(ESA/NASA)
Of all the types of pollution that exist, there is one we overlook because it is so counter-intuitive. It is not hard for anyone to imagine how, because of human activity, the environment in which we live is sullied, overloaded and damaged by our massive waste, in the air, in the waters and on the land. With artificial light, however, the opposite is true. It is useful, we need a degree of illumination at night, and it gives us a sense of security. It can also be captivatingly beautiful and photogenic, as shown by the night-time images taken from the International Space Station (ISS) featured in this article.
Cette vue de la Péninsule ibérique illustre clairement la manière dont la pollution lumineuse se projette jusque dans l’espace, créant un éclat puissant dans l’atmosphère. Pour les astronautes qui sont en orbite autour de notre planète, à 420 kilomètres au-dessus du niveau de la mer, cette lumière rend nos villes plus brillantes que les étoiles. Bien que certaines zones côtières ne soient pas urbanisées, tout le littoral apparaît clairement durant la nuit. Portugal, Espagne, Maroc et France, le 26 juillet 2014.
Seen from space, the light from our cities is, for astronauts, much brighter than the stars, and makes our nights a world riddled with open, glowing wounds, the beauty of which hides the fact that our balance is bleeding through them, the rhythms of nature : the alternation of light and darkness, on which virtually all forms of life we know, including ourselves, are based.
The form of night lighting that humankind has adopted on a massive scale is not only excessive and inefficient but is also doing far more damage than we, from the comfort of our urban environments, tend to realise. Our artificial light is not only altering the planetary ecosystem in hundreds of different and increasingly worrying ways, but it is also undermining the health of countless animals, humans included. We are only now beginning to understand how this problem is linked to diseases ranging from obesity and diabetes, at the very least, to several types of cancer. We are so used to the night not being dark that we do not realise that we are condemning ourselves, and all life forms around us, to exhaustion under perpetual light, to a night without darkness and without rest.
La ville italienne de Milan a changé son éclairage urbain en 2014, installant plus de 85.000 luminaires à diodes LED blancs. Les Milanais ont vu alors leurs rues inondées d’une lumière froide bleutée. Celle-ci éblouit davantage, elle a en outre une incidence négative sur la santé humaine et sur celle de la faune et la flore, ainsi qu’un coût environnemental accru. Milan, le 9 mai 2021.
Major European cities began to be lit by whale oil in the 18th century, then coal and oil lamps, but most of the world was still covered in darkness every night. That all changed with the light bulb, patented by the American inventor Thomas Edison in 1879, a cheap and reliable technology that soon spread across the globe. In cities still in the midst of development, such as Los Angeles in 1908, the orange glow of its illumination in the sky, so ubiquitous today, was already clearly visible from tens of kilometres away, and the same was true of other major cities around the globe. In the same city, after the earthquake of 17 January 1994, as night fell, the emergency services were inundated with calls from people concerned about the strange, gigantic, luminous cloud that had appeared overhead, hours after the event. The blackout meant that millions of the city’s inhabitants were in fact beholding the Milky Way in all its splendour for the first time in their lives.
Sur Terre, l’éclat nocturne de la ville de Las Vegas se perçoit à des centaines de kilomètres dans l’horizon désertique du Nevada. Depuis l’espace, le centre de cette capitale étasunienne du jeu brille comme une tranche d’incandescence, surtout blanche. En termes de pollution lumineuse, de toute évidence ce qui éclaire Las Vegas ne reste pas à Las Vegas. Las Vegas, 27 août 2021.
The problem goes far beyond missing out on a mystical experience that we have almost forgotten as a species. The lack of darkness condemns plants to relentless stress, causes many animals to become disoriented in their natural cycles of reproduction, hunting or avoiding being hunted, and it has even been shown that the human body itself becomes unbalanced if it is exposed to blue light at night, as this delays and decreases its secretion of melatonin, which in addition to regulating our sleep patterns is an antioxidant, making it an important natural defence against ageing and diseases such as cancer. Light at all hours depletes life.
Fortunately, in recent years, night-time images brought to us from ISS astronauts are starting to enable us to measure the scale of the disaster for the first time. “The better we understand this problem, the more we realise that it is a cross-cutting issue,” says astrophysicist Alejandro Sánchez de Miguel of Madrid’s Complutense University, one of the world’s few specialists in light pollution taking an interdisciplinary approach, working with researchers ranging from biologists and environmentalists to doctors, sociologists and criminologists. He also collaborates with the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) in the United States, compiling and analysing night-time images of the world taken from the ISS, enabling them to map the real impact of this form of pollution on our planet.
Cette image, prise l’année de l’installation de Nightpod dans l’ISS quelques années avant que ne prolifèrent les lampadaires à LED blanches, englobe une des métropoles les plus éclairées d’Asie : Shanghai. L’éclairage décoratif y est considéré comme un symbole de luxe et de prestige, raison pour laquelle la ville compte non seulement des lampadaires pour illuminer les rues, comme dans bon nombre de villes chinoises, mais aussi un abondant éclairage ornemental au niveau des routes, dans la publicité urbaine et dans la plupart des milliers d’immeubles élevés. L’on voit déjà, dans cette image datant de 2012, la forêt de gratte-ciels du quartier financier de Lujiazui, point blanc brillant visible depuis l’espace. Shanghai, 21 mars 2012.
“The uncertainty we still have in this area is such that we are not yet sure whether the growth in light pollution between 1992 and 2017 was 49 per cent, as the average indicates, or as much as 270 per cent, due to blue light emissions – the most harmful,” says Sánchez. The reason for this is that the information available was obtained from the satellites in orbit, which are light-sensitive but colour-blind, so the only source capable of providing all the data needed to measure the full complexity of light pollution on our planet are the images from astronauts.
“We were very lucky because, in 2012, ESA installed the Nightpod,” a motorised tripod that helps compensate for the station’s orbital motion during the exposure time needed for night photography. As a result, “a vast number of images were taken of the earth before the advent of LEDs” (light-emitting diodes). Although LEDs are not necessarily white, this is the type that has been taking public lighting by storm in much of the world for just under a decade.
Au bord de la côte de l’île sous-tropicale de Hainan, dans la mer de Chine méridionale, au large de la localité touristique de Sanya, l’on distingue dans l’eau de nombreux points d’une puissante lumière blanche : ce sont des projecteurs embarqués sur des navires de pêche, utilisés, comme dans d’autres régions du monde, pour attirer les poissons. La photopollution ne provient pas uniquement de l’éclairage urbain, mais aussi de sources de lumière artificielle telles qu’usines, navires ou plateformes pétrolières maritimes, et chacune d’entre elles a un impact particulier sur l’équilibre naturel nocturne de l’environnement qui l’entoure. Sanya, 21 mars 2012.
“Until around 2013, the global trend was to have orange lighting, which is less aggressive for the environment,” owing to the ubiquity of low-pressure sodium lamps, which are less polluting during their manufacture, but more expensive to produce, Sánchez explains. “Since 2014, LED lamps have been appearing and spreading at an ever-increasing rate,” as they are cheaper to manufacture and install (although at the cost of a greater initial environmental impact), so there has been a tendency to install street lights in greater numbers and with greater intensity than before, almost always in white with cold colour temperatures, which is aggravating the situation at an alarming rate.
There are parts of the world, such as India, Egypt or the Arabian Peninsula, where blue-white light has been spreading massively in a very short space of time. There are places like Singapore, where night-time darkness is almost non-existent, and whole regions where we are seeing a huge rise in the problem, especially in Asia (China, Vietnam, India and South Korea, for example), as well as in Africa and South America. “In the West we stuck with what we had until we started putting in LEDs”, so the challenge from now on will be to make good use of the LEDs that are installed when the lighting needs to be replaced (installing lights that are closer to amber, and that decrease in intensity as the night progresses).
L’Égypte est un des endroits de la planète où s’est multiplié le recours massif aux lampadaires dotés de LED à grande intensité, particulièrement polluants ». C’est aussi l’un des pays qui absorbe les versions les moins chères de ce type de lampes, et en grande quantité. L’éblouissement qui en résulte saute aux yeux depuis l’espace. La comparaison avec les zones du Caire qui disposent encore de lampadaires à lumière orangée est éloquente. Le Caire, 5 mai 2021.
“The introduction of bright white LED light fixtures has made it simple and cheap to flood the world with more light than is needed – wasting energy and money at the same time,” says Ruskin Hartley, executive director of the International Dark-Sky Association (IDA), which has helped protect more than 110,000 square kilometres from light pollution, around the globe, with its outreach and best practice certification.
Light pollution is “one of the most pervasive and least understood forms of pollution. Fortunately, it is among the easiest to solve – and it does not mean turning off all the lights,” explains Hartley. Instead, we need to understand that more light does not always mean better light – in fact, it is often quite the opposite. “One of the primary challenges is breaking down the myth that more light will make you safer. It is quite the reverse. We are learning that more light, and in particular glare, makes it harder to see. Unfortunately, over the past decade, the situation in the United States and many Western countries has gotten much worse.”
La capitale espagnole a procédé en 2016 au plus grand changement d’éclairage urbain en Europe. Bien que ponctuellement, dans certaines zones de nouveaux luminaires dotés de lampes à LED de couleur blanche ont été installés (qui ont un impact environnemental plus pernicieux), la plus grande partie de la ville reste éclairée de manière traditionnelle avec des lampes à vapeur de sodium sous basse pression de couleur ambre. Madrid, 24 juillet 2021.
There is an urgent need to build awareness about the issue and to learn to make proper use of the technology available, which Sánchez summarises in the form of five good practices : “Do not put light where it is not needed, turn it off when it is not going to be used, direct it towards the ground [preventing part of the light from creating glare and escaping towards the surroundings and the sky], lower the level of lighting when it is not needed so much [reducing its intensity as the night progresses] and use as little blue light as possible. And if you don’t do all five things at the same time, you’re not doing it right.”
In this regard, Sánchez highlights two very illustrative European cases. A bad example, well-intentioned but with disastrous results, was that of Milan, which in 2014 suddenly changed the lighting in a large part of the city to bright white LEDs, with a profusion of street lights and the same light intensity all night long. The opposite happened in 2016, in Madrid, which although it also put in some white LEDs, improved its energy efficiency and the quality of its lighting in most of the city by reducing, by up to 60 per cent, the intensity of all the city’s street lights at the same time during the night. The people of Madrid are not even aware of this, as human vision works by contrast. Without bright beams of light and, above all, blue light, and with uniform lighting, you see better and have a much lower environmental impact.
Sur cette photo, on aperçoit les villes frontalières de Ciudad Juárez (Mexique) au sud, et d’El Paso (États-Unis) au nord. Bien que les frontières politiques ne soient pas visibles depuis l’ISS, les différences d’éclairage sont révélatrices ici : une épaisse ligne jaune, correspondant à la frontière physique, qui divise la masse lumineuse inégalement dense des deux côtés. Pour l’ESA, « la lumière que les astronautes voient est un gaspillage total d’énergie qui pourrait être mieux utilisée à d’autres fins ».
“The solution is to measure, measure and measure again,” concludes Sánchez, who calls for lighting policies to be based on scientific data that shows that every change made delivers what it promises when it is implemented, such as increasing safety (in a real, not perceived, way) and reducing energy consumption and environmental impact. “Solution number two is to follow good practice, and LED is wonderful technology – it costs more to manufacture but it allows you to dim the light, to regulate the colour [...]. The only complicated thing is the colour, because when you have already installed white (and not amber) it is more difficult to change, but within the next decade we know that we are going to have to change all the street lights on the planet, so let’s do it right.”
