Bel Air Rivière Sèche vs Saint-Denis
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.
Bel Air Rivière Sèche has more tree cover — 82.6% against 41.8%.
Bel Air Rivière Sèche has cleaner air right now — AQI 17 against 21.
- Tree cover gap
- 40.8 points
- Bel Air Rivière Sèche is ahead.
- Air quality gap
- 4 AQI
- Bel Air Rivière Sèche is cleaner.
- Trees between them
- 168K
- Bel Air Rivière Sèche has more standing.
Mauritius
Reunion
Tree cover
Share of the 2 km radius under canopy.
82.6%
41.8%
Air quality index
US EPA index, live, with its band. Lower is better.
17 · Good
21 · Good
Trees standing
Estimated from the measured canopy area.
259K
91.1K
Trees still needed
To reach the same canopy target. Fewer is better.
0
0
CO₂ absorbed each year
By the trees already standing.
5.7M kg
2.0M 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. Saint-Denis is read from nearby ground stations and Bel Air Rivière Sèche is modelled — worth knowing, since the two are not quite like for like.
PM2.5
Fine particles, the pollutant that usually sets the index.
4 µg/m³
3.9 µg/m³
PM10
Coarser particles — dust, pollen, road grit.
5.9 µg/m³
7.2 µg/m³
Nitrogen dioxide
Mostly traffic and combustion.
3.8 µg/m³
1.1 µg/m³
Ozone
Forms in sunlight; peaks on hot, still afternoons.
30 µg/m³
46.7 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 | Bel Air Rivière Sèche | Saint-Denis |
|---|---|---|
| 22 Sept | 28 | 30 |
| 23 Sept | 38 | 42 |
| 24 Sept | 42 | 52 |
| 25 Sept | 36 | 42 |
| 26 Sept | 26 | 35 |
| 27 Sept | 24 | 31 |
| 28 Sept | 21 | 25 |
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. Bel Air Rivière Sèche leads here at 82.6%.
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: Bel Air Rivière Sèche reads 17 (good) and Saint-Denis reads 21 (good) right now.
Frequently asked
Bel Air Rivière Sèche and Saint-Denis, answered
Which has more trees, Bel Air Rivière Sèche or Saint-Denis?
Bel Air Rivière Sèche, with roughly 259,496 trees inside its 2 km radius against 91,135. Tree cover tells a slightly different story from raw count: Bel Air Rivière Sèche has the denser canopy at 82.6%.
Which has better air quality, Bel Air Rivière Sèche or Saint-Denis?
Bel Air Rivière Sèche right now, at AQI 17 against 21 — a gap of 4 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?
Bel Air Rivière Sèche needs about 0 more to reach its canopy target, and Saint-Denis 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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