Dual forces at play: how artificial light and canopy cover affect firefly populations in an urban park

Artificial lights at night (ALAN) is a growing phenomenon that poses a significant threat to fireflies, which depend on natural darkness for bioluminescent communication. Yet, firefly populations persist near brightly lit urban areas, suggesting that certain environmental features may buffer the impact of ALAN. This study investigates how firefly populations respond to artificial lighting and whether canopy cover supports higher firefly occurrence in urban parks. We conducted field surveys at Bukit Kiara, an urban park in Kuala Lumpur, by recording firefly occurrences and measuring canopy cover, streetlight density and distance to the nearest streetlight. Using a negative binomial generalised mixed model (GLMM), we found that each additional streetlight was associated with a 36.7% reduction in expected firefly count, while a moderate positive correlation was observed between firefly occurrences and distance from streetlights. Conversely, the expected firefly count increased by 75.1% for every 18.7% increase in canopy cover. These findings suggest that canopy cover plays a key role in mediating the impact of artificial light on fireflies, potentially by providing localised shading that maintains low ambient light conditions. Urban park strategies that prioritise tree retention and connectivity of canopy cover may, therefore, support firefly persistence in light-polluted areas, though future research should account for species-specific responses and additional microhabitat and environmental variables.