Ecological implications of electric lighting altered by weather and sky conditions in suburban environments

82 ALAN 2025 Ecological implications of electric lighting altered by weather and sky conditions in suburban environments Theme: Technology and Design Seren Dincel,1,* Arne Lowden,2 1School of Architecture, KTH Royal Institute of Technology, Stockholm, Sweden 2Department of Psychology, Stockholm University, Stockholm, Sweden [email protected], a[email protected] *presenting author Introduction Areas where electric lighting systems are installed and their far-reaching effects increasingly intersect with where wildlife communities inhabit. Recent investigations point out towards technological adaptations, e.g., changing illumination levels, spectral composition (Jägerbrand & Spoelstra, 2023; Longcore, 2023) and optical distribution of light sources (Abelson et al., 2023), to enable the reduction of ecological effects while keeping lighting infrastructures for affording pedestrian visual functions. Ecological studies conducted in lab environments may either conceal responses produced in a real-world context (Aulsebrook et al., 2022) or neglect linkages between animal physiology, life history and sensory stimulation (Dominoni et al., 2020). Temporal atmospheric shifts could alter electric lighting effects, thus affecting the magnitude of sensory pollutants in masking or deceiving natural cues from moonlight animals need to moderate their behaviours. Illumination from moonlight varies between 0.001 lux on a clear starry sky and a full moon at 0.1-0.3 lux (Rich & Longcore, 2006), where even very low illuminances of 0.001 demonstrated movement changes, distressing breeding and singing behaviours (Aulsebrook et al., 2022). Other environmental factors that transiently affect light environments are derived from cloud cover, which has been shown to reproduce light pollution (Kyba et al., 2011), and when combined with the albedo of snow that has reflectance up to 95% (Demers, 2015) indicated two times higher illuminance of full moon under overcast skies (Jechow & Holker, 2019). Field investigation and methods We conducted fieldworks on a pedestrian pathway traversing an urban forest of Uppsala, Sweden as part of the NorDark research project to study the produced effects of diverse lighting scenarios. The two light sources included in the study were an LED lamp of 3000K with a light output of 2100 lm (LED A) and a prototypical LED of 2300K, 2100 lm (LED B), designed by using clear and amber-coloured optic lenses. LED A and LED B installations were measured at the fully operational level (100%); additionally, LED B was measured under dimmed conditions at 10% level. Illuminances were recorded at horizontal and vertical planes with hand-held measurement devices (GL Spectis regular probe and Salli diffusor) on the points defined by a grid stretching from the path every 4 meters up to 20 meters into the woods between two lamp posts at the testbed (Dincel, 2023) between November 2022 and January 2025. Six scenarios included in our study were recorded in overcast skies after dark with and without snow coverage on site. Results The lowest average horizontal illuminance was 0.01 lux when LED B operated at 10% level without snow starting from 12 to 20 meters into the woods. The highest average horizontal illuminance was 56.97 lux on the path when LED B fully operated under snow cover (Fig. 1). Additionally, results from the statistical analysis of horizontal values indicated that the effect 83 ALAN 2025 of each light source (A and B), snow coverage (snow and no-snow) and illumination level (100% and 10%) are significant (P>0.001) when logged lux values were used in calculations. Fig. 1: The average horizontal illuminances estimated on the grid section crossing two lamp posts at the testbed illustrating six scenarios from two light sources (A and B) and two light settings (100% and 10%). Conclusions Fluctuating real-world conditions can inform adaptive lighting technologies more realistically in accommodating species' habitats. Provisional changes, e.g., weather and sky, could become the basis for shifting between lighting scenarios via lowered light output and spectral alteration given the significant effects electric lighting might produce on local ecology. Additionally, lowering light levels can save energy, while simultaneously modifying spectral composition by reducing short-wavelength content might counter energy efficiency and present visual challenges for pedestrians. Different metrics can be prioritised (Fotios, 2019) based on the specific habitat, visual demands and temporal conditions. Acknowledgments This study is supported by NordForsk (Grant #105116) and the Swedish Energy Agency (Grant #P2021-00024). References Abelson, E., Seymoure, B., Jechow, A., Perkin, E., Moon, H., Hölker, F., White, J., & Longcore, T. (2023). Ecological Aspects and Measurement of Anthropogenic Light at Night. SSRN. https://doi.org/https://dx.doi.org/10.2139/ssrn.4353905 Aulsebrook, A. E., Jechow, A., Krop-Benesch, A., Kyba, C. C. M., Longcore, T., Perkin, E. K., & van Grunsven, R. H. A. (2022). Nocturnal lighting in animal research should be replicable and reflect relevant ecological conditions. Biol Lett,18(3), 20220035. https://doi.org/https://doi.org/10.1098/rsbl.2022.0035 Demers, C. (2015). Lighting diversity and adaptability to climate: a quantitative and qualitative urban survey methodology PLDC 5th Global Lighting Design Convention, Rome. Dincel, S. (2023). Technical Report, Part I: NorDark Testbed, Uppsala/SE Light Level Measurements, Methods and Values. K. R. I. o. Technology. https://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-329469 Dominoni, D. M., Halfwerk, W., Baird, E., Buxton, R. T., Fernandez-Juricic, E., Fristrup, K. M., McKenna, M. F., Mennitt, D. J., Perkin, E. K., Seymoure, B. M., Stoner, D. C., Tennessen, J. B., Toth, C. A., Tyrrell, L. P., Wilson, A., Francis, C. D., Carter, N. H., & Barber, J. R. (2020). Why conservation biology can benefit from sensory ecology. Nat Ecol Evol,4(4), 502-511. https://doi.org/10.1038/s41559-020-1135-4 Fotios, S. (2019). 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