Maintenance and management of urban nature

The Waliwa project, launched in 2017 by the municipality of Sainte-Luce, is a collaborative effort dedicated to restoring marine biodiversity, enhancing the ecological balance of the bay area, revitalizing the local ecosystem and supporting sustainable economic activities. By focusing on marine biodiversity conservation, Waliwa addresses several critical environmental challenges. The project helps mitigate coastline erosion, support the blue economy through artisanal fishing and tourism, and foster an environmentally friendly culture among the local community.
So far, the Waliwa project has implemented three initiatives: it restored the Gros Raisin backshore to address erosion and provide nesting sea turtles with protected space (Ref 4). The project also intervened to restore the Pont Café pond, which was covered in Salvinia Molesta, preventing the intake of oxygen and hampering its role as a water filter, habitat for species and flood regulator .
Furthermore, the project has conducted studies and raised awareness about the challenges posed by wastewater management on the health of municipal water bodies. Through these efforts, Waliwa is working to create a more sustainable and resilient marine environment for future generations. (Ref 4, 5, 6; 12)

In May 2020, CityLAB Berlin launched "Gieß den Kiez", an interactive platform designed to support Berlin's urban trees by fostering collaboration between citizens and the city. The platform enables voluntary civil society efforts to help water the city's endangered tree population. It features a map that visualizes nearly all of Berlin's street and park trees, complete with data such as water requirements, age, and species. Citizens can create profiles, adopt trees, and mark them as ‘watered’ within the app, making it easy to track contributions to the health of Berlin’s trees. (Ref. 2)
Berlin's trees face growing challenges due to increasing temperatures, reduced rainfall, and exposure to road salt in winter. The hot summers of 2018 and 2019 highlighted the urgency of supporting the city’s trees, which provide cooling shade, clean air, and habitats for numerous animal and plant species. To address this, "Gieß den Kiez" was developed as a platform where authorities, volunteers, and civic society could collaborate to prevent tree dehydration.
The platform maps over 625,000 trees across Berlin and offers additional tools, such as rainfall data from the last 30 days and the locations of public water fountains, which can be used for watering trees. By connecting data from city authorities, the German Weather Service, and OpenStreetMap, the fully open-source platform allows for transparency and accessibility in its operation. (Ref. 6)
The project has proven highly successful in Berlin, with over 10,000 participants actively watering trees, and its model has been adopted in other German cities like Leipzig. "Gieß den Kiez" not only exemplifies a practical response to urban climate challenges but also fosters a sense of shared responsibility and community engagement in caring for urban green spaces. (Ref. 6)

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].

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)

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)

This project involves collaboration among government, private, and educational entities focused on developing an agroforestry initiative that integrates economic activity, labor market integration, and educational opportunities for young children at the “Foyer de l’Espérance” [school and child welfare center] in Fort-de-France. The objective is to plant 1,500 cacao trees on the Foyer's premises by 2025. These trees will serve as pedagogical support for teachers and children. Planting activities commenced in 2022, and the first cacao pods are expected to mature in 2-3 years. Subsequently, these pods will be processed and transformed by the Martinican Lauzéa chocolate factory under the brand “Chocolat de l’Espérance” (Refs 2; 4).
The idea for this project emerged in June 2022 when young students engaged in a discussion about cocoa farming with Thierry Lauzéa during "Business Thursdays," organized by “Espérance Formation Insertion.” These meetings allow young beneficiaries to explore the business world and discuss their career paths with professionals. During one of these sessions, the young participants inquired about the origins of the cocoa used in Lauzéa's chocolates, leading to the concept of producing cocoa for the Frères Lauzéa company (Refs 3; 5).

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).

Located in the municipality of Morne Rouge, the Domaine d’Émeraude was once an agricultural site but was transferred to the Martinique Regional Natural Park (PNRM) in the early 2000s. It underwent significant renovations in 2005 to transform it into a sanctuary for Martinican biodiversity, reflecting the need to protect and conserve the island's unique ecosystems. In 2011, it opened its doors to the public, serving as an important educational resource that raises awareness about the island's historical, natural, and cultural heritage (Refs 4, 7, 8).
Today, the site encompasses 25 hectares protected from anthropogenic pressures and is primarily characterized by a humid tropical forest environment, which makes up 80% of the area (Ref 7). It is home to over a hundred native species (Ref 4) and offers nearly 4 kilometers of walking trails accessible to both adults and children, complete with recreational stops and educational amenities.
The Domaine d’Émeraude was designed to enhance the conservation of native species while developing sustainable economic activities that benefit the local community. Moreover, the site emphasizes the well-being that forested areas provide to visitors, highlighting that "the air can be heard, the smells can be savored, and the sounds can be experienced. The freshness of the place is a source of change and relaxation..." (Ref 4).

In Berlin, at the palace park and garden Charlottenburg, approx. 40 to 70 horned Gotland sheep are used to maintain the grass fields and meadows. The project is part of a garden and landscape conservation programme that is to be seen as a contribution to practical nature conservation by the Prussian Palaces and Gardens Foundation Berlin-Brandenburg, which manages the park. From May to November, the sheep are grazing on the palace property, whereby the exact length of time the sheep are kept and the duration of the project depend largely on the developing weather conditions. This is because prolonged drought significantly reduces the growth of the grasses. (Ref. 1)
The garden had already been grazed earlier in its history, but no longer in the post-war period. The garden was created by Electress Sophie Charlotte in 1695. (Ref. 3) Since 2018, sheep can be found again in the park space where they graze on extensive meadows with groups of chestnut, lime, maple, oak, beech and solitary trees. At the beginning of May, they move into their first station there, usually the meadow in front of the late baroque-classical Belvedere tea house. Once this has been grazed, they move on to the next meadow; with an area of 55 hectares, there is plenty of pasture. (Ref. 4)
Sheep from his flock also graze on the green flat roof of the Max-Schmeling-Halle in Pankow, the palace garden of Sanssouci and other public and private patches of land around Berlin. Reasons to use sheep over machinery for the maintenance of the park space are monetary and a reduce loss of biodiversity. Sheep are cheaper compared to machinery, the needed labour and wear, and also don't kill insects living in the fields as machinery does. Furthermore, the sheep dung fertilises the grass area, sheep limit the spread of invasive plants and are more gentle to the soil. At the same time, palace visitors enjoy observing the sheep and can learn about them in guided tours. (Ref. 4; Ref. 6)