Improved air quality

Cagliari's waterfront is currently characterized by extensive soil sealing, which has rendered the soil impermeable, leading to a loss of biodiversity and contributing to the urban heat island effect. Additionally, the waterfront is disconnected from the city due to heavy traffic. In 2023, the Municipality of Cagliari launched the "Green Promenade for Cagliari’s Seafront" project, aimed at revitalizing the waterfront and reconnecting the city with its coastal heritage. Led by Stefano Boeri Architetti, the project seeks to transform the area into a continuous green space that integrates pedestrian pathways with shaded public areas, functioning as a "green lung" to mitigate urban heat and enhance biodiversity.
The initiative will introduce over 200 new trees and 5,700 square meters of green space, creating a park that beautifies the area, improves air quality, and lowers local temperatures. A key focus of the project is fostering cultural and social inclusion by developing new community hubs that encourage diverse activities and strengthen social cohesion. Additional features include recreational areas, sports fields, and outdoor seating. (Ref. 1, 2,3)
The project also aims to enhance social inclusion, environmental sustainability, and urban connectivity, ultimately transforming the waterfront into a vibrant public space that reflects Cagliari’s identity.
However, the lengthy construction process has disrupted local businesses and reduced foot traffic, making the area less attractive during the redevelopment phase. (Refs. 10, 11, 12 & 13).

In 2021, the real estate company Inamstro, in collaboration with the Municipality of Iași, the civil organization "Glasul Vieții" (Voice of Life), and local citizens, initiated a tree-planting initiative that involved planting 250 trees near a residential area and a parking lot in the Frumoasa neighborhood of Iași. This neighborhood is smaller compared to other areas of the city and was developed during the communist systematization of the 1970s and 1980s. It consists of groups of four-story blocks arranged around common spaces, situated near the Frumoasa Monastery complex.
The main goals of the 2021 planting action were to enhance green space, lower air temperatures, reduce urban air pollutants—such as fine particulate matter—absorb CO2, and improve overall health and quality of life (1–5). Additionally, the implementing company concluded that the trees planted near residential areas can significantly reduce energy needs for air conditioning and heating, leading to an average cost decrease of 30% during summer and winter (1, 2).
Volunteers participating in the project received a "tree certificate," signifying their commitment to planting and adopting a tree (7). In this initiative, volunteers were also tasked with monitoring the growth of their adopted trees to ensure their health (1–6).

Barranco, the smallest district of Metropolitan Lima, is suffering from serious environmental problems that are affecting its inhabitants. Environmental degradation is a consequence of the increase in large buildings (real estate boom), which reduces green space areas and causes a deficit of vegetation in the district. Additionally, there are high levels of air pollution due to car traffic, which has been accentuated by the lack of green areas in the area, which affects the environmental quality and the population's quality of life (1).
Additionally, the district doesn't have more free public areas where new green areas can be created. Due to these combined pressures, the local government has looked for alternatives, considering private areas, which have a high potential to implement green roofs and vertical gardens, which can contribute to face Climate Change as a mitigation strategy and improve the quality of life (1). The Green Roofs and Green Walls strategy is proposed to build citizen culture, nature appreciation, landscape, and ecosystems (2, 3). The aim is, therefore, to encourage the inhabitants of the district to progressively install green roofs and walls, employing an economic incentive in the taxes paid to maintain public green areas (4).
The programme is oriented to generate environmental benefits such as the reduction of air pollution, acoustic insulation, thermal comfort, and increase of green areas (m2) per inhabitant, and social benefits such as the improvement of the living conditions and health of the inhabitants of the district (1, 3), the promotion of social relations (1), the aesthetic improvement of the city, and the possibility of producing food for self-consumption, as there is support in the implementation of hydroponic systems in the green walls and roofs (1, 3). Its implementation focuses on new, under construction or existing residential, commercial, office or lodging buildings (3).

The project features a vertical garden, or "living wall," on the facade of a residential building in Berlin’s Kreuzberg district. Constructed in 2016, the building replaced a WWII-damaged plot situated between two existing structures. With a strong emphasis on sustainability, the project minimizes its ecological footprint in various ways. The 660-square-meter plot retained original elements of the location’s history: the two surviving sections along Glogauer and Reichenberger Strasse were restored after the war, while the rubble from the destroyed corner was used to fill in the basement. This approach allowed the new construction to be built over the original foundations, preserving historical integrity while reducing construction costs and material use.
At the core of the building’s design is a green agenda, embodied in the vertical garden that helps absorb noise and pollution from the bustling street below, improving air quality for residents and passersby. The selection of winter-hardy plants ensures that the facade remains green year-round, while also cooling the surrounding area and mitigating the urban heat effect, which is especially valuable in densely populated neighborhoods. The greenery contributes to the local microclimate, providing both environmental and aesthetic benefits.
For residents, the garden is made accessible through rectangular box balconies that project from the green wall, allowing them to engage closely with the plants and enjoy the immersive garden atmosphere. The plants grow on a support structure that is securely anchored in the brickwork, receiving water and nutrients through an integrated, precision-controlled irrigation and fertilization system. Maintenance of the plants occurs twice a year, with new additions planted each spring to maintain the garden’s health and visual appeal.
The building itself, privately owned, contains a mix of holiday rentals and residential apartments. Architect Sarah Revière designed the project. (1-6)

The Cinturón Verde de Independencia initiative is a pilot intervention that seeks to plant an urban forest in the lower middle-class district of Independencia (1) in the northern part of the urban territory (3). Here, 19% of the population lives in high-risk conditions, settled on steep slopes, and threatened by landslides (3).
It is part of a broader planning strategy that involves proposals engaging different levels of government (4). This project seeks to afforest the district's hillsides to improve the environment, reduce air pollution, improve the quality of life of its inhabitants, manage waste, regulate shade, control erosion, increase wild biodiversity, and provide spaces for environmental education (2). The Independence Green Belt is linked to a wide range of plans, projects, and decrees that have been developed by actors at different levels of government since 2016 (4). It works hand in hand with the EBA Lomas programme and seeks to create a green belt along the Lomas-city interface, which acts as a buffer zone for this sensitive ecosystem and creates a protective boundary against the expansion of irregular human settlements while providing a space for environmental awareness (2).
This program was developed by a consortium of multiple private, public, national, and international parties with strong community support (3). In two phases, an urban forest park of 4,800 of native trees irrigated with treated wastewater has been planted. During the first phase, PREDES planted 3,300 trees with USAID support in 2015, and another 1,500 were recently planted by PERIFERIA (consultants) (3).
The Independencia Green Belt occupies the hill areas of the district of the same name and relates to a possible metropolitan-scale buffer belt.
Its boundaries take advantage of the seven Sustainable Ecotourism Forest Parks (PFES) in the District Municipality of Independencia (MDI), as well as 115 hectares of the Amancaes Lomas (4). It aims to conserve 400 hectares (4).

The Heat Action Planning project in the Lindo Park-Roesley Park Neighborhood in Phoenix, Arizona, specifically addresses the heat-related challenges residents face in this area. Phoenix is particularly vulnerable to extreme heat events, and this project aims to provide both mitigation and adaptation strategies to reduce the direct impacts of heat and help residents cope more effectively with these conditions. As part of the city’s broader Heat Action Plan, the Lindo Park-Roesley Park initiative is one of three target areas, including Edison-Eastlake, just east of downtown Phoenix, and the Water Tower Improvement District in the City of Mesa. The project focuses on heat hazards such as extreme temperature events and the urban heat island effect, which disproportionately affect vulnerable populations.
This project is a collaborative effort, uniting a range of stakeholders including The Nature Conservancy, Maricopa County Department of Public Health, the Central Arizona Conservation Alliance, the Urban Resilience to Extremes Sustainability Research Network, Arizona State University’s Urban Climate Research Center, and the local residents. Together, these partners are working to develop comprehensive heat mitigation and adaptation strategies that address social equity and strengthen community engagement. Furthermore, the Heat Action Planning process was designed to serve as a model for future heat resilience efforts and create a local, contextual, and culturally appropriate vision of a safer, healthier future. The iterative planning and engagement method used by the project team strengthened relationships within and between
neighborhoods, community-based organizations, decision-makers, and the core team, and it combined storytelling wisdom and scientific evidence to better understand current and future challenges residents face during extreme heat events.The ultimate aim is to foster a more resilient and equitable neighborhood (1-7).

The Bahlui Forest project consists of a tree-planting initiative along the banks of the Bahlui River, which flows over a distance of 11 km through Iasi, practically dividing the city in two (1, 2, 6). The project aims to reduce the high levels of air pollution prevalent in the city, increase green spaces along the river and in the urban area, and enhance the aesthetic appeal of the surroundings, thereby improving the quality of life for local residents (1–3, 8, p. 188). The initiative was planned by the Municipality of Iași in collaboration with the Prut-Bârlad Water Basin Administration, the regional authority responsible for the river’s proper management (1–6). Furthermore, the "Ion Ionescu de la Brad" University of Agricultural Sciences and Veterinary Medicine in Iași provided the technical expertise needed to select and plant appropriate species (1–3, 7).
The planting completed in 2024, covers the river section between the Sf. Ioan bridge and the Stone Bridge (3–5). In total, 1,200 native species were planted, including four tree species—Willow, Malin, Red Maple, and Birch—and three shrub species (3–6).
This initiative is part of a broader municipal strategy to revitalize the riverbanks and address key issues (8, 9). Due to its natural geomorphology, the river represents a barrier in terms of accesibility between different parts of the city, and infrastructure and improvements need to be carried out to manage this problem (8 & 9). Therefore the areas around the river are sought to be revitalised to fullfil its touristic and recreational potential, ultimately becoming a green corridor and representing a new axis of development for Iasi (8, p. 344). Improving its green surfaces would also support efforts to increase green space sq.m. per inhabitant in the city, which falls short of the national requirement of 26 sq.m. per inhabitant (8, p. 189).

The Circle Forest project, led by Arboretum Detroit in partnership with Detroit Future City, is transforming a vacant lot the size of a football field in the Poletown East neighborhood into a green space. Once used as a dumping site, the area is being revitalized with 200 native trees, including oak, elderberry, white pine, and juniper. Supported by local groups like Detroit Audubon, Singing Tree, and the US Fish and Wildlife Service, the project aims to improve environmental quality and provide better access to nature for residents. Since 2019, over 120 trees have been planted, with plans to develop a native meadow. This initiative offers a space for recreation and reflection, benefiting the local community, including a nearby nursing home and rehabilitation center. Beyond ecological restoration, Circle Forest fosters connections to indigenous knowledge and respects the wisdom of the original stewards of the land. (Ref.1, 2)

The Bosque Vertical do Centro Cultural de Belém (CCB) in Lisbon (Vertical Forest at CCB), designed by Francisco Caldeira Cabral, is an innovative vertical garden inaugurated in 2020. Spanning two 17-meter-high walls with 7,524 plant pots, it enhances urban biodiversity by attracting birds and insects (Ref 3). This project offers recreational and aesthetic benefits, making the entrance of the cultural centre into a green space (Ref 4).
The garden helps reduce air pollution by absorbing pollutants and producing oxygen. It uses a drop-by-drop irrigation system made from recycled PVC, ensuring efficient water usage and retention (Ref 1). Furthermore, the garden improves air quality, aims to mitigate urban heat island effects, and conserves water (Ref 2, Ref 5).

Iasi has limited access to green-blue open spaces and fails to meet national and European standards for per capita green space and proximity to larger green areas. Additionally, the city experiences significant fragmentation in its green spaces. To address these issues, the municipality of Iasi launched a project in 2020 to restore a vacant and degraded area, transforming it into a park. Funded by European resources, the project aims to rehabilitate the neglected land by constructing a green park and introducing local vegetation. The primary goal is to provide a leisure and relaxation space for local citizens and visitors while improving the quality of the surrounding air by converting much of the terrain into green space. The vacant land is situated in the historic Ticau neighborhood, which has been affected by municipal neglect, characterized by poor infrastructure and limited connectivity to the city's main areas. Furthermore, the project aims to reduce the heat island effect by creating green oases in a city marked by many “hard surfaces,” such as paved areas, which contribute to this phenomenon expected to intensify in the coming years. Originally scheduled for completion by the end of 2022, the project has been delayed due to a lack of funds and is now expected to be finished by the end of 2024 (Refs 1, 2, 3, 4, 6, 7, 11).