Search

Among the most prevalent sources of biodiversity declines, Artificial Light At Night (ALAN) is an emerging threat to global biodiversity. Much knowledge has already been gained to reduce impacts. However, the spatial variation of ALAN effects on biodiversity in interaction with landscape composition remains little studied, though it is of the utmost importance to identify lightscapes most in need of action. Several studies have shown that, at local scale, tree cover can intensify positive or negative effects of ALAN on biodiversity, but none have – at landscape scale – studied a wider range of landscape compositions around lit sites. We hypothesized that the magnitude of ALAN effects will depend on landscape composition and species’ tolerance to light. Taking the case of insectivorous bats because of their varying sensitivity to ALAN, we investigated the species-specific activity response to ALAN. Bat activity was recorded along a gradient of light radiance. We ensured a large variability in landscape composition around 253 sampling sites. Among the 13 bat taxa studied, radiance decreased the activity of two groups of the slow-flying gleaner guild (Myotis and Plecotus spp.) and one species of the aerial-hawking guild (Pipistrellus pipistrellus), and increased the activity of two species of the aerial-hawking guild (Pipistrellus kuhlii and Pipistrellus pygmaeus). Among these five effects, the magnitude of four of them was driven by landscape composition. For five other species, ALAN effects were only detectable in particular landscape compositions, making the main effect of radiance undetectable without account for interactions with landscape. Specifically, effects were strongest in non-urban habitats, for both guilds. Results highlight the importance to prioritize ALAN reduction efforts in non-urban habitats, and how important is to account for landscape composition when studying ALAN effects on bats to avoid missing effects.

International audience; Artificial light at night (ALAN) is considered as a major threat to biodiversity, especially to nocturnal species, as it reduces availability, quality and functionality of habitats. However, its effects on the way species use landscape elements such as rivers are still largely understudied, especially the effect of crossing infrastructure lighting on bridges. These elements are nevertheless key commuting and foraging habitats in heavily urbanised landscapes for several taxa such as bats that are particularly affected by ALAN. We studied the effects of the illumination of facades and undersides of bridges on the relative abundance of pipistrelle bats, on their 3D distribution and their behavioural response (i.e. flight speed) close to bridges. We set-up an innovative approach based on a microphone-array to reconstruct positions and flight trajectories in 3D. We studied the effect of lighting on bats in the close proximity of six similar bridges, mostly differentiated by the presence or absence of lighting (3 lit and 3 unlit). All bridges cross the same waterway, within a uniformly and highly urbanized agglomeration (Toulouse, France). We found that bat activity was 1.7 times lower in lit sites. Bats tended to keep a larger distance, and to fly faster close to illuminated bridges. These results suggest that bridge lighting strongly reduces habitat availability and likely connectivity for bats. In that case, results call for switching off the illumination of such bridges crossing riverine ecosystems to preserve their functionality as habitats and corridors for bats.

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.© 2018 Elsevier B.V., We thank the Association Nationale Recherche Technologie and Auddice Environnment for funding. We deeply thank all the volunteer of the Vigie-Nature for data collection and identification, especially Mathieu Abouladze, Yoann Allanic, Avana Andriamboavonjy, Michel Bonnavenc, Jean Burger, Alix Cosquer, Cecile Edelist, Caroline Fromont, Andreas Goli, Anne-Laure Gourmand, Anne Guezou, Clement Heroguel, Arzvael Jeusset, Robin Julien, Marine Legrand, Julie Marmet, Pierre mathieu, Shankar Meyer, Lara Millon, Jean Pierre Moussu, Julien Penvern, Emmanuelle Porcher, Marie Agnes Rabillard, Isabelle Schmidt, Assaf Shwartz, Celine Teplisky, Anne Tessedre, William Travers, Pauline Van Laere, Alan Vergnes. The field work in Lille was realized within the project TRAMENOIRE funded by the Region Nord Pas de Calais and the Fondation for Research on Biodiversity (FRB) and coordinated by Baptiste Faure and Alexandre Haquart. We deeply thank Alexis Laforge, Anaelle Bissonet and Vanille Thuillier for their help in data collection and identification in Lille.

Light pollution is a major threat to biodiversity worldwide. There is a crucial need to elaborate artificial lighting recommendations to mitigate its impact on wildlife. In the present study, we investigated how streetlight spatial position and light trespass impacted the use of ecological corridors by transiting bats in anthropogenic landscapes. Through a paired, in situ experiment, we estimated how streetlight distance of impact and vertical and horizontal illuminance influenced the transiting activity of 6 species and 2 genera of bats. We selected 27 pairs composed of 1 lit site and 1 control unlit site in areas practicing either part-night or full-night lighting. We recorded bat activity at 0, 10, 25, 50 and 100 m, and measured vertical and horizontal light illuminance at the 5 distance steps (range = 0.1–30.2 lx). While streetlight attraction effect was mostly limited to a 10 m radius for Pipistrellus sp. and Nyctalus sp., streetlight avoidance was detected at up to 25 and 50 m for Myotis sp. and Eptesicus serotinus, respectively. Streetlight effects on Myotis sp. and Nyctalus sp. remained after lamps were turned-off. Illuminance had a negative effect on Myotis sp. below 1 lx, a mixed effect on E. serotinus, and a positive effect on the other species, although a peak of activity was observed between 1 and 5 lx for P. pipistrellus and N. leisleri. We recommend separating streetlights from ecological corridors by at least 50 m and avoiding vertical light trespass beyond 0.1 lx to ensure their use by light-sensitive bats.

Habitat suitability models (HSMs) have so far been used mainly to study broad-scale patterns of species distribution based on environmental variables; however, they can also be applied to address conservation needs at finer scales. In this study, we evaluated the feasibility of using HSMs based on presence-only data to predict bat foraging habitat suitability around maternity roosts using radio-tracking location data. We radio-marked 34 Rhinolophus ferrumequinum and 29 Myotis emarginatus from two mixed-species maternity roosts (21.5 km apart) in a Mediterranean landscape. We generated foraging habitat suitability maps for the two species and the two colonies incorporating 17 land cover variables as well as distance from the maternity roosts. We then compared the performance of four presence-only models: Mahalanobis distance, ENFA, MADIFA and MaxEnt. Our study found that all four models generated foraging habitat suitability maps that performed well at predicting the species-specific quality of foraging habitat based on the configuration of the landscape. Riparian vegetation, woodland and distance from roosts play a key role in foraging habitat selection around colonies both for R. ferrumequinum and M. emarginatus. MaxEnt was the model that best predicted suitable foraging habitats. These are also the best models at predicting foraging habitat suitability with relatively good performance around another colony maternity roost using independent radio-tracking locations. Because many bat species are threatened by foraging habitat loss, habitat suitability modeling offers a useful tool in defining appropriate conservation guidelines that protect foraging habitats around bat maternity roosts.

As light pollution is currently considered to be a major threat to biodiversity, different lighting management options are being explored to mitigate the impact of artificial lighting on wildlife. Although part-night lighting schemes have been adopted by many local authorities across Europe to reduce the carbon footprint and save energy, their effects on biodiversity are unknown. Through a paired, in situ experiment, we compared the activity levels of 8 bat species under unlit, part-night, and full-night lighting treatments in a rural area located 60 km south of Paris, France. We selected 36 study locations composed of 1 lit site and a paired unlit control site; 24 of these sites were located in areas subject to part-night lighting schemes, and 12 sites were in areas under standard, full-night lighting. There was significantly more activity on part-night lighting sites compared to full-night lighting sites for the late-emerging, light-sensitive Plecotus spp., and a similar pattern was observable for Myotis spp., although not significant. In contrast, part-night lighting did not influence the activity of early emerging bat species around streetlights, except for Pipistrellus pipistrellus for which there was significantly less activity on part-night lighting sites than on full-night lighting sites. Overall, no significant difference in activity between part- and full-night lighting sites were observed in 5 of the 8 species studied, suggesting that current part-night lighting schemes fail to encompass the range of activity of most bat species. We recommend that such schemes start earlier at night to effectively mitigate the adverse effects of artificial lighting on light-sensitive species, particularly along ecological corridors that are especially important to the persistence of biodiversity in urban landscapes.

International audience; The Natura 2000 network is the largest conservation effort in Europe. However, despite the known importance of conserving common and widespread biodiversity, criteria used to designate a Natura 2000 site are oriented toward rare and/or emblematic biodiversity. In this study, we took advantage of the fact that the management of Natura 2000 is just beginning to assess whether the five most common bat (Chiroptera) species and one genus in France exhibit a greater relative abundance within rather than outside Natura 2000 boundaries, and three bats communities index: total relative abundance, species richness, Community Habitat specialization index. We model the relative abundance of each taxa and indices using data from a nationwide volunteer-based acoustic survey. We found that three of the six taxa studied exhibit greater relative abundance within Natura 2000 sites (this increase is noteworthy for E. serotinus (× 2.1) and Myotis ssp. (× 3.6)). We also provide evidence that total relative abundance of bat activity and richness are globally higher in Natura 2000 sites (respectively + 24% and + 14%) and on average communities are more specialized within Natura 2000 sites. In addition, when the effect of Natura 2000 is adjusted to the main land use types, a significant positive effect of Natura 2000 remains for most metrics. The positive Natura 2000 effect appears relatively small compared to the main land use pressure: intensive agriculture and artificial light at night. However, Natura 2000 has a comparable sized effect as habitat widely recognized as having a positive impact on bats, such as streams.

Light pollution is a global change affecting a major proportion of global land surface. Although the impacts of Artificial Light At Night (ALAN) have been documented locally for many taxa, the extent of effect of ALAN at a landscape scale on biodiversity is unknown. We characterized the landscape-scale impacts of ALAN on 4 insectivorous bat species Pipistrellus pipistrellus, Pipistrellus kuhlii, Eptesicus serotinus, Nyctalus leisleri, and compared the extent of their effects to other major land-use pressures. We used a French national-scale monitoring program recording bat activity among 2-km car transect surveys, and extracted landscape characteristics around transects with satellite and land cover layers. For each species, we performed multi-model averaging at 4 landscape scales (from 200 to 1000 m buffers around transects) to compare the relative effects of the average radiance, the proportion of impervious surface and the proportion of intensive agriculture. For all species, ALAN had a stronger negative effect than impervious surface at the 4 landscape scales tested. This effect was weaker than the effect of intensive agriculture. The negative effect of ALAN was significant for P. pipistrellus, P. kuhlii and E. serotinus, but not for N. leisleri. The effect of impervious surface varied among species while intensive agriculture had a significant negative effect on the 4 species. Our results highlight the need to consider the impacts of ALAN on biodiversity in land-use planning and suggest that using only impervious surface as a proxy for urbanization may lead to underestimated impacts on biodiversity.

International audience