Botanical gardens are not just beautiful – they can cool the city air by 5°C during heatwaves, according to the most comprehensive review of its kind led by the University of Surrey

As cities face increasingly scorching temperatures due to climate change, a study led by the University of Surrey unveils a powerful ally in the battle against urban heatwaves: green spaces. The research, which is the largest of its kind, underscores how wetlands, parks, and botanical gardens serve as vital coolants during extreme heat events.

Contrary to mere aesthetic appeal, botanical gardens emerge as unsung heroes, capable of reducing city air temperatures by a staggering 5°C during heatwaves. Parks and wetlands exhibit a similar cooling effect.

Botanical gardens-5.0°C-2.2°C to -10°C
Wetlands-4.7°C-1.2°C to -12°C
Rain gardens-4.5°C-1.3°C to -7°C
Green walls-4.1°C-0.1°C to -18°C
Street trees-3.8°C-0.5°C to -12°C
City farms-3.5°C-3.0°C to -3.9°C
Parks-3.2°C-0.8°C to -10°C
Reservoirs-2.9°C -1.8°C to -5°C
Playgrounds-2.9°C-2.8°C to -3°C

Professor Prashant Kumar, Director of Surrey’s Global Centre for Clean Air Research (GCARE), said: 

“We have known for some time that green spaces and water can cool cities down. However, this study provides us the most comprehensive picture yet. What’s more – we can explain why. From trees providing shade, to evaporating water cooling the air.”   

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The importance of scale becomes evident, with larger green spaces yielding greater cooling benefits, up to a point. Cities can unlock greater benefits by connecting green spaces into ‘green corridors’.   

Moreover, greening initiatives extend beyond cooling; they mitigate carbon emissions and bolster resilience against flooding, presenting multifaceted resilience to the challenges posed by global warming.

Professor Kumar said:  

“This will help town planners around the world confront the challenges of global heating. By implementing just some of the measures we describe, cities can become more resilient, and their citizens can be healthier and happier too.” 

Yet, the study uncovers regions vulnerable to heat stress, lacking adequate research on harnessing green spaces for cooling purposes. Maria de Fatima Andrade, a Professor at the University of Sao Paulo, underscores the need for tailored approaches, stressing that there’s no universal solution, but rather a need to adapt strategies to local contexts.

“Our paper confirms just how many ways there are to keep cool. But it also reveals how much work is left to do. Institutions around the world need to invest in the right research – because what’s very clear from our study is that there is no one-size-fits-all solution. It depends on what works for your community.” 

In essence, by embracing nature’s cooling arsenal, cities can forge resilient pathways towards a cooler, more sustainable future, safeguarding both the environment and the well-being of urban dwellers.