City report · South Holland, The Netherlands
Leiden Air quality today
Air quality in Leiden currently reads AQI 118 (Unhealthy for sensitive groups): Sensitive groups should limit long or intense outdoor activity.
AQI 118
Air quality right now
Unhealthy for sensitive groups
- PM2.5, fine particles (µg/m³)
- 42.3
- tree cover
- 30.0%
- trees in this area
- 93.7K
- more trees needed
- 15.6K
Measured across a 2 km radius around Leiden, Netherlands (12.57 km²), from a satellite image of Aug 12, 2026. Lower AQI is better: 0–50 is Good, above 300 is Hazardous.
Leiden · AQI 118 (Unhealthy for sensitive groups)
Leiden's tree count comes to 93,682 trees across 12.49 km² of land, 5 points below the 35% tree-cover level considered healthy for this area, so roughly 15,614 more trees would close the gap.
Air quality detail
Air quality in Leiden today: AQI 118, Unhealthy for sensitive groups
Main pollutant: PM2.5 · Observed Nov 11, 18:00 local time via OpenAQ ground stations, US EPA index. Values in µg/m³.
Ground station · Leiden - Stevenshof, 3.3 km away · median of 2 stations
Health signal
Sensitive groups should limit long or intense outdoor activity.
PM2.5
42.3
PM10
—
NO₂
—
O₃
—
SO₂
—
CO
—
Data: OpenAQ · AirGradient
- Outdoor exercise
- Children, older adults and people with asthma or heart disease should cut down long or hard exercise
- Windows
- Close them to keep the outside air out
- Mask
- Sensitive groups: an N95 outdoors
- Air purifier
- Run one, especially in bedrooms
Over the last 7 days, the CAMS air-quality model put Leiden's daily AQI at 71 on average, from 44 on Nov 4 to an hourly peak of 102 on Nov 7.
Where Leiden stands: the most polluted cities in the world right now · the cleanest
Tree cover detail
Tree cover in Leiden: Below target
30.0% tree cover against a 35% healthy-neighborhood target, across 12.49 km² of land.
Trees in this area
93,682
Target trees
109,296
More trees needed
15,614
CO₂ if planted / yr
343.5 t
Deforestation · 2001–2025
How much forest has Leiden lost?
Since 2001, the area within 10 km of Leiden has lost about 75 hectares of forest (about 100 football pitches): 1.7% of the forest it had in 2000. Most of it (74%) was deforestation, forest cleared for good, mainly for towns and roads.
2017: satellite photo from August 2017 of a 5 × 5 km area in the city center.
- Forest lost since 2001
- 75 haabout 100 football pitches
- Share of its forest
- 1.7%of what there was in 2000
- Cleared for good
- 55 hadeforestation: turned into farms, mines or towns
The worst year was 2023, when about 12 hectares of forest were lost.
Hectares of forest lost each year
Show the figures as a table
| Year | Cleared for good | Can grow back | Total |
|---|---|---|---|
| 2001 | under 1 ha | under 1 ha | 2 ha |
| 2002 | 2 ha | under 1 ha | 2 ha |
| 2003 | under 1 ha | under 1 ha | 1 ha |
| 2004 | under 1 ha | under 1 ha | under 1 ha |
| 2005 | 1 ha | under 1 ha | 2 ha |
| 2006 | 1 ha | under 1 ha | 2 ha |
| 2007 | 1 ha | under 1 ha | 2 ha |
| 2008 | 2 ha | 3 ha | 5 ha |
| 2009 | 2 ha | under 1 ha | 2 ha |
| 2010 | 6 ha | under 1 ha | 7 ha |
| 2011 | 2 ha | under 1 ha | 2 ha |
| 2012 | 2 ha | under 1 ha | 3 ha |
| 2013 | under 1 ha | under 1 ha | under 1 ha |
| 2014 | under 1 ha | under 1 ha | under 1 ha |
| 2015 | 2 ha | under 1 ha | 2 ha |
| 2016 | 2 ha | under 1 ha | 2 ha |
| 2017 | under 1 ha | under 1 ha | 2 ha |
| 2018 | 6 ha | under 1 ha | 7 ha |
| 2019 | 1 ha | under 1 ha | 2 ha |
| 2020 | 3 ha | 3 ha | 5 ha |
| 2021 | 5 ha | 3 ha | 7 ha |
| 2022 | 1 ha | under 1 ha | 2 ha |
| 2023 | 10 ha | 1 ha | 12 ha |
| 2024 | 2 ha | under 1 ha | 3 ha |
| 2025 | under 1 ha | 1 ha | 1 ha |
What is causing deforestation around Leiden?
- Towns and roadscleared for good66% · 49 ha
- Loggingcan grow back13% · 10 ha
- Mining and energycleared for good7.9% · 6 ha
Also: unknown causes.
Causes for 2025 are estimates, based on what caused forest loss in the same places up to 2024.
Forest gained and lost, 2000–2020
- Forest in 2000
- 3,070 ha
- Forest in 2020
- 3,250 ha
- Overall change
- +177 hamore forest than in 2000
Comparing satellite maps from 2000 and 2020, the forest around Leiden grew from about 3,070 hectares to 3,250 hectares, a net gain of about 177 hectares (+5.8%). New forest grew on about 296 hectares, while 119 hectares were lost.
These 2000 and 2020 maps, from the University of Maryland, count any land with trees taller than 5 m as forest, including plantations and orchards. Forest that was cut or burned and had grown back by 2020 counts in both years, so the loss here is smaller than the yearly figures.
These figures cover everything within 10 km of the city center, a wider area than the report above, because forest is usually lost at a city's edges.
Source: Hansen/UMD/Google/USGS/NASA, Global Forest Change (GFC-2025-v1.13); causes: WRI/Google DeepMind drivers of forest loss; both CC BY 4.0, summed by Airleaf for each area. Forest gained and lost 2000–2020: Potapov et al. 2022, UMD GLAD Global Land Cover and Land Use Change, CC BY 4.0. Images: contains modified Copernicus Sentinel data. How it's measured
In the same region
Measured cities near Leiden
Same 2 km radius, same index — so they compare directly.
- The Hague16.1 km
The Netherlands
- Tree cover
- 22%
- Air quality
- 71
- Hoofddorp20.9 km
The Netherlands
- Tree cover
- 23%
- Air quality
- 66
- Rotterdam26.2 km
The Netherlands
- Tree cover
- 26%
- Air quality
- 73
- Haarlem26.6 km
The Netherlands
- Tree cover
- 25%
- Air quality
- 65
- Amsterdam36.1 km
The Netherlands
- Tree cover
- 21%
- Air quality
- 70
- Zaanstad39.4 km
The Netherlands
- Tree cover
- 23%
- Air quality
- 73
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Frequently asked
Questions about Leiden
What is the air quality (AQI) in Leiden right now?
The latest reading for Leiden shows an AQI of 118 (Unhealthy for sensitive groups), measured Nov 11, 18:00 local time by 2 ground monitoring stations via OpenAQ (the median of their readings; the nearest is Leiden - Stevenshof, 3.3 km away). The main pollutant is PM2.5. Sensitive groups should limit long or intense outdoor activity.
Is it safe to exercise outside in Leiden today?
At AQI 118 (Unhealthy for sensitive groups): children, older adults and people with asthma or heart disease should cut down long or hard exercise. Windows: close them to keep the outside air out. Masks: sensitive groups: an N95 outdoors. The reading changes through the day, so check again before a long run or ride.
What has the air quality in Leiden been like this week?
Over the last 7 days, the CAMS air-quality model put Leiden's daily AQI at 71 on average, from 44 on Nov 4 to an hourly peak of 102 on Nov 7. No day averaged above 100, the level where the air turns unhealthy for sensitive groups.
How much forest has the area around Leiden lost since 2001?
Since 2001, the area within 10 km of Leiden has lost about 75 hectares of forest (about 100 football pitches): 1.7% of the forest it had in 2000. Most of it (74%) was deforestation, forest cleared for good, mainly for towns and roads. Comparing satellite maps from 2000 and 2020, the forest around Leiden grew from about 3,070 hectares to 3,250 hectares, a net gain of about 177 hectares (+5.8%). New forest grew on about 296 hectares, while 119 hectares were lost.
What is the tree count in Leiden?
Leiden has an estimated 93,682 trees across the 12.49 km² of land measured — 30.0% tree cover, 5 percentage points short of the 35% tree-cover target set for this area.
How many more trees does Leiden need?
Leiden needs roughly 15,614 more trees to close a 5-point shortfall against its 35% tree-cover target — about 343.5 t of extra CO₂ absorbed per year once grown.
How are Leiden's air quality and tree cover measured?
Air quality is measured by ground monitoring stations near Leiden, via OpenAQ; the 7-day trend is the Open-Meteo / CAMS model's estimate. Tree cover is measured from Sentinel-2 L2A (ESA Copernicus) via Earth Search satellite imagery at 10 m detail across a 2 km radius around Leiden; the tree count is an estimate derived from that cover.
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