Accounting for artificial light impact on bat activity for a biodiversity-friendly urban planning

Light pollution constitutes a major threat to biodiversity by decreasing habitat quality and landscape connectivity for nocturnal species. While there is an increasing consideration of biodiversity in urban management policies, the impact of artificial light is poorly accounted for. This is in a large part due to the lack of quantitative information and relevant guidelines to limit its negative effects. Here we compared the potential of two sources of information on light pollution, remote sensing (nocturnal picture taken from the International Space Station ISS) and ground-based (location of streetlights) data, to measure its impact on bats. Our aims were to (i) evaluate how light pollution affected Pipistrellus pipistrellus activity at the city scale, (ii) determine which source of information was the most relevant to measure light pollution's effect and (iii) define a reproducible methodology applicable in land management to account for biodiversity in lighting planning. We used citizen science data to model the activity of P. pipistrellus, a species considered light tolerant, within three cities of France while accounting for artificial light through a variable based on either source of information. We showed that at the city scale, P. pipistrellus activity is negatively impacted by light pollution irrespective of the light variable used. This detrimental effect was better described by variables based on ISS pictures than on streetlights location. Our methodology can be easily reproduced and used in urban planning to help take the impact of light pollution into consideration and promote a biodiversity-friendly management of artificial light.