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Colored map of Europe at night for 2014-2020, on the top right is Paris.
The map was created from images taken from the ISS
Photo: - / dpa
The conversion from street lamps to light-emitting diodes (LEDs) in many European countries has changed the color spectrum of night-time lighting - scientists from the University of Exeter Penryn are now warning of the possible consequences for humans and animals in the journal "Science Advances".
Using photos taken from the International Space Station ISS, they found that the proportion of emissions in the blue range of the spectrum in particular had increased as a result of the whiter LEDs.
However, Germany is relatively unaffected by this effect.
Since blue light inhibits the release of the hormone melatonin, which has a sleep-inducing effect, switching to LEDs can have an impact on animals and humans, writes Kevin Gaston's research team.
"The benefits that LED technology can bring to public lighting, and street lighting in particular, have been widely touted, with a focus on increased energy efficiency and the associated reduction in energy bills and carbon emissions," the study reads .
From the researchers' point of view, the negative environmental consequences of using white LEDs in street lighting should not be ignored.
At the very least, the color spectrum of nighttime lighting should be measured regularly.
"While data on the spatial and temporal variation in the intensity of artificial light was available at regional and global levels, data on the variation in its spectral composition was only collected for a few locations," the researchers write.
The reason for this lies in the usual satellite sensors that are used to measure artificial lighting and only register the intensity of the light, but not its color.
In addition, these sensors are hardly sensitive to the wavelength of blue light.
Gaston and colleagues therefore resorted to less systematically taken photos: photos taken by astronauts from the ISS.
Around 1.25 million recordings have been made since 2003.
The scientists selected photos from 2012 and 2013 showing Europe at night and compared them with photos of the same regions in the years 2014 to 2020. The boundary between the two periods marks the point at which LEDs are ready for the market as a light source for street lamps.
Only slight change in Germany and Austria
The researchers found an 11.1 percent increase in green light but a 24.4 percent increase in blue light during the second period.
A shift in the light spectrum towards blue light occurs above all when so-called sodium vapor lamps with orange-yellow light are replaced by white LED lamps, which emit a significantly larger proportion of blue light.
The scientists observed such a change in Italy, Romania, Ireland and Great Britain in particular.
The smallest change was in Germany and Austria.
With regard to the effects of these changes on the biological environment, Gaston's team cites four aspects: Because blue light inhibits the release of melatonin, the biorhythm in animals, but also in humans, can be disrupted.
Previous studies have shown that nocturnal lighting has negative consequences for the movement and feeding behavior of bats.
The use of LEDs is also causing even fewer stars to be seen in cities and further changing the movement of moths and other insects approaching or avoiding light sources.
mgo/dpa