of canal shoreline and 800 linear feet along Fox Creek to create or improve habitats for fish and herpetological species. In Riverfront-Lakewood East Park, 28 acres are targeted for the establishment or enhancement of native vegetation to support birds, mammals, and pollinators. If feasible, the creation of about 7 acres of wetlands, along with shallow and deep-water habitats, is also part of the vision.
The project is guided by the City of Detroit's 2017 Parks and Recreation Improvement Plan and represents part of a broader strategy to revitalize the city’s green spaces after years of underfunding. With renewed commitment, the city has allocated nearly $12 million to enhance neighborhood parks, particularly in areas that have lacked investment over the past decade.
However, the project was temporarily halted in 2020 due to high water levels causing flooding in the adjacent neighborhood. As of 2024, it remains on hold while the City of Detroit conducts a flood mitigation study. Despite this delay, the project remains a critical step toward fostering community stewardship and creating sustainable green spaces that improve the quality of life for all Detroit residents.
(Ref. 1, 4, 5)

The Africatown Connections Blueway project aims to create a recreational water trail by linking 14 culturally and historically significant points along a 10-mile route (Ref 1). Central to this initiative is the preservation of Africatown's rich heritage and natural resources. The project seeks to reconnect residents of Africatown, descendants of the original founders of this self-governing community, which maintained a strong sense of African cultural heritage, to waterways that were historically vital for food, transport, and spiritual practices (Ref 1). By restoring access to these waters, the community can address both environmental and social issues, promoting eco-tourism and business growth while safeguarding cultural heritage (Ref 2). Local leaders emphasize the environment’s role in healing the community and preserving history, highlighting how this initiative can provide economic opportunities and improve quality of life (Ref 2). The project seeks to address the environmental injustices that Africatown communities have endured for decades. The area surrounding Africatown has long been dominated by harmful industries, including aluminium plants and paper mills, which have heavily polluted the water and restricted residents' access to it (Ref 1). With support from the National Park Service and contributions from Mississippi State University, the Blueway transforms neglected river access points into recreational areas, promoting environmental stewardship and cultural awareness (Ref 2).

The Lower Salt River Restoration Project (LSRRP) is a riparian restoration initiative located along the Lower Salt River within the Mesa Ranger District of the Tonto National Forest. This collaborative project seeks to restore a section of the Lower Salt River Recreation Area that was severely impacted by the 2017 Cactus Fire. The Cactus Fire was a significant wildfire that caused extensive damage to vegetation and habitat in the area, highlighting the need for targeted restoration efforts to rebuild the ecosystem and mitigate future fire risks.
The LSRRP’s primary activities focus on removing invasive tamarisk trees, which are highly flammable and contribute to the intensity of wildfires, and planting native seedlings to reestablish local flora. By removing tamarisk trees, the project aims to create a landscape that is more resistant to fire, reducing the wildfire risk for the region. Additionally, the project supports the abundance and diversity of native plant species by removing invasive plants and planting thousands of native riparian tree species.
The restoration efforts also aim to enhance the riparian habitat by expanding two critical vegetation communities—the mesquite bosque and the cottonwood-willow gallery forest. These communities support rich biodiversity and offer essential habitats for local wildlife.
Beyond ecological restoration, the project emphasizes community involvement and awareness. It provides opportunities for the local community to participate in the project through environmental education events for K-12 students and ongoing volunteer involvement in monitoring and maintaining restored areas.
Overall, the Lower Salt River Restoration Project is a proactive effort to protect and revitalize the Lower Salt River Recreation Area, enhancing its ecological resilience and engaging the community in long-term conservation. (2-4, 6, 8, 11)

The ROOF WATER-FARM is an innovative demonstration site located in the heart of Berlin, near Potsdamer Platz, showcasing sustainable urban infrastructure that integrates wastewater treatment and food production. Situated in the "Block 6" quarter of the 1987 International Building Exhibition in Berlin-Kreuzberg, the site transforms wastewater and rainwater collected from nearby buildings into usable resources for farming and fertilizer production (Ref. 1). This project provides a real-world example of how sustainable systems can be incorporated into everyday urban design to enhance resilience and functionality.

At the ROOF WATER-FARM, water from rooftops and surrounding households is channeled into a treatment plant, where it is analyzed for micropollutants and purified. The treated water is then used for both fish farming in aquaponics systems and plant irrigation in hydroponic farming. The nutrient-rich water from the fish tanks nourishes plants, while also contributing to the production of food. This integrated approach actively supports climate protection by managing rainwater runoff and using plants for CO2 storage, helping to mitigate the urban heat island effect (Ref. 4).

This demonstration site embodies how cities can move toward a circular economy, where wastewater is reused for both farming and water management. The project also serves as a hub for learning and experimentation in sustainable urban design, with the greenhouse acting as a space for collaboration and innovation in infrastructure development (Ref. 2; Ref. 5). By incorporating these technologies into urban environments, the ROOF WATER-FARM demonstrates a future where buildings and neighborhoods efficiently recycle water, produce food, and reduce environmental impact.