City report · Ibaraki, Japan
Koga Air quality today
Air quality in Koga currently reads AQI 28 (Good): Air quality is satisfactory for everyone.
Air quality right now
AQI 28
Good
- PM2.5, fine particles (µg/m³)
- 4.2
- tree cover
- 10.3%
- trees in this area
- 32.4K
- more trees needed
- 61.9K
Measured across a 2 km radius around Otsutsumi, Koga, Ibaraki 306-0236, Japan (12.57 km²), from a satellite image of Jul 22, 2026. Lower AQI is better: 0–50 is Good, above 300 is Hazardous.
Koga · AQI 28 (Good)
Koga's tree count comes to 32,358 trees across 12.57 km², 20 points below the 30% tree-cover level considered healthy for this area, so roughly 61,889 more trees would close the gap.
Air quality detail
Air quality in Koga today: AQI 28, Good
Main pollutant: PM2.5 · Observed Nov 11, 11:00 local time via Open-Meteo / CAMS, corrected with 16 ground-station cities within 125 km, US EPA index. Values in µg/m³.
Estimate · model corrected with 16 station cities within 125 km, e.g. Noda and Kawaguchi
Health signal
Air quality is satisfactory for everyone.
PM2.5
4.2
PM10
17.9
NO₂
18.3
O₃
63.0
SO₂
15.0
CO
165.0
- Outdoor exercise
- A good day to be active outside
- Windows
- Open them to air the house
- Mask
- Not needed
- Air purifier
- Not needed
Over the last 7 days, the CAMS air-quality model put Koga's daily AQI at 56 on average, from 26 on Nov 7 to an hourly peak of 147 on Nov 5.
Where Koga stands: the most polluted cities in the world right now · the cleanest
Tree cover detail
Tree cover in Koga: Critically low
10.3% tree cover against a 30% healthy-neighborhood target, across 12.57 km².
Trees in this area
32,358
Target trees
94,247
More trees needed
61,889
CO₂ if planted / yr
1,362 t
Deforestation · 2001–2025
How much forest has Koga lost?
Since 2001, the area within 10 km of Koga has lost about 106 hectares of forest (about 150 football pitches): 6.8% of the forest it had in 2000. Most of it (87%) was deforestation, forest cleared for good, mainly for towns and roads.
2017: satellite photo from July 2017 of a 5 × 5 km area in the city center.
- Forest lost since 2001
- 106 haabout 150 football pitches
- Share of its forest
- 6.8%of what there was in 2000
- Cleared for good
- 92 hadeforestation: turned into farms, mines or towns
The worst year was 2016, when about 16 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 | 2 ha | 1 ha | 3 ha |
| 2002 | 1 ha | 1 ha | 2 ha |
| 2003 | under 1 ha | under 1 ha | under 1 ha |
| 2004 | 2 ha | under 1 ha | 2 ha |
| 2005 | under 1 ha | under 1 ha | 1 ha |
| 2006 | 2 ha | under 1 ha | 3 ha |
| 2007 | under 1 ha | under 1 ha | under 1 ha |
| 2008 | under 1 ha | under 1 ha | 1 ha |
| 2009 | 1 ha | 1 ha | 2 ha |
| 2010 | 2 ha | 1 ha | 4 ha |
| 2011 | under 1 ha | under 1 ha | 1 ha |
| 2012 | 2 ha | under 1 ha | 3 ha |
| 2013 | under 1 ha | under 1 ha | under 1 ha |
| 2014 | 3 ha | under 1 ha | 3 ha |
| 2015 | 4 ha | under 1 ha | 4 ha |
| 2016 | 15 ha | 1 ha | 16 ha |
| 2017 | 7 ha | under 1 ha | 7 ha |
| 2018 | 9 ha | under 1 ha | 9 ha |
| 2019 | 6 ha | under 1 ha | 7 ha |
| 2020 | 3 ha | under 1 ha | 4 ha |
| 2021 | 4 ha | under 1 ha | 4 ha |
| 2022 | 14 ha | under 1 ha | 14 ha |
| 2023 | 3 ha | under 1 ha | 3 ha |
| 2024 | 7 ha | 2 ha | 9 ha |
| 2025 | 3 ha | under 1 ha | 3 ha |
What is causing deforestation around Koga?
- Towns and roadscleared for good87% · 92 ha
- Loggingcan grow back1% · 1 ha
- Unknown causescause unknown12% · 13 ha
Also: farms, pasture and plantations.
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
- 1,640 ha
- Forest in 2020
- 1,540 ha
- Overall change
- −97 haless forest than in 2000
Comparing satellite maps from 2000 and 2020, the forest around Koga shrank from about 1,640 hectares to 1,540 hectares, a net loss of about 97 hectares (−5.9%). New forest grew on about 77 hectares, but 174 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
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Frequently asked
Questions about Koga
What is the air quality (AQI) in Koga right now?
The latest reading for Koga shows an AQI of 28 (Good), observed Nov 11, 11:00 local time via Open-Meteo / CAMS, corrected with 16 ground-station cities within 125 km, US EPA index. The main pollutant is PM2.5. Air quality is satisfactory for everyone.
Is it safe to exercise outside in Koga today?
At AQI 28 (Good): a good day to be active outside. Windows: open them to air the house. Masks: not needed. The reading changes through the day, so check again before a long run or ride.
What has the air quality in Koga been like this week?
Over the last 7 days, the CAMS air-quality model put Koga's daily AQI at 56 on average, from 26 on Nov 7 to an hourly peak of 147 on Nov 5. No day averaged above 100, the level where the air turns unhealthy for sensitive groups.
How much forest has the area around Koga lost since 2001?
Since 2001, the area within 10 km of Koga has lost about 106 hectares of forest (about 150 football pitches): 6.8% of the forest it had in 2000. Most of it (87%) was deforestation, forest cleared for good, mainly for towns and roads. Comparing satellite maps from 2000 and 2020, the forest around Koga shrank from about 1,640 hectares to 1,540 hectares, a net loss of about 97 hectares (−5.9%). New forest grew on about 77 hectares, but 174 hectares were lost.
What is the tree count in Koga?
Koga has an estimated 32,358 trees across the 12.57 km² measured — 10.3% tree cover, 20 percentage points short of the 30% tree-cover target set for this area.
How many more trees does Koga need?
Koga needs roughly 61,889 more trees to close a 20-point shortfall against its 30% tree-cover target — about 1,362 t of extra CO₂ absorbed per year once grown.
How are Koga's air quality and tree cover measured?
Air quality comes from ground monitoring stations via OpenAQ where one reports nearby, and otherwise, as here, from the Open-Meteo / CAMS model, which may differ from street-level monitors. 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 Otsutsumi; the tree count is an estimate derived from that cover.
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