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"We count lights because the night counts."

Citizen science campaigns map artificial light sources to better understand nighttime satellite imagery.


In recent years, public awareness of light pollution and the health and environmental effects of artificial light has grown – as have Earth’s light emissions according to satellite imagery. What satellite images don't show is what kind of light sources on the ground, and how many there are. To close this data gap, a team of citizen scientists and researchers from the Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences have developed the ‘Nachtlicht’ (NightLights) app. The web application allows artificial light sources on the ground to be systematically recorded at large scale for the first time. In September and October 2021, the app will be used by numerous citizen science measurement campaigns. Preparations for Nachtlicht campaigns are underway in Bochum, Dresden, Erlangen, Fulda, Würzburg, Potsdam and in the community of Preußisch-Oldendorf near Detmold. Abroad, groups in Spain, Ireland, Canada and Italy are also participating in the citizen science project.

The citizen scientist and researcher team invites everyone who is interested to participate in generating scientific data. Maria Zschorn and Sicco Bauer from the Dresden campaign organizing team have already tried out the app. "The nice thing is that counting with the app feels a bit like a game, but at the same time advances science," said Maria Zschorn, who is doing her PhD on light pollution and landscape planning at TU-Dresden. Sicco Bauer has been part of the team that developed the app as a citizen scientist volunteer since 2019, and says "it's a great feeling to use the app for the first time, after almost two years of joint work".

Understanding light emissions to illuminate more sustainably

The web app allows participants to record a wide variety of light sources on public streets and squares, as well as their brightness, color and emission direction - from street lamps and shop window lighting to neon signs and garden lights. This data does not yet exist. While information about public lighting is often in public databases, comprehensive data on private lights has never been produced in the past. "Street lighting only accounts for part of light emissions from cities," explains Dr. Christopher Kyba of GFZ. The physicist has been researching the extent and changes in artificial lighting at night for years using remote sensing techniques such as aerial photography and satellite imagery. "Satellite data documents radiance, how brightly different locations emit light towards space," Kyba explains. "But they don't tell us exactly what's shining on the ground." Kyba led the development of the app in order to help scientists understand the light sources on the ground, but says the data will also providing a scientific basis for a transition to more sustainable lighting in the future.

The citizen science effort has also had interesting side effects. "Even as we were developing the app, we found that counting lights had a mind-opening and awareness-raising effect on us. Many of us were amazed at how many different lights shine out there, in different colors and shapes," reports Dr. Nona Schulte-Römer, who provides social science support for the project at GFZ. "Our measurement campaigns in Dresden and other cities allow us to talk with citizen scientists about where and when they might appreciate artificial lighting, or could even do without it."  

The question of which light sources illuminate the night and for what purpose is increasingly being recognized as a sustainability issue, beyond only energy savings. Sabine Frank, the night protection officer of the district of Fulda and the Rhön Biosphere Reserve explains: "outdoor lighting is too often poorly installed in inappropriate light colors and quantities. Instead of shining only where light is needed, the light shines in all directions, dazzles people, and disturbs the day-night rhythm of animal and plant life within a radius of several kilometers". Frank was also actively involved in the app development, and is co-directing the Nachtlicht campaign in the “star city” of Fulda in early September

Night Lights Campaigns - coming soon to your neighborhood!

In September and October, teams of citizen scientists will fan out in their cities and towns after dark and use the Nachtlichter app to record all the light sources they find along pre-defined streets in selected areas. The researchers say that anyone who wants to join in is welcome at any time, provided they first complete a short online app training course (see link below) that ensures data quality. Throughout Germany, kickoff events are planned to launch the campaigns. People who would like to participate in the research but do not live in one of the measurement areas can still take part by defining their own transects. More information can be found on the project website nachtlicht-buehne.de/nachtlichter.

After the campaigns, GFZ scientists will evaluate the collected data, compare it with satellite data of the measuring areas and publish the data, findings and experiences of the campaigns in openly accessible venues, in collaboration with the core project participants that developed the app.

Background and further information on the citizen science project.

The app development and campaigns are part of the pilot project Nachtlicht BüHNE (Bürger-Helmholtz-Netzwerk für die Erforschung von nächtlichen Lichtphänomenen) funded by the Helmholtz Association of German Research Centers. As part of the citizen science project, an app for documenting fireballs was also developed at the German Aerospace Center DLR in Jena (see: nachtlicht-buehne.de/feuerkugeln).

Scientific contact:
Dr. Christopher Kyba
Remote Sensing and Geoinformatics
14473 Potsdam
Phone: +49 331 288-28973
Email: christopher.kyba@gfz-potsdam.de

Nona Schulte-Römer
Scientist Remote Sensing and Geoinformatics
14473 Potsdam
Phone: +49 331 288-1135
Email: nona.schulte-roemer@gfz-potsdam.de

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