Alcobendas vs Donostia / San Sebastián
Tree cover and air quality for both, measured the same way: Sentinel-2 imagery at 10 m detail over a 2 km radius from each city centre, and the live US EPA air quality index. Same radius and same index, so the two numbers compare directly.
Donostia / San Sebastián has more tree cover — 47.4% against 12.8%.
Alcobendas has cleaner air right now — AQI 22 against 63.
- Tree cover gap
- 34.6 points
- Donostia / San Sebastián is ahead.
- Air quality gap
- 41 AQI
- Alcobendas is cleaner.
- Trees between them
- 90.7K
- Donostia / San Sebastián has more standing.
Spain
Tree cover
Share of the 2 km radius under canopy.
12.8%
47.4%
Air quality index
US EPA index, live, with its band. Lower is better.
22 · Good
63 · Moderate
Trees standing
Estimated from the measured canopy area.
40.2K
131K
Trees still needed
To reach the same canopy target. Fewer is better.
54.0K
0
CO₂ absorbed each year
By the trees already standing.
885K kg
2.9M kg
Air quality in detail
What each city is breathing
Concentrations in µg/m³, measured at the same moment as the index above. Lower is better in every row. Both are read from nearby ground stations.
PM2.5
Fine particles, the pollutant that usually sets the index.
3.4 µg/m³
18 µg/m³
PM10
Coarser particles — dust, pollen, road grit.
24.5 µg/m³
31 µg/m³
Nitrogen dioxide
Mostly traffic and combustion.
20.5 µg/m³
36 µg/m³
Ozone
Forms in sunlight; peaks on hot, still afternoons.
48 µg/m³
9 µg/m³
The last week, day by day
A single reading can catch a city on a bad afternoon. The week says whether it was the weather or the place.
| Day | Alcobendas | Donostia / San Sebastián |
|---|---|---|
| 22 Sept | 31 | 31 |
| 23 Sept | 30 | 34 |
| 24 Sept | 34 | 40 |
| 25 Sept | 34 | 45 |
| 26 Sept | 32 | 39 |
| 27 Sept | 31 | 36 |
| 28 Sept | 30 | 35 |
Reading these numbers
What is actually being measured
Tree cover
The share of ground under canopy inside a 2 km radius of each city centre, read from Sentinel-2 satellite imagery at 10 m detail. It is a measurement of that circle, not of the whole municipality — which is exactly what makes the two comparable, since city boundaries are drawn to wildly different rules around the world. Donostia / San Sebastián leads here at 47.4%.
Air quality index
The live US EPA index, computed from current pollutant concentrations — ground stations where a city has them nearby, and a model everywhere else. It moves hour to hour, so this is a snapshot rather than a verdict on either place: Alcobendas reads 22 (good) and Donostia / San Sebastián reads 63 (moderate) right now.
Frequently asked
Alcobendas and Donostia / San Sebastián, answered
Which has more trees, Alcobendas or Donostia / San Sebastián?
Donostia / San Sebastián, with roughly 130,893 trees inside its 2 km radius against 40,212. Tree cover tells a slightly different story from raw count: Donostia / San Sebastián has the denser canopy at 47.4%.
Which has better air quality, Alcobendas or Donostia / San Sebastián?
Alcobendas right now, at AQI 22 against 63 — a gap of 41 points. This is a live reading rather than an annual average, so it can reverse within a day.
How many more trees does each city need?
Alcobendas needs about 54,035 more to reach its canopy target, and Donostia / San Sebastián about 0. The target is the same share of ground for both, so the figures are directly comparable.
Are these two measured the same way?
Yes — that is the point of the page. Identical radius, identical satellite source at 10 m detail, and the same US EPA index for air. Nothing here is adjusted for population, city limits or climate, so the numbers describe the same-sized circle of ground in each place.
Keep going
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