New findings from a research project at the Universidad de Granada show how cities should organise their green spaces to cope with rising heat: connectivity between parks, squares and rows of trees is crucial – not simply the number of trees. After two years of temperature measurements in Parque Federico García Lorca in Granada, the team behind the project BioCiTrees identified five species that cool the area beneath their canopy by an average of around two degrees, with peak reductions of up to 3.5 degrees compared with areas without vegetation: olivo (olive tree), fresno (ash), plátano de sombra (plane tree), níspero (loquat) and naranjo amargo (bitter orange tree).
The researchers stress that continuous, connected green corridors extend the cooling effect across a wider area. Where rows of trees, small squares and larger parks form a network, temperatures fall over a broader area and more consistently than at isolated sites. From an urban climate perspective, the team recommends filling gaps between existing green spaces and prioritising links to particularly exposed residential districts. The aim is to ease urban heat islands in densely built-up areas and create comfortable walking routes through the city.
Measurements were taken over two summers at comparable points beneath tree canopies and in unshaded areas. According to the project team, the differences are mainly due to shade and the cooling effect of water evaporating from leaves. Species with dense canopies and good adaptation to the southern European summer showed the strongest effects. Alongside choosing suitable species, maintenance – such as ensuring adequate water supply during heatwaves – is crucial to effectiveness, the team at the Universidad de Granada.
The findings should be viewed in the local context: summer temperatures in Granada frequently exceed 40 degrees. As heatwaves become more frequent and prolonged, pressure is growing on urban planners to create robust, low-maintenance and socially equitable cooling infrastructure. The BioCiTrees analysis offers practical pointers: rather than isolated tree planting, it recommends developing connected corridors that link existing parks, streets and squares to provide climate benefits and prioritise the most affected neighbourhoods.
The results form part of a broader Andalusian debate on climate adaptation. In practice, they mean that while species selection, location and maintenance remain important, the spatial arrangement of green spaces determines the strength and reach of the cooling effect. The focus therefore shifts from simply counting trees planted to creating a connected, city-wide green system – with measurable benefits for health and quality of life in densely built-up parts of Granada.
Editor: Andreas M. Brucker (Article created with AI assistance).