While Europe swelters, 84% 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 last week, 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:
- 84% 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.
- In France, poorer neighbourhoods are measurably hotter and less shaded. In the UK and Germany the relationship is more complex — but exposure is unequal everywhere.
- Neighbourhoods with proper shade can be 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 — 5.5 million buildings across seven countries. The question: does each building have the 30% canopy threshold needed to reduce dangerous urban heat island effects? Sixty metres is the critical zone; a park three blocks away doesn’t cool your street. Tree canopy data comes from Google’s Environmental Insights Explorer (0.2m, 19 cities) with a 1m dataset for the remainder (full methods).
5.5M
Buildings analysed
84%
Below the canopy threshold
25
European cities mapped
7–37%
Of French city residents in hot, deprived areas
The ranking
Cologne and Hamburg perform best, with around 45% of buildings adequately protected. Nice is next at 41%. After that the picture deteriorates fast. The worst is Sevilla, a city that regularly hits 44°C, where 98% of buildings fall short.
Some highlights from the data:
- Paris: 96% of 119,000 buildings below threshold. Mean tree canopy within 60m: just 12%.
- London: 93% of 1.5 million buildings.
- Lyon: 84% below threshold, in a city that hit 41°C last week.
- German cities are the best in Europe (54–80% below), with Cologne and Hamburg benefiting from extensive garden vegetation. Southern European and UK cities are the least protected (69–98%). 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.
Shade is unequal — but the pattern varies by country
This heatwave isn’t being felt equally. Using national income and deprivation datasets, I tested whether poorer areas bear more of the heat burden. I could now do this for 17 of the 25 cities, spanning France, the UK, Germany, Spain, Italy and Portugal. (Not every city is shown; for the rest, we couldn’t source suitable heat and/or income data at short notice.)
One thing holds everywhere: canopy is the great predictor of heat. In every city I tested, neighbourhoods with less tree cover run hotter, and the link is often very strong — Nice (ρ = −0.81), Milan (−0.77), Madrid (−0.70), Bristol (−0.64). Whatever else varies, the trees do the cooling.
What varies is who ends up without them.
In Spain the pattern is stark and familiar: poorer means hotter. Sevilla has the steepest income–heat gradient in the whole dataset (ρ = −0.59) in a city that routinely tops 44°C; its affluent, compact core stays comparatively cool while the sprawling eastern districts bake. Madrid tells the same story (income–heat ρ = −0.43) — the wealthy north-central core is shaded and protected, the poorer south hot and exposed.
France echoes it. In Marseille and Nice, poorer neighbourhoods have dramatically less tree cover and measurably higher temperatures (Marseille income–heat ρ = −0.55; Nice’s wealthy hillsides are lush while the dense coastal flats are exposed). Lyon and Toulouse show the same gradient, more gently.
But the relationship isn’t universal, and Italy shows why. In Milan the pattern inverts: the dense, historic, wealthy centre is the hot core, while more-deprived outskirts are greener and cooler. Rome sits closer to the familiar pattern — more-deprived districts do run hotter (ρ = +0.23). In both, canopy still governs temperature; it’s the social geography that flips.
The UK and Germany are the murkiest. London’s most deprived areas aren’t uniformly the least shaded — inner-city estates sit alongside legacy green space while some bare regeneration zones are wealthy (173,000 dwellings still sit in hot, low-canopy cells across London alone). In German cities, income barely predicts heat at all: the inequality there is geographic rather than socioeconomic, with trees clustered in outer districts and parks rather than the dense neighbourhoods where most people live.
The throughline: wherever trees are scarce, it’s hot — and in most of Europe, it’s the poorer neighbourhoods that got left without them.
But density isn’t the problem; cool spots are often dense
This is the finding that should change how we think about urban greening.
Within the same density band, the coolest tree-shaded neighbourhoods are 4 to 10°C cooler than the hottest tree-poor ones. In Paris, even at 40–60 dwellings per hectare, the gap reaches 12°C. In Birmingham, 8°C.
These are urban areas with apartments, shops, and 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 Dr 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, 19 cities) + Meta/WRI 1m canopy height (2020, remainder), Landsat 9 LST (30m), BD TOPO / Overture Maps buildings, INSEE Filosofi (FR) / IMD 2025 (UK) / Zensus 2022 (DE) / INE ADRH 2023 (ES) / Istat 2021 (IT) / 2021 census (PT) income and 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.