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Voigt, C. C., Scholl, J.M., Bauer, J. et al. (2020). Movement responses of common noctule bats to the illuminated urban landscape. Landscape Ecology, 35, 189–201.
Cities are a challenging habitat for obligate nocturnal mammals because of the ubiquitous use of artificial light at night (ALAN). How nocturnal animals move in an urban landscape, particularly in response to ALAN is largely unknown.
We studied the movement responses, foraging and commuting, of common noctules (Nyctalus noctula) to urban landscape features in general and ALAN in particular.
We equipped 20 bats with miniaturized GPS loggers in the Berlin metropolitan area and related spatial positions of bats to anthropogenic and natural landscape features and levels of ALAN.
Common noctules foraged close to ALAN only next to bodies of water or well vegetated areas, probably to exploit swarms of insects lured by street lights. In contrast, they avoided illuminated roads, irrespective of vegetation cover nearby. Predictive maps identified most of the metropolitan area as non-favoured by this species because of high levels of impervious surfaces and ALAN. Dark corridors were used by common noctules for commuting and thus likely improved the permeability of the city landscape.
We conclude that the spatial use of common noctules, previously considered to be more tolerant to light than other bats, is largely constrained by ALAN. Our study is the first individual-based GPS tracking study to show sensitive responses of nocturnal wildlife to light pollution. Approaches to protect urban biodiversity need to include ALAN to safeguard the larger network of dark habitats for bats and other nocturnal species in cities.
Sung, C. Y., & Kim, Y.-J. (2020). Analysis of the Status of Light Pollution and its Potential Effect on Ecosystem of the Deogyusan National Park. Korean Journal of Environment and Ecology, 34(1), 63–71.
Abstract: This study characterized the spatial and seasonal patterns of light pollution in the Deogyusan National Park and examined the potential effects of light pollution on ecosystems in the park using light intensities derived from VIIRS (Visible Infrared Imaging Radiometer Suite) DNB (Day and Night Band) nightlight images collected in January and August 2018. Results showed that the Muju Deogyusan resort had the greatest light intensity than other sources of light pollution in the park, and light intensity of the resort was much higher in January than in August, suggesting that artificial lights in ski slopes and facilities were the major source of light pollution in the park. An analysis of an urban-natural light pollution gradient along a neighboring urban area through the inside of the park indicated that light radiated from a light pollution source permeated for up to 1km into the adjacent area and contaminated the edge area of the park. Of the legally protected species whose distributions were reported in literature, four mammals (Martes flavigula, Mustela nivalis, Prionailurus bengalensis, Pteromys volans aluco), two birds (Falco subbuteo, Falco tinnunculus), and nine amphibians and reptiles (Onychodactylus koreanus, Hynobius leechii, Karsenia koreana, Rana dybowskii, Rana huanrenensis, Elaphe dione, Rhabdophis tigrinus, Gloydius ussuriensis, Gloydius saxatilis) inhabited light-polluted areas. Of those species inhabiting light-polluted areas, nocturnal species, such as Prionailurus bengalensis and Pteromys volans aluco, in particular, were vulnerable to light pollution. These results implied that protecting ecosystems from light pollution in national parks requires managing nighttime light in the parks and surrounding areas and making a plan to manage nighttime light pollution by taking into account ecological characteristics of wild animals in the parks.
Kyba, C. C. M., Conrad, J., & Shatwell, T. (2020). Lunar illuminated fraction is a poor proxy for moonlight exposure. Nat Ecol Evol, 4, 318–319.
Abstract: San-Jose et al. recently demonstrated that the colouration of barn owls impacts their hunting success under moonlit conditions, and therefore affects their reproductive success1. They found that near full-moon conditions, the youngest nestlings with white fathers were fed more and were likelier to survive than those with redder fathers. While the study is interesting, the percentage of the Moon that is illuminated (lunar illuminated fraction) is unfortunately a poor proxy for moonlight exposure. We suggest that lunar illluminated fraction should, in general, never be used in biological studies, as alternative variables such as horizontal illuminance better represent moonlight exposure, and therefore offer a greater chance of detecting the effects of moonlight. Here, we provide a brief explanation of how moonlight varies with season and time of night, and stress the need for greater collaboration between biologists and astronomers or physicists in such studies in the future.
Secondi, J., Davranche, A., Théry, M., Mondy, N., Lengagne, T., & Isaac, N. (2019). Assessing the effects of artificial light at night on biodiversity across latitude – Current knowledge gaps. Global Ecol Biogeogr, in press, geb.13037.
Exposure to artificial light at night (ALAN) is a risk factor for organisms. Considering the spread and increasing intensity of night brightness across the globe, and the key role of light at all biological levels, alterations of ecosystems are expected. Yet, we cannot predict the severity of the effects of ALAN in several biomes because little information is available outside the temperate zone. We reviewed current knowledge and identified traits that could be targeted to fill this knowledge gap in order to contribute to the elaboration of a biogeographical framework for the study of ALAN at the global scale.
Current and next decades.
We analysed the latitudinal variation in ALAN and focused on environmental factors that vary with latitude but that have been overlooked. We reviewed biological traits that exhibit latitudinal variation and depend on light and photoperiod and compiled information about the predicted changes in human demography and road networks across different world regions.
Cloud cover amplifies ALAN far away from urbanized areas. Because of the higher frequency of overcast sky nights, exposure effects may be stronger both at high latitudes and across a large fraction of the intertropical zone, although at different times of the year. Intertropical biomes host the largest fraction of global biodiversity. Although currently they are not the most exposed to ALAN, their human populations are growing, and urbanized areas and road networks are expanding. Hence, ALAN could have strong ecological consequences, with cloud cover as an aggravating factor.
Knowledge gaps currently limit our ability to predict the effects of ALAN in different biomes. Therefore, it will be important to start investigating the consequences of this novel environmental factor across the globe, in order to develop a relevant theoretical framework.
Maggi, E., Bongiorni, L., Fontanini, D., Capocchi, A., Dal Bello, M., Giacomelli, A., et al. (2019). Artificial light at night erases positive interactions across trophic levels. Funct Ecol, in press, 1365–2435.13485.
Abstract: Artificial light at night (ALAN) is one of the most recently recognized sources of anthropogenic disturbance, with potentially severe effects on biological systems that are still to be fully explored. Among marine ecosystems, high shore habitats are those more likely to be impacted by ALAN, due to a more intense exposition to outdoor nocturnal lightings (mostly from lamps along coastal streets and promenades, or within harbors, ports and marinas).
2.By performing in situ nocturnal manipulations of a direct source of white LED light and presence of herbivores in a Mediterranean high‐shore habitat, we assessed the interactive effects of light pollution and grazing on two key functional components of the epilithic microbial community (the cyanobacteria, as the main photoautotrophic component, and the other bacteria, mainly dominated by heterotrophs) developing on rocky shores.
3.Results showed an unexpected increase in the diversity of epilithic bacterial biofilm at unlit sites in the presence of grazers, that was more evident on the other (mainly heterotrophic) bacterial component, when giving weight to more abundant families. This effect was likely related to the mechanical removal of dead cells through the grazing activity of consumers. ALAN significantly modified this scenario, by reducing the density of grazers and thus erasing their effects on bacteria, and by increasing the diversity of more abundant cyanobacterial families.
4.Overall, direct and indirect effects on ALAN resulted in a significant increase in the diversity of the photoautotrophic component and a decrease in the heterotrophic one, likely affecting key ecosystem functions acting on rocky shore habitats.
5.ALAN may represent a threat for natural systems through the annihilation of positive interactions across trophic levels, potentially impairing the relationship between biodiversity and functioning of ecosystems and interacting with other global and local stressors currently impinging on coastal areas.