Scientists believe that urban greening is unlikely to provide a single solution to extreme weather events brought on by climate change.
By introducing strategies such as green roofs, living walls, vegetated urban spaces and parks, a team led by researchers at Cardiff University will not be able to reduce heatwaves and flooding at the same time. show.
Publish their findings today in the journal Nature Communications, The team showed that the cooling or flood protection potential of green urban spaces is highly dependent on the prevailing climate of the relevant city, with flood protection likely to be more successful in arid environments and a cooling effect more likely in wetter climates.
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Each urban area has a unique climate that poses significant risks, especially as climate change increases the likelihood and severity of future extreme weather events.
Heatwaves within our cities can be attributed to the urban heat island effect (UHI), which is caused by the dominance of concrete and steel that absorb and retain heat, and the lack of cooling by water evaporating from plants.
Flooding is part of the Urban River Syndrome (USS), where urban structures and systems can negatively impact the return of natural stormwater runoff to the environment.
To address these issues, a commonly proposed strategy is to implement urban greening in our cities in the form of green roofs, living walls, vegetated urban spaces or parks.
These measures not only reduce the impact of UHI and USS on our cities, but also support local wildlife, reduce pollution, and improve the general well-being of the local population.
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For their study, the team used global climate model outputs and weather information for 175 cities around the world, spanning 15 years of daily observations from 2000 to 2015.
This data is used in conjunction with theory from soil science to calculate the water that seeps into the soil, which acts like a sponge to reduce rainwater runoff, and the evaporation of water from plants, which produces the desired cooling effect.
“Our study found that urban greening’s ability to mitigate local flooding and overheating is not automatic and in some areas even impossible,” said lead author Mark Cuthber from Cardiff University’s School of Earth and Environmental Sciences Dr. T said.
“Local and regional climatic conditions significantly affect the ability of urban soils and plant growth to withstand both flooding and extreme heat. In fact, our findings suggest that in many (probably most) global cities urban greening will not be able to simultaneously mitigate cooling and floods.”
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The team also found that increased variability in rainfall patterns due to climate change may degrade the performance of thinner green structures, such as green roofs, more rapidly than larger green areas with thicker soil and root systems.
Urban planners must consider these things in order to find the best solution for each city, balancing performance, cost and feasibility, they say.
“While urban greening may not be a panacea, our results show what is possible in designing cities of the future,” concluded Dr. Cuthbert.
The research was led by Cardiff University in collaboration with scientists from UNSW, Karlsruhe Institute of Technology and Nottingham Trent University.
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Brendan Montague is the editor of The Ecologist. This article is based on a press release from Cardiff University.
