Climate change mitigation

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 municipal real estate company Higab partnered with The Foodprint Lab Architects, an architecture firm specialising in food system design, in a three-year pilot project to create urban farms in three of their properties in Gothenburg. The Foodprint Lab designed the urban farms based on the conditions of each property and connected Higab with potential farmers. The urban farms are located at Slakthuset (an old industrial area), Kviberg (by an empty building undergoing renovation) and Musikens hus (an old building used for music events and a restaurant). The farms are established in unused, mostly grey areas such as parking lots. In all sites, the farming is run by local farming associations; some sell vegetables on site and in Kviberg, there has also been a commercial production of vegetables. Sustainable food production, entrepreneurship opportunities, a nicer and safer environment, and the promotion of biodiversity are highlighted as benefits of the project. In total, about 50 different plant species are found across the locations. The establishment of the urban farms was part of the Grow Gothenburg project within the Sharing Cities Sweden program, which provided some of the funding [Ref. 1-5, 7].

Civic Space Park, located in the heart of Phoenix, Arizona, is a notable example of urban design aimed at addressing the region’s increasing urban heat. In Phoenix, rising temperatures affect health, safety, comfort, and economic growth, and this impact is expected to worsen over time. In response, the park was developed to transform an underused site into a vibrant public space that prioritizes community engagement, sustainability, and urban revitalization.
The project was realized through a public-private partnership between the City of Phoenix and Arizona State University, with strong community involvement shaping its development. This collaboration led to the “Urban Weave” concept, a design that embodies the identity and values of the local community.
Civic Space Park was designed with several goals in mind. Increasing the tree canopy was essential to help reduce the urban heat island effect and improve air quality. Creating a welcoming area for social interaction, recreation, and relaxation was equally important to enhance community well-being. Water conservation was also prioritized, achieved through innovative stormwater management techniques such as permeable paving and underground infiltration. The park incorporates renewable energy generation as well, with on-site solar power helping to reduce energy consumption.
One of the park’s unique features is its extensive use of pervious concrete paving, designed to allow stormwater to permeate directly into the subsurface. However, during installation, it became clear that placing the material over highly compacted soil limited water infiltration. To improve its effectiveness, future designs could include a plastic vapor barrier beneath the permeable paving to capture water and direct it to planting beds. This adjustment would enable the paving to act as a collection and storage system, gradually releasing water into the surrounding vegetation.
(1-6)

The Juan Angola River is an urban channel included in the system of rivers and channels of Cartagena, and it connects the Ciénaga de la Virgen wetland and the Bay of Cartagena, facing similar issues as the Cienaga de la Virgen such as illegal occupation of its shores, illegal waste dumping, deforestation of mangroves, and pollution. The recovery plan for the Juan Angola River is led by the EPA Cartagena (Environmental Protection Agency), with the support of other institutions, aiming to restore the Juan Angola’s ecosystem. This includes targeting the mangrove forest, dredging the natural channel, and delineating buffer zones with urban infrastructure to create public recreational spaces. The activities involve relocating people illegalling cupping informal settlements from the river shore, moving an existing bridge (the Benjamín Herrera bridge) which obstructs the current, recovering the low tide and riverbed areas, building pedestrian paths, clean the riverbank, recover mangrove areas and establish programs of education and environmental awareness (ref 1 and 2).

Ireland’s native trees have developed over thousands of years, forming a vibrant ecosystem alongside surrounding plants, animals, fungi, and microbes. These trees provide critical habitats for plants and wildlife, offering essential food and shelter while producing oxygen vital to animals and humans alike. Historically, native trees supplied early Irish communities with fuel, food, shelter, and building materials. Today, they play a modern role in filtering dust, reducing pollution, and enriching urban spaces.
To highlight these benefits in Dublin, the Native Tree Trail in St. Anne's Park was created by DCC Parks and Landscape Services in 2008. This trail, featuring 15 different types of native trees, invites visitors to explore and appreciate the natural and cultural heritage of Ireland's native trees, underscoring the value of green spaces for both biodiversity and community well-being.
Strategic tree placement contributes to Dublin’s sustainability by reducing soil erosion, sequestering carbon, and mitigating urban heat. A green city is a healthy city, and preserving open spaces enhances its appeal as a place to live, work, and visit. The trail also plays an essential role in environmental education and community engagement. Over the years, St. Anne's Park has hosted multiple tree-planting events, including a 2019 collaboration with local schools for National Tree Week and National Tree Day, in partnership with the Tree Council of Ireland. The NGO has also offered family-friendly guided walks along the trail, helping to instill an appreciation for nature in visitors of all ages (1, 2, 3, 4, 5, p.93).

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).

Phoenix faces substantial challenges related to extreme heat, air quality, and social inequity (1-11). The Phoenix Tree Equity Pledge, launched in 2021, is a comprehensive city-wide initiative focused on addressing urban tree inequity and reducing the effects of extreme heat, especially in communities most vulnerable to these conditions (1-12). Partnering with American Forests, the country’s oldest conservation nonprofit, the initiative aims to achieve “tree equity” by 2030, ensuring all neighborhoods receive the benefits trees offer (1).
To reach this goal, the city will focus on enhancing tree coverage in underserved neighborhoods through the development of a Residential Tree Equity Accelerator, which plans to plant 20,000 trees across 25 neighborhoods by 2030 (1-12). By utilizing the Tree Equity Score developed by American Forests, the city can monitor progress, identify areas of need, and measure the impact of these projects (2-4, 9, 11).
To foster public engagement, the initiative will collaborate with residents, businesses, and local organizations to support tree-related projects, raise awareness of the benefits of trees, and promote tree stewardship (1, 4, 15). Additionally, the project aims to create green opportunities within the community by establishing supportive policies and regulations for tree planting and care and by creating pathways to green jobs (1, 7-9, 13-14). Recognizing that heat affects communities unequally, the Tree Equity Pledge seeks to increase canopy coverage in targeted neighborhoods, improving air quality, reducing the urban heat island effect, and enhancing overall community health (1, 7-9, 13-14).

The Dublin Urban Rivers LIFE (DURL) project incorporates two interconnected wetlands in Griffeen Park as part of its broader initiative to improve water quality, natural water management and aquatic biodiversity in urban areas. These wetlands were specifically designed as a natural sewage system to treat wastewater from the surrounding areas, addressing a significant environmental issue known as "domestic misconnection." Domestic misconnection occurs when household appliances, such as washing machines, dishwashers, and kitchen sinks, are incorrectly linked to surface water drains rather than the sewage system. This leads to untreated wastewater being directly discharged into local waterways, contributing to contamination.
In the River Griffeen catchment, which includes approximately 12,000 dwellings and associated infrastructure, domestic misconnections are a considerable threat to water quality. The DURL project focuses on identifying and rectifying these misconnected appliances to ensure that wastewater is properly treated before entering the river. This process will not only improve water quality but will also provide flood alleviation and support healthier aquatic ecosystems in the area.
The project is aligned with broader environmental policies, including the River Basin Management Plan 2022-2027, the Water Framework Directive, the Climate Change Action Plan, the Floods Directive, and the draft Biodiversity Plan. One of the key strategies is to use a Geographic Information System (GIS) to streamline inspections for domestic misconnections, making the process faster and more cost-effective.
The constructed wetlands in Griffeen Park, with a standing water depth of approximately 30 cm, are planted with a variety of native Irish species. These wetlands offer a natural, sustainable solution to wastewater treatment, with the potential for similar applications across Europe. (Ref. 2, 4)

The NatureRx Rain Garden Pilot is a community-driven initiative aimed at addressing urban runoff and its associated challenges, implemented by Bí URBAN, a community hub and social enterprise in Dublin focused on urban regeneration. The pilot project developed in Stoneybatter, Dublin involves diverting rainwater from residential rooftops into specially designed rain gardens (1). The area is used as the first trial area by installing around 100 rain gardens (3, 11). Built to fit neatly into available spaces, these self-sustaining planters will filter rainwater through the garden, with overflow pipes in place to prevent flooding during heavy downpours (1).
It is expected that these gardens will transform sterile urban spaces into green areas, enhancing biodiversity, providing habitats for pollinators, and acting as carbon sinks (1,3).

Birmingham faces several immediate risks due to climate change, including heatwaves, water shortages from droughts, floods, and extreme weather (Ref 11). To address these challenges, Birmingham City Council has set a goal to reduce carbon emissions by 60% by 2027. As part of this effort, the new Birmingham Library project, initiated by the council, includes a rooftop garden designed to contribute to this target (Ref 3). The library was designed by the Dutch firm Mecanoo Architecten, with a design process spanning from 2008 to 2012 (Ref 5). The two outdoor rooftop gardens, located on levels 3 and 7, were completed in 2013 (Ref 1). These gardens provide green spaces in the city center, enhance water management through rainwater harvesting, serve as educational facilities for sustainable food innovation, and create natural habitats for wildlife (Ref 1, 3, 4, 6). Their contributions helped the library achieve a BREEAM 'Excellent' rating and have garnered various awards (Ref 1, 10). The new library aligns with Birmingham City Council's Big City Plan to regenerate the city center, with the green roof gardens playing a key role (Ref 4).