Urban or built environment

Alexandria is one of the world’s most climate-vulnerable cities, facing serious environmental challenges that threaten its landscape, culture, and livability. The city is grappling with rising sea levels, pollution, extreme fluctuations in temperature, and the intensifying urban heat island effect, all of which are worsened by climate change. The past decade has seen a steady decline in Alexandria’s parks and green areas, a trend that has raised significant concerns among environmentalists and the public. The shrinking green spaces are largely due to rapid urban expansion and the development of commercial projects, which are gradually pushing Alexandria's environmental balance and cultural heritage to the edge.
In recognition of these pressing issues, Egypt launched the "100 Million Trees Initiative" in 2022 as part of its Egypt Vision 2030, a national plan for sustainable development. The initiative aims to increase the per capita share of green space throughout the country, with objectives that include improving air quality, enhancing public health, countering the urban heat island effect, and reducing greenhouse gases. The initiative is also focused on improving the beauty and cultural value of Egypt's urban areas, aligning with broader goals to build sustainable and climate-resilient cities. Alexandria, being a coastal city that is both environmentally sensitive and culturally significant, has been a focal point of these efforts.
As part of this national campaign, the Governor of Alexandria was tasked with overseeing the enhancement and expansion of green spaces across the city, focusing on both the aesthetics and cultural aspects of the urban landscape. In 2023, these efforts took root in the Al-Muntazah 2 neighborhood, where 596 trees were planted as a contribution to the 100 Million Trees Initiative. This project included the Al-Samad Preparatory and Secondary Schools campus as one of its primary planting sites. (1-5)

The initiative consists of an afforestation campaign promoted by the local government of La Paz, with the objective of planting 10,000 trees and shrubs (1 & 2). Carried out between 2023 and 2024, the campaign included plantations across all the macrodistricts of La Paz (1). To ensure the campaign's success, the municipality encouraged the participation of volunteers from various institutions, such as public services, environmental groups, schools and universities, neighborhood associations, church groups, and even Army and Navy units (1 & 2). The trees play specific roles in mitigating climate change, improving air quality, reducing odors from nearby landfills, and decreasing the risk of landslides and soil erosion (3 & 4). Furthermore, the campaign aims to foster environmental awareness among citizens and replace trees lost due to illegal deforestation (1).

The species selected for planting were provided by EMAVERDE, the public company responsible for managing green spaces in the city. The selection included primarily native species, along with a few introduced ones, all chosen for their resilience to La Paz's varying climate conditions (1, 2 & 4). Given the challenging climate and difficult soil conditions, the municipality informed volunteers about the importance of maintaining the saplings, particularly during drought periods, to ensure their proper growth (1 & 2). The campaign also supported the municipality’s urban development plan (Plan Territorial de Desarrollo Integral "Para Vivir Bien") and the "Plan Integral de Recuperación de la Tormenta a la Esperanza," the latter developed in response to extreme rain events and floods that occurred during the campaign months (5).

The Institute of Physics at Humboldt University of Berlin is an outstanding example of ecological urban development and a global pilot project integrating rainwater management with building cooling through greening. A key feature is the cooling system, which relies on air circulation processes supported by green roofs, facades, and an artificial wetland/pond incorporated into the building's exterior and courtyard.
Rainwater is collected in cisterns and used to irrigate the green façade, enabling evaporative cooling in air conditioning systems. Excess water is either evaporated in the inner courtyard through a pond or allowed to seep away. (Ref. 1; Ref. 4) The greening of the façade is directly linked to energy optimization. During summer, the green façade provides solar shading against extreme heat, while in winter, sunlight passes unobstructed through the glass façade. Additionally, evaporative cooling improves the microclimate inside the building and its surroundings. (Ref. 3)
Berlin, as a densely built city, faces challenges like urban heat and high energy demands for cooling. This project offers a research-driven solution. Monitoring measures water usage for various plants, evaluates evaporative cooling effects, and assesses impacts on the building's energy balance and overall economic and ecological performance. The findings aim to create a foundation for the long-term implementation of innovative, cost-effective technologies. This process is conducted by multiple regional universities. (Ref. 1)
The project was initiated and financed by the state of Berlin and implemented after the building's construction. (Ref. 4; Ref. 5) It serves as a benchmark for sustainable urban development and a research model for similar initiatives worldwide.

The Alexandria Governorate is especially susceptible to the impacts of climate change, a vulnerability exacerbated by its dense coastal communities and rapidly growing population (2). Both demographic shifts and urban development intensify how climate phenomena affect the people and infrastructure of Alexandria (1). Buildings, roads, and other concrete structures absorb and release solar heat, significantly contributing to the urban heat island effect, which is causing temperatures in the city to rise faster than in less developed areas (1). Despite Alexandria’s growing need for cooling green spaces, they currently make up only 0.25 percent of the total area within the Governorate, highlighting an urgent need for environmental interventions (3-6).
In response, Ahmed Gaber, chairman of the Alexandria Water Company, initiated a public awareness campaign in 2023 focused on the numerous benefits of planting green roofs (3-6). Green roofs serve multiple purposes: they extend the longevity of buildings, lower energy consumption, improve air quality, increase biodiversity, manage rainwater runoff, and mitigate the urban heat island effect (3). Furthermore, Gaber has emphasized the visual appeal of eco-friendly roofs, noting that green roofs offer an aesthetically pleasing option that enhances the urban landscape while serving critical environmental functions (4).
This initiative by the Alexandria Water Company marks a pioneering step among governmental organizations in the region, as they lead efforts to address climate and environmental challenges actively. The company has begun planting green roofs across its facilities, including the new Al-Mashishya water station, where green spaces atop buildings are set to bring lasting environmental benefits to Alexandria. Through these efforts, the Alexandria Water Company is working to set an example for public and private sectors alike (3-6).

The City of Mobile has developed and implemented a Storm Water Management Program (SWMP) as required by the regulations of the Environmental Protection Agency (Ref 1). Flooding is a significant issue in Mobile, occurring frequently throughout the town (Ref 3). The SWMP aims to protect water quality and prevent harmful pollutants in stormwater runoff from entering the Municipal Separate Storm Sewer System (MS4) area (Ref 1). Stormwater runoff refers to rainfall that does not seep into the ground but instead flows over yards, streets, parking lots, and buildings, eventually entering the storm sewer system, which directs it into creeks, rivers, bays, and the Gulf of Mexico (Ref 1). Stormwater can collect pollutants such as trash, debris, sediment, heavy metals, oils, and hazardous household materials. Additionally, development increases impervious surfaces, leading to more stormwater runoff (Ref 2).

Established in 1996, the United Nations Office at Nairobi (UNON) is the UN's official headquarters in Africa, located just 9.7 km from the heart of Nairobi. In line with the UN's global sustainability goals, the office took significant steps to reduce its environmental footprint as it expanded. According to the United Nations Environment Programme (UNEP), buildings contribute to a third of global energy use and are major sources of greenhouse gas emissions. To address these issues, new buildings were designed to prioritize energy and water efficiency, with a focus on sustainability.
Completed in 2011, the new headquarters reflect the UN's broader commitment to reducing greenhouse gas emissions. The design includes 6,000 m² of solar panels, rainwater harvesting systems, energy-efficient lighting, and natural ventilation, making the complex energy-neutral and water-efficient. It generates as much solar energy as it consumes, supporting over 1,200 staff members. Additionally, the project carefully preserved indigenous trees and created micro-ecosystems within the interior gardens, further aligning with the UN’s environmental mission.
By embedding these green features, the UNON complex serves as a model for sustainable development in urban settings, echoing the UN’s efforts to combat climate change and promote ecological resilience globally. (Ref. 1, 2, 3, 4)

The increasing volume of solid waste, driven by Nairobi's growing population, has become one of the city's major challenges (Ref 1, 2). To address this issue and promote better environmental practices, authorities plan to convert all reclaimed illegal dumpsites into recreational and green spaces. The transformation of the former Kangemi Cemetery, abandoned for over 20 years and used as an illegal dumpsite, was the first initiative in this effort.
Led by Nairobi's Governor, H.E. Mike Sonko, and supported by the City County, the project was completed in 2018 and serves as a key example of these transformative measures (Ref 1, 2, 3). Previously, Kangemi Cemetery contained over 500 loads of illegal waste, but following a successful clean-up, it has been rehabilitated into a children's playground with recreational area, now named Kangemi Cemetery Memorial Park (Ref 3).

The project ‘Planting the Future and Cultivating Life’ aims to create an ecological corridor in the city by reforesting an area of 28 hectares, under the direction of the Porto Velho City Council. It encourages citizen participation in tree planting activities or the management of green areas. To this end, the municipality is carrying out tree planting programmes in parks, squares and along public roads, encouraging citizens to get involved in this endeavour by actively participating in tree planting actions, caring for trees already on their property or raising awareness of the importance of these actions. (1) They seek to involve organisations such as schools, colleges, companies, associations and public organisations to increase the community's and young people's interest in responsible practices and positive attitudes to value and preserve the environment (1).
To achieve this goal, the Porto Velho city council organised a tree-planting day on October 23rd 2023, where 31,000 tree seedlings of native and fruit trees were planted in the Park Passarela Espaço Alternativo (1, 7). This was done with the support of the Municipal Secretariat of Environment and Development (1). This activity is part of the project Virada Ambiental, which seeks to promote the planting of native trees in municipalities across the country, raising awareness of the importance of planting native species and training municipal civil servants and the general public (3, 5). The National Confederation of Municipalities also supports this project and aims to mobilise society to encourage the planting of native trees to rescue biodiversity and recover environmental services, favouring social welfare by promoting tourism, and outdoor sports activities (6), providing shade, protecting the soil and combating high temperatures (2).

The John Michuki Memorial Park was transformed from a vast dumpsite in 2008 and established in honor of John Michuki, the Environment Minister during the Kibaki administration, in 2012. Michuki garnered admiration and accolades for his enthusiasm and determination to clean and preserve the environment (Ref 1, 2). Situated along the Nairobi River, the park serves as a historically rich recreational facility (Ref 3).
However, several issues arose after the park was transferred to the county administration in 2013 (Ref 2). A section of the Nairobi River flowing through the park experienced severe environmental degradation due to illegal discharges and poor waste management, negatively impacting the riparian ecosystem and biodiversity (Ref 4). Additionally, the park became a refuge for drug users, street children, and thieves, with stray dogs posing safety threats in the area (Ref 1, 2).
As the first project within the Cleaning Up Kenya Campaign, the restoration of Michuki Memorial Park was launched in 2020 by the government (Ref 5). The park is now managed by the Kenya Forest Service (KFS) following a directive from the national government (ibid.). With funds from the treasury, a perimeter fence was erected, a 2.4 km walkway was constructed, and 4,200 seedlings and 6,357 indigenous trees were planted, along with the establishment of a nursery (Ref 1, 6). A total of 20,000 tons of solid waste were removed (Ref 6). Additionally, a community forest association was formed to ensure community engagement (Ref 2).

The riparian forest of Montgérald, through which the “Monsieur” River flows, is located within Fort-de-France and boasts rich biodiversity, featuring around 100 species of shrubs and trees and about 30 animal species, including 16 types of birds. It is one of the last remnants of the mesophilic forest type and the only example in a French peri-urban setting. This unique ecosystem is recognized as a Natural Area of Ecological, Faunal, and Floral Interest (ZNIEFF) and a Classified Wooded Area (EBC), underscoring the need for conservation efforts.
Covering nearly 21 hectares, this site offers ecological benefits like air quality improvement and temperature regulation, providing a "fresh air island" near the city center. However, it faces significant challenges, including flooding caused by climate change and heavy rains, which exacerbate erosion along the Monsieur River. The area is also threatened by invasive alien species, making conservation measures even more crucial.
Since 2015, the municipality of Fort-de-France, along with project partners, has been working on developing this natural space for both conservation and public engagement purposes. The most recent actions occurred in 2020, including riverbank restoration, clearing invasive species, and creating walking paths and educational installations. Additionally, the project features an awareness campaign targeting local schools. The ongoing initiative aims to merge biodiversity conservation with community recreational use and environmental education, ensuring the resilience of this vital ecosystem against the impacts of climate change. (Refs. 1, 2, 3)