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Artificial light on earth (satellite image): deadly trap for some animal species
Photo: NASA EARTH OBSERVATORY / AFP
Our world is getting brighter every year.
A British-French research group reports that the range and intensity of human illumination of the planet is increasing by around two percent annually.
According to their findings, this creates a problem that is comparable to other types of environmental pollution - and must be treated that way.
In an article in the journal "Nature Ecology and Evolution", the team led by Kevin Gaston from the University of Exeter in the UK reports on a meta-analysis of 126 earlier papers on the effects of light pollution.
For example, the increase in brightness affects changes in hormone levels, reproductive cycles and activity patterns in animals.
"The effects have been found everywhere - in microbes, invertebrates, animals and plants," Gaston said in the Guardian.
"We need to start thinking about lighting the way we think about other major system pressures like climate change."
The effects on the animal world are varied.
Rodents, which foraging mainly at night, were active for a shorter time due to the lack of nighttime darkness.
On the other hand, birds began to sing and look for worms earlier in the day.
For other animals, artificial light has even become a deadly trap, for example with newly hatched sea turtles that mistakenly run into the interior instead of the ocean - and are easy prey for predators there.
According to the researchers, all of the animal species examined showed decreased levels of the hormone melatonin, which is responsible for regulating the sleep cycle.
The light can also be dangerous for insects, which are attracted by street lamps or car headlights - and die in a collision.
For this reason, the federal government is planning a partial ban on sky searchlights.
Street lights are not the main problem
The researchers pointed out that there were also positive effects in some animal species.
For example, some plants would grow faster with continuous lighting, and some bat species could also benefit.
Overall, however, the light is disturbing, especially for the insects.
In January, a group of experts led by Jeff Harvey from the Dutch Institute for Ecology and the Vrije University of Amsterdam had already written the fight against light pollution as one of eight points in their proposed immediate insect protection program.
The problem of light pollution can be clearly seen on satellite images.
Part of the phenomenon can be explained by the fact that in many places street lighting has been switched from lightbulbs to LEDs in order to save energy.
This is not without difficulties due to the associated change in light color - from more yellow to more white - the LED lights are often brighter than before.
In a study published last week in the specialist magazine "Lighting Research & Technology", a team led by Christopher Kyba from the GFZ German Research Center for Geosciences specifically dealt with the role of street lighting in light pollution.
During measurements in the city of Tucson in the US state of Arizona, they were able to show that, amazingly, only about 20 percent of the city's light emissions visible on satellite images are due to the lanterns.
For the rest, for example, bright windows, illuminated signs and facades and sports fields are responsible, according to the researchers.
Authorities therefore have to think about more than just street lighting when trying to reduce light pollution.
Kevin Gaston's team, in turn, draws attention to the fact that such efforts make a decisive difference to the fight against other environmental problems: Making less light more saves money than it costs.
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