For years, the light of cities has been shining brighter than that of the stars, and increasingly so, because light pollution is a widespread problem throughout the developed world and is increasing, as evidenced by a study published in the journal Science Advances. , in which ESA astronauts have collaborated.
Since 2003, a European cosmonaut team has taken more than a million photos of Earth, at night, with digital cameras. Comparing them over time has allowed them to observe a clear increase in light pollution in urban areas, as well as a change towards whiter and bluer emissions, due to the introduction of LED technology in lighting systems. lighting.
Although the energy crisis has led the European Union to take measures to help save energy, such as turning off shop window lights, illuminated advertisements and unoccupied public buildings, starting at ten at night, scientists warn that this does not It is only important to reduce costs, also to ensure our health and that of the environment, since light pollution has great harmful effects, altering the night cycle of human beings, animals and plants.
“Seen from space, the resulting image looks like the result of a CT scan for cancer, or a fluorescent spider web that doesn’t stop growing,” explains Alejandro Sánchez de Miguel, researcher at the Complutense University of Madrid and lead author of the recent article.
The changes vary by country and reflect the existence of different systems and policies when it comes to street lighting. While Italy and the United Kingdom have seen a notable increase in light pollution, countries such as Germany and Austria show a less drastic change in their spectral emissions.
Milan was the first city in Europe to carry out a full conversion to white LEDs in its street lighting, while more than half of all public streetlights in the UK adopted the technology in early 2019. Germany, for its part, Many fluorescent and mercury vapor streetlights are still in use, although their night lighting is fading.
On the warmer side of the spectrum, Belgium glows a deep orange thanks to the widespread use of low-pressure sodium streetlights. These lights cause the Netherlands to emit a golden glow.
White and blue hues of light have a greater impact on the day and night circadian rhythm of living organisms, including humans. The study focuses on three major negative effects. First, the suppression of melatonin, a hormone that plays an important role in sleep and whose production and release is related to the time of day (it increases when it is dark and decreases when it is light). “When we turn on streetlights, we deprive our body of the hormone melatonin and alter our natural sleep pattern,” explains Sánchez de Miguel.
Second, the impact on the phototoxic response (ability to move and react to a light source) of insects, such as moths, and bats. For example, almost all species of bats that populate Europe live in regions where the spectral composition of nighttime lighting has become whiter, which affects their flight and hunting.
And thirdly, the worsening visibility of stars in the night sky, which especially influences the fields of geolocation and astronomical observation, as well as human perception of “nature” and its place in the universe. .
Addicted to light
Although the LED lighting revolution promised to reduce energy consumption and improve human vision at night – and with it, the feeling of security – the study shows that global emissions have increased. Paradoxically, the cheaper and better the lighting, the more addicted to light society becomes.
The article speculates on the existence of a “rebound effect” in outdoor lighting, according to which energy efficiency, with the consequent associated cost reduction, would increase the demand for lighting, thus reducing any increase in efficiency.