Artificial light at night may decrease predation risk for terrestrial insects

Current evidence in support of insect-friendly lighting practices

Anthropogenic light pollution is an emerging threat to natural ecosystems with myriad effects on insects in particular. Insect conservationists are increasingly interested in mitigating this driver of insect declines via sustainable lighting practices. Current recommendations often follow the five principles for responsible outdoor lighting developed by DarkSky International, a nonprofit organization founded by astronomers. While these principles unquestionably increase star visibility, their ecological costs and benefits remain relatively unexplored. Herein, we review recent research into the effects of each principle on insect fitness broadly defined. Most studies test the efficacy of spectral tuning, followed by dimming, although both mitigation methods seem generally ineffective in practice. In contrast, both shielding and motion detectors show promise as mitigation methods but remain remarkably understudied. Nonetheless, a preponderance of evidence now demonstrates that removing unnecessary light sources from natural habitats can reverse their varied impacts on diverse insect taxa and greatly benefit insect conservation.

A framework for untangling the consequences of artificial light at night on species interactions

Although much evidence exists showing organismal consequences from artificial light at night (ALAN), large knowledge gaps remain regarding ALAN affecting species interactions. Species interactions occur via shared spatio-temporal niches among species, which may be determined by natural light levels. We review how ALAN is altering these spatio-temporal niches through expanding twilight or full Moon conditions and constricting nocturnal conditions as well as creating patches of bright and dark. We review literature from a database to determine if ALAN is affecting species interactions via spatio-temporal dynamics. The literature indicates a growing interest in ALAN and species interactions: 58% of the studies we analysed have been published since 2020. Seventy-five of 79 studies found ALAN altered species interactions. Enhancements and reductions of species interactions were equally documented. Many studies revealed ALAN affecting species interactions spatially, but few revealed temporal alterations. There are biases regarding species interactions and ALAN-most studies investigated predator-prey interactions with vertebrates as predators and invertebrates as prey. Following this literature review, we suggest avenues, such as remote sensing and animal tracking, that can guide future research on the consequences of ALAN on species interactions across spatial and temporal axes. This article is part of the theme issue 'Light pollution in complex ecological systems'.