Hong Kong vs Tanzhou
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.
Hong Kong has more tree cover — 50.6% against 28.3%.
Tanzhou has cleaner air right now — AQI 87 against 94.
- Tree cover gap
- 22.3 points
- Hong Kong is ahead.
- Air quality gap
- 7 AQI
- Tanzhou is cleaner.
- Trees between them
- 20.7K
- Hong Kong has more standing.
Tree cover
Share of the 2 km radius under canopy.
50.6%
28.3%
Air quality index
US EPA index, live, with its band. Lower is better.
94 · Moderate
87 · Moderate
Trees standing
Estimated from the measured canopy area.
108K
87.6K
Trees still needed
To reach the same canopy target. Fewer is better.
0
5.3K
CO₂ absorbed each year
By the trees already standing.
2.4M 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. Hong Kong is read from nearby ground stations and Tanzhou is modelled — worth knowing, since the two are not quite like for like.
PM2.5
Fine particles, the pollutant that usually sets the index.
32.7 µg/m³
14.6 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 | Hong Kong | Tanzhou |
|---|---|---|
| 22 Sept | 127 | 125 |
| 23 Sept | 105 | 126 |
| 24 Sept | 94 | 99 |
| 25 Sept | 99 | 89 |
| 26 Sept | 102 | 83 |
| 27 Sept | 69 | 64 |
| 28 Sept | 54 | 44 |
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. Hong Kong leads here at 50.6%.
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: Hong Kong reads 94 (moderate) and Tanzhou reads 87 (moderate) right now.
Frequently asked
Hong Kong and Tanzhou, answered
Which has more trees, Hong Kong or Tanzhou?
Hong Kong, with roughly 108,255 trees inside its 2 km radius against 87,573. Tree cover tells a slightly different story from raw count: Hong Kong has the denser canopy at 50.6%.
Which has better air quality, Hong Kong or Tanzhou?
Tanzhou right now, at AQI 87 against 94 — a gap of 7 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?
Hong Kong needs about 0 more to reach its canopy target, and Tanzhou about 5,261. 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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- Hong Kong vs Zhongshan26% tree cover · AQI 51Compare
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