Citizen science illuminates the nature of city lights

Abstract The image of Earth at night from space, with its constellations of cities, has become iconic. However, our understanding of the source and scale of artificial light emissions is still in the dark, hampering urban environmental protection efforts. In 2021, our citizen scientists used the Nachtlichter app to count and classify 234,044 light sources across a 22-km 2 area, primarily in Germany. We show that such a dataset can be used to translate space-based radiance observations to the more understandable unit of installed lights per km 2 on the ground. We find that in German city centers, more total light sources are used for advertising and aesthetic purposes than for street lighting. Furthermore, we estimate that 78 ± 3 million individual light sources remain illuminated at midnight across Germany, highlighting great potential for mitigation. These findings not only offer direct knowledge for artificial light research but also serve as a practical resource for policymakers to mitigate urban light pollution.

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Publication Details

Journal
Nature Cities
Published
2025-06-16
DOI
https://doi.org/10.1038/s44284-025-00239-5
Citations
7
Primary Topic
Impact of Light on Environment and Health
Type
article
Field-Weighted Citation Impact
7.74

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article

Citizen science illuminates the nature of city lights

G. Anton, Tamara Rom, Johannes Schultz, M. Langejahn et al.
7 citations
Nature Cities
Impact of Light on Environment and Health
7.74
article

Citizen science illuminates the nature of city lights

G. Anton, Tamara Rom, Johannes Schultz, M. Langejahn, Reinhart Binder, Arne Dröge-Rothaar, Nona Schulte-Römer, A. Hänel, Maria Zschorn, David Gruber, Melanie Brauchler, Andrea Gokus, Sebastian Falkner, Christopher C. M. Kyba, Gilbert A. Esquerdo, J. Veh, Daniel Fischer, Andreas Ruby, Maximilian Blaschke, Andreas Rienow, Jacqueline Degen, Yiğit Öner Altıntaş, Helga U. Kuechly, Janina Mattern, John C. Barentine, Georg Sulzer, Henning von Brandis, Isabell Charis Wuthenow, Nathalie Küppers, Normän Naboulsi, Petra Bilela, René Curwy, Steffen Liese, Thomas Kunzemann, Vita Tičinović, Benno Gillen, Bettine von Heereman, Brita Kuechly, Burhan Altıntaş, Achim Tegeler, Daniele Dell’Osbel, Florian Distelrath, Frank Vohla, Aleksander Marz, Hatice Altıntaş, Irina von Maravić, Jonas Schreibweis, Kilian Modersitzki, Peter Stumpf, Russell Kyba, Anna Marie Kyba, Team Nachtlichter, Axel Schwiesow, Anja Glinka, Lena Klein, Eva Constanze Weiß, Friedrich Heine, Katharina Leiter, Marijana Pavić, Cormac McNally, Sabine Frank, C. A. Brock, Jacob Koglin, Sicco Bauer, Georgia MacMillan, Maximilian Köcher, M. Leipold
article en
7 citations

Abstract

Abstract The image of Earth at night from space, with its constellations of cities, has become iconic. However, our understanding of the source and scale of artificial light emissions is still in the dark, hampering urban environmental protection efforts. In 2021, our citizen scientists used the Nachtlichter app to count and classify 234,044 light sources across a 22-km 2 area, primarily in Germany. We show that such a dataset can be used to translate space-based radiance observations to the more understandable unit of installed lights per km 2 on the ground. We find that in German city centers, more total light sources are used for advertising and aesthetic purposes than for street lighting. Furthermore, we estimate that 78 ± 3 million individual light sources remain illuminated at midnight across Germany, highlighting great potential for mitigation. These findings not only offer direct knowledge for artificial light research but also serve as a practical resource for policymakers to mitigate urban light pollution.

Nature CitiesVol. 2(6)
Helmholtz Centre for Environmental Research (DE), Hasso Plattner Institute (DE), Leipzig University of Applied Sciences (DE), Ollscoil na Gaillimhe – University of Galway (IE), Fulda University of Applied Sciences (DE), University of Erfurt (DE), Washington University in St. Louis (US), University of Würzburg (DE), Kütahya Dumlupınar Üniversitesi (TR), Humboldt-Universität zu Berlin (DE), European Organisation for the Exploitation of Meteorological Satellites (DE), Universitätsklinikum Erlangen (DE), Ospedale di Bolzano (IT), Ministerio de Desarrollo Agropecuario (PA), Thüringer Aufbaubank (DE), Adidas (Germany) (DE), University of Applied Sciences Erfurt (DE), Groundwater Center (DE), Link Consulting (PT), BDH-Klinik Hessisch Oldendorf (DE), Film Independent (US), Center for Astrophysics Harvard & Smithsonian (US), Bochum University of Applied Sciences (DE), Theologische Fakultät Fulda (DE), Comprehensive Cancer Center Erlangen (DE), GFZ Helmholtz Centre for Geosciences (DE), Klinikum Leverkusen (DE), Oldham Council (GB), Technical University of Munich (DE), Bayer (Germany) (DE), Universität Trier (DE), Ruhr University Bochum (DE), University of Split (HR)
Bundesministerium für Bildung und Forschung
Openalex Percentile: Top 2%
Impact of Light on Environment and Health
7.74
DOIOpen Access PDFOpenAlex
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