Climate change is causing more extreme weather, including heavy rainfall that is flooding cities worldwide. Massive monsoons and rising sea levels are making the homes and businesses of millions in coastal regions vulnerable to billions of dollars worth of damages. A recent study by global environmental consultancy firm Arup surveyed seven major cities around the world that are at risk of increased rainfall and flooding: Auckland, London, Mumbai, Nairobi, New York, Shanghai, and Singapore. Using the AI technology Terrain-AI, Arup assessed their “sponginess,” or ability to absorb and manage excess water to mitigate floods with elements such as parks, trees, and lakes. Each city was assessed based on the quantity of green and blue spaces (areas with plants or water) as well as the area’s type of soil, vegetation, and water runoff potential.

Why This Matters

It is estimated that by 2100, 85% of humanity will be living in cities. Megacities already produce 75% of global carbon emissions, but they have the potential to become climate-neutral, sustainable beacons of the future if governments encourage the construction of green infrastructure and nature-based solutions (NbS). Arup’s report demonstrates how cities can become more “spongy” in order to mitigate severe flooding by incorporating more nature into their infrastructure. Additionally, Arup released a different report in January that found NbS are "on average 50% more cost-effective than man-made alternatives,” despite the fact that only 0.3% of urban infrastructure spending in 2021 is allocated to them.

A Case Study In Tirana, Albania

The city of Tirana in southeastern Europe has seen rapid development since the 1990s. As a consequence of urbanization, it’s fallen victim to pollution, poor air quality, traffic congestion, urban heat, and limited green spaces. However, Tirana Mayor Erion Veliaj intends to transform the city into a vision of sustainability and climate neutrality.

The city is currently working with Arup and Stefano Boeri Architetti to build an orbital forest around the perimeter of the city, an NbS to many of Tirana’s urban issues. The proposed mix of forest, recreational areas, and agricultural land would help to clean the air, mitigate flooding, reconnect citizens with nature, and decrease urban heat. Not only presenting major environmental, economic, and social benefits, it could transform the city into a role model for sustainable development using NbS.

“Nature-based solutions like the Tirana Orbital Forest are effective climate measures that address both global and local environmental challenges,” stated Dr. Nigel Jollands, co-lead of the EBRD Green Cities program. “We hope that this project can set an important precedent for EBRD and other financial institutions to demonstrate the economic incentives of such investments, and will spur further investment in this space.