Urban (main city)

In the city of Cagliari, in the location of Mount Urpinu, 6400 new trees have been planted. The project, initiated in 2022, sought to restore the area's biodiversity and to revitalize the park for the benefits of the citizens (Refs. 1, 3 & 8). In fact, in previous years, the park has been subject to various environmental and social hazards because of its conditions: the area has been subject to wildfires and abandoned wastes, and with time, it became a gathering point for drug addicts and homeless people, thus becoming unsafe for citizens and especially for children (Refs. 1 & 6).
Therefore, the Metropolitan City of Cagliari decided to reclaim the area and plant thousands of trees of various species (holm oaks, oaks, pine, carob and olive trees) over more than 6 hectares of land (Refs. 3 & 8). The project's goal is to restore biodiversity, mitigate temperatures, decrease air pollution, and increase citizens' sense of community (Ref. 1).

The Grangegorman Community Garden is a collaborative project involving several stakeholders in restoring a neglected space within the TU Dublin campus and transforming it into a community garden. The project emerged from a partnership between academic and service departments of the university, a primary school, a land development agency, a multinational organization, and a property estate agent.
The project's ultimate goal is to establish a permanent community garden with strong investment, ensuring ongoing support for current users and welcoming a new, diverse group of participants. (1,6)
Launched at the start of 2024, the project focuses on rejuvenating the space, with restoration efforts continuing until December 2024. The garden features four allotment-style beds separated by gravel paths and is surrounded by 12 foliage beds (Ref 1). The initiative aims to provide educational opportunities centered on sustainability and horticulture, while also developing a sustainable, collaborative governance framework for the garden (Ref 6). It aligns with various national, local, and inter-organizational frameworks, strategies, and plans related to community engagement, biodiversity, and climate action (Ref 1).

Lomas are endemic seasonal ecosystems found in Peru and Chile. They provide a variety of benefits such as soil stabilisation, air purification, recreational spaces, water retention, and are habitats for endemic and threatened species (Ref 7). They are of great ecosystem value to the city of Lima, as green areas have been reduced in the urban area, occupying up to 24% of urban green ecosystems. These ecosystems are threatened by unplanned urban growth, traffic, pollution and lack of government regulation. Given this context, Eab Lomas is a project that focuses on the conservation, management and rehabilitation of the ecosystems found in the Lomas of Lima (Ref 1, 2, 3, 4, 5). It focused on 4 lines of action: conservation of Lomas' ecosystems; implementation of territorial planning; economic diversification focused on the conservation and recovery of vegetation through low-impact recreational activities; and management of water resources (Ref 1, 2, 3, 4).

Air pollution is one of the most pressing sustainability challenges in the UK, with particulate levels exceeding both WHO guidelines and EU safe limits in many cities (Ref 6). In 2014, Birmingham was identified by the WHO as one of nine UK cities breaching air pollution safety guidelines (Ref 2, 3).

In 2012, a soil-based green wall was installed at Birmingham New Street Train Station as part of a project aimed at improving air quality, as diesel train services contribute significantly to nitrogen oxide (NOx) pollution. However, most of the plants did not survive. In 2017, Network Rail commissioned a private company to reconstruct the wall using a hydroponic system (Ref 3). The new green wall was installed in 2018 and completed in May 2019 (Ref 1, 3).

This hydroponic green wall not only enhances the urban environment with calming green infrastructure, but also helps mitigate air pollution and promotes biodiversity with the addition of 16,600 plants (Ref 1, 2, 3).

The Rio Salado Habitat Restoration Area is a urban green space that transformed a former 5-mile-long city dump into a thriving riparian corridor (2, 3, 7, 9). The project, spearheaded by the City of Phoenix in collaboration with the U.S. Army Corps of Engineers, Maricopa County Flood Control District, and the Arizona Water Protection Fund, has revitalized a degraded ecosystem (9). Through decades of concerted effort, involving government agencies, non-profits such as the Arizona Sustainability Alliance, and community engagement, the area has been restored to a lush habitat supporting diverse wildlife, including over 200 bird species (1, 2, 7). The project aimed to mitigate the pressing issues of urban heat, air pollution, and habitat loss that Phoenix grappled with (1). By creating green spaces, improving air quality, and offering recreational opportunities, the Rio Salado Habitat Restoration Area stands as a testament to the power of collaborative conservation and community resilience (1, 6, 7, 9). The restoration area now boasts hiking and biking trails, a nature center, and various educational programs, making it a community space (3, 7, 9).