Light pollution: torment for animals

Light pollution: torment for animals

Illuminated churches and monuments, spotlights in stadiums and bright street lighting – in many places people are turning night into day, with devastating consequences for wildlife and biodiversity.

The trend towards permanent lighting at night is torture for many animals The UN cultural organization UNESCO celebrates the beneficial role of lighting in science, technology, culture and art on May 16, International Day of Light. But light also has a dark side.

“Light pollution is likely the main cause of global species extinction,” says chronobiologist Stephanie Moneke. Take, for example, street lamps, where you can often see dense flocks of insects: “The light attracts thousands and thousands of insects that buzz around the light source, get tired or burn out. The whole food chain is going astray: animals that hunt insects in the dark will find less food.”

Many species of bats are sensitive to light, avoid light sources and therefore have smaller and smaller hunting grounds, according to Swiss conservation organization Bird Life. Robins, which usually sing at dusk, sometimes sing all night in bright light. Even runners, Moneke says, could knock wild animals off course with powerful headlights.

Animals’ internal clocks are disturbed

But not only that: artificial light throws off the internal clocks of many animals. European hamsters, for example, perceive shorter days and set their annual body clock to mid-July, which determines the start and end of hibernation, says Moneke, a visiting scientist at the Ludwig Maximilian University in Munich.

If they are disturbed by the city bell or the lights of the cars on the street, there is a great risk that their clocks will not keep up. Then they will not come out of hibernation in time in the spring and will not be ready to mate at the same time. “Today, field hamster breeding starts two and a half months later than in the 1980s,” Moneke says. “Instead of 20-25 cubs per year, the female field hamster now raises only five. With a strong downward trend.

According to Moneke, the number of some species is drastically reduced “not because too many animals die, but because, like hamsters, they have fewer and fewer offspring.” In their opinion, local pollution and destruction cannot explain this factor, but they can explain light pollution. Today, the field hamster, which was found in millions of fields until the 1980s, is endangered throughout its distribution range between the Rhine Valley and Lake Baikal.

Light pollution is considered an underestimated hazard

According to the International Union for Conservation of Nature (IUCN), light pollution is an “often underestimated hazard” that can also be significant to hamsters. In addition, she mentions climate change, industrial agriculture, habitat loss, and poisoning as pests.

Humans also synchronize their internal clocks with the rhythm of light and dark, says chronobiologist Achim Kramer of the Charite University Hospital in Berlin. Cells in the eye transmit light pulses that “set” the internal clock and ensure that people sleep when it’s dark outside at night and stay active during the day. “If you turn off the biological clock in mice, they will become fat and sick,” Kramer says. Also, those who constantly live by their internal clock when working shifts have a higher risk of cardiovascular, metabolic or oncological diseases and depression than people with a preserved day-night rhythm. “A well-synchronized internal clock is very important for health.”

However, unlike animals, people can protect themselves from excessive lighting in the evening and at night with the help of curtains. “One of the main problems that people face is artificial light pollution: using screens for hours and often late,” Kramer says.

Street lighting does not prevent crime

People who light up their backyard or communities who provide bright street lighting often do so with the argument that they want to scare off criminals. However, a 2015 British study found that in more than 60 cities in England and Wales, more street lighting prevented neither accidents nor crime.

That’s why the cure for animal plight is actually simple: less outdoor lighting. It will also save a lot of energy. “Lighting streets, squares and bridges in Germany, in dire need of modernization, wastes three to four billion kilowatt-hours of electricity every year – more than a million private households together consume,” the German Nature Conservation Association (Nabu) calculates. ). In some cities, energy consumption has been reduced by 50 percent with smart lighting, including motion sensors.

In street lighting, light bulbs are often replaced by LED bulbs with the same amount of electricity, says physicist and engineer Martin Löffler-Mang from the Saarland University of Applied Sciences. But these lamps gave much more light. “If the amount of light was okay before, you could significantly reduce the number of LEDs and reduce energy consumption by up to one-fifth,” he says. Löffler-Mang helps affected communities to detect and reduce strong light sources through light monitoring.

To do this, nightly records are automatically made at a fixed location over a long period of time, which are then evaluated. Andermatt in Switzerland did this successfully. St. Wendel in the Saarland now wants to do something to attract more tourists with a “less light” concept. In 2019, the Dark Sky Association recognized Fulda as Germany’s first “star city”. She consistently directs her lighting down and controls it as needed. The city says it has reduced energy consumption.

Leffler-Mang also refers to this scientific discovery: “If we turned on less light, we would become more sensitive and see more.”

Christian Olrich, doctor-operator

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