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Local ecological knowledge reveals combined landscape effects of light pollution, habitat loss, and fragmentation on insect populations

Abstract:

Recent reports of drastic declines in insect populations have raised global concerns about their conservation. Light pollution is a near inseparable feature of human-altered landscapes and is a potential contributing factor to insect declines. However, despite the wide recognition of the deleterious effects of lights on insects, whether these effects scale up to impact insect populations remains unclear. Here, 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 had more individuals attracted to lights, but the opposite was true in areas with less than 4 km2 of remaining forest cover. We suggest this pattern arises as landscape light pollution intercepts individuals during inter-patch dispersal. This hinders habitat connectivity, potentially disrupting metapopulation dynamics, being populations inhabiting areas with scarce fragmented habitat more vulnerable to this process. We show light pollution acts in combination with habitat loss and fragmentation in detriment of insect populations at the landscape scale.