Fatal glare | Canary Islands7

Cities are excessively illuminated with artificial light. / CR

"Light pollution threatens astronomical observations, ecosystems and our health," warns expert Alicia Pelegrina, from the CSIC


First it was the fire. After campfires and torches, oil lamps served to brighten the night from the Roman Empire to the Renaissance. At the end of the 18th century, gas began to be used and, about a hundred years later, electric lighting had already spread throughout Europe and the American continent. Human beings' innate fear of the dark pushed them to look for sources of light to protect themselves from their predators, and this strategy has been maintained from the first settlements to the big cities. Artificial light has meant an exponential leap in the development and welfare of society, but its abusive use has turned an element of progress into a threat.

Alicia Pelegrina, who participated in the start-up of the Sky Quality Office of the Institute of Astrophysics of Andalusia (IAA) of the CSIC, explains in 'Light pollution', the latest book in the collection What do we know about? (CSIC-Cataract), the causes of this phenomenon and warn about its effects. “We associate light with wealth, happiness and security, but the inappropriate use of artificial lighting has become a serious environmental problem. It is a type of contamination that does not hurt, is not heard, or smelled. We do not perceive it as a problem, but excess light is responsible for the massive mortality of some birds, unbalances ecosystems, is a key element in the disappearance of insects and causes alterations in our organism", declares the author, doctor in Environmental Sciences from the University of Granada (UGR).

99% of the European population cannot enjoy the scenery of a starry sky nor can they see the grandeur of the Milky Way

The new world atlas of sky brightness already warned in 2016 that 80% of the planet's inhabitants live under polluted skies and that a third of the world's population cannot see the Milky Way. If we look at Europe or the United States, the numbers skyrocket: 99% of the population cannot enjoy the scenery of a starry sky.

But what is light pollution and how does it originate? In Spain, the Cel Fosc association defines it as an alteration of the natural darkness of the nocturnal environment produced by artificial light sources. There are two characteristics that make artificial light a very dangerous polluting agent: its ability to spread in all directions and the speed with which it does so, 300,000 km/s when it travels through a vacuum.

The Iberian Peninsula, at night. /


The scientific community dedicated to astronomy has been warning of this problem for some time. But in addition to that artificial brightness of the night sky that makes it difficult to investigate the cosmos, there are other ways in which light pollution manifests itself, such as intrusion, produced when the luminous flux exceeds the space to be illuminated and floods other areas. This happens when light from street lamps enters your bedroom, or in coastal areas, where large bodies of water are reached by artificial light.

"The least polluting lamps are those that emit an orange light, which is the least dispersed in the atmosphere"

The streetlights in our cities are made up of lamps, the light emitting source, and luminaires, the structure that contains and supports the lamp. The correct design of both parts is essential for adequate lighting. According to Pelegrina, "the least polluting lamps are those that emit light of the spectrum visible to the human eye with longer wavelengths, that is, the lamps that emit an orange light, which is the least scattered in the atmosphere, and the most respectful are those that do not emit light in the upper hemisphere. This minimizes their impact on increasing the brightness of the night sky."

light and dark, essential

The cycles of light and dark are essential for living things. The author compares natural light with “a referee that guarantees the smooth running of the match, because it controls biological mechanisms and functions such as reproduction, the search for food, migration or flowering. Artificial light breaks these cyclical patterns and, due to its ability to travel long distances, affects natural areas far from large urban centers where there are large concentrations of points of light.

«Artificial lights disorient and change the breeding patterns of birds and thus become a retaining wall for the migratory movements of insects»

In fact, the International Union for Conservation of Nature states that light pollution affects two-thirds of the Earth's key biodiversity areas. 30% of vertebrate living beings and 60% of invertebrates are nocturnal. From this data, we can deduce the imbalances caused by a light that appears in unexpected places and times. Insects are the most abundant group of living beings on our planet and one of the most vulnerable to light pollution. Those who are nocturnal identify light as a sign of safety and orientation. This explains why they remain 'captive' flying around, for example, a lamppost, which causes their death, burned by the hot bulb, due to exhaustion due to continuous flight, or predated. Artificial lights thus become a retaining wall for the migratory movements of insects and the movement of organisms that feed on them.

Birds also become disoriented and change their breeding patterns. Seabird hatchlings suffer from constant lighting as they travel from the nest to the sea. In the Canary Islands thousands of chickens die every year when they fall to the ground in streets and highways dazzled in their first flights. For their part, the turtles do not come out to lay their eggs on the beaches. And those that do have no guarantee of their offspring, as their offspring confuse streetlights with the glow of the moon and fail to reach the shore.

«The abuse of artificial light at night is associated with the appearance of cardiovascular diseases, insomnia, lack of concentration or eating disorders»

Offshore the situation does not improve. The first world atlas of underwater light pollution published in 2021 by the University of Plymouth indicates that, at a depth of one meter, almost two million square kilometers of coastal oceans are exposed to artificial light at night.

health suffers

Almost everyone has heard of the biological clock that governs our body and gives orders to activate a series of functions depending on whether it is day or night. These fluctuations that repeat day after day every 24 hours are known as circadian cycles, and we are changing them. In the words of the IAA-CSIC specialist, “our cities have become a '24/7 non-stop' system that involves an alteration of the natural light-dark cycle due to the abuse of artificial light at night. In this way, our clock goes crazy and starts sending signals at night that it should send in the morning. This chaos is what is known as chronodisruption. Many studies associate this phenomenon with the appearance of cardiovascular diseases, insomnia, lack of concentration, fertility problems, nutritional alterations and even some types of cancer».

In our country, the Barcelona Institute for Global Health conducted a study in 2018 with more than 40,000 people between the ages of 20 and 85 from 11 autonomous communities. The results were clear: there is an association between high levels of exposure to blue light at night (emitted by most white LED lights and the screens of tablets and mobile phones) and an increased risk of breast and prostate cancer. .

To solve this problem, you do not have to press the switch and return to the bonfires. The doctor in Environmental Sciences proposes some measures that can already be applied. «It is a question of better lighting, in a more sustainable way, avoiding the emission of light directly to the sky, using only the amount of light that is necessary directed at what we need to see, in the spectral ranges in which our eyes they can perceive it and at a suitable time”, he affirms.

Legislation is a basic tool to achieve these goals. Italy and France have the most advanced dark sky protection laws in the world, but in our country we still do not have a state law on light pollution; There is only some measure in autonomous communities such as the Canary Islands and Catalonia. The Royal Decree of the Government that establishes the switching off of the lighting in shop windows and public buildings will have repercussions on the levels of light pollution, but “we are facing an environmental problem with enough weight to draw up our own approach strategy. It all adds up, but we cannot stay here”, clarifies Pelegrina, who asks to become aware of the situation and bring this knowledge closer to the public. »We have a moral obligation to preserve the starry sky, for ourselves and for those to come«, she concludes.

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