Increased number of species present

In response to rising food prices and knowing that much of the country's agriculture depends on imported chemical fertilisers, the Municipality of La Molina has developed the Molihuertos programme to provide the residents of the district of La Molina with organic crops for their own consumption and to improve their food security (1, 3). As part of the programme, the municipality implemented municipal plots in different parks in the district. Eleven plots were installed in O'Higgins Park, where residents actively participate in the planting and subsequent harvesting of vegetables, aromatic and medicinal plants, which they consume by themselves (2, 3). Through the programme, the municipality trains and provides different varieties of vegetables and aromatic herbs to more than 800 currently enrolled residents (2). These gardens are managed under organic agriculture, which would help to mitigate a possible overpricing and/or shortage of vegetables in Lima, as they do not depend on chemical fertilisers such as urea, but on organic fertilisers such as compost and manure (3). In addition, residents can sign up to receive drawers with planted vegetables so that they can plant and harvest them at home, either for self-sufficiency or to sell if they wish to do so in the itinerant markets organised by the municipality (9).

Planting Oxygen in the Community is an initiative initiated by the medical company Antibiotice S.A., one of the largest drug producing company in Romania, with headquarters in Iasi. The initiative involves an annual tree plantation campaign that has been carried out over the past four years. Originally implemented in cooperation with the municipality of Iași, the campaign is now independently managed by the medical company Antibiotice S.A. The selected planting area is located adjacent to the company headquarters in Iași and consists of undeveloped grassland.
Throughout the campaign, a total of 1,175 trees and 6,000 shrubs have been planted, including species such as oaks, lindens, and maples. The initiative has engaged 310 volunteers from the company to assist with the planting efforts.
The campaign aims to achieve several goals: rehabilitating green spaces, protecting the environment, reducing carbon emissions, mitigating the effects of climate change, and providing cleaner air for future generations. Additionally, it seeks to enhance the company’s environmental impact and foster social interaction among employees by reconnecting them with nature.
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The Grand Parc des Aygalades project involves the creation of a 14-hectare metropolitan park (connecting Aygalades Park with Bougainville Park and François Billoux Park) that will connect the northern neighbourhoods of Marseille to the port located further south (Ref 1). This project is part of the green conversion of Marseille's northern districts, historically among the most disadvantaged areas in France (Ref 1). The Grand Parc des Aygalades project will enhance the city's greenery, reduce flood risks, create cool zones, restore and develop biodiversity, and significantly improve residents' quality of life and air quality (Ref 1, Ref 2). The environmental and social challenges include reconnecting the populations of these neighborhoods to green spaces, services, education, sports opportunities (Ref 2).
The park project includes redesigning urban infrastructure to improve rainwater absorption and reduce flood risks, addressing the issue of impermeable and artificialized soils that exacerbate flooding during heavy rainfall (Ref 1). It also involves renaturing a 17-kilometre-long stream currently buried under railway tracks, improving flood management and rainwater drainage (Ref 1, Ref 4). The project will also convert a heavily degraded former industrial site, requiring the rehabilitation of polluted soils (Ref 1). Additionally, creating green corridors aims to mitigate the heat island effect, particularly severe in these northern districts due to the high concentration of buildings and concrete surfaces, and the lack of green spaces. Public participation will be encouraged through information meetings, thematic workshops, and an online platform for submitting ideas and feedback (Ref 4).

The ReDuna project, initiated in 2014, focuses on restoring the sand dune ecosystem in Costa da Caparica (Almada) in response to severe coastal erosion exacerbated by sea-level rise and winter storms. It aims to strengthen the resilience of dunes to environmental pressures while restoring ecological balance. Actions include sand nourishment, the installation of willow sand fences, and the planting of 100,000 native species. Community engagement was a key factor, involving local residents, NGOs, and schools in maintenance and replanting efforts. The project has been successful, with significant biodiversity recovery, establishing deep-rooted vegetation, and stabilising the dunes. Ongoing monitoring and adaptive management are central to its strategy, ensuring long-term sustainability. The ReDuna project serves as a replicable model for similar coastal protection initiatives globally (Ref 1).

Eliseo Collazos is located in the coastal desert ecosystem of the Lomas or ‘fog oasis’, an area that receives less than 10 mm of rainfall per year. Vegetation cover is of particular importance in the hills surrounding Lima, as it provides critical solutions to erosion, landslides and soil degradation in the ecologically degraded ecosystem of the Lomas. However, this ecosystem is facing risks from urbanisation, illegal mining and agricultural practices, resulting in the lack of the delicate mist-fed greenery for which the Lomas are known (2). This has led to increased particulate matter in the air due to exposure to sand and wind, aggravating respiratory diseases such as tuberculosis, which is prevalent in Lima's informal communities (2).
Low-income communities have inhabited this area, forced to migrate from the rainforest, highlands and city to the desert slums (4), who have only been able to settle in these landscapes with little access to resources, prone to disaster risk, little public investment in infrastructure and little access to green spaces (2). As a result, these communities live in poor conditions (1). For this reason, in 2013, the University of Washington, under its Urban Informal Communities Initiative programme (1), initiated a participatory project that sought to address the challenges faced by the inhabitants of this area (1, 2). In a series of participatory workshops, residents identified greenspace and food security as top priorities in their community; the Gardens, Greenspace and Health project responds to these priorities as an initial step towards the expansion of greenspace, agriculture and ecological restoration in and around the Eliseo Collazos community (2, 4).
Although individual families constructed them, the front yard gardens contribute to a shared public realm and community greening (4). The general project also involved the installation of fog catchers and the creation of common recreational spaces (4).

In Phoenix, many residents live in dead zones with little or no access to fresh food. These zones are called 'food deserts,' which represent a low-income area with low access to a grocery store (3). Out of the 43 food deserts identified by the city, 18 are fully or partly in south Phoenix (2-3). In 2017, Two researchers from Arizona State University’s School of Sustainability and Leuphana University Lüneburg in Germany began exploring the idea of creating a sustainable food forest cooperative in Phoenix to provide fresh, healthy food, supporting local entrepreneurs, and promote environmental sustainability (1). The project's development team spent months immersing themselves in the world of food forests, by exploring different types of community gardens, discussing preferred characteristics, anticipating local challenges, and identifying potential collaborators (1). As a result, The Food Forest Cooperative was established and planted roots in a 0.5 acre (0.20 ha) plot within the Spaces of Opportunity Community Garden in 2022 (1). This food forest engages the local community by offering educational opportunities around the value of culturally relevant, whole fruits and vegetables, medicine making, and learning about the many uses of edible/medicinal plants (4). The Food Forest Cooperative as a multi-generational project that members preserve for their children, and their children’s children (2). The intention behind the project is to address food insecurity in south Phoenix and empowering the community to take ownership of it and reconnect with their ancestors through the land and food (2). Through the Cooperative, members can contribute different skills, from administrative work to manual labor to community education and traditional medicine (2). It was created to empower community members and challenge the patterns of our food system through the blending of environmental, social and economic goals (4).

The regreening project is located in Seestadt Aspern, a newly developed urban area in Vienna's Donaustadt district. Two years after the completion of buildings, streets, and squares, the ground was reopened in 2022 to address the challenges posed by urban heat islands. Pavement was removed, and trees and shrubs were planted to provide shade, create insect habitats, and open seepage areas for rainwater. Additional features like benches, a water station, and water jets were installed to enhance the area's livability. These measures improve the overall quality of life, offering residents green spaces to relax and opportunities to cool down through water play.
The project spans three connecting squares in Seestadt: Wangari Maathai Square, Simone de Beauvoir Square, and Eva Maria Mazzucco Square. In 2022, Wangari-Maathai-Platz and Simone-de-Beauvoir-Platz underwent intensive regreening. By 2023, Eva-Maria-Mazzucco-Platz in the Seeparkquartier was similarly transformed with additional greenery and cooling features. Under the slogan "Out of the Asphalt," one of Europe's largest and most innovative urban development projects took a significant step toward improving quality of life.
In 2023, over 1,100 square meters of asphalt were removed and greened. This effort included the creation of 12 new green beds planted with grasses, perennials, and shrubs. The design also introduced two square-like recreation areas with existing seating elements surrounded by green beds, providing shaded, pleasant spaces for relaxation.
The Eva-Maria-Mazzucco square was designed by a local NGO specializing in citizen engagement in urban development, while the project's overall initiation and implementation were led by the City of Vienna, the Donaustadt district, and Wien 3420 Aspern Development AG. This collaborative effort demonstrates how regreening initiatives can mitigate heat islands, foster urban biodiversity, and create more attractive, livable spaces. (Ref. 1-3)

The Färjenäs Agroforestry Garden started in 2013 in the Färjenäs park in Hisingen, Gothenburg. A group of people interested in agroforestry started a study circle on the topic the year before and then formed an association to apply their knowledge in practice. The City of Gothenburg helped the project get started by providing some funding and finding a 2000 sqm spot for the garden on land owned by the city. The Färjenäs agroforestry garden association is run by volunteers, who have planted about 200 different species of trees, bushes and herbs that produce produce. The planting and management of the garden aims to promote soil health and biodiversity. The association received funding from the Swedish Environmental Protection Agency in 2020 and partnered with the Natural History Museum in Gothenburg to further promote biodiversity and wild pollinators, and has partnered with a local beekeeping association to establish a beehive in the garden. The garden is open to the public and invites the public to educational activities and working events such as planting. The association aims to be a meeting place for locals and visitors from all over the city, with different cultural backgrounds and generations. Several courses and educational programs within agroforestry, agriculture and gardening have been held at the garden. [Ref. 1-7]

In 2024, Ozanam (a housing private company) and the French Development Agency (AFD) formalized a partnership to modernize an ecological wastewater treatment plant in Saint-Joseph, a neighborhood in Fort de France. The project focuses on replacing an outdated 30-year-old installation that no longer meets current standards with a plant-based water filtration system based on the ‘Rhizosph’air’ patent. This innovative treatment process utilizes "filter gardens," which combine mechanical systems, a gravity network, and a phytoremediation approach. The system employs filters made of gravel and the roots of local plants, specifically Strelitzia reginae and Cyperus alternifolius, to naturally and effectively filter wastewater without odor (Refs 2, 3, 4).
The nature-based system purifies wastewater over an area of 2,000 square meters, with a capacity equivalent to serving 900 residents. This approach offers several advantages, including reduced maintenance costs due to its simplicity, decreased energy consumption compared to traditional treatment methods, and improved water quality released back into the environment (Ref 2). Beyond its technical efficiency, the filter gardens enhance biodiversity (Ref 2) by improving the quality of water discharged into the environment and providing habitats for various species. The solution also integrates seamlessly into the landscape, showcasing vibrant flowers native to the area (Ref 1).
Additionally, the project implementers plan to construct a walking path, provide recreational equipment, and install benches to encourage residents to utilize the area as a public green space (Refs 2, 5).

The "Plan Arbre" is a tool for ecological planning and renaturation aiming to plant 308,000 trees between 2023 and 2029, sourced from the municipal nursery with seeds purchased from local suppliers (Ref 1, Ref 2). In 2023, 14,922 trees were planted, with plans to double this number in 2024 (Ref 1). The project addresses the loss of 50% of Marseille's natural spaces over the past 75 years, aiming to reverse this trend and reintroduce nature into the urban environment (Ref 2). It also tackles issues like drought and heatwaves, particularly in summer, by using trees and shrubs to cool the air, restore biodiversity, reduce air pollution, and enhance public spaces while absorbing CO2 (Ref 2).

The plan is divided into two phases. Phase I focuses on planting in Marseille's 58 parks and 273 squares and gardens, as well as around childcare centres, schools, socio-cultural centres, and sports facilities (Ref 2, Ref 3). From 2020 to 2023, various improvements were made, including playground renovations, installation of misting systems, automatic watering, and the creation of a CrossFit area (Ref 3). Phase II will involve identifying major boulevards, avenues, and streets lacking trees to enhance the urban canopy (Ref 2).
A diverse range of tree species were selected for their drought resistance, water efficiency, and ability to attract biodiversity (Ref 2, Ref 3). The project also focuses on increasing biodiversity and managing invasive species through natural methods to protect trees from pests without chemicals (Ref 3). Furthermore, the initiative includes de-impermeabilizing soils and implementing a smart irrigation system with tensiometric sensors, developed with the start-up GreenCityZen, which has saved 66% of water in two years (Ref 3). The Plan Arbre also promotes citizen participation, with 23 parks selected for community gardening projects, where ten winning associations will receive plants from the municipal nursery (Ref 1).