Greening Cities

Greening cities is essential for combating climate change, enhancing urban resilience, and fostering healthier, more sustainable environments. Today, cities account for more than 55% of the global population, 80% of global GDP, 75% of global energy consumption and more than 70% of annual global carbon emissions. These factors are expected to grow significantly in the coming decades: it is anticipated that by 2050 more than 68% of the world’s population will live in cities ¹ ².

Urban areas are today especially vulnerable to climate change, with rising temperatures worsening public health issues and increasing energy demands for cooling due to the urban heat island effect. Existing sewer systems struggle with the heavier rainstorms linked to climate change. Urban green spaces offer crucial environmental benefits by filtering air and water, cooling cities through tree canopies, and supporting biodiversity. They help absorb carbon dioxide, regulate temperatures, and manage stormwater, making cities more resilient. These spaces also promote physical and mental health, offering areas for exercise, relaxation, and social interaction, while reducing stress and improving overall urban quality of life.

Several global frameworks align with and support the greening of cities, highlighting its importance for sustainable development, climate resilience, and human well-being. The 2030 Agenda for Sustainable Development, particularly Goal 11, emphasises creating sustainable cities that prioritise green spaces, resilient infrastructure, and improved air quality ³. Similarly, the Paris Agreement’s goals to limit global warming to well below 2°C, preferably 1.5 °C, rely on both reducing emissions and enhancing carbon sinks – roles that urban greening directly supports ⁴. Together, these frameworks underscore the importance of green urban development as a critical step toward climate resilience and the sustainable transformation of cities worldwide.

The impact of increasing populations in cities

The global urban population has increased from 1 billion in 1960 to over 4.5 billion today and is expected to continue to increase in the future. Urbanisation has brought a host of challenges including increased pressure on essential resources such as food and water, increased air pollution, loss of biodiversity, and increased risk of ill health. These challenges are in turn magnified when coupled with climate change. Climate change is leading to more extreme weather events in the form of severe floods, droughts and heat waves. Such events can spell disaster for a city, especially when it is already dealing with the challenges that increasing urbanisation presents ⁵.

To meet increased demands from a growing population in parallel to an increased impact of climate change while safeguarding the natural environment and ensuring the health and well-being of urban residents, cities must ensure they are adopting sustainable practices ⁶.

FIG 1. Urban pressures caused by urbanisation and climate change challenges ⁷

Cities around the world are recognising the environmental benefits of a green approach to urban planning, as it has the potential to help cities adapt to and mitigate the effects of climate change including increasing urban temperatures and air pollution while building resilience ⁸.

Furthermore, cities are also recognising the health benefits of a green approach to urban planning. Healthy, functioning ecosystems and rich local biodiversity provide a range of benefits to people’s health and are also vital to building and strengthening the resilience of communities in and around cities and towns ⁹.

Nature-Based Solutions

There is no single definition of Nature-Based Solutions (NBS). The European Commission defines them as “solutions that are inspired and supported by nature, which are cost-effective, simultaneously provide environmental, social and economic benefits and help build resilience. Such solutions bring more, and more diverse, nature and natural features and processes into cities, landscapes and seascapes, through locally adapted, resource-efficient and systemic interventions” ¹⁰.

As such, NBS refer to interventions that utilise nature or mimic natural processes to address urban challenges. These solutions focus on integrating natural elements into urban planning and design, enhancing urban environment quality. The overarching goal of NBS is to address a wide range of challenges related to ecosystem resilience, climate change, human health and overall well-being. These solutions achieve this by incorporating established approaches focused on protecting biodiversity, conserving ecosystem services and implementing green infrastructure. By integrating these approaches, NBS can comprehensively address social, economic and environmental issues while enhancing resilience to future threats ¹¹.

Examples of NBS include creating green roofs and walls, restoring wetlands, planting urban forests, and implementing rain gardens to manage stormwater. By harnessing the power of nature, these holistic solutions work in harmony with the environment, offering cost-effective, resilient, and adaptable alternatives to traditional engineered approaches.

Watch this video about Augustenborg and how it used NBS to become a sustainable and livable city:

Green and Blue Infrastructure

Green and Blue Infrastructure (GBI), in contrast to the traditional grey infrastructure, is typically urban-focused and refers to solutions that incorporate green spaces and water elements into urban planning and design¹², creating spaces that blend nature with the urban fabric such as urban parks, green roofs, rain gardens, and restoring waterways to improve water quality. While still offering broad benefits like NBSs, green and blue infrastructure is often implemented with specific goals such as improving air quality, mitigating urban heat islands, managing stormwater, and providing recreational spaces.

Green urban infrastructures primarily involve vegetation, such as parks, gardens, tree-lined streets, and green roofs. These areas provide ecological, aesthetic, and social benefits, acting as lungs for the city by purifying the air, reducing heat, supporting biodiversity, and offering spaces for recreation and relaxation. Trees and green spaces provide shade and cool the air through evapotranspiration, lowering temperatures and reducing the energy demands for cooling buildings. This cooling effect is essential as heatwaves become more frequent and severe due to global warming, making cities more comfortable and less vulnerable to extreme heat.

Watch this video about Paris’ plan to become Europe’s greenest city:

Blue urban environments focus on water-related features within cities, such as rivers, lakes, wetlands, ponds, and even constructed elements like fountains and stormwater management systems. These blue spaces are crucial for managing water resources, improving water quality, and protecting cities from flooding. They also provide important ecological habitats, contribute to the cooling of urban areas, and offer recreational opportunities, such as boating or walking along waterfronts. This natural water management not only protects infrastructure but also ensures that cities can better cope with the uncertainties of a changing climate.

Watch this video about Manhattan’s race against climate change:

Together, green and blue urban environments form a comprehensive approach to urban planning that promotes resilience, enhances quality of life, and supports environmental sustainability by harmonising natural systems with urban development.

Watch this video about blue green solutions:

Multiple Benefits of Urban Greening

Integrating green spaces into urban environments offers numerous advantages for both the planet and people, such as:

Offsets Carbon Emissions
Incorporating vegetation into urban areas can help offset carbon dioxide emissions from vehicles and other sources. Trees and plants in cities act as carbon sinks, capturing emissions through carbon sequestration.
Improves Inhabitants’ Well-being
Living closer to nature improves health and quality of life. For example, one study found that access to residential green space reduced mental health issues in children by 55% ¹³. Additionally, green public spaces have been linked to lower stress levels, improved morale, stronger immune systems, and a decreased risk of chronic diseases like asthma.
Enhances Air Quality
According to the World Health Organisation (WHO), ambient air pollution in urban and rural areas causes around 4.2 million premature deaths each year ¹⁴. As cities expand, improving air quality becomes increasingly important. Green spaces can help by absorbing pollutants and releasing oxygen, reducing health risks for residents.
Reduces Noise Pollution
Noise pollution negatively impacts urban residents’ health by driving hearing loss, tinnitus, and hypersensitivity to sound as well as causing or exacerbating a range of preventable noncommunicable diseases ¹⁵. Green developments can help reduce noise, as trees and plants act as natural sound barriers, dampening noise from cars, aircraft, and industrial activities.
Mitigates Urban Heat
Urban residents can experience greater heat exposure during heatwave events than the general population because of the urban heat island effect, the phenomenon of higher temperatures over urban land than over the surrounding rural land ¹⁶. Urban greening can counteract this phenomenon by creating cooling effects.
Reduces Flood Risk
Urban infrastructure, including transportation networks and critical facilities, is increasingly vulnerable to urban flooding, worsening the impact on people’s lives and businesses ¹⁷. Integrating green infrastructure into urban planning can help increase the resilience of cities to urban flooding as green spaces slow down rainwater runoff, and help prevent it from overwhelming waterways and sewage systems.
Provides Wildlife Habitats
Urban green spaces offer new habitats for a variety of species. Bees, whose populations have been declining due to urbanisation, could find the resources they need in these areas. Birds, which depend on trees, would also benefit from more green spaces in cities ¹⁸.

Case Studies

Explore some of the many excellent nature-based solutions case studies:

Bibliography

Bozovic, Ranko & Maksimovic, Čedo & Mijic, Ana & Smith, Karl & Suter, Ivo & Van Reeuwijk, Maarten. “Blue Green Solutions. A Systems Approach to Sustainable, Resilient and Cost-Efficient Urban Development.” Imperial College. 2017. 10.13140/RG.2.2.30628.07046.
CEEweb for Biodiversity, Green Infrastructure and Nature-Based Solutions for Urban Biodiversity (Position Paper), 2020, https://www.ceeweb.org/ducuments/publications/green_infrastructure_and_nature-based_solutions_for_urban_biodiversity_-_with_case_studies.pdf
Deloitte, “Green Planning of Public Spaces Cities tend to be planned and designed for people”. No date, https://www.deloitte.com/global/en/Industries/government-public/perspectives/urban-future-with-a-purpose/green-planning-of-public-spaces.html
Dutchen, Stephanie. Harvard Medicine, “Noise and Health – Noise pollution is more than a nuisance. It’s a health risk”, Harvard Medicine. 2022, https://magazine.hms.harvard.edu/articles/noise-and-health
European Commission, “Green infrastructure – Promoting the use of green infrastructure in all EU policies, to help restore nature and boost biodiversity”, https://environment.ec.europa.eu/topics/nature-and-biodiversity/green-infrastructure_en
European Environment Agency, Nature-based solutions in Europe: Policy, knowledge and practice for climate change adaptation and disaster risk reduction, 2021, https://www.eea.europa.eu/publications/nature-based-solutions-in-europe
Gangani Dharmarathne et al. Elsevier, “Adapting cities to the surge: A comprehensive review of climate-induced urban flooding”, Gangani Dharmarathne et al.Elsevier, 2024, https://www.sciencedirect.com/science/article/pii/S2590123024003773
ICLEI, “How cities are using nature-based solutions for sustainable urban development”, https://cbc.iclei.org/cities-using-nature-based-solutions-sustainable-urban-development/
International Energy Agency, Empowering Cities for a Net Zero Future, 2021, https://www.iea.org/reports/empowering-cities-for-a-net-zero-future
Luis Valenca Pinto et al, “Green and blue infrastructure (GBI) and urban nature-based solutions (NbS) contribution to human and ecological well-being and health”, Oxford Open Infrastructure and Health, 2023, https://academic.oup.com/ooih/article/doi/10.1093/ooih/ouad004/7322050
Lukasz Dylewski et all, “Are all urban green spaces a favourable habitat for pollinator communities? Bees, butterflies and hoverflies in different urban green areas”, Ecological Entomology, 2019, https://www.researchgate.net/publication/332967952
Net Zero Cities, “NBS and Green Infrastructure plans and strategy design and governance”, https://netzerocities.app/resource-1823
Nissa Towe-Goodman et al., “Pediatrics, Green Space and Internalizing or Externalizing Symptoms Among Children”, Jama Network OPEN, 2024, https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2817354
UCEM, “What is urban greening (and how is it creating the cities of the future)?,” 2024, https://www.ucem.ac.uk/whats-happening/articles/what-is-urban-greening/
United Nations. “Transforming our world: the 2030 Agenda for Sustainable Development”. United Nations (no date)N Agenda 2030, https://sdgs.un.org/2030agenda
United Nations Climate Change, “Paris Agreement”, United Nations, (no date), https://unfccc.int/process-and-meetings/the-paris-agreement
Zihan Liu et al., “Communications Earth & Environment, Surface warming in global cities is substantially more rapid than in rural background areas”, Nature, 2022, https://www.nature.com/articles/s43247-022-00539-x

Notes

1
United Nations. “68% of the World Population Projected to Live in Urban Areas by 2050, Says UN,” United Nations, 2018, https://www.un.org/
2
IEA, “Empowering Cities for a Net Zero Future”, 2021, https://www.iea.org/
3
United Nations. “Transforming our world: the 2030 Agenda for Sustainable Development”. United Nations (no date), https://sdgs.un.org/2030agenda
4
United Nations Climate Change, “Paris Agreement”, United Nations, (no date), https://unfccc.int/
5
Bozovic, Ranko & Maksimovic, Čedo & Mijic, Ana & Smith, Karl & Suter, Ivo & Van Reeuwijk, Maarten. “Blue Green Solutions. A Systems Approach to Sustainable, Resilient and Cost-Efficient Urban Development.” Imperial College. 2017. 10.13140/RG.2.2.30628.07046.
6
Deloitte, “Green Planning of Public Spaces Cities tend to be planned and designed for people”. No date. https://www.deloitte.com/
7
Bozovic, Ranko et al, “Blue Green Solutions”.
8
Deloitte, “Green Planning of Public Spaces Cities”.
9
ICLEI, “Biodiversity and Nature Based Solutions”. No date. https://iclei-europe.org/
10
European Environment Agency, “Nature-based solutions in Europe: Policy, knowledge and practice for climate change adaptation and disaster risk reduction,” 2021, https://www.eea.europa.eu/
11
CEEweb for Biodiversity, Green Infrastructure and Nature-Based Solutions for Urban Biodiversity (Position Paper), 2020, https://www.ceeweb.org/
12
Oxford Open Infrastructure and Health, Green and blue infrastructure (GBI) and urban nature-based solutions (NbS) contribution to human and ecological well-being and health, Luis Valenca Pinto et al, 2023
13
Jama Network OPEN, Pediatrics, Green Space and Internalizing or Externalizing Symptoms Among Children, Nissa Towe-Goodman et al., 2024.
14
WHO, 2018, https://www.who.int/
15
Stephanie Dutchen, “Noise and Health – Noise pollution is more than a nuisance. It’s a health risk”, Harvard Medicine, 2022, https://magazine.hms.harvard.edu/
16
Zihan Liu et al., Communications Earth & Environment, Surface warming in global cities is substantially more rapid than in rural background areas, 2022, https://www.nature.com/
17
Gangani Dharmarathne et al., “Adapting cities to the surge: A comprehensive review of climate-induced urban flooding”, Elsevier, 2024, https://www.sciencedirect.com/
18
Lukasz Dylewski et all, “Are all urban green spaces a favourable habitat for pollinator communities? Bees, butterflies and hoverflies in different urban green areas”, Ecological Entomology, 2019, https://www.researchgate.net/

Greening cities