These are the Spanish cities that pollute the most with their light | Science

These are the Spanish cities that pollute the most with their light | Science

Spain seen from the International Space Station. In video, Cities at Night, an 'online' nighttime world map to combat light pollution.

Look where you look is hopeless: light pollution in Spain has soared in the last 10 or 15 years that Madrid, Barcelona, ​​Valencia, Zaragoza, Bilbao and many other cities stain the horizon with its parasitic light at distances of hundreds of kilometers. This is demonstrated by the latest scientific studies, with impressive images in which the glow of peninsular cities pollutes the sky inexorably. The Canary Islands is the exception thanks to the protective legislation that keeps the natural heritage of its starry nights safe.


Power emitted per km2 (thousands of W)

Source: SaveStars Consulting SL.

Madrid and the surrounding towns, due to the size of the urban agglomeration, make up the great monster of light that can be seen from any point of the Peninsula, but Bilbao is the one that has the most polluting lighting, according to the study of a team led by the Spanish astrophysicist Alejandro Sánchez de Miguel, currently a researcher at the University of Exeter (United Kingdom), with the participation of Rebeca Benayas Polo, from the company GEASig, for SaveStars Consilting SL.

A study led by astrophysicist Alejandro Sánchez assesses the situation in 2,000 Spanish municipalities

The situation is so alarming that it is no longer just about the deterioration of the quality of the sky for astronomical observatories, but one of the problems with the greatest environmental impact in Spain, since the excess of light directly affects human health and the flora and fauna, fundamentally pollinating insects and birds, which have been altered their existence by the distortion caused by the waste of night light. "We are not the only astronomers in the animal kingdom, so the impact goes further and is currently a huge environmental problem," says Sánchez. Ranking of light pollution in Spain, has just been published in the European scientific repository Zenodo.


Power emitted per km2 (W)

Source: SaveStars Consulting SL.

The research work analyzes the situation in 2,000 Spanish municipalities, from which numerous aspects related to light pollution are evaluated: total power emitted towards the sky, number of luminaries, density of streetlights per square kilometer, power emitted per person and per surface , as well as other parameters with which several rankings have been developed. In the total power output there is no doubt: Madrid is the one that sends more light into space and tops the list thanks to its size. However, the rest of the leading group does not exactly fit their population and size, as they are followed, in this order and up to the tenth place, Zaragoza, Seville, Barcelona, ​​Valencia, Murcia, Malaga, Cartagena, Vitoria and Cordoba .

Light pollution in an image taken from Calar Alto.
Light pollution in an image taken from Calar Alto.

Likewise, the research has made it possible to obtain a total list that can be considered as a reference standard, since it is formulated from all the parameters (not only size and population), forming a profile-type of the municipalities with the most polluting lighting. In this case, interestingly, Madrid improves and the worst result (the gold medal among the most intense sources of light pollution) is for Bilbao, followed by Hospitalet de Llobregat (Barcelona), Baracaldo (Vizcaya), Valencia, Cádiz, Melilla, San Fernando (Cádiz), Puertollano (Ciudad Real), Parla (Madrid) and Badalona (Barcelona). Therefore, the problem does not concern only provincial capitals, but other municipalities with smaller population also have very polluting lighting.

In any case, Bilbao, Valencia and Barcelona are the stars of the study, since they score badly in almost all the parameters analyzed. In these three cities the problems of their large size are combined with the poor results regarding the type and number of streetlights and the power emitted to the sky per square kilometer. In the latter case, the first positions correspond to comparatively small municipalities: Perafort (Tarragona), Palos de la Frontera (Huelva), Teo (A Coruña), Gozón (Asturias) and Ascó (Tarragona), but as soon as a little progress is made Valencia, Bilbao and Barcelona reappear in the list.

The contaminating color temperature

Alejandro Sánchez's study has been prepared with data from the year 2012, since the current ones do not work. The VIIRS radiometer (acronym for Visible Infrared Imaging Radiometer Suite), a detection instrument installed in international satellites, with which many of the current measurements of light pollution are obtained, is blind to blue light, which presupposes that it can not capture a large part of the polluting emissions of LED-type luminaires that have proliferated extraordinarily in Spain in the last five years. Therefore, to obtain a realistic analysis, we opted to evaluate the 2012 data, before the implementation of the LED, always from the evidence that the current situation is much worse, despite the fact that the VIIRS data, since it is not sensitive to blue light, they seem to erroneously suggest a more optimistic view.

Public spending on lighting goes up to more than 1,600 million euros per year

The problem of the LED resides in the widespread belief of its greater energetic efficiency, that is contradicted with the extraordinary cost that supposes for the public coffers of the municipalities that bet by him. And its environmental impact is remarkable, since the vast majority of installed bulbs have a very polluting color temperature, between white and blue, which usually exceeds 4,000 Kelvin.

The Joint Research Center The EU recommends that, if LED lights are used, the bulbs are of color temperatures below 3,000 Kelvin, although the scientific community recommends reducing them to 2,200, ie amber instead of white, as they are much less polluting . Despite this, few municipalities install them and most opt ​​for white LED without taking into account some good experiences, such as those made in the Canary Islands with amber bulbs of low temperature, very efficient and non-polluting.

The proliferation of streetlights with white LED is causing a great environmental impact that affects human health and nature

The switch to LED for which hundreds of Spanish municipalities have bet implies investments of the order of 600 euros per lamp. Alejandro Sanchez thinks that instead of that it would be much more advisable to rehabilitate the luminaries with sodium bulbs, since it only implies an expense of 12 euros for each one, they are equally efficient and do not contaminate if the beam of light is adjusted downwards . Obviously, this option is much less profitable for the suppliers. Be that as it may, it is estimated that the annual cost in public lighting in Spain is exorbitant: around 1,600-1,800 million euros per year in recent years. Until recently the global data on electricity consumption was known, but these specific figures on the lighting constitute an important novelty to specify the waste in this matter, especially if this disbursement is compared with the amounts that are destined to other necessary chapters of the public investment.

Horizons too bright

Photograph taken with a camera with a special lens of the fisheye type, which obtains framings from horizon to horizon.
Photograph taken with a camera with a special lens of the fisheye type, which obtains framings from horizon to horizon.

Alejandro Sánchez, author of one of the first doctoral theses on light pollution, is also the driving force of the project Cities at night, an international initiative to raise awareness about the impact of light pollution through the use and processing of Night photographs of the International Space Station (ISS). Precisely, the photos of the Earth carried out by the ISS astronauts could serve to achieve the true measure of that impact, since, unlike the VIIRS images, they are sensitive to the emissions of the LED street lamps, so which are a more reliable and useful reference.

From the ground, however, photography is also contributing to that goal. Joan Manuel Bullón, one of the Spanish non-professional astronomers most involved in the defense of the night sky, is currently working on the development of an atlas on light pollution in Spain and a project called Lost horizons versus dark skies.

Some of his recent photographs are shocking, such as those taken this winter, which illustrate this information and corroborate the worst auguries. To measure the quality of the starry skies, Bullón takes photos from different parts of Spain through a camera with a special lens of the fish eye type, which obtains framings from horizon to horizon.

These photographs constitute an extraordinary document, since it has managed to place with them on the map the enormous arcs of light pollution of numerous Spanish cities. Although it may seem astonishing, the pollutant lighting of the great capitals appears at the edges of the circle of the image as a disturbing halo, even at distances of the order of 500 kilometers.


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