Lichtgedanken 04

Rubrik 55 04 | LICHT GEDANKEN Where there is a lot of light, there is also a lot of shade. In other words: there is a dark side to having a lot of light. It may sound like a platitude, but it actu- ally relates to a serious problem: light pollution. An excess of nocturnal light has a negative impact on both humans and animals. The effects are especially disastrous for nocturnal insects. Al- though moths and other insects don’t burn in lamps, the draw of the lamps has enormous consequences: »The ani­ mals neglect their search for food and partners, and pollinate fewer flowers«, says Dr Gunnar Brehm, zoologist at the Phyletic Museum. There is no reliable data for light pollu- tion in Germany; but it is highly likely that there is a correlation with the de- cline of certain species. Increasing light pollution also has a negative impact on humans. »The intensity of light at night means that we are losing our starry skies; the Milky Way can no longer be seen in many places«, says Brehm. It also has an impact on our health, for example through a disturbed night. The sheer number of light sources is only one side of the coin, however. With the increasing use of modern LEDs, conventional sodium-vapour lamps are disappearing. The old lamps emit an orange light; whilst the new lamps shine in a white colour and often ap- pear brighter. »Insects notice this short- wave light emitted by the LEDs«, says Gunnar Brehm. How can light pollution be reduced to make the nights darker again? On the one hand, street lighting could be dimmed on side streets. On the other hand, lights don’t need to shine the whole night long. Gunnar Brehm thinks the following: »It is not about making cities pitch black at night«. Small altera­ tions could have an effect. The use of long-wave light would protect the in- sect world. This redder light would take some getting used to, but it would still fulfil its principle purpose. »Protecting the night« is a declared goal of Jena City of Light In Jena, the city council has responded to the problem: in December 2017, a resolution was passed to »protect the night«. The Kommunal Service Jena (KSJ) has been tasked with presenting a lighting concept for public spaces in the city by the end of 2018. The objec­ tive is to »reduce [light pollution] to as great a degree as possible through the avoidance of excessive lighting and to reduce lighting based on the local situ- ation«, amongst other things. Flora and fauna, as well as public health, are to be protected through adapted light spectra, light distribution and operating hours, taking natural spaces, protected natural environments and the plains near the Saale river into account. The justifica- tion for the proposal refers to the impact that biologically effective blue colour components in LEDs have, which attract nocturnal insects. Around 620 of a total of 700 butterfly species in the city centre remain active at night. The illumination of bridges even has an effect on the fish in the Saale. Take the example of the Austrian capital Vienna. After ten o’clock at night, the street lamps run at half power—there have been few complaints. An encour- aging sign. Reflection Bright nights Both humans and animals suffer when night-time is no longer dark. What can we do to prevent the increasing light pollution? COMMENTARY BY STEPHAN LAUDIEN Attractive LED light: Entomologists use it to attract butterflies and moths in the South American rain- forest, but it is leading to the downfall of the animals in our brightly lit cities.