rural Spain is turning blue at night

In 2023, data from the Chinese SDGSAT-1 satellite made it possible for the RALAN-Map EU project, of the Complutense University of Madrid and the International Research Center of Big Data for Sustainable Development Goals, to develop the first high resolution calibrated map of the Iberian Peninsula and the archipelagos of the Canary Islands, the Balearic Islands and Madeira.

Thanks to the level of detail of this cartographyyou can see how the artificial brightness changes and what type of light predominates in each region at night. And observing the color temperature of light sources has revealed something unexpected: hundreds of small towns have changed the warm tone of their traditional lighting for a bluish light.

I have seen a light. The map reaches an unprecedented resolution in this type of study, 40 meters, which has made it possible to verify that while large cities maintain warm tones, municipalities with less than 5,000 inhabitants present colder and bluish lighting.

The reason? A change in infrastructure: many municipalities in rural Spain have left behind the old lighting with LED streetlights to save energy, and this update translates into a different color, noticeable even from space.

The RALAN-MAP 0 map of light pollution

Why it is important. Both the UCM and the SINC Agency They agree that the map represents, in the words of the university itself, “a significant advance” to more accurately evaluate the environmental and health impact of light pollution, and opens new avenues for the management of lighting and the protection of the night sky.

The reason is that blue light, in addition to looking different, has a wavelength that spreads further into the atmospherewhich increases nighttime glow and worsens sky visibility for astronomical observations, including summer classics like the Perseids. Besides, There are studies that support that this type of light interferes with the biological rhythms of species such as pollinating insects or migratory birdswhich orient themselves at night.

Context. The SDGSAT-1 was launched in 2021 by the Chinese Academy of Sciences as a satellite designed to monitor the progress of the UN Sustainable Development Goals, which gives it a nighttime detail capacity unprecedented until now.

The RALAN-Map EU project is also part of a broader line of research on light pollution that astrophysicist Alejandro Sánchez de Miguel and his team have been developing for more than a decade, including Previous studies on the energy consumption of public lighting in Spain using satellite data.

In detail. The map is publicly accessible and can be consulted online, allowing anyone, whether a city council, research or urban planning, to precisely identify where blue light predominates and prioritize changing streetlights there.

The geographical pattern is clear: it is precisely small municipalities, many of them surrounded by protected natural spaces, that have renewed their lighting the most in recent years, prioritizing energy savings over the ecological or astronomical impact of the chosen color temperature. Thus, warm sodium lights have given way to white lights rich in blue components.

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Cover | KEVIN CLYDE BERBANO