Improved air quality

The Urban Forestry Plan for Cartagena, led by EPA Cartagena, outlines a comprehensive strategy for enhancing the city's green infrastructure. The plan focuses on selecting suitable tree species, planting, and management to achieve several goals: reducing heat through shade, creating microclimates, protecting against climatic events such as coastal erosion and windstorms, enhancing food security, and enhancing the landscape's beauty. Over 10 years, the plan aims to establish at least 100,000 additional trees, increase overall tree cover, enhance accessibility to green spaces, and build a main ecological structure based on natural resources and biodiversity. It also emphasises the importance of local knowledge and resources (ref 1).
Formulated with community input, the plan commenced in 2013 and involved a detailed assessment of existing urban vegetation and climate conditions, utilising tools such as iTree. The development included international conferences and expert consultations to ensure a robust and informed approach (ref 1).

Liquid 3 is the first urban photo-bioreactor in Serbia, developed by an interdisciplinary team at the Institute for Multidisciplinary Research at the University of Belgrade (Ref. 1,2,3). Prompted by an appeal of the United Nations Development Programme (UNDP), the team was eager to find novel approaches to combat the city's severe air pollution issues while being space efficient and providing year-round benefits (Ref. 3). The key to the bioreactor are algae which are very efficient in sequestering carbon and filtering heavy metals from the air (Ref. 2). A Liquid 3 feature can be quickly set and occupies a plot of only 3 m². Some of its benefits include its ability to withstand high levels of air pollution and its ease of installation on surfaces like walkways and other sealed infrastructure (Ref. 2,3). Additionally, by design, Liquid 3 integrates amenities such as power outlets, a bench, and nighttime lighting (Ref. 1). The selected strain of algae can tolerate temperatures between 5-35°C making it deployable all year. However, monthly maintenance is required, during which the water and algae are replaced—both of which can be repurposed, for example, as fertilizers (Ref. 6).The project has received global media coverage as well as a prize for the best innovative and climate-smart solution in Serbia. Its success has prompted the installation of two more such bioreactors in Serbia, with interest coming from other countries such as Hungary and the UAE (Ref. 1,4).

In the city of Ciudad Juárez, the municipality, in collaboration with UN-Habitat, aims to design and create a park that encompasses the yards and unmaintained areas surrounding the railway station, transforming these spaces into an accessible and safe public area. This project covers over 500,000 square meters and addresses not only degraded areas but also several public squares. Described as "a coordinated urban recycling strategy," this initiative seeks to repurpose existing public squares and rehabilitate neglected spaces into vibrant green areas that feature universal accessibility, native vegetation, and urban furniture designed to enhance safety. The project also aims to provide increased recreational opportunities, improve permeability, and introduce additional shaded areas. A key component of improving permeability involves the restoration and incorporation of acequias—traditional historical irrigation systems that absorb and manage excess rainwater, thereby reducing the likelihood of flash floods.
Additionally, the project focuses on the restoration and promotion of significant historical buildings, such as the old railway station and the whiskey factory, integrating them into a larger cultural and sports facility area at the municipal scale. The overarching goal is to revitalize the site through effective coordination with the relevant authorities responsible for the spaces adjacent to the railway station, stretching from Plaza Misión de Guadalupe to Blvd. Municipio Libre. This collaborative effort aims to accommodate both sports and cultural facilities while also creating a green corridor.
Furthermore, the project intends to reforest, redesign, and enhance Plaza Misión de Guadalupe, Plaza Monumento a Benito Juárez, and other residual public spaces and gardens. This initiative aligns with its Public Space Strategy, which emphasizes the development of gender-inclusive and resilient public spaces.(Ref 1, 3, 4).

The Silk District is a real estate project by Prime Kapital in partnership with MAS P.L.C., integrating green spaces into its urban design (1-10). It focuses on regenerating a brownfield site, an abandoned industrial area left undeveloped in one of Iasi's neighborhoods (1). The project aims to revitalize the area, improving its aesthetics, reducing pollution, and repurposing it into a commercial and residential space (1). A key feature of the project is the incorporation of green spaces throughout its design (1).
The development spans 101,000 square meters, with 40,500 square meters (combined) dedicated to green spaces and "car-free" open areas (1, 2, 6, p.2). These green elements are designed to offer spaces for relaxation, recreation, and social interaction, while also contributing to environmental benefits such as air filtration, temperature regulation, rainwater drainage, and soil erosion prevention, all promoting better health for residents (1, 2, 4, 6, p.12). The landscape design includes “green islands” and vegetation-covered roofs for parking structures (4).
Launched in 2021 after receiving municipal approval, the project is ongoing and has already made significant progress, with over 10,000 perennial plants and 401 trees planted (4, 9). Upon completion, the landscape will feature 7,100 square meters of perennials, 3,000 square meters of shrubs, and an urban forest containing 2,400 trees (6, p.12).
The total investment in the project is €20,000,000 (7). In 2024, one of the completed office buildings earned a BREEAM green certification, achieving one of the highest possible scores, in collaboration with the consulting firm BuildGreen (5, 8). The landscape design was carried out by the architectural firm Beros Abdul+ (4). Before receiving approval, the project was opened for public consultation, and an independent online survey showed strong support from the community (15, 16).

Tempelhofer Feld stands as an innovative green solution in the heart of Berlin, addressing several issues of environmental justice, biodiversity, and urban resilience. Within the S-Bahn ring, only one in 20 residents lives in areas well-served by green spaces, and districts like Neukölln, Kreuzberg, and Tempelhof would face even greater scarcity without this vast expanse. Many residents in these neighborhoods lack access to private green spaces such as gardens or balconies. Without nearby parks, people are compelled to travel to other districts, exacerbating the congestion of green spaces and increasing local traffic.
Since its opening in 2010, Tempelhofer Feld has provided Berlin with over 300 hectares of open, green, leisure, and recreational space, making it one of the largest urban open spaces globally. Once the site of bustling air traffic, it is now a sanctuary for activities such as skating, strolling, gardening, picnicking, birdwatching, kiteboarding, and more. These wide-ranging uses showcase its transformation into an accessible, multifunctional green space that serves as a social equalizer, particularly for disadvantaged neighborhoods, a significance amplified during the Covid-19 pandemic.
The field is not just a recreational haven but also a vital ecological refuge. With over two-thirds of its area designated as green space, it hosts diverse ecosystems, including extensive natural meadows, lawns, and protected habitats for birds and other species. Certain areas are closed to the public to preserve these sensitive environments, emphasizing the balance between human activity and ecological conservation. Since 2019, animal landscape keepers, including around 100 resident sheep, have contributed to sustainable land management practices, promoting biodiversity and ecological health (Ref. 2).
Managed collaboratively by political, administrative, and societal actors, the site exemplifies integrated citizen participation in urban planning. (Ref. 3)

The Chaowan Nursery Garden Base Project (潮玩苗圃基地), located along the Dianchi Greenway in Kunming, was established by the Kunming Gardens Virescence Bureau (昆明市园林绿化局) in 2022 as part of the city's efforts to transform into a "city of parks" (Ref 2, 3). Covering 639 mu (42.6 hectares), the Chaowan Nursery Garden has introduced over 1.4 million plants, including trees, flowers, and grasses, greatly expanding the city's green spaces (Ref 3). It serves as a key resource for the Kunming Greening Service Center (昆明市绿化服务中心), providing seedlings for major greening projects along roads like Guangfu Road, Airport Road, Beijing Road, and the Second Ring Elevated Road (Ref 4).
Innovatively designed, the nursery also functions as a park, offering an "immersive" experience with various themed areas such as rainwater gardens, rural gardens, Chinese gardens, and scenic balconies. These spaces allow visitors to stroll through and enjoy the beauty of various flowers and natural surroundings (Ref 4). The project also collaborates with local universities on seedling research, capacity building, and resource sharing, further enhancing its multifaceted role (Ref 3).
Since opening to the public in 2023, the Chaowan Nursery Garden has become a popular destination for families, young people, and children, offering both recreational and educational experiences (Ref 5, 6, 7, 8).

The "Line Park" project in Belgrade aims to create a continuous green belt spanning 4.6 kilometres and covering over 48 hectares. As such, the project will revitalize the former railway corridor from "Beton Hala", just below the Belgrade Fortress, to the Pancevac Bridge. Inspired by notable urban parks like New York's "High Line", Moscow's "Zagrađe," and Toronto's "Rail Corridor," it will become a major recreational destination and also help to alleviate the pressures from the city's heavy air pollution and summer heat (Ref. 5, 6).
The park will be divided into ten thematic sections dedicated to aromatic plant and flower gardens, urban gardening and beekeeping, sports facilities, a newly built university campus and more. Additionally, there will be an amphitheatre and facilities for outdoor education. To further integrate green infrastructure, new buildings will have green roofs and walls (Ref. 2,5). Ultimately, the park integrates a number of amenities into the entire city.
The development of the park also introduced innovative co-creation mechanisms in terms of governance and planning. Since Belgrade is part of the multinational CLEVER Cities Initiative, the city's Secretariat for Environmental Protection suggested the use of the site as a pilot test for introducing nature-based solutions in urban planning and with diverse stakeholders' input. Several workshops, focus groups, and consultations took place between 2019 and 2021, which facilitated the diversity of ideas that have been adopted into the official construction plan (Ref. 1, 2). Despite these successes, civil society groups raise concerns over the extraordinary cost of 70 million euros, displacement of Roma communities and the interest of real estate developers that may undermine the project's original cause (Ref. 3, 8).

The "Ruas Verdes+" (green streets) project, implemented in the parishes of Areeiro and Arroios in Lisbon, is part of a broader European initiative, Conexus, aimed at promoting green solutions in highly urbanized areas (Ref 3). The project primarily focuses on creating a tree-lined pedestrian corridor along Carlos Mardel and Francisco Sanches streets, establishing a continuous axis between the Casal Vistoso Urban Park and the Caracol da Penha Garden (Ref 1). This corridor is designed to mitigate urban heat island effects, enhance ecological connectivity, and improve residents' quality of life (Ref 5). The pilot phase includes planting 20 trees on Rua Carlos Mardel and removing a minimal number of parking spaces to balance urban greening with local needs (Ref 1). Additionally, planters are being introduced in the Bairro dos Actores area to test the community’s response to greening initiatives (Ref 1). The project also involves public participation through gardening workshops, encouraging residents to contribute to the greening effort by adding plants to their balconies (Ref 4). This initiative aims not only to enhance the urban environment but also to foster social inclusion and community engagement while addressing the challenges of climate change in Lisbon's densely populated areas (Ref 5).

The Belt Line Center building, located in Detroit, Michigan, property of Letts Industries, features a green-blue roof, along with a rain garden, showcasing the benefits of green infrastructure in historic properties. The idea for this retrofit emerged in 2015 after a major renovation, when Chip Letts, CEO of Letts Industries, recognized the potential of green infrastructure for long-term energy efficiency and storm-water management.
The initiative gained momentum in 2018, following the Detroit Water and Sewerage Department's (DWSD) introduction of new drainage fees, which charged $750 per acre of impermeable surfaces. The DWSD also offered up to 80% discounts for properties implementing green solutions, further incentivizing the project.
The project officially began in 2020 after securing PACE funding (Property Assessed Clean Energy funding, a financing mechanism that enables property owners to fund energy efficiency, renewable energy, and water conservation projects) from CounterpointeSRE (financial institution), marking the first use of commercial PACE financing for a green roof in Michigan. The green roof, covering 17,250 square feet, includes 300 square feet of pedestal pavers and a 2,500 square foot blue roof. These features enhance stormwater management, energy efficiency, and roof longevity; the center also incorporates two beehives to support local biodiversity.
These systems work in tandem with the ground-level rain garden to capture and infiltrate stormwater runoff, significantly reducing the impact on Detroit’s stormwater system. The project aligns with the city’s broader sustainability goals, including the Beltline Greenway initiative, which will pass directly behind the property, integrating the building into Detroit’s expanding network of green spaces and bike paths.
The Belt Line Center serves as a model for revitalizing historic buildings through innovative financing and sustainable design, enhancing Detroit’s environmental resilience. (Ref.1-5)

The Joe Louis Greenway is a 27.5-mile recreational pathway designed to create safe, connected, and equitable spaces throughout Detroit. It will link 23 neighborhoods across Detroit, Hamtramck, Highland Park, and Dearborn, connecting them to each other and to the Detroit riverfront. The greenway will transform a blighted, abandoned rail corridor into a park that runs through the heart of Detroit's communities. (Ref. 2, 3)
This project is guided by a Framework Plan funded by the Ralph C. Wilson, Jr. Foundation and shaped by extensive community input. Residents voiced a strong desire for the greenway to provide off-street recreation and increased access to green spaces across Detroit. Additionally, they advocated for the restoration and remediation of former industrial sites, which the Conrail section of the greenway will address. (Ref. 4) The design incorporates stormwater management to mitigate flooding, native meadow plantings to support bird habitats, and tree-lined paths for shade and improved air quality. The Framework Plan ensures the Joe Louis Greenway will transform infrastructure that once divided neighborhoods into one that unites them, reconnects natural systems, drives economic redevelopment, and fosters a resilient social network. (Ref. 13)
The concept originated in 2007 with the Friends of the Inner Circle Greenway local NGO and became part of the Detroit Greenways Coalition Network Vision in 2009. The Detroit Greenways Coalition Network Vision is a comprehensive plan developed by the Detroit Greenways Coalition (NGO), an organization dedicated to promoting non-motorized transportation and green infrastructure throughout the city. After years of advocacy and collaboration with the city of Detroit, the project’s route was finalized. In 2017, Mayor Mike Duggan announced the greenway would be renamed in honor of Joe Louis, the legendary boxer and Detroit native who championed African Americans' rights and symbolized social justice. (Ref. 1, 2,)