Impacts de la pollution lumineuse et de ses mesures de réductions sur les dynamiques spatiotemporelles des chiroptères en France

Light pollution induced by the widespread use of nighttime artificial lighting is a global change affecting substantial part of terrestrial and marine ecosystems. As a result, major concerns have been raised about its hidden impacts on biodiversity and ecosystem functioning. Light pollution has major impacts on the circadian and seasonal cycles of organisms, and on their movements and spatial distributions. As a whole, light pollution likely disrupts the spatiotemporal dynamics of biological communities and ecosystems. In this context, the aim of this PhD was to characterize the impacts of nighttime artificial lighting on bat activity (order: chiroptera) at multiple spatial scales in order to propose reduction measures that can effectively limit the adverse impacts of light pollution on biodiversity. We used bats as model species as they are nocturnal and directly exposed to light pollution and they are considered to be good indicators of the response of biodiversity to anthropogenic pressure.We first intended to characterize the extent of effect of light pollution at a landscape scale relative to major land-use pressures that are threatening biodiversity worldwide. Using a French national-scale citizen science database, we found that landscape-scale level of light pollution negatively affected common bat species, and that this effect was significantly stronger than the effect of impervious surfaces but weaker than the effect of intensive agriculture. This highlighted the crucial need to account for outdoor lighting in land-use planning in order to restore darkness in human-inhabited landscapes.Thus, through an in situ experiment, we investigated whether i) restoring darkness in a landscape for a part of the night through part-night lighting schemes, or ii) restraining the spatial extent of lighting at the vicinity of natural elements were effective options to enhance dark ecological corridors in human-inhabited landscapes. We found that part-night lighting schemes were unlikely to effectively mitigate the impacts of artificial lighting on light-sensitive species. However, we revealed that streetlights should be separated from ecological corridors by at least 50 m, and that the light trespass should be lower than 0.1 lux to allow their effective use by light-sensitive species.Overall, this PhD thesis revealed the major importance of addressing light pollution issues at multiple spatial scales to characterize its impacts on biodiversity. It also exposed the crucial importance of integrating outdoor lighting in land-use planning strategies and proposed to implement ecological criteria in future European standards for outdoor lighting.La pollution lumineuse, induite par l’utilisation massive d’éclairage artificiel la nuit, est un changement global qui affecte une partie importante des écosystèmes terrestres et marins, et qui soulève de nombreuses inquiétudes quant à son influence sur la biodiversité et le fonctionnement des écosystèmes. En effet, la pollution lumineuse induit de nombreux impacts sur les rythmes circadiens et saisonniers des organismes, et affecte leurs mouvements et leurs distributions spatiales. L’accumulation de ces impacts dans le temps et dans l’espace sur les différentes espèces peut ainsi entrainer des perturbations en cascade sur les dynamiques spatiotemporelles des communautés et sur les écosystèmes.Dans ce contexte, l’objectif de cette thèse est de caractériser les impacts de l’éclairage artificiel sur les activités de chauves-souris (ordre: chiroptère) à de multiples échelles spatiales afin d’élaborer des mesures de gestion de l’éclairage public qui limitent ses impacts négatifs sur la biodiversité. Nous avons utilisé les chauves-souris comme modèle d’étude car elles sont nocturnes et directement exposées à la pollution lumineuse, et sont considérées comme des espèces bio indicatrices de la réponse des espèces aux pressions anthropiques.Dans un premier temps, nous avons caractérisé l’impact relatif de la pollution lumineuse à l’échelle du paysage par rapport aux autres pressions de changements d’usage des sols en utilisant une base de données nationale de sciences participatives. Nous avons trouvé que la pollution lumineuse avait un impact négatif sur l’activité et la probabilité de présence des espèces de chiroptères les plus communes en France, et que cet impact était significativement plus fort que celui de l’artificialisation des sols, mais moins important que celui de l’agriculture intensive. Ces résultats confirment l’importance de prendre en compte l’éclairage public dans les stratégies d’aménagement du territoire pour restaurer efficacement de l’obscurité dans les paysages anthropisés.Ainsi, nous avons élaboré une expérience in situ pour déterminer si i) restaurer de l’obscurité dans le temps en éteignant les lampadaires pour une partie de la nuit (extinction nocturne), ou ii) limiter l’étendue spatiale de l’éclairage à proximité d’éléments naturels pouvaient être des mesures efficaces pour créer des zones corridors et des zones de refuges obscurs dans les paysages anthropisés. Nos résultats ont montré que les mesures actuelles d’extinction ne limitaient pas efficacement l’impact de l’éclairage sur les espèces de chiroptères sensibles à la lumière. Par contre, nous avons déterminé que les lampadaires devraient être séparés d’au moins 50 m des corridors écologiques, et que l’intrusion de lumière dans la végétation autour des zones éclairées ne devrait pas dépasser 0.1 lux pour permettre l’utilisation de ces espaces par les espèces sensibles à la lumière.En conclusion, cette thèse a mis en lumière l’importance de traiter la question de la pollution lumineuse à de multiples échelles spatiales pour bien caractériser ses impacts sur la biodiversité. Elle a par ailleurs permis de souligner l’importance de la prise en compte de cette pollution dans l’aménagement du territoire, et de proposer des critères écologiques qui pourraient être intégrés dans les futur normes et standards européens pour l’éclairage public

Evidence for distance and illuminance thresholds in the effects of artificial lighting on bat activity

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Bats seek refuge in cluttered environment when exposed to white and red lights at night

International audienceBackground: Artificial light at night is recognized as an increasing threat to biodiversity. However, information on the way highly mobile taxa such as bats spatially respond to light is limited. Following the hypothesis of a behavioural adaptation to the perceived risks of predation, we hypothesised that bats should avoid lit areas by shifting their flight route to less exposed conditions. Methods: Using 3D acoustic localization at four experimentally illuminated sites, we studied how the distance to streetlights emitting white and red light affected the Probability of bats Flying Inside the Forest (PFIF) versus along the forest edge. Results: We show that open-, edge-, and narrow-space foraging bats strongly change flight patterns by increasing PFIF when getting closer to white and red streetlights placed in the forest edge. These behavioural changes occurred mainly on the streetlight side where light was directed. Conclusions: The results show that bats cope with light exposure by actively seeking refuge in cluttered environment, potentially due to involved predation risks. This is a clear indication that bats make use of landscape structures when reacting to light, and shows the potential of vegetation and streetlight orientation in mitigating effects of light. The study nevertheless calls for preserving darkness as the most efficient way

Bats seek refuge in cluttered environment when exposed to white and red lights at night

Background: Artificial light at night is recognized as an increasing threat to biodiversity. However, information on the way highly mobile taxa such as bats spatially respond to light is limited. Following the hypothesis of a behavioural adaptation to the perceived risks of predation, we hypothesised that bats should avoid lit areas by shifting their flight route to less exposed conditions. Methods: Using 3D acoustic localization at four experimentally illuminated sites, we studied how the distance to streetlights emitting white and red light affected the Probability of bats Flying Inside the Forest (PFIF) versus along the forest edge. Results: We show that open-, edge-, and narrow-space foraging bats strongly change flight patterns by increasing PFIF when getting closer to white and red streetlights placed in the forest edge. These behavioural changes occurred mainly on the streetlight side where light was directed. Conclusions: The results show that bats cope with light exposure by actively seeking refuge in cluttered environment, potentially due to involved predation risks. This is a clear indication that bats make use of landscape structures when reacting to light, and shows the potential of vegetation and streetlight orientation in mitigating effects of light. The study nevertheless calls for preserving darkness as the most efficient way

Landscape composition drives the impacts of artificial light at night on insectivorous bats

International audienceAmong 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 haveat landscape scalestudied 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 aerialhawking 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

Artificial light may change flight patterns of bats near bridges along urban waterways

International audienceArtificial 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

Impact de l’éclairage artificiel sur l’usage des continuités écologiques par les chiroptères

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Forêts françaises en crise : nature, climat, société. Analyse et propositions des ONG de conservation de la nature

International audienceThe six conservation NGOs that wrote this article present their arguments for an evolution of the French forest policy. Their arguments are based on 5 main principles for the management of forest commons, i.e. 1) ensure a multifunctional management valuing all the ecological services of forests, 2) place biodiversity at the heart of forest policies to adapt management more easily, 3) be more aware of societal expectations in order tobetter meet them, 4) enable forests and foresters to fully respond to the unprecedented challenges of the climate crisis, and 5) integrate forests into land planning as a green infrastructure of the economy. Then, the six NGOs recommend a general political orientation basing any forestry policy on the constitutional environmental charter of 2004, and they propose 21 structural or operational measures.Les six ONG de conservation de la nature auteures de cet article proposent leur argumentaire pour une évolution de la politique forestière nationale. Celui-ci est fondé suivant cinq grands principes de gestion du bien commun que sont les forêts : 1. Assurer une gestion multifonctionnelle valorisant tous les services écologiques des forêts ; 2. Mettre la biodiversité au coeur de la politique forestière pour faciliter l’adaptation de la gestion ; 3. Accroître l’écoute des attentes de la société, pour mieux y répondre ; 4. Mettre forêts et forestiers en capacité de répondre pleinement aux enjeux inédits de la crise climatique ; 5. Insérer les forêts dans l’aménagement du territoire comme infrastructure verte de l’économie. Ensuite, les six ONG recommandent une orientation politique générale consistant à fonder toute politique forestière sur la charte constitutionnelle de l’environnement de 2004 et proposent 21 mesures structurelles ou opérationnelles