Scientists from the University of Granada have demonstrated the effectiveness of five tree species in reducing urban temperatures by an average of about 2°C, and even in achieving maximum cooling reductions of up to 3.5°C.

These trees are the olive, the wild cherry, the medlar, the London plane, and the bitter orange, according to a study conducted by researchers from the Department of Ecology at the University of Granada and the Interuniversity Research Institute for Geosystems in Andalusia.

The study, which is featured on the website of the Spanish news agency Efe and was presented Tuesday at a press conference, is part of the “Biocitrees” project.

The study focused on how vegetation improves human health and biodiversity, cools the microclimate, and is sustainable in the face of climate change.

The study is based on the hypothesis that trees help combat high temperatures in cities, where the urban heat island effect causes a sharp rise in temperatures during the summer.

To obtain their results, between July 2024 and early 2026, the scientists installed sensors on trees and measured thermal comfort under the canopy of 19 different species.

Part of the experiments was conducted in Federico García Lorca Park in Granada, a city where summer temperatures exceed 40 degrees Celsius.

In cities with these characteristics, proper management of green spaces is key to mitigating the effects of extreme heat, explained researchers Nuria Pistón and Regino Zamora during the presentation of the results.

The scientists compared the data they collected with records from control areas without vegetation, an approach that “allows for the precise quantification of the climate-regulating ecosystem services that each tree provides to its immediate surroundings.”

In an earlier phase of the research, the team mapped critical locations in Granada and its metropolitan area. Using the InVEST model and high-resolution data (Rediam and Ine), four priority areas were identified where heat exposure coincides with high social vulnerability—specifically, low income and a population over the age of 65.

These areas are located in three neighborhoods in the center of Granada and in part of the northern municipality of Armilla in Granada.

The study reveals a fundamental finding for urban planning: that the spatial configuration of green spaces within the city is just as important as their size.

The results show that a mosaic distribution—that is, smaller but interconnected green spaces with a high edge density—is more effective at reducing temperature than a large, isolated forest.

In addition to mitigating urban heat islands, the project aims to understand how trees act as pollutant sinks and are essential for sustaining urban insect populations, ensuring a more equitable and resilient green infrastructure.

Source: CNA