Improved prevention of respiratory problems

The Mediterranean climate in Lisbon, already characterised by low precipitation, has been further exacerbated by climate change. The city faces challenges related to biodiversity loss, urban loneliness, and climate anxiety (1). To address these issues, Lisbon's urban development plans have prioritised the re-naturalisation of urban spaces and the integration of ecological networks. Urban nature is now a central component of the city's Master Plan (2012) and other strategic agendas (1).
It is being developed by the LISGREEN project, which aims to enhance ecological connectivity and mitigate the effects of urban heat islands in Lisbon. By establishing nature-based solutions, it aims to restore forests within the city (1, 2, 3). This project encompasses different strategies, such as the RENATURA pilot project. It is a collaboration with the NGO URBEM and involves active public participation in tree planting and forest maintenance. This initiative aims to educate the community about nature, promote well-being, and mitigate extreme climate events (1), through the creation of urban forests.
The main strategy is to create fast forests using the Miyawaki method, which involves dense planting of native trees, removal of invasive plants, and intensive initial care. This approach accelerates the growth of natural forests within a short period, using native species and reducing the need for watering (1)
The first fast forest was developed in Parque Casal Vistoso within Bela Vista Park, within the Eastern Green Corridor of Lisbon. The park is being underutilised because of the lack of shade (1). Thus, this initiative encouraged volunteers to participate in tree planting and forest maintenance activities (3). The NbS intervention began with a 300m² experimental plot near the Vale da Montanha pedestrian bridge and has since expanded to a new 1,500m² plot on the opposite side of the bridge (2). Over 500 volunteers joined the effort, planting more than 3,800 trees (1)

"Adopt a linden tree" is a project that involved the planting and adoption of linden trees in the city of Iași, spanning from 2019 to 2023 across three editions (1 to 8). The campaign was spearheaded by the National Athenaeum of Iași, in collaboration with the Mihai Eminescu Association from Vienna (2). This initiative was launched in celebration of the Athenaeum's 100th anniversary, and it specifically chose the linden tree because of its deep-rooted symbolism in the city of Iași. The tree is not only a natural landmark but also carries cultural and historical weight, as it is closely associated with Romania’s national poet, Mihai Eminescu, who is known for his love of linden trees.
In 2019, 100 linden trees were planted, a number that was repeated in 2020. In the 2023 edition, 50 trees were added, bringing the total number of trees planted through this project to 250 (1 & 4 & 5). An important and unique aspect of the initiative is the "adoption" of the trees by volunteers who participated in the campaign. These volunteers not only lent their names to the trees but also took on the responsibility for their care, ensuring the trees' survival and growth until they reached maturity .
Volunteers were encouraged to participate, and the campaign was supported by donations from individuals, businesses, and public institutions. The municipality of Iași also contributed by providing funds, approving the initiative, and preparing the land through its subsidiary, Servicii Publice Iași S.A., reflecting strong public-private collaboration.
Beyond its cultural significance, the campaign aimed to achieve several other objectives. These included enhancing the city’s aesthetics, promoting community engagement, and improving the quality of life in Iași by contributing to cleaner air and a healthier environment . The initiative also aimed to raise environmental awareness among residents and foster a stronger sense of responsibility toward the natural world. (1-8)

In 2020, the European Fund for the Balkans (EFB) launched the Trees of Friendship project, which plants over 400 trees annually across six Western Balkan capitals, known to be some of the most air-polluted cities in Europe (Ref. 5). Tirana has been involved from the start, having planted over 110 trees in locations such as Great Lake Park in 2020 and Farka Park in 2022 (Ref. 1,2).
The project is carried out with the support of local municipal and civil society partners, including Tirana's Parks and Recreation Agency and the Environmental Territorial Management Institute, along with activists and volunteers (Ref. 1,2). The initiative was planned in 2019 when the EFB board decided to mitigate its CO2 emissions from business-related flights and enhance local and regional cooperation on air pollution (Ref. 3,4,5). Despite challenges in citizen engagement during the COVID-19 pandemic, the Trees of Friendship project continues to raise awareness about the role of trees in mitigating the impact of air pollution on health and well-being (Ref. 2). Its strong and well-established local and regional partnerships have facilitated the project's implementation in the past and continue to benefit in scaling the project (Ref. 1,5).

The Green and Blue Axis (Eixo Verde e Azul, EVA) is an inter-municipal green corridor project connecting the municipalities of Sintra, Oeiras, and Amadora through a 15-kilometre green ecological axis along the Jamor River (Ref 2). It aims to renaturalize the river, improve water quality, and control flooding while promoting sustainable mobility through pedestrian and cycling routes (Ref 5). The project also enhances public access to green spaces and cultural heritage sites, such as the Queluz National Palace (Ref 6). EVA supports the Lisbon Metropolitan Area’s regional strategy for climate change adaptation, risk prevention, and low-carbon economy (Ref 4). Funded by the European Regional Development Fund and municipal budgets, the project has an overall investment of €11 million (Ref 1). EVA exemplifies inter-municipal cooperation, overcoming policy conflicts to achieve shared environmental, social, and economic goals, making it a model for integrated territorial development (Ref 4). The project’s long-term impact includes reduced carbon footprint and increased territorial cohesion.

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).

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)

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).