Climate change mitigation

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)

Two new wetlands were established in Dodder Valley Park as part of the Dublin Urban Rivers Life Project (DURL). This project aimed to create integrated constructed wetlands (ICWs) at strategic locations in South Dublin County to purify wastewater and storm-water before it discharged into rivers.
The ICWs consisted of a series of cells resembling shallow ponds, typically 200 to 300 mm deep. Heavily planted with specific vegetation, these cells treated water by removing nutrients and harmful impurities, resulting in cleaner, purer water being discharged. The water flowing into the wetlands came from wastewater of misconnected appliances and storm-water pipes located under public roads, which collected rainwater from roads, footpaths, and the roofs and patios of houses.
These wetlands also provided important benefits, including flood alleviation, bioretention of particulates and nutrients, improved habitat conditions, and enhanced biodiversity. The project aimed to promote the relationship between green infrastructure and public well-being, creating a complex biological system that supports a diverse range of plants, animals, microorganisms, and hopefully attracts frogs, newts, and birds.
To increase native biodiversity, the wetlands were designed with pollinator-friendly plants and trees, making them visually appealing for park users and the public. A Wetland Planting Day took place on September 9, 2022, with over 40 participants, including residents and representatives from local organizations. This phase of the project fulfilled not only the objectives of the LIFE project but also those of the River Basin Masin Management Plan 2022–2027, the Water Framework Directive, the Climate Change Action Plan, the Floods Directive. (1, 2, 5)

The Cartagena-Barranquilla Road Corridor project, led by the National Infrastructure Agency (Agencia Nacional de Infraestructura (ANI)), covers 146.7 km to enhance connectivity between Cartagena and Barranquilla (ref 2). While primarily a transportation initiative, the project stands out for its focus on environmental conservation and community development. A major goal is the restoration of ecosystems and biodiversity protection. To this end, over 40,000 mangrove seedlings have been planted in the 34.13-hectare Ciénaga de la Virgen, a vital coastal wetland in Cartagena. These mangroves play a crucial role in restoring habitats, capturing carbon, and acting as natural flood barriers, thereby safeguarding nearby communities (ref 1,4,6). The project also tackles hazards like wildlife-vehicle collisions and habitat fragmentation. Seven wildlife crossings have been built to facilitate the safe movement of species, including the endangered Blue Crab (Cardisoma guanhumi) in the Ciénaga de Mallorquín. These crossings are essential for preserving local wildlife (ref 1,7).
In terms of socio-economic impact, the project has created over 9,000 jobs and established six bioclimatic nurseries, which provide sustainable livelihoods for communities in La Boquilla, Villa Gloria, Tierra Baja, and Puerto Rey. These nurseries support mangrove restoration and offer local people opportunities to participate in planting, monitoring, and maintenance activities. This approach fosters a circular economy, empowering community members, both men and women, to engage in sustainable economic practices (ref 1,2,6).
Overall, the Cartagena-Barranquilla Road Corridor is more than a transport project; it acts as a green corridor with a comprehensive approach that combines environmental conservation, hazard mitigation, and socio-economic development.

San Borja has 1,347,000 square metres of green areas, equivalent to 12 square metres of green space per inhabitant, one of the highest ratios in the capital (1, 2). In total, there are 75 parks within its jurisdiction (1, 3). However, in recent years it has consolidated its role as a metropolitan urban centre and has become denser with new multi-family construction projects replacing traditional single-family homes with gardens (2). As a result, tree cover has decreased, affecting the creation of shaded areas and air quality, putting the health of residents at risk (2). Nevertheless, this municipality has reaffirmed its participation in the Global Covenant of Mayors for Climate and Energy, committing to implement policies and take measures to reduce (or limit where appropriate) greenhouse gas emissions and prepare for the impacts of climate change, as it is vulnerable to heat waves and droughts, as well as high wind and thunderstorm hazards and fires (1). Thus, since 2014, 56,000 trees have been planted, which is one tree for every two residents in the district (2). The mitigation programme includes 40 measures, including the creation and conservation of green areas, which involve planting trees to create urban forests to help regulate temperature, prevent heat waves, improve CO2 absorption, and preserve endemic species (1). In addition, the programme promotes the use of organic farming practices and the propagation of plants using natural methods (1).
One of the sectors where there has been the most progress is Sector 12, with 31% of the green areas created (3). Within this sector, the district is planting and creating an urban forest within the premises of the Army Headquarters, better known as ‘Pentagonito’. Its objective is to educate neighbours and promote greater environmental awareness (3, 4, 5).

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)

Urban areas are particularly vulnerable to climate change due to the extensive use of concrete and asphalt, higher levels of pollution, increased population densities, and the concentration of infrastructure, all of which amplify the effects of extreme heat, drought, and severe weather. Urban tree cover play a vital role in helping cities mitigate the impacts of climate change by reducing greenhouse gases and alleviating the effects of extreme heat and other climate alterations that negatively impact human health. In 2023, dozens of volunteers from Bethune Elementary School planted 33 trees on the school grounds to provide future shade and help cool the environment. The project was funded by Arizona’s Public Service (APS) Community Tree Program, which aims to reduce the urban heat island effect by increasing tree canopy coverage in vulnerable communities.
The initiative was driven by Trees Matter, a local nonprofit organization focused on enhancing tree infrastructure in schools while educating students and staff on the importance of trees and tree care. Involving children in the tree planting process allows them to take what they’ve learned in textbooks and apply it in real-life situations, while also fostering a sense of community and belonging. This hands-on involvement not only educates but also creates lasting memories. The project’s goal is to combat the urban heat island effect by expanding tree canopy coverage, thus creating cooler, healthier shaded spaces for students in areas of Phoenix most affected by high temperatures.
With support from APS and Trees Matter, the volunteers worked together to plant trees that will provide much-needed shade on the school campus. APS’s Community Tree Program aims to provide shade and cooler spaces in neighborhoods that need it most, helping to reduce temperatures by 20 to 45 degrees. This effort is part of a broader initiative to improve the quality of life and mitigate the impacts of extreme heat in Phoenix (1-5).

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)

St. Anne's Urban Farm and Ecology Center, nestled within Dublin’s historic St. Anne’s Park and surrounded by the suburban neighborhoods of Dublin 3 and 5, is a unique not-for-profit initiative dedicated to community engagement, environmental awareness, and sustainable urban agriculture. Established in 2019, this farm is the first urban farm within Dublin City Council’s boundaries and aims to reach even more people, believing that every child and adult should have access to a garden space and that everyone in the garden is equal.
Run by a team of over 20 dedicated community volunteers, the farm provides hands-on educational experiences for visitors of all ages and a safe, open space for sharing knowledge and learning from others. Featuring traditional Irish farm animals, such as heritage breeds of chickens, pigs, and goats, alongside native plants grown from heirloom seeds, the farm preserves Ireland’s agricultural heritage while promoting biodiversity and sustainable practices.
With a goal of becoming 75% self-sustaining, the farm is working toward off-grid solutions through solar power and eco-friendly techniques. St. Anne’s Urban Farm empowers local residents with its community allotments and self-management model, which foster greater control and pride in maintaining the shared space. Aligned with Dublin’s Climate Change Action Plan, the farm aspires to improve the quality of life within the city by promoting healthy neighborhoods and sustainable communities. Through this green space, St. Anne’s Urban Farm encourages social and environmental engagement, aiming to ensure that gardens and green spaces remain accessible, welcoming, and educational for generations to come. The initiative is supported by a €50,000 donation from Google and is designed to serve as a community resource rather than a traditional petting farm.
(1-6)

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)