The animals are left behind in the Christmas race to see who lights up their city the most. Their ecosystem is altered and their rhythms of life may be affected. A research team with experts from the National Museum of Natural Sciences, the Doñana Biological Station and the Institute of Marine Sciences – all from the CSIC – has verified through satellite images, between 2014 and 2019, how the great festivities of the different Human societies alter light pollution patterns on a global scale. This study, published in the journal People and Nature, shows that a peak of this pollution occurs during Christmas in countries where the Christian religion is practiced, during the Chinese New Year, during the Muslim Ramadan and during the Hindu Diwali. With artificial lighting, the night landscape is transformed and the intensity of light increases which, added to the large concentrations of people, increases light pollution, which has already been studied to affect species.
More municipal authorities join the recent competition between several cities in Spain for the best Christmas lighting. At the Puerta del Sol in Vigo, the mayor, Abel Caballero, inaugurated Christmas on November 24 with a total of 11.5 million LED light bulbs. The size of the tree, the number of lights and the amount of decorations star in the championship, but light pollution sneaks into the magic of Christmas.
Astrophysicist Alejandro Sánchez de Miguel clarifies that there is no place in the Mediterranean that is free of diffuse light pollution throughout the year. He assures that this can be seen up to 400 kilometers away. “From Cabo de Gata you can see Algiers and from Madrid, the Pyrenees.” For this reason, the halo of the great Murcia Christmas tree, which reaches 1,000 meters in height, not only impacts the city, it reaches the rural areas where more species live.
Most living beings, including humans, are regulated by circadian rhythms, the cycles of day and night. Artificial alteration of light levels has effects on rest, communication, reproduction, behavior and predation. This is stated by the nature conservation NGO SEO/BirdLife, which asks city councils to stop this race in which the impact on the ecosystem has not been studied.
Experts are more concerned since Christmas shows are held in green areas, in a context of climate emergency and loss of biodiversity. This year, functions of this type have been scheduled in places such as the Torre Girona park in Barcelona, the Palmetum Botanical Garden in Santa Cruz de Tenerife, the Artxanda viewpoint in Bilbao or the Enrique Tierno Galván park in Madrid. “All of them are public environments that serve as refuge for many species of wildlife within the urban fabric,” SEO/BirdLife insist.
In Vigo this year 2,308 trees have been decorated. “It is quite likely that some of them serve as winter roosts for sparrows, wagtails and other birds for which it will be difficult to find an alternative resting place during these two months,” the NGO explains.
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The royal decree on energy efficiency in outdoor lighting installations, which came into force in 2008, specifies the type of Christmas lights that must be used, with low consumption and high energy efficiency bulbs, but does not clarify the total number of luminescent curtains that can be used. decorate public roads. This sometimes leads to excess. In addition, the Environmental Assessment Law of 2013 protects RED Natura 2000 protected spaces from direct and indirect contamination. Still, migratory birds are affected by light pollution up to 250 kilometers away, according to Sánchez de Miguel.
Biologist Airam Rodríguez explains that white and blue lights, typical of LED lighting decorations, have a more harmful effect on species than the traditional orange bulb. “They emit a part of the light spectrum to which most living beings are more sensitive.” The color blue also prevents the correct secretion of melatonin, the sleep hormone, which affects animals and humans, and can affect their immune system. The impact of light pollution throughout the year, aggravated during these Christmas periods, has an impact on the ecosystem of most living beings.
Affectation in birds
The coordinator of the SEO/BirdLife Urban Biodiversity Program, Beatriz Sánchez, insists that the lighting, the setup, the accumulation of visitors and the noise of the Christmas shows, which are also audible, can cause disturbances to the birds. “They have to find another remote place where they can sleep, with the consequent energy expenditure,” she adds.
Light pollution is harmful to birds throughout the year. Sánchez remembers the death of thousands of migratory birds every year, when they become disoriented as a result of the lighting of the monument in memory of the victims of the terrorist attack on the Twin Towers, on September 11, 2001. Although on these Christmas dates the birds do not They usually migrate, they can also become dislocated when displaced from their usual environment.
Baby shearwaters become disoriented during their first flights to the sea. “They think they are following the sun, but they end up on land,” Sánchez insists. Between October 20 and November 10, 3,200 chicks, which were born in that period, died in Tenerife as a result of the port lights, according to Rodríguez. This winter period is not the cause of these deaths, but the birth of the babies does coincide with the installation of lighting in some cities.
The show held in the Palmetum of Santa Cruz de Tenerife, says Rodríguez, can affect seabirds if it attracts adult individuals: “Losing a chick is not the same as losing a long-lived species. “Adults are reproductive and mate for life, therefore, if one dies, the population dynamics are broken.” He clarifies that these events occur more sporadically, and are associated with bad weather.
The Madeira storm petrel and the little shearwater, which nest in winter in coastal areas, can also be harmed by light pollution. Songbirds, Rodríguez clarifies, begin to chirp earlier because they think that it is already dawn, or, on the contrary, with noise pollution, which can be the noise of people and Christmas carols, they change their singing schedule and vary the tone to be audible. “This has an impact on finding a partner, marking territoriality or dominance,” Rodríguez specifies.
Damage to mammals
About 60% of mammals are nocturnal. Therefore, light pollution has an impact on their daily activity, such as predation. Meanwhile, daytime sleepers see their sleep altered, as explained by astrophysicist Sánchez de Miguel. Some types of bat change their hunting habits and begin to hover around illuminated areas that attract insects. They can eat more in the short term, but in the future it will be a problem if the invertebrates are depleted.
Insect damage
Insects are attracted to the lights and stop pollinating. “They can even die from exhaustion,” explains Rodríguez. The time they spend circling the light bulb is not spent performing their vital functions. The amount of seeds in illuminated areas is lower than that found in places that remain dark. “Diurnal pollinators have less nectar to live on if nocturnal pollinators do not do their job,” concludes Sánchez de Miguel.
Artificial light can also alter the behavior of diurnal insects because they activate their activity period for a longer period of time. In places where Nile fever or malaria diseases, transmitted by mosquitoes, are abundant, cases skyrocket when permanent night lighting is installed, according to the astrophysicist.
Impact on amphibians
Some species of frogs are also harmed by altered light and are less selective when choosing a mate. They even interrupt their reproductive activity if it is clear at night. On the other hand, “in Australia, the cane toad, which is an invasive species, benefits from lighting to hunt invertebrates,” explains Rodríguez.
Another Christmas is possible
“Although Christmas lighting does not cause population declines, it causes individual impacts and alters communities and their quality of life,” insists the biologist. It increases the levels of light pollution that already affect species throughout the year. For this reason, Sánchez de Miguel considers it important to abandon this light bulb competition and opt for more natural ornaments such as decorative figures, which are already a trend in Europe. The astrophysicist does not see the need to “put up an aluminum frame” to represent a tree and regrets the loss of the traditional connection of Christmas with the stars and nature: “If the Three Wise Men had to find the star now, it would be impossible ”.
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