Light pollution in the city: is it worse with LED streetlights?

Maxence Glineur

January 27, 2023 at 2:30 p.m.


street lamp street lamp © © Anton Massalov/Pexels

© Anton Massalov/Pexels

Public lighting remains harmful to the environment, despite significant changes in recent years.

LED lamps have replaced the technologies that have been used for several decades to light our streets. Consuming less energy for similar results, they are strongly encouraged by public authorities who see them as an ideal solution to reduce electricity bills and tick the ecological box. However, this technology has its own shortcomings, and its generalization has its own impact on the environment.

Satellite data not comprehensive enough

The stars disappear from the urban ceiling. This finding is not recent, but the activism of many organizations is gradually changing things. If it is necessary to preserve the astronomical observatories whose night sky is nibbled away by urbanization, it is also a question of offering future generations the possibility of contemplating it as well as possible.

Unfortunately, the current situation is not encouraging. According to Christopher Kyba, a researcher at the GFZ center in Potsdam, the ambient brightness caused by artificial light increases by 10% per year. At this rate, a child born today under a sky with 250 stars will only be able to see half of them when they come of age.

Kyba and his team wanted to conduct a new study on the subject. They crossed two different approaches to conduct it: in addition to data obtained by satellites, they solicited thousands of contributors to observe the sky. Using maps, they were able to identify the amount of stars visible, and thus allow a more comprehensive assessment of light pollution from Earth.

Blue light is implicated

With 51,351 observations collected, researchers were able to see what satellites cannot. Indeed, if the Earth’s atmosphere is capable of retaining part of the light from the stars, it is also likely to retain part of that which we emit. Therefore, it is not entirely perceptible from space.

In addition, the cameras on our satellites are not designed to properly capture certain wavelengths of blue light. However, the lamps used today emit a greater quantity than these, because the diodes which equip them consume less energy, thus distorting the data obtained.

Current urban lighting is designed to emit more towards the ground rather than towards the sky, which goes some way to solving the problem of light pollution. However, because LED bulbs consume less energy, many communities have been able to light their streets more brightly without breaking their budget, often with the goal of improving city safety. Light rays have the unfortunate tendency to bounce off surfaces, so we end up with streets lighting up more and in spite of themselves, the sky indirectly.

If the effects of this pollution are observable by looking up at night, it also has a significant impact on living beings. It affects biological cycles and interactions between species, thus destabilizing the nocturnal activity of fauna, and at the same time influencing biodiversity. Especially since blue light has a high scattering power, up to sixteen times more than red light for example, thus illuminating places that would not be otherwise.

Source : Reporterre

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