Graz vs Koper
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.
Graz has more tree cover — 35.1% against 30.4%.
Koper has cleaner air right now — AQI 31 against 71.
- Tree cover gap
- 4.7 points
- Graz is ahead.
- Air quality gap
- 40 AQI
- Koper is cleaner.
- Trees between them
- 52.0K
- Graz has more standing.
Tree cover
Share of the 2 km radius under canopy.
35.1%
30.4%
Air quality index
US EPA index, live, with its band. Lower is better.
71 · Moderate
31 · Good
Trees standing
Estimated from the measured canopy area.
110K
58.2K
Trees still needed
To reach the same canopy target. Fewer is better.
0
0
CO₂ absorbed each year
By the trees already standing.
2.4M kg
1.3M 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.
21.6 µg/m³
7.5 µg/m³
PM10
Coarser particles — dust, pollen, road grit.
44.1 µg/m³
10.2 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 | Graz | Koper |
|---|---|---|
| 22 Sept | 29 | 34 |
| 23 Sept | 31 | 30 |
| 24 Sept | 30 | 31 |
| 25 Sept | 32 | 33 |
| 26 Sept | 39 | 31 |
| 27 Sept | 46 | 34 |
| 28 Sept | 59 | 57 |
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. Graz leads here at 35.1%.
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: Graz reads 71 (moderate) and Koper reads 31 (good) right now.
Frequently asked
Graz and Koper, answered
Which has more trees, Graz or Koper?
Graz, with roughly 110,160 trees inside its 2 km radius against 58,162. Tree cover tells a slightly different story from raw count: Graz has the denser canopy at 35.1%.
Which has better air quality, Graz or Koper?
Koper right now, at AQI 31 against 71 — a gap of 40 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?
Graz needs about 0 more to reach its canopy target, and Koper 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.
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