Raising our gaze to the firmament any night, with a clear sky and without the presence of the Moon, has ceased to be the magnificent spectacle with which our ancestors were surprised, at least in the vicinity of towns and cities. The enormous amount of light given off by artificial lighting has not only made most of the stars and the Milky Way disappear from our view, but the process of deterioration continues to increase. The change is not only evident to those of us who inhabit the earth’s surface, but is also reflected in the images collected from space. On the right we offer a couple of images that attest to this.
Although human beings have been trying to light up at night for thousands of years, the fundamental change began to affect large areas of the Earth after the proliferation of electric light and the increase in world population. During the last decades the problem of artificial night lighting has acquired such great dimensions that it has given rise to a new form of pollution: light pollution.
Today, in Talking to Scientists, we interview a person who is dedicated to investigating this phenomenon. He is Alejandro Sánchez de Miguel, a researcher at the Complutense University of Madrid and the University of EXETER in the United Kingdom. Alejandro and a large team of collaborators from the two universities recently published an article in Science Advances, whose title we have translated as The environmental risks of artificial night lighting are expanding and increasing in Europe
The study complements the information obtained in recent decades on the erosion of the night environment caused by artificial lighting. Traditionally, these studies have been fundamentally based on images obtained with artificial satellites, data that have made it possible to draw conclusions both on the magnitude and evolution of the problem and on the effects on ecosystems. However, these satellite images had a limitation because they were preferably panchromatic, that is, they contained information about the intensity of the illumination, but not about the spectral composition, that is, the colors of the light.
Nocturnal illumination has been found to affect a wide diversity of biological phenomena ranging from physiology to individual or collective behavior of creatures of many species (including humans), but its effect is uneven across different frequencies of light. light. One of the most notable effects is the suppression of melatonin, a hormone that our bodies and those of many other creatures generate at night and regulates the sequence of sleep and wakefulness. It has been found that the generation of melatonin is fundamentally influenced by light of blue wavelengths.
With the advent of light emitters LED Its use has become widespread in domestic lighting and in public lighting. Alejandro Sánchez de Miguel comments that there is a notable difference between the two types of lighting. While in past decades our houses were illuminated with incandescent light bulbs, which were very inefficient, sodium vapor lamps were used in public lighting, which were highly efficient and more environmentally friendly. Sodium vapor lamps also have the advantage of emitting an orange color, with a reduced spectrum, without blue components and whose intensity can be regulated. With the advent of light-emitting diodes LED With a “broad white” spectrum, in many places the sodium vapor lamps were replaced by the new emitters, significantly increasing the nocturnal emissions of blue light which, as we have said, is more harmful to ecosystems.
The team has used, in addition to satellite images, photographs taken with digital cameras by astronauts on the International Space Station, images that collect a wide collection of colors of light. With these data, they have produced maps of the variation in the spectral composition of lighting throughout Europe in two periods: 2012-2013 and 2014-2020. The results of the study show that there has been a generalized spectral change, although to a different extent depending on the regions and countries of Europe. The change shows the move from a state associated primarily with high-pressure sodium lighting to one associated with increased deployment of emitting diodes LED of broad white light, with higher emissions of blue tones. The data analyzed maps the changes as a function of the frequencies of emitted light and shows that light pollution continues to spread and increase in Europe, increasing the risk of harmful effects on ecosystems.
I invite you to listen to Alejandro Sánchez de Miguel, a researcher at the Department of Earth Physics and Astrophysics, at the Institute of Particle Physics and the Cosmos, of the Complutense University of Madrid, and at the Environment and Sustainability Institute of the University of EXETER
References:
Sánchez de Miguel et al. Environmental risks from artificial nighttime lighting widespread and increasing across Europe. Science Advances 14 Sep 2022 Vol 8, Issue 37 DOI: 10.1126/sciadv.abl68