Artificial light at night (ALAN) is increasing worldwide by about 3-6% a year without regard to its potential impacts on humans and the environment. The increasing brightening of the nightscape is probably the most evident sign of anthropogenic impact worldwide. The multiple effects of increasing ALAN worldwide require transdisciplinary and supra-regional research approaches. CS can involve people with multiple expertises simultaneously at various sites worldwide. Furthermore, CS research increases public awareness and outreach.

In this session CS projects at different stages focussing on ALAN were presented:

1. The “Loss of the Night” -app involves observations of sky brightness by determining the number of visible stars in the night sky. Over 10.000 observations from over 100 countries were contributed from users, which benefit from knowledge of stars. The platform “myskyatnight.com” gives the data and tools back into the hands of the public.
2. “Tatort Gewässer” asks German citizens to measure the CO2-concentrations and microbial diversity at their closest water body, and analyses the artificial light conditions. More than 600 participants contributed so far, which allows mapping sediment metabolism and biodiversity pattern in aquatic systems under different levels of artificial light at night.
3. The EU-project STARS4ALL project will establish a network for involving citizens to collect data on the worldwide changing nightscape. Light pollution initiatives will be developed, especially in cross- disciplines such as Energy Saving, Biodiversity, and Human Health and will organize open competitions among them. The project aims several initiatives which will be the basis for an open self-sustainable platform to host any other future initiatives.