Abstract

Background: Lichens are widely recognized as bioindicators of air pollution due to their sensitivity to atmospheric contaminants. However, species-level responses in Southeast Asia, particularly in Malaysia, remain underreported. This study investigates the relationship between lichen diversity and ambient air pollution across three land-use types in Peninsular Malaysia: urban (Shah Alam), suburban (Jerantut), and rural (Kuala Selangor). Results: Lichen samples were collected from 10 Mimusops elengi trees per site using 20 cm × 30 cm quadrats and identified morphologically and chemically. Air quality data (PM10, PM2∙5, NO2, SO2, O3, and CO) from 2023 were obtained from the Department of Environment Malaysia. Urban sites exhibited the highest pollution levels, while suburban areas had the lowest. Interestingly, the rural site showed moderately high pollution levels, possibly due to local sources such as open burning, nearby markets and coastal aerosol. Correspondingly, the suburban site recorded the highest lichen diversity and index of atmospheric purity (IAP = 37.83). A strong negative correlation between IAP and PM10 (r = –0.957) underscores the impact of fine particulates on lichen community structure. Environmental variables such as bark pH, temperature, and humidity also influenced species distribution but played a secondary role compared to air pollutants. Conclusions: This study provides evidence that epiphytic lichen communities respond clearly to varying levels of atmospheric pollution, supporting their use as low-cost, effective bioindicators in tropical regions. While lichen sampling was conducted as a one-time event, the results remain ecologically meaningful due to lichens’ long-term integration of environmental conditions. These findings offer a valuable baseline for future ecological assessments and contribute to the development of long-term lichen-based air quality monitoring frameworks in Malaysia.