Public space owned by the city

Assemini, a municipality in Cagliari, has long grappled with hydrogeological instability, marked by major floods in 1999 and 2002. To mitigate future risks, the municipality launched a series of interventions focused on improving the hydraulic management of its waterways. These projects are part of a broader strategy to address recurring flood hazards exacerbated by the effects of rapid urbanization in the 1970s, which disrupted the natural water drainage systems (1,3). The central goal of the project is to reduce the risk of flooding by enhancing the functionality of existing waterways. This includes both preventative measures and structural improvements to the canal system to manage stormwater more effectively. These efforts aim to safeguard urban and rural areas from severe meteorological events. The project development involved a multi-phased approach starting in 2013, focusing on cleaning and maintaining minor waterways such as the Gutturu Lorenzu, Sa Nuxedda, and Giaccu Meloni streams. These efforts expanded over time, culminating in an agreement with the Land Reclamation Consortium of Southern Sardinia in 2015, securing both local and regional financial support. The interventions have covered over 24 kilometers of canals and streams, targeting key flood-prone areas (1,2).
Key interventions include the cleaning and maintenance of over 35 km of canals and streams, in partnership with the Land Reclamation Consortium of Southern Sardinia, supported by regional funding. A separate, large-scale intervention in Truncu Is Follas involves constructing an open-air diversion canal, a retention basin (44,500 m³), and new pipelines to redirect floodwaters, thus reducing risk for residents downstream in both Assemini and Elmas.

The urban garden in Miraflores park (Huertas las Moreras) was established already in 1991 on an old waste dump and contains 10500 m2 of plots for locals to grow fruits and vegetables [Ref. 1]. The creation of the gardens was initiated by citizens who formed an association and implemented it in cooperation with the City of Seville. The citizens were discontent with the lack of green space in the area, and the urban gardens came to be alongside Miraflores Park, which was also pushed by the locals. The initial goals of the gardens were to allow locals to produce their own food and to host educational activities [Ref. 2]. More recent developments exemplify the focus on education and knowledge. In 2022, the citizen science project "Planta Bienstar" was carried out in the gardens, where high school students measured the lead levels in the soil and crops. The project aimed to investigate if lead levels posed a health risk and if the gardens could reduce levels over time. The project was organised by the non-profit Descubre Foundation and funded by the foundation and the regional Government of Andalusia. The project relied on the knowledge and efforts of the citizens, the students and gardeners in an intergenerational collaboration where the young could learn methods from their elders [Ref. 3, 4].

In 2022 an afforestation initiative was implemented near a landfill located in the Tutora commune (1 - 6). Organized by the City Hall of Tutora, the event brought together representatives from the regional government of Iasi County, the "Asociația de Dezvoltare Intercomunitară pentru Salubritate" (ADIS), and volunteers from SC Girexim SA, SC Salubris Iasi, and Edil Industri Iasi. Together, they planted 2,000 acacia saplings, donated by the Forestry Directorate of Iasi (6). The afforestation action took place under the umbrella of the regional environmental campaign "Iasi Mai Verde" (Iasi More Green), led by the County Council of Iasi. This campaign promotes a range of eco-friendly activities, including educational programs in schools, waste cleanup events, and afforestation initiatives in partnership with ADIS, while actively encouraging the support and participation of local municipalities from across the region (1, 3, & 7).
"Iasi Mai Verde" aligns with national environmental strategies such as the Ministry of the Environment's "Curățăm România" (Let's Clean Romania) and the annual Planting Forest Month (3 & 6).
On the same day, as part of the Iasi Mai Verde initiative, students from a local school in Tutora were given a practical education workshop on how waste management operates at the regional level. The students were also invited to witness the afforestation action and participate, fostering a deeper understanding of environmental stewardship (1- 5).
The newly planted trees are acting as a natural barrier, and help improve air quality by filtering dust, pollution, and waste particles originating from the nearby Tutora landfill. In turn, this contributes to better living conditions for the residents in close proximity to the landfill, enhancing both their health and overall quality of life (5).

The Cagliari Canal project is an initiative aimed at revitalizing and transforming the urban and natural landscape of the Cagliari Metropolitan Area in Sardinia. The project is rooted in the city's strategic metropolitan plan and seeks to restore and enhance the navigability of the Terramaini-La Palma canal, which had become disused and neglected over time​ (3,4). The primary goal of the Cagliari Canal project is to develop a connected, innovative, and sustainable urban environment by re-establishing the canal as a green and blue infrastructure​ (2). It aims to provide alternative, sustainable mobility options, improve connectivity between municipalities, and enhance the natural and urban environments. It strives to foster a sense of community by creating a shared space for residents and integrating modern amenities that align with environmental sustainability (1,4). It involved a highly participatory process, emphasizing community involvement from the initial planning stages. The Metropolitan Authority of Cagliari, in collaboration with local stakeholders, launched a series of consultations to gather public input on the canal's design and function​(3). These consultations were part of a broader initiative called LabMet, the Metropolitan Laboratory for Innovation, which facilitated the collection of ideas and feedback (1). The project was partly developed in response to the increasing environmental challenges faced by Cagliari, including the need to adapt to climate change. The canal's revitalization is seen as a key measure for enhancing the city's resilience to climate-related risks, such as flooding and heat waves​(1). By restoring the canal and its surrounding areas, the project aims to mitigate these risks through improved water management, reducing pollution, and the creation of green spaces that can absorb excess rainwater and provide cooling effects​ (2)

Located between the Rotes Rathaus, Karl-Liebknecht-Straße, Nikolai Quarter, Spreeufer and the television tower, the old founding centre of Berlin is one of the capital's most important urban open spaces. This open space between the TV tower and the Spree is being redesigned on the basis of an international open space planning competition and many years of public participation. With further development, this touristically significant location in the historic centre of Berlin will undergo a climate-resilient redesign and upgrade with great design and functional quality. (Ref. 1)
The listed areas of the Rathausforum and the Marx-Engels-Forum will in future be connected to form a continuous ribbon of open space that runs from Alexanderplatz to the Spree. Central areas will be unsealed and green spaces will be created that can be used in a variety of ways, which will also be attractive places to spend time and improve the microclimate. Trees and shrubs will be planted on already existing and new green areas. The aim is to respectfully consider the numerous visible and hidden historical references and at the same time transform the site into a sustainable urban open space that combines a high quality of recreation, sustainability and culture. Next to plants, a new rainwater management system is being implemented that stores rainwater and uses the created green spaces to evaporate water. Playgrounds and a water fountain are further additions to a new recreational area. (Ref. 3; Ref. 4; Ref. 5)
The project is characterized by a years-long participation process. Around 10.000 citizens participated in feedback rounds, workshops, dialogues, and information sessions in which they could voice they wishes and ideas for the area. The project is implemented and organized by the state-owned company Grün Berlin, which engage with various stakeholders since 2015. Preparations for the construction start in late 2024 and the project is expected to be finished in 2030. (Ref. 5; Ref. 9)

For thousands of years the Rio Salado, also known as the Salt River, and its larger mainstem, the Gila River, served as an important perennial source of life and growth for indigenous people residing in central Arizona, including the Akimel and Piipaash (3). Today, the Salt River is an ephemeral river corridor connecting diverse urban communities across an expansive and growing Maricopa County (3). While the river is now typically defined by intermittent flow as a function of water conservation and distribution in an arid urban climate, it also has powerful flows during the Arizona monsoon season providing a diverse and unique ecosystem for the region (3). To foster the health of the River, a regional multi-decade project was initiated in 2018 called Rio Reimagined, which includes six cities and two tribal communities (1). Rio Reimagined is a planning initiative in a very early concept stage, centered around the mission to support and enhance this treasured river corridor (3). The goals of Rio Reimagined consist of connecting communities, Equitable & Sustainable Development, and Restoring and Revitalizing Healthy Rivers (3). As part of the Rio Reimagined, the City of Phoenix founded a collaborative project called Rio PHX that will help promote a 20-mile Rio Salado (Salt River) corridor as a local and regional destination that attracts positive investment for the benefit of existing/future businesses, residents, and tourists (1). The final aim with this project is to improve health outcomes for existing and future residents by address outstanding needs in the area and create opportunities for housing, employment, recreation, art, and ecological restoration (1). From May 2024 to May 2025 Rio PHX will engage in creating a community profile, an existing conditions assessment, community engagement & visioning, developing implementation strategies and drafting the master plan (1). Public hearings and final plan adoption are set to take place in fall 2025 (1).

Booterstown Marsh, the only remaining saltmarsh on the south shore of Dublin Bay, plays a crucial role in the Dublin Bay Protection Plan. As part of South Dublin Bay's protected landscape, this unique 4.3-hectare brackish water marsh provides vital environmental and educational value within an urban setting. It supports three key habitats, ranging from freshwater to saltwater, creating essential feeding and roosting grounds for an array of migratory birds. The marsh attracts numerous bird species, including Moorhen, Reed Bunting, Sedge Warbler, Teal, Snipe, Lapwing, Oystercatcher, Redshank, Dunlin, and Brent Geese, establishing it as the only bird sanctuary in South Dublin Bay.
Booterstown Marsh’s ecological significance is underscored by its inclusion in the Dún Laoghaire-Rathdown County Council’s Biodiversity Action Plan 2021-2025: Nature Recovery, Restoration & Reconnection. Managed by the Biodiversity Section of the council, this initiative focuses on protecting and enhancing Booterstown Marsh as part of a broader effort to restore natural habitats across the area. The council’s project addresses key factors in biodiversity loss—such as land use pressures, climate change, and invasive species—by implementing an annual monitoring program to prevent deterioration of critical EU Annex habitats and species.
An Taisce, a local NGO has managed the marsh reserve since the 1970s, dedicating efforts to conservation and public education. This habitat, along with other local ecosystems like the wetlands at Ballycorus and woodlands at Loughlinstown, serves as an essential natural defense against climate change, removing carbon dioxide from the atmosphere and helping stabilize local landscapes by slowing floodwaters in catchment areas.(1-6)

The Bee Park Molentargius is a project located in the Molentargius-Saline Regional Natural Park, in Cagliari. It is part of a broader effort to regenerate abandoned and underutilised urban spaces, transforming them into areas that support biodiversity, promote sustainability, and engage the local community in environmental stewardship (3,4). The primary goal of the Bee Park Molentargius project is to restore specific areas of the Molentargius Park to their original ecological and productive functions. It aims to enhance biodiversity, support sustainable agricultural practices, and promote environmental education. The project includes the creation of shared gardens and an educational apiary, designed to reclaim the park’s identity and encourage local participation in the management and preservation of this important natural resource (1,3). It was developed with financial support from the Autonomous Region of Sardinia and the European Union's Horizon Europe Framework Programme. Inaugurated in March 2024, the project is a collaborative initiative involving local citizens, institutions, and park beneficiaries. It includes various educational components, such as beekeeping and olive growing training courses, along with sensory analysis workshops for honey and olive oil. These activities are intended to educate the public while fostering a sense of community ownership and responsibility toward the park​ (1,2). The project indirectly addresses environmental hazards related to the degradation of urban green spaces and loss of biodiversity. By restoring the park’s natural and productive functions, the Bee Park Molentargius helps mitigate risks associated with urbanisation, such as habitat loss and the decline of pollinator populations, which are crucial for maintaining ecological balance and food security​ (3)

The former Kulturpark Plänterwald, once the only permanent amusement park in the GDR, closed in 2001 due to declining visitor numbers. Over time, the 23-hectare site became a ‘lost place,’ falling into disrepair. In 2014, the state of Berlin reacquired the area, and two years later, Grün Berlin initiated its redevelopment with a sustainable development concept that places significant emphasis on rainwater management.
The project’s goal is to avoid discharging rainwater into the sewer system and instead manage all precipitation on-site. This approach addresses both heavy rainfall events and extreme drought conditions, creating a sustainable rainwater management system. A central element of this concept is the historic but dried-up water basin located near the iconic Ferris wheel. Plans include redesigning and reactivating the basin, incorporating terraces and a shallow water zone, transforming it into a key part of the rainwater cycle while providing an attractive recreational and adventure area. (Ref. 1; Ref. 2)
In the future, the water basin will no longer be purely decorative but will serve as a critical artificial water reservoir. To support this function, it will be equipped with a natural horizontal filter system featuring reeds for rainwater purification. Pre-treated water will flow into the newly designed 3,000-square-metre basin near the Ferris wheel. Rainwater collected in the basin, along with water stored in cisterns throughout the park, will irrigate the site’s vegetation. This innovative approach ensures sustainable water use and contributes to the ecological revitalization of the park. (Ref. 1; Ref. 3)
By integrating sustainable rainwater management into its redevelopment, the former Kulturpark Plänterwald is being transformed into a resilient and environmentally conscious space, combining historical preservation with modern ecological practices.

The Far West Detroit neighborhood faces significant challenges with its aging infrastructure. The neighborhood’s stormwater and sewer systems are combined into a single system that is only capable of handling a limited volume. During heavy rain events, the system's capacity is exceeded, causing excess stormwater and untreated sewage to overflow into the Rouge River, which negatively impacts the environment (Ref. 1).
Detroit is investing $40 million in a transformative stormwater management system in the Far West neighborhood near Rouge Park. Described by the Detroit Water and Sewerage Department as the largest project of its kind, it will redirect 98 million gallons of rainwater and snowmelt into two new detention basins and a renovated sewer system. The new wastewater system is expected to significantly reduce water volumes in Detroit’s combined sewer system during heavy rainfall and to provide flood relief for approximately 1,200 homes that have experienced flooding in recent years. This expansion, informed by community feedback, marks one of the city's most notable investments in green infrastructure to improve its overextended wastewater management system.
The project has been planned through extensive studies and community coordination since 2016, with construction set to occur in three phases, extending through 2026. Crews broke ground on the South Basin, North Basin, and sewer overhaul in July 2022, and progress is reportedly on track. In addition to the basins, the stormwater management initiative includes neighborhood improvements to enhance recreational opportunities for residents and visitors alike. Planned enhancements in Rouge Park will introduce wetland spaces with native flora, creating greener, more inviting areas in the community for residents to enjoy (Ref. 2).