Improved air quality

Once empty paved area between the houses on Marat Street in St. Petersburg now has been turned into a cosy green garden [4, 5, 6]. The project was developed by a group of students and initiated by the Green Petersburg Foundation, Plants for Friends, "Vladimirsky" Municipal District and others [1, 3, 4, 5]. The square landscaping project contributes to the city's adaption to climate change, a need to increase urban green zones, reducing excessive heat and rainfall levels, and the creation of habitat for birds, among others [3]. The square acquired the concept of a harmonious combination of natural motives and the mood of the Russian landscape [4].

The city of Algiers initiated in 2010 a project in order to establish a green belt around its areas and some northern municipalities. The project aims to create agro parks, allotment gardens as well as parks as a strategy for reintegrating the concept of the green belt into the Algerian territory. Through this intervention, the municipality aims to put into practice environmental values ​​linked to improved quality of life and social well-being, for the benefit of the local community. The intervention plans to introduce different species of trees and include for the first time in Africa agro parks as spaces which are designed to reconcile urban and agricultural functions in a win-win strategy. The action was thought to respond to the impacts of climate change in the country, which faces rain events that are less frequent but more intense, and droughts that are more common and longer. (1,2,3,4)

The Orbital Forest of Tirana is an innovative urban forest that as a green belt forms a natural growth boundary for the City. Tirana has experienced rapid development in the past decades that led to population growth challenging municipal services and infrastructure, while climate change also posed extensive pressures to the urban area with intense flooding, precipitation, urban heat and degrading environment (1, 4). The Orbital Forest is a ring on the periphery of the City that connects 14,000 ha of Tirana’s parks, agricultural fields, and forests, maintaining the ecosystem and supporting biodiversity. (3, 4) The NBS aims to increase urban greenery through the plantation of 2 million trees that fit well to the existing ecosystem while also creating a natural boundary to halt urban sprawl (1,4,5). The afforestation of the Orbital Forest has been done through the “Donate a Tree For Tirana” campaign started in 2017 where citizens, businesses and international organisations can plant a tree adding to the green belt. As of 2021, more than 440,700 trees in the framework of the "Donate a Tree" campaign are also bringing urban nature closer to residents (3).

The Gangxia 1980 green roof, a pilot of the Green Cloud project, was launched by The Nature Conservancy (TNC) in collaboration with key partners, including: Zhubo-AAO; Glocal Estate Management; and Urban Planning & Design Institute of Shenzhen (UPDIS) [1]. Located on an old building in Gangxia village in Shenzhen, the project utilizes three-dimensional light steel structures that are simple to construct and have the capacity to hold over 420 plant containers, filled with plants mostly native to Southern China [1, 2]. The original concrete rooftop is transformed by vegetation, which is capable of absorbing and preserving rainwater, creating a nature-based stormwater management system for the residential building, achieving a 65% of run-off control rate [1, 2]. As a result, a living “green cloud” is formed on a rooftop of Gangxia village, showcasing “a model to improve the urban village’s stormwater management system and its living environment” [1. p.33].

In 2014, a rooftop farming project was initiated in the informal settlements of the Greater Cairo Region to address challenges brought by climate change and to empower the local community. The project was initiated by the German Corporation for International Cooperation and a local NGO with the objective to "reduce ambient temperatures (microclimate) in a densely populated area through green spaces on rooftops, and reduce the impacts of the urban heat island effect and increasing heat." (1) The initiative also addressed four of the Aichi Biodiversity Targets by tackling biodiversity loss, encouraging sustainable agriculture practices, fostering ecosystem services and developing local knowledge (1,11)
Besides environmental benefits, the project and its scaled-up project in 2017 brought several socio-economic benefits by reducing vulnerability to food price changes and by developing the local community. Rooftop Farming Hubs were also established to foster the training and knowledge sharing of rooftop farmers in Cairo (1).

The Krubong landfill site has been proposed to undergo a "thorough and safe environmental rehabilitation program[me]" so that the site can be developed as a public park (Ref. 1). Following completion of a feasibility study, it is envisaged that significant rehabilitation work to address environmental degradation and restoration of natural habitats will be required, after which the site will be developed into a public park (Ref. 1). The programme remains in its planning stage, but seeks to address Sustainable Development Goals (SGDs) 11.6 and 15.1 through protecting, restoring and promoting sustainable use of ecosystems and reversing land degradation and/or biodiversity loss; and reducing the environmental impact of cities by paying special attention to waste management and providing access to safe, open public spaces (Ref. 1). At a more local level, the programme intends to complement additional programmes laid out in Melaka's Resilience strategy document, including promoting both cycling and pedestrian networks and reshaping public spaces in the city (Ref. 1).

Santalaia is a high-end, multi-family residential building located in the heart of downtown Bogota, Colombia. Santalaia is often referred to as "the green heart of Bogota" and is seen as an icon of sustainability [1]. The 11-story building was completed in 2015 and all eleven floors are engulfed in many species of plant wildlife to encourage biodiversity. There are 115,000 native plants of 10 different species covering a total area of 3117 m² [2,3].
The plants included on the exterior of the building rely on a hydroponic system and provide a model of how to increase green zones in urban areas. A vertical garden of this size provides natural beauty in the middle of concrete Bogota while mitigating the carbon footprint of more than 700 people. An additional benefit of Santalaia’s vertical garden is that the plants create a “green carpet” that serve as insulation and reduce the use of air conditioners, an increasingly valuable contribution during times of rising temperatures due to climate change [5,6].

The Wuqing District of Tianjin is a rapidly developing suburban district, northwest of the city core, containing 4 larger 5 smaller rivers, 5 water reservoirs, Wetland area that partially protected by the DaHuangPu Nature Reserve, the Jinbei Forest Park, several public parks, greenery near buildings, green roofs and vegetation along roads. A spike in population growth going from 130.000 in 2000 to 1.2 million in 2018 brought the need for wide urban development where the district focused on implementing blue and green infrastructures (1). "The urbanized area of the district is reported to meet the requirements of the national ‘Garden City’ standard with over 36% green coverage, currently aiming to achieve 45% on the long run, and was selected as a pilot national ecological demonstration area for green urban development in 2014. Since 2014, over 500 million EUR was invested into blue and green infrastructure projects (1 p26). The three flagship projects evaluated here are 1) the South Lake (Nanhu) Area that combines business, recreational, residential, and ecological development around in a waterside area, 2) the North Canal Suburban Park which is a recreational, entertainment and wetland area on 2.53 km2 where over 72.000 trees were planted in recent years, 3) and the 400 meter wide, multi-functional green corridor running along the Cuiheng Road (1).

The green belt was created not only as an aesthetic element but also to serve as the lungs of the city. The forest planting works around Nur-Sultan have been carried out since 1997 [6, 7]. The area of ​​the green belt of Nur-Sultan is 100 thousand hectares, of which 15 thousand hectares are planted within the city limits. The main idea of the project was to provide comfortable conditions for the residents of Nur-Sultan city, which would serve as a mechanism for improving air quality, mitigating climate and as a natural barrier to protect the city from dust winds and snowstorms [2, 4, 5, 6, 7]. An important aspect that was taken into consideration are the animal species of the forest, as the territory of the green belt is inhabited by foxes, hares, corsacs, white and grey partridges, roe deer, wild boars, etc [1, 2, 7, 8]. The primary importance of biodiversity efforts is assigned to the breeding of birds, especially pheasants [1, 2, 3, 4, 5], as pheasants are an element of local cultural heritage, and on the territory of the green belt, traditions and cultural events related with the pheasants are organised every year [2, 4]. The young forest should turn into an improved recreation area, a favourite pastime for city residents at any time of the year [2,7].

The Cheonggyecheon Stream Restoration Project saw the dismantling and removal of an elevated freeway and the uncovering of a 5.84km section of the Cheonggyecheon historic stream in the centre of Seoul, South Korea (Ref. 2). One of the world’s largest and most densely populated cities, the revitalisation of the Cheonggyecheon Stream has provided Seoul with an ecologically sensitive green pedestrian corridor in an area that was previously recognised as being congested, overpopulated and polluted (Ref. 4). The restoration has provided environmental, social and economic benefits within its immediate proximity (Ref. 2). In addition to becoming a "vehicle for revitalisation, urban renewal and economic development", it has "also signified a shift in Korean planning priorities", with both city authorities and residents now placing an emphasis "on health, sustainability and social responsibility" (Ref. 4). It has further "become a template for planning intention and action across South Korea" (Ref. 4).