Linking urban tree coverage with PM10 and PM2.5 pollution concentration in Malaysia

¹ Faculty of Civil Engineering & Technology, Universiti Malaysia Perlis, Jejawi, 02600 Arau, Perlis, Malaysia
² Sustainable Environment Research Group (SERG), Centre of Excellence Geopolymer and Green Technology (CEGeoGTech), Universiti Malaysia Perlis, Jejawi, 02600 Arau, Perlis, Malaysia

^* Corresponding author: norazrin@unimap.edu.my

Abstract

Urban tree coverage helps reduce air pollution by filtering particulate matter (PM₁₀, PM_2.5). This study investigates the relationship between tree coverage and PM levels in five Malaysian cities: Penang, Kuala Lumpur, Johor Bahru, Kuching, and Labuan. Landsat 8 Collection 2 Level 2 imagery (30 m resolution) from the United States Geological Survey (USGS), acquired between 2022 and 2023, was processed in ArcMap with atmospheric correction. The Normalised Difference Vegetation Index (NDVI) was used to measure tree cover, and areas with NDVI values greater than 0.3 were considered vegetated. The earth observation data (satellite remote sensing), with a temporal revisit cycle of 16 days, allowed for consistent annual estimates of urban tree cover. Air quality data from the Department of Environment’s (DOE) monitoring stations in Cheras, Minden, Larkin, Kuching, and Labuan was analysed using Pearson's correlation in SPSS. Among the cities, Kuching had the highest tree coverage and lowest PM levels, while Kuala Lumpur had the lowest coverage and highest PM concentrations. A negative correlation was observed between tree coverage and PM levels, particularly PM_2.5, indicating that greener cities tend to have better air quality. These findings emphasise the need to promote urban greenery as a strategy for air pollution mitigation, urban sustainability, climate resilience, and air quality management in Malaysia.