While Europe swelters, 83% of its buildings are unprotected
Dr Thami Croeser · Vice-Chancellor’s Research Fellow, RMIT Centre for Urban Research, Melbourne
In March, we published an article in Nature Communications about heatwaves. Sure enough, there is now a record-breaking heatwave crushing Paris, and things aren’t looking too safe in Germany, Italy or Spain either. London’s feeling it too.
When I read about the suffering in France yesterday, I imagined all the hot concrete and asphalt in each city, and decided to run some big data analytics to map out exactly how many buildings in each city have enough shade around them to keep people cool. I was worried about deadly ‘urban heat island’ effects that occur when lots of asphalt and concrete get hot (and stay hot) in unshaded parts of cities.
My analysis managed to cover quite a few of the most heat-impacted cities right now and… just… wow.
I’ll mostly let the maps speak for themselves, but the takeaway messages are brutal:
- 83% of homes and workplaces lack the basic tree canopy they need to avoid extreme impacts of heat.
- Most of us are not even close to safe levels of protection. In the majority of cities I looked at, more than half of all buildings have less than half the canopy they need around their homes.
- Poor neighbourhoods are consistently much more exposed, both in terms of heat, and low tree cover.
- Neighbourhoods with proper shade are 4 to 10 degrees cooler than the hotspots we see in each city.
What I measured
I mapped tree canopy within 60 metres of every building in 25 European cities. I looked at 5.5 million buildings across France, Spain, Italy, Germany, Portugal, Greece and the UK. We were looking for the heat-safe threshold of 30% canopy; the bare minimum to reduce dangerous ‘heat island’ effects that happen when there’s lots of exposed asphalt and concrete around. Sixty metres is the crucial zone, close to home, where shade has the best impact. Below that, the cooling effect is negligible. A lush park three blocks away isn’t much use when your street is a sea of unshaded tarmac. For eight cities we have high-resolution (0.2m) data from Google’s Environmental Insights Explorer, where a machine-learning model identifies trees specifically from aerial imagery. For the remaining cities we use a 1m canopy height dataset without a height filter, meaning it counts all detected vegetation, including hedges, shrubs, and lawn edges, not just shade trees. So our results are generous, especially for those cities.
5.5M
Buildings analysed
83%
Below the canopy threshold
25
European cities mapped
7–37%
Of French city residents in hot, deprived areas
The ranking
Only one city, Nice, gets more than half its buildings above the threshold (56% protected), thanks to its hillside vegetation. After that the picture deteriorates fast. The worst is Sevilla, a city that regularly hits 44°C, where 99% of buildings fall short.
Some highlights from the data:
- Paris: 82% of 119,000 buildings below threshold. Mean green cover within 60m: 19.5%. Paris uses the 1m canopy product, which counts all vegetation including lawns and hedges, so the true shade-tree figure is likely lower.
- London: 93% of 1.5 million buildings. This data is from the May 26 heatwave, the one happening right now.
- Lyon: 75% below threshold, in a city that hit 41°C this week.
- German cities are the best in Europe (54–80% below), with Cologne and Hamburg benefiting from extensive garden vegetation. Mediterranean cities and the UK are the worst (64–99%). In all cases, the deficit is acute.
How far off are we?
It’s not just that most buildings are below the threshold. It’s how far below. In most cities, half of all buildings have less than 10% canopy nearby. That’s not a small gap to close. We’re talking about tripling canopy cover close to homes.
Drag the slider above. Even at a bare-minimum 20% shade target, the picture barely improves for many cities.
Poor neighbourhoods are more exposed
This heatwave isn’t being felt equally. Using national deprivation datasets, I tested whether poorer areas bear more of the heat burden. (Not every city is shown; this project started on Tuesday, and we couldn’t source suitable heat and/or income data for all 25 cities at short notice.)
Lower income neighborhoods have significantly lower canopy, in almost every city.
In London, the most deprived neighbourhoods are significantly hotter and have significantly less canopy. In Marseille, the income-heat correlation is even stronger (rho = −0.57). In Birmingham, the most deprived areas have 35% less canopy than the least deprived.
But density isn’t the problem; cool spots are often dense
This is the finding that should change how we think about urban greening.
I compared neighbourhoods with similar dwelling densities (around 50 dwellings per hectare) and found temperature gaps of 4 to 10°C between those with adequate canopy and those without. In Paris, the gap is 9.8°C. In Birmingham, 6.7°C.
These are dense urban areas. Apartments, shops, offices. The difference isn’t density. It’s whether someone kept the trees, or managed to get them planted in the first place.
In fact, we found some really remarkable sites where there were activity centres and reasonable amounts of dense housing, yet they stayed cool. Explore these gems for each city below, and toggle to “Hot Spots” to see the contrast.
A note on timing. The surface temperature figures in this analysis aren’t even from the current, more severe heatwave. Landsat satellite imagery takes about a week to process, so the thermal data comes from previous heatwave events: summer 2024 for most continental cities, May 26 for the UK’s recent record-breaking Spring heatwave. The spatial pattern of heat islands is stable across heatwave events, but the absolute temperatures right now are worse than what’s shown in these graphics.
Three hurdles for cooler cities
In our Nature Communications paper (free to read), we identify three hurdles that urban forestry needs to clear before trees can actually cool cities:
- The canopy must be close to homes. City-wide averages of 15–20% canopy cover hide the reality that individual homes have far less. A park two suburbs away doesn’t cool your apartment. A core part of the problem is that trees tend to be planted very far apart in urban settings. This data makes that visible for the first time at building scale.
- Trees need space to grow, and water. Many of the hottest, most canopy-deprived areas are also the most paved. A tree planted in a one-square-metre pit surrounded by asphalt delivers a fraction of the cooling of one with adequate soil volume and water.
- Trees need much better protection. A newly planted tree won’t shade a building for 15–20 years. The heatwaves hitting Europe today were locked in by planting decisions (or non-decisions) made a generation ago. Every mature tree we lose now is irreplaceable on any timeline that matters.
These things are worth getting right: the difference canopy makes is huge.
The team on our Nature Communications paper was Dr Arnab Ghosh (Medical Doctor), myself, and Mohammad Rahman (Tree Physiologist).
Full methodology, data sources, and validation: Methods & Data →
Unpublished spatial analysis by Dr Thami Croeser, June 2026. Data: Google EIE 0.2m ML tree classification (2020–2024, 8 cities) + Meta/WRI 1m canopy height (2020, remainder), 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.