Landscape light pollution interacts with habitat loss and fragmentation to affect insect populations

Light pollution is a near inseparable feature of human-altered landscapes and is a potential contributing factor to global insect declines. However, despite the wide recognition of the lethal effects of lights on insects, studies addressing its effects on populations are scarce. We relied on a combination of ecological niche modeling, geographical information systems, and interviews on local ecological knowledge to assess the synergistic effects of landscape light pollution and habitat loss and fragmentation on populations of the Chocó golden scarab Chrysina argenteola. Sightings of C. argenteola by locals revealed individuals are scarcer in areas with reduced forest cover and rely on inter-patch dispersal to cope with habitat fragmentation, where they were constantly attracted to urban lights. Increasingly lit landscapes saw more individuals attracted to lights, but the opposite was true in areas with little remaining forest cover. We suggest this pattern arises as landscape light pollution intercepts individuals during inter-patch dispersal. This hinders habitat connectivity, potentially disrupting meta-population dynamics, being populations inhabiting areas with scarce fragmented habitat more vulnerable to this process. We, thus, show light pollution may act in synergy with habitat loss and fragmentation to affect insect populations at the landscape scale.