Combating Urban Heat Islands with Deep-Rooted, Large-Canopy Trees

Johan Leman, 14 July 2026

An interesting study on urban heat islands in Italy’s major cities has recently been published. The research project, MIRIFICUS (Monitoraggio degli Interventi di RIForestazione per l’Isola di Calore Urbana tramite i Satelliti), was carried out in collaboration with ISPRA, CNR, and ASI.

The study identifies the following as the main causes of urban heat islands:

Large areas of asphalt and concrete that absorb and retain solar heat;
A lack of trees and natural soil;
Buildings that restrict air circulation;
Heat generated by human activities, including traffic, air conditioning, and buildings.

Based on its findings, the study recommends and evaluates the following measures:

Plant more trees, especially species with deep root systems and large canopies. These trees draw substantial amounts of water from the soil, which evaporates through their leaves. Evaporation requires a considerable amount of energy, which is taken from the heat stored in the trees and the surrounding air, producing a cooling effect. In Florence, densely built-up areas reach temperatures of 44.6°C, whereas areas with urban forests remain around 35.9°C.
Reduce paved surfaces and increase the use of permeable soils to improve water infiltration.
Use lighter-coloured, heat-reflective materials for streets and public squares, while avoiding dark asphalt whenever possible.

The authors note that these measures are straightforward and do not fundamentally alter the housing stock or the overall layout of neighbourhoods. As a result, they are likely to be readily accepted by local residents.

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