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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)

Arizona is experiencing an unprecedented drought, now nearing 15 years and surpassing the most severe drought in over 110 years of recorded history (1). For Phoenix residents, accustomed to extreme heat and minimal rainfall, rising temperatures are bringing new health risks (3). Diminished rainfall not only leads to water scarcity but also raises temperatures, as the sun’s energy, instead of being absorbed to evaporate moisture, intensifies the heat on the ground (2). In 2023 alone, extreme heat claimed at least 147 lives, with Arizona seeing the majority of these fatalities. By early August, over 100 heat-related deaths had been reported in the state (2).
In response to these challenges, the Watershed Management Group (WMG) has collaborated with Arizona State University’s Sustainability Teachers’ Academies to develop a program that maximizes the desert’s limited rainfall to build community resilience (3). Their Schoolyard Water Education Program brings educational services to Phoenix schools, focusing on designing and installing rain gardens as part of outdoor learning initiatives (3). This hands-on approach transforms schoolyards into interactive laboratories where students learn the principles of sustainability through direct engagement with their surroundings (3).
A project at Clarendon Elementary School in Phoenix involved constructing a rain garden with native plants and wood chip mulch to help retain moisture (3). These gardens offer students a living classroom, where they can observe seasonal changes in native plant life, distinguish beneficial species from invasive weeds, and track rainfall to measure the garden’s water intake from rooftops and direct rain (3). Beyond the academic learning, rain gardens provide cooler, safer spaces for students to gather, fostering a lasting connection with nature and a deeper understanding of sustainable water practices (3).

In an architecturally important area of Berlin, situated between the Landwehr Canal, the Kulturforum (the Berliner Philharmonie and the Berlin State Library) and the new construction on Potsdamer Platz, a combination of green and grey infrastructure has been realised to minimise the burden on Berlin’s existing water infrastructure.
Green and non-green roofs harvest annual rain, which flows through the site’s buildings and is used for toilet flushing, irrigation, and fire systems. The roofs retain and then release water to the large on-site buffer pond, which has five underground storage tanks. Next to the roofs, a series of urban ponds and connecting canals have been implemented, with a combined area of approximately 1.2 hectares. They are filled with rainwater, creating an oasis for urban life. Vegetated biotopes are integrated into the overland landscape and serve to filter and circulate the water that runs along streets and walkways. The lake’s water quality is excellent, forming a natural habitat for animals and cooling the surroundings, while fresh water usage in the buildings has been reduced. (Ref. 1; Ref. 2; Ref. 3; Ref. 6)
The project was implemented in the 1990s as part of the development of Potsdamer Platz in the wake of the reunification of Germany. Several architects collaborated on the implementation that was completely privately funded. Beyond its ecological and technical features, the site is a blue natural site in the heavily built city centre of Berlin and allows people to linger and enjoy natural features. The drainage system won several sustainability prices and is considered a successful integration of nature and technology-based mechanisms to foster climate change adaptation. As the rainwater system stores rainwater in underground tanks and ponds, the urban sewage system is relieved during heavy rain, and water can evaporate. Therefore, the small water circle is closed, and the microclimate is cooled. (Ref. 2; Ref. 6)

The Vale da Ameixoeira Urban Park is a key part of Lisbon's Peripheral Green Corridor, covering 20 hectares and aiming to enhance the city's ecological and social resilience. It includes pedestrian and cycling paths, rest areas, picnic spots, skate parks, and playgrounds, enabling recreational activities while providing scenic views (Ref 1). The park has undergone several requalification initiatives, including the tree planting project in 2018, which saw the community and municipal bodies plant over 130 native trees and shrubs, promoting biodiversity and environmental sustainability (Ref 3). Additionally, the park supports community-based vegetable gardens, integrating horticultural practices to promote local engagement and foster social inclusion (Ref 3). More recently, as part of the Life Lungs project, another 600 drought-resistant trees were planted to mitigate climate change impacts, such as urban heating and water scarcity (Ref 5). The Lisbon Participatory Budget funds the project and reflects the community’s demand for sustainable urban development (Ref 2).

The "Plan Arbre" is a tool for ecological planning and renaturation aiming to plant 308,000 trees between 2023 and 2029, sourced from the municipal nursery with seeds purchased from local suppliers (Ref 1, Ref 2). In 2023, 14,922 trees were planted, with plans to double this number in 2024 (Ref 1). The project addresses the loss of 50% of Marseille's natural spaces over the past 75 years, aiming to reverse this trend and reintroduce nature into the urban environment (Ref 2). It also tackles issues like drought and heatwaves, particularly in summer, by using trees and shrubs to cool the air, restore biodiversity, reduce air pollution, and enhance public spaces while absorbing CO2 (Ref 2).

The plan is divided into two phases. Phase I focuses on planting in Marseille's 58 parks and 273 squares and gardens, as well as around childcare centres, schools, socio-cultural centres, and sports facilities (Ref 2, Ref 3). From 2020 to 2023, various improvements were made, including playground renovations, installation of misting systems, automatic watering, and the creation of a CrossFit area (Ref 3). Phase II will involve identifying major boulevards, avenues, and streets lacking trees to enhance the urban canopy (Ref 2).
A diverse range of tree species were selected for their drought resistance, water efficiency, and ability to attract biodiversity (Ref 2, Ref 3). The project also focuses on increasing biodiversity and managing invasive species through natural methods to protect trees from pests without chemicals (Ref 3). Furthermore, the initiative includes de-impermeabilizing soils and implementing a smart irrigation system with tensiometric sensors, developed with the start-up GreenCityZen, which has saved 66% of water in two years (Ref 3). The Plan Arbre also promotes citizen participation, with 23 parks selected for community gardening projects, where ten winning associations will receive plants from the municipal nursery (Ref 1).

The project aims to protect seagrass meadows, which are vital habitats for the prey of resident dolphins and essential to the local fishing economy. The initiative involves local fisherwomen, called "Keepers of the Sea," in activities such as marine education, awareness campaigns, and monitoring the health of the seagrass meadows (Ref 1). Founded in 2015, Ocean Alive aligns with several UN Sustainable Development Goals, including ocean conservation, gender equality, quality education, and climate action (Ref 4). The project is supported by partnerships with UNESCO and other organizations, and it extends its efforts to Portuguese-speaking African countries. Ocean Alive’s activities also include advocacy for blue carbon ecosystems and programs that involve community engagement and social innovation (Ref 2, Ref 5).
One of several implementation projects targeted safeguarding the young seagrass meadow at Cambalhão Bay, at the entrance of the Sado estuary, as an Ocean Alive’s initiative in partnership with SeaTrees by Sustainable Surf (Ref. 2). The Cambalhão meadow is made up of 202 patches of seagrass. Unregulated shipping is one of the factors in the degradation of the prairie, and to protect it, Ocean Alive is running a campaign to raise awareness about recreational boating (Ref. 6).

Since the 1980s, the Graefekiez neighborhood in Berlin's Friedrichshain-Kreuzberg district has been a traffic-calmed area where all road users are treated equally, driving is limited to walking speed, and cars are permitted to stop anywhere. However, this once-progressive concept no longer functions effectively due to the significant increase in cars and delivery vehicles over the years. The streets no longer resemble a traffic-calmed zone, with traditional layouts featuring roadways, sidewalks, and parking spaces. As a result, many users fail to recognize the traffic-calmed nature of the area, leading to safety issues: vehicles drive too fast, delivery traffic causes conflicts, and streets are difficult to navigate safely.
Berlin’s transport sector faces the challenge of meeting legally mandated CO₂ reduction targets. Achieving these goals requires bold measures, including limiting private motorized transport (MIV), especially in densely populated areas where residents and visitors have access to alternative modes of transportation.
The "Graefekiez" project addresses these challenges through urban redevelopment aimed at improving livability and promoting sustainable urban mobility. Car parking has been banned from the streets, freeing up space for communal use such as lounge areas. As part of the "Graefekiez" project, the district office is converting parking spaces into green spaces and expanding tree disks to adapt to the climate and promote a sponge city.
The project was developed collaboratively with residents and NGOs through a participatory process led by the Friedrichshain-Kreuzberg district office, in partnership with the Berlin Social Science Center and Paper Planes e.V. Implementation began in 2023 on Graefestraße and Bockhstraße.After a six-month trial period, the district office decided in 2024 to make the measures permanent.
This initiative advances a safer, greener, inclusive urban environment while meeting climate and community goals. (Ref. 1, 2, 3)

The Africatown Heritage House Bioswale is a gently sloping green space with multiple functions which include catchment of runoff water and filtration of pollution in the runoff water (Ref 2), erosion control (Ref 2), and creation of habitat for biodiversity (Ref 1). It also has an educational purpose for students and the local community (Ref 2) and contributes to overall beautification (Ref 5).
The Bioswale was built by Birmingham-Southern College’s Environmental Center (Ref 6) and developed through the collaboration between the Mobile County Commission, the Mobile Area Lodging Association, Mobile County Training School, Mobile County Training School Alumni Association, and the National Academies of Science (NAS) Gulf Research Program (Ref 2). The project aims to address heavy rainwater management (Ref 5) and drainage issues (Ref 3).