Improved air quality

Over the past 10 years, Lima's population has grown from 8.2 to 9.6 million people. As the city's urban sprawl and population density have increased, green spaces have been replaced by grey infrastructure. Consequently, it has become challenging to ensure that residents enjoy a good quality of life (1, 2, 3). In December 2019, Lima City Hall launched "Limeños al Bicentenario," an initiative to revitalise the city's public spaces (1, 3). This program seeks to transform public areas through low-cost interventions, based on criteria such as vulnerability, citizen participation, and catalytic potential, among others (3). It also aims to foster social cohesion by involving residents in the maintenance of these newly renovated areas, while improving the city's resilience to climate change (1, 2, 3). Since its inception, the project has reclaimed 17 public spaces, covering an area of 41,000 m² (3). 430 trees have been planted, and the project has benefited from the collaboration of civil society and private sector partners (3). The programme also focuses on addressing climate change. Heat waves, droughts, floods and mass migration are the main climate-related risks affecting the city. In particular, the expansion of grey infrastructure at the expense of green spaces has exacerbated the risk of heat waves, causing temperatures to rise by up to 3.5 °C in certain areas of Lima (3).
One of the projects involved the recovery of public spaces in Teniente Pavia. For many years, the space was used as a public parking lot, and at night it accumulated garbage, there was alcohol consumption, drug use, and other problematic issues. There was no vegetation, benches or infrastructure for recreation. The neighbours, especially children, did not have access to green areas or recreational spaces (5). For this reason, in 2020 the project was initiated to repair sidewalks, plant vegetation, create gardens, and install infrastructure for play, rest, and exercise (3, 4).

The Adana Urban Park was created in 2024, replacing an aged sports stadium (Ref. 6). The park, located in a densely populated part of the city, was designed to enable access to a place for socializing and recreation in the city centre (Ref. 1,2,5). Especially families, youth, and the elderly will benefit from the installed amenities - they include a large public coffeehouse of about 850m², diverse playgrounds, walking, running and cycling paths, as well as several gardens hosting orchards, aromatic plants and other local vegetation (Ref. 1,3,4,5). The park has a total area of ca. 4.8 ha and was approved by the Government of Türkiye - Ministry of Environment, Urbanization and Climate Change (Ref. 3,6). Beyond its social benefits, Adana Urban Park is expected to aid in alleviating the pressure of air pollution in the city (Ref. 4).

Phoenix is one of the hottest cities in the United States, with temperatures regularly exceeding 40°C (104°F) for more than 90 days each year. The urban heat island effect is severe here, posing a significant health risk. Many communities in Phoenix lack equal access to shade cover—often, the impact of extreme heat disproportionately affects low-income neighborhoods that lack resources for tree planting and maintenance. In contrast, wealthier areas tend to have more trees and are visibly greener, which helps reduce the heat residents experience.
To address these disparities, the City of Phoenix partnered with SRP, a not-for-profit public power utility, to launch the "Right Tree, Right Place" program in 2018. This initiative aims to bring shade relief to areas most in need, such as parks, public transit stops, and schools, while replacing older trees that interfere with SRP power lines. SRP and the city work together to identify trees that pose risks to overhead power lines, and for each tree removed, three new trees are planted—either in a different location or with a species better suited to coexist with power lines.
One of the program’s notable projects took place in West Phoenix’s Cortez Park, where 24 drought-tolerant trees from four different species were planted. This diversity helps protect the trees against pests and other natural threats, ensuring their longevity and resilience. Through initiatives like these, the "Right Tree, Right Place" program contributes to Phoenix’s larger goal of developing a robust, biodiverse urban forest. By expanding green infrastructure, the city aims to reduce local temperatures, improve air quality, and create cooler, healthier neighborhoods for all residents. (1-8)

Parque Lácides Segovia is an urban park located on Isla de Manga in Cartagena, Colombia. The park was inaugurated and revitalizated in June 2014 to serve as a multifunctional green space promoting cultural, social, and environmental activities. Named after General Lácides Segovia, a notable figure in Cartagena's history, the park aimed to provide a family-friendly and culturally enriching environment (ref 1). The primary goal was to transform a neglected urban area into a dynamic public space that fosters community interaction and enhances local culture. The park aimed to create a safe, inclusive, and accessible environment for residents of all ages, promoting social integration and cultural activities. Additionally, the project sought to establish a green area contributing to the ecological health of the city through urban greenery (ref 1, 2).
The first revitalization in 2014 involved facilities, planting native trees, and setting up public amenities such as Wi-Fi, seating, and cultural spaces(1, 2, 3).
This new revitalization in 2024, led by the local government of Cartagena, will focus on enhancing the infrastructure of both the park and the surrounding sports area in Manga to improve sustainability. The project has an estimated budget of approximately USD 675,000. The improvement works to provide better facilities and infrastructure to support recreational and sports activities, benefiting the community and promoting a healthier urban environment (ref 6). The park is essential for the community; it was recently the subject of several citizen science projects led by the Montessori School, including research identifying the park's ecosystem services (ref 3).

The last large-scale park in Iași was opened in 1923, and since then, the city has lacked any significant new green spaces. With the European Union recommending at least 26 square meters of green space per resident and the city's increasing urban density, the need for a new park is undeniable.
To address this, the Municipality of Iași is launching its first major park project in over a century. The project aims to transform the current CTP depot (tram station) into a 4.5-hectare, accessible green space in a densely populated area with strong development potential. This new park is envisioned as a green oasis that will enhance residents' quality of life while promoting environmental sustainability and urban renewal.
The initiative has received widespread public support, with citizens proposing the creation of a local museum to honor the tram station’s historical significance—one of the oldest in the city, with over 100 years of history. A consultation process has been established, involving local residents, NGOs, and a group of experts, including urban planners, architects, and mobility and environment officials, all contributing to the planning stage. Public suggestions for the park include underground parking, recreational and exercise facilities, and a diverse range of vegetation. Ensuring accessibility for all citizens and visitors is also a key priority in the park's design.
The municipality has allocated 300,000 euros for a solutions contest to finalize the approach to redeveloping the tram station. (1, 2, 3, 4, 5, 8, 9)

The Green Wall of Tomesti was an initiative launched by the commune of Tomesti to combat air pollution from the nearby city of Iasi, which often drifted into the area (1, 2). The municipality decided to implement this solution after consulting specialists on how to address pollution from the main urban area. It was also integrated into the objectives of their 2014 General Urbanistic Plan, which aimed to transform Tomesti into a "modern, clean, and ecological area" (1, 2, 5). In addition to mitigating air pollution, the forest wall was expected to help lower local air temperatures (1).
The municipality purchased seedlings and planted the trees at the end of 2019, near the D.D. Patranascu school (1-3). While the overall goal was to protect the entire commune and improve the health of Tomesti's residents, particular attention was given to safeguarding the school closest to Iasi (1, 2). Before planting, the organizers called for volunteers to help with the plantation (3). In total, approximately 1,500 trees were planted (linden, acacia, oak and willow), with a space of 1,5 m between each other (2).
The action also follows on a 20-year national plan to increase forest walls to improve the quality of the air in the country (6).

Phoenix is grappling with severe urban heat problems. As the city continues to grow, it is expected to experience a rise in temperatures of three to five degrees on average in the coming years. This makes urban heat a significant concern, especially for vulnerable populations. Phoenix’s extensive urban sprawl, combined with a lack of green space, has exacerbated the urban heat island effect, where cities become significantly hotter than surrounding rural areas due to the high concentration of concrete, asphalt, and infrastructure. In 2022, Nick Lodato, the principal of Emerson Elementary School, wanted to mark the school's 100th anniversary in a meaningful way. He decided that planting trees would be the perfect way to celebrate this milestone while also benefiting the community. The tree planting event not only symbolized the school's strong sense of community but also represented an investment in its sustainable future. Prior to the project, Emerson had only 9% tree canopy cover, which was far below what is necessary to address some of the pressing environmental challenges Phoenix faces.
Tree cover has become critical infrastructure for heat mitigation. Trees provide natural shade and help cool the environment by reducing surface temperatures, which in turn lowers energy consumption and promotes better public health. In addition to offering shade, the native, drought-tolerant trees and plants planted at Emerson will also contribute to carbon sequestration, purify the air, and improve mental health by creating more green spaces for relaxation and outdoor activities.
To complete this project, Emerson Elementary partnered with the Arizona Sustainability Alliance (ASA), a local nonprofit. Together, they planted over 100 trees and plants across the school’s campus, with approximately 125 people attending the event. Volunteers included students and their parents, Tau Psi Omega fraternity members, APS employees, neighbors, former Emerson students and teachers. (1-3)

The municipality of Ciudad Juarez, in collaboration with UN-Habitat, has drafted a redevelopment strategy for an area known as "Paso de Oñate." This intervention falls within the broader framework of "Vision Ciudad Juarez 2040." The plan involves constructing a forested green belt along the southern edge of the Rio Grande (/Bravo) in the northwest part of Juarez, bordering the USA.
Currently in the planning stage, the project aims to restore the ecological function of various degraded areas along the Rio Grande, transforming them into a continuous, green, walkable, and recreational space. The strategy includes allowing vegetation to recover, introducing native plant species, and increasing tree cover to rehabilitate unmaintained parks, derelict areas, and degraded riverbanks. These areas will be equipped with new features and integrated with existing parks, schools, and playgrounds. The envisioned green corridor will enhance walking conditions, improve the perception of safety, offer recreational opportunities for all age groups, and deliver valuable ecosystem services such as temperature regulation, improved air quality, and water retention.
In addition to its ecological goals, the project has a historical and geographical dimension. It aims to incorporate cultural heritage elements, such as the monument of the New Citizen, Paso de Oñate, Turtles Park, and the beginning of the Acequia Madre. It will also connect with other green space initiatives, including the Mega Park "El Chamizal" and the "Corredor Cultural," which runs through the city center.
This intervention is being prioritized due to the area's ongoing social and ecological decline. Paso de Oñate is a critical border crossing point, which negatively affects mobility and air quality. The area also suffers from a high concentration of vacant housing, which contributes to the residents' perception of insecurity. (Ref. 1, 2, 3, 4)

Maya’s Farm is a small, CSA (Community Supported Agriculture) sustainable urban farm located in Phoenix, Arizona, where urban development has limited farmland availability. In 2020 alone, Phoenix lost nearly 200 acres of farmland to urban sprawl, putting farms like Maya’s at risk. The farm faced potential closure until the City of Phoenix intervened, providing funding through the Farm Preservation Program, which established the city's first urban agricultural conservation easement. Maya's Farm strives to inspire a local appreciation for sustainable food and to bring renewed value to local food systems.
The farm’s mission is to provide accessible, fresh, locally grown produce to the community while promoting awareness of healthy, sustainable food practices. Through its CSA program, members receive a weekly produce box and have opportunities to come together, honor food traditions, and share stories over locally harvested food. As a CCOF (California Certified Organic Farmers) certified organic farm, Maya’s Farm is committed to organic practices that exclude GMOs, nurture the soil, foster biodiversity, and innovate growing systems. These methods result in healthy soil and cleaner air, contribute to carbon sequestration, and support critical wildlife habitats.
To broaden educational outreach, Maya’s Farm offers several programs that promote sustainable food practices, including its CSA program, an edible classroom series, and a partnership with Arizona State University (ASU). Through this ASU partnership, students gain hands-on experience by participating in daily farm operations.
Building stronger community connections is another cornerstone of Maya's Farm’s work. The farm collaborates with local restaurants, farmers' markets, and community groups to expand its impact. Maya’s Farm, ASU, and Arizona Sustainability Alliance launched an agrivoltaics project with solar-shaded crops. (2, 9, 11, 13, 15)

For a Forest in Your Neighborhood" is an afforestation campaign by the DDOR insurance group, launched in 2022 as part of their Environment, Society, and Governance (ESG) commitments (Ref. 1). Site selection was based on online votings, with thousands of votes being casted from 188 towns across Serbia (Ref. 2). In the end, the fifteen most popular cities were selected for project implementation. As a result, hundreds of trees were planted, including 25 trees along the promenade of Belgrade’s Ušće Park in 2023 (Ref. 3). Ultimately, the initiative aims to create and enhance urban green spaces, to improve air quality and living conditions in Serbian cities (Ref. 5). The success of the campaign encouraged DDOR to extend the campaign in 2024, financed through their eco-insurance schemes (Ref. 4)