Mitigating Urban Heat Island Effect: Enhancing Resilience through Urban Design and Tree Canopy


New research conducted by Pennsylvania State University in the US highlights the importance of urban factors in reducing the urban heat island (UHI) effect. The UHI effect refers to the tendency of cities to trap heat, leading to dangerously high temperatures during summer. The study, published in the journal Buildings, suggests that enhancing tree canopy, implementing reflective pavements, and constructing taller buildings adjacent to thinner streets can significantly mitigate this effect.

The researchers discovered that trees play a crucial role in cooling outdoor air temperature, reducing mean radiant temperature (heat emitted by buildings and infrastructure), and improving thermal comfort levels. Additionally, the study found that taller buildings positioned alongside narrower streets create shade, thereby lowering the mean radiant temperature and enhancing comfort levels. Furthermore, pavements with higher albedo, which reflect sunlight more effectively, also contribute to reducing the UHI effect.

One noteworthy finding from the research is that urban blocks with socially disadvantaged populations tend to have higher UHI hotspots and mortality rates. This is attributed to a combination of physical factors, such as impervious surfaces and lack of vegetation, as well as social factors that make these communities more vulnerable to heat-related health issues.

Guangqing Chi, professor of rural sociology, demography, and public health sciences, emphasized the impact of global warming on socially and historically disadvantaged communities, stating that such habitats become unbearably hot. The interdisciplinary nature of the study provides an effective and equitable urban design solution to enhance resilience against extreme heat.

The research was conducted in Philadelphia, a city experiencing high rates of poverty and extreme weather. The study utilized the social vulnerability index and tree coverage data to identify two neighborhoods—one with the lowest social vulnerability and high tree coverage, and the other with the highest social vulnerability and lowest tree coverage. By running simulations for different scenarios, the researchers analyzed the impact of various factors on the UHI effect.

While the study confirms that trees have a cooling effect, it also reveals that their benefits are limited to their immediate surroundings. Areas without tree canopy exhibit significantly higher mean radiant temperatures, and the cooling effect of trees diminishes with distance.

This research sheds light on the importance of urban design and tree canopy in mitigating the urban heat island effect. Implementing strategies such as enhancing tree coverage, incorporating reflective pavements, and designing taller buildings adjacent to thinner streets can help cities combat extreme heat and improve the resilience of communities, particularly those that are socially and historically disadvantaged. By adopting these measures, cities can create more comfortable and sustainable environments for their inhabitants.


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