Your city’s trees aren’t where you need them
Dr Thami Croeser · Analysis supporting Croeser, Rahman & Ghosh (2026), Nature Communications
Right now, a record-breaking heatwave is crushing Paris. Germany, Italy and Spain aren’t far behind. London’s feeling it too.
I ran building-level analytics across 21 European cities to map exactly how poorly protected they are. 3.8 million buildings. The results are brutal:
- Over 90% of homes and workplaces lack the basic tree cover needed to reduce dangerous heat effects. 60–80% have less than half the shade they need.
- Poor neighbourhoods are consistently more exposed — both hotter and less shaded.
- Neighbourhoods with proper tree cover are 4 to 10 degrees cooler than the hotspots in each city.
A lush park three blocks away isn’t much use when your street is a sea of unshaded tarmac.
3.8M
Buildings analysed
96%
Below the canopy threshold
21
European cities mapped
6°C
Cooler with adequate trees
Surface temperature across 21 cities
Note: These surface temperatures are from previous heatwave events — Landsat imagery takes about a week to process. The spatial pattern is stable across events, but absolute temperatures right now are worse.
What I measured
Using 1-metre resolution canopy data from Meta and the World Resources Institute, every building in 21 major cities was assessed for tree canopy within 60 metres — the distance research shows cooling needs to reach to protect residents. The threshold: 30% canopy cover, the minimum linked to measurable cooling in peer-reviewed studies.
The result is stark. Across all cities studied, an average of 96% of dwellings fall short. In Paris, it’s 99%. In Sevilla, 99.8%.
Below that threshold, the cooling effect is negligible.
The canopy deficit, city by city
The injustice pattern
The data reveals a consistent spatial injustice: in every city studied, lower-income neighbourhoods have less canopy and higher surface temperatures.
In Marseille, the poorest quartile of neighbourhoods average 43.8°C at the surface during heatwave events, with just 8.5% canopy — while wealthier areas are cooler and greener. In Nice, 36.7% of the population lives in areas that are simultaneously the hottest and most income-deprived.
Cool spots prove it works
The analysis also identifies “cool spots” — dense urban neighbourhoods that have managed to maintain adequate tree cover and are measurably cooler as a result. At the same dwelling density, these leafy pockets are 6°C cooler than their canopy-deprived counterparts.
Three hurdles
In our Nature Communications paper (free to read), we identify three hurdles that urban forestry needs to clear before trees can actually cool cities:
- Scale — Most cities are planting thousands of trees a year. They need millions. Current rates won’t close the canopy deficit within a generation.
- Targeting — New trees go where they’re easiest to plant, not where they’re most needed. The hottest, poorest neighbourhoods — hardscape-heavy, politically marginalised — get the least investment.
- Survival — Young trees die at alarming rates in extreme heat. The very conditions that make trees essential also make them hardest to establish. Without irrigation and maintenance commitments spanning decades, plantings fail.
Every mature tree we lose today is a decision to let someone bake in 2040. The question isn’t whether trees cool cities — this data settles that. The question is whether we’ll act on it fast enough.
Full methodology, data sources, and validation: Methods & Data →
Unpublished spatial analysis by Dr Thami Croeser, June 2026. Data: Meta/WRI 1m canopy (2020), Landsat 9 LST (30m), BD TOPO / Overture Maps buildings, INSEE Filosofi / IMD 2025 / GISD deprivation indices. Analysis conducted in support of: Croeser, T., Rahman, M. & Ghosh, A. (2026). Urban forestry for cooler cities faces three critical hurdles. Nature Communications.