Green Urban Infrastructure: A Critical Asset to Make Cities More Resilient Against the Impact of Climate Change

Cities are often defined in terms of their gray—aka concrete-based—infrastructure: office buildings; manufacturing facilities; residential areas; road networks; squares and other paved areas; systems for sewage and electricity; water and gas distribution; and a range of microcities, such as airports, ports, sports stadiums, and shopping malls. However, there is another category of urban infrastructure that is entirely based on nature (trees, plants, and wildlife): parks and urban forests; blue spaces like ponds, lakes, and wetlands; vertical and rooftop gardens; and pedestrianized green areas that are central to many of the recently proposed new urban concepts.

Cities across the globe are increasingly optimizing and upgrading existing green assets while planning and implementing new green developments. What we are witnessing is nothing less than an urban greenification revolution. Some eye-catching projects include the green makeover of the Champs Elysees in Paris for the 2024 Olympics (€250 million), the redevelopment of the former Athens International Airport into the Metropolitan Park and Coastal Front (€8 billion), and the NEOM Regreening Initiative and Saudi Green Initiative (US$187 billion). Other examples include Madrid’s Nuevo Norte Urban Forest, Melbourne’s green infrastructure plan, Bangkok’s Benchakitti Forest Park (covering an area of 0.7 km2), and Boston’s Green New Deal. 

While green infrastructure offers many benefits, the single most important benefit is the role green infrastructure is expected to play in making cities more resilient against the impact of climate change—flooding, heat islands, drought, and other natural disasters—on urban living. Green infrastructure offers the combined advantage of functioning as a natural reservoir for excess storm water and excessive heat due to its innate water absorption and heat-storage capacity, substantially reducing flooding of inhabited areas and the number and severity of heat islands.

However, green urban infrastructure offers many additional benefits.

• It is a key tool for urban decarbonization and contribution to net-zero cities.
• It improves air quality and reduces noise pollution.
• It increases urban biodiversity, “bringing nature back to cities.”
• It improves urban living quality, health, and mental well-being.
• It has a positive impact on economic development.

From a technological perspective, digital twins are the ultimate tool for city governments and developers to design, model, plan, simulate, and manage green urban infrastructure. Detailed information about trees, shrubs, and other green assets can be captured through ground-based and airborne LiDAR sensor-scanning systems that are often complemented by satellite imagery. Artificial intelligence–based recognition capabilities allow for the building of complex models featuring a wide range of metrics, including predictive data about expected tree lifetimes. Digital twin modeling and simulation use cases include the identification of current and future heat islands, assessment of vulnerable populations, percentage of permeable surface and vegetation levels, water retention potential of green rooftops, detailed tree analytics, and water run-off and carbon storage metrics. Urban digital twin solutions are offered by vendors like Siradel (ENGIE) and Dassault Systèmes. Singapore-based Greehill develops digital twin technology that is exclusively optimized for green infrastructure.

Various organizations and individual cities are enabling the adoption of green assets as well as defining objectives and setting targets for the percentage of green urban infrastructure.

• C40 cities: Thirty-one member cities of the C40 cities network have signed the Urban Nature Declaration and are committed to investing in green spaces to fight the effects of climate change. The C40 Urban Nature Accelerator has set a goal of 30% to 40% of a city’s total built-up surface area to be occupied by green spaces and streets and/or permeable spaces to absorb water and prevent flooding.
• City of Bangkok, Thailand: The Bangkok Metropolitan Authority’s Green Bangkok 2030 goals include an increase of urban green space per head from seven m2 currently to 10 m2 in 2030 via park-building programs and tree planting initiatives.
• Urban Carbon Credits: Organizations like City Forest Credits are trading permits that represents the amount of CO2 (or any equivalent greenhouse gases) removed from the atmosphere. Polluters can buy such permits to offset/neutralize their carbon emissions. Carbon credits are certified through blockchain-enabled mechanisms and traded on markets such as Regen Marketplace.

ABI Research forecasts the average percentage of global urban areas covered by green infrastructure will increase from 15% in 2020 to 18.2% in 2030 and includes rooftop gardens and urban forests. This represents public and private investment levels of US$606 billion in 2022 that is expected to increase to US$978 billion in 2030.

Clearly, the era of urban concrete jungles is coming to an end. Ironically, while major rural forests in countries like Brazil and Indonesia continue to disappear alarmingly fast, new urban forests are being created and/or integrated in cities like Singapore and Bangkok—a positive occurrence. Whether this is happening fast enough and at a large enough scale to offset the loss of forests remains to be seen, but at least it provides a glimpse into a greener future for next-generation urban populations.