Chiayi City vs Yuanlin
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.
Yuanlin has more tree cover — 27.9% against 17.9%.
Chiayi City has cleaner air right now — AQI 55 against 60.
- Tree cover gap
- 10.0 points
- Yuanlin is ahead.
- Air quality gap
- 5 AQI
- Chiayi City is cleaner.
- Trees between them
- 31.4K
- Yuanlin has more standing.
Taiwan
Taiwan
Tree cover
Share of the 2 km radius under canopy.
17.9%
27.9%
Air quality index
US EPA index, live, with its band. Lower is better.
55 · Moderate
60 · Moderate
Trees standing
Estimated from the measured canopy area.
56.2K
87.7K
Trees still needed
To reach the same canopy target. Fewer is better.
38.0K
6.6K
CO₂ absorbed each year
By the trees already standing.
1.2M kg
1.9M 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 modelled, with no ground station close enough to either.
PM2.5
Fine particles, the pollutant that usually sets the index.
14.2 µg/m³
16.6 µg/m³
PM10
Coarser particles — dust, pollen, road grit.
19.1 µg/m³
21.7 µg/m³
Nitrogen dioxide
Mostly traffic and combustion.
7.8 µg/m³
16.6 µg/m³
Ozone
Forms in sunlight; peaks on hot, still afternoons.
114 µg/m³
79 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 | Chiayi City | Yuanlin |
|---|---|---|
| 22 Sept | 103 | 89 |
| 23 Sept | 106 | 86 |
| 24 Sept | 121 | 88 |
| 25 Sept | 135 | 101 |
| 26 Sept | 116 | 86 |
| 27 Sept | 83 | 74 |
| 28 Sept | 59 | 56 |
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. Yuanlin leads here at 27.9%.
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: Chiayi City reads 55 (moderate) and Yuanlin reads 60 (moderate) right now.
Frequently asked
Chiayi City and Yuanlin, answered
Which has more trees, Chiayi City or Yuanlin?
Yuanlin, with roughly 87,650 trees inside its 2 km radius against 56,235. Tree cover tells a slightly different story from raw count: Yuanlin has the denser canopy at 27.9%.
Which has better air quality, Chiayi City or Yuanlin?
Chiayi City right now, at AQI 55 against 60 — a gap of 5 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?
Chiayi City needs about 38,013 more to reach its canopy target, and Yuanlin about 6,597. 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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