Words by Annukka Larsen
“Ultimately, light pollution is wasted energy, and we need to address it to deliver many of our shared aims, from meeting commitments on climate change, to improving public safety”
The modern city lives and works around the clock, and after dark it depends on good lighting. Street lights provide comfort, safety and a sense of security, and enable us to get around, whether by foot, bike, car or public transport. But as the amount of light in the urban environment has increased, we’re also seeing a number of detrimental effects.
The International Commission on Illumination (CIE) defines obtrusive light as “light directed above the horizontal and to directions not needed”. It can take the form of a dazzling glare from a private yard or construction site, illuminated advertising screens or facades, or over-lit sports grounds or public spaces. This is unpleasant and irritating, and makes it difficult for people to take in essential information about their environment. In other words, light pollution can undermine the sense of comfort and safety that it is expressly intended to convey.
Light pollution can also have more serious consequences for our health. Light is the most important factor in our circadian rhythms, regulating our internal clock. Exposure to too much light at night disrupts production of the sleep hormone melatonin, and has been associated with many adverse affects on our physical and mental wellbeing, from sleep deprivation, fatigue and anxiety to an increased risk of cancer. Nature suffers too: 28% of vertebrates and 64% of invertebrates are nocturnal, and a significant proportion of pollinators are night-active. Light interferes with migration patterns, the growing seasons of plants and the health of natural habitats. Clouds are not supposed to glow at night.
Happily, controlling obtrusive light is a relatively quick win — this is one of the easiest environmental pollutants to eradicate. Street and road lighting are typically assumed to be the greatest contributors, but research has shown that advertising, facades, accent lighting, and parking and sports facilities all provide a significant share. A 2020 experiment in Tucson, Arizona saw scientists dim 14,000 points of light in the city’s street network, and then use satellite images to examine changes in its radiance. They found that streetlights accounted for just 13% of the total visible light after midnight.
Ultimately, light pollution is wasted energy, and we need to address it to deliver many of our shared aims, from meeting commitments on climate change, to improving public safety, to supporting healthier communities and ecosystems. A more harmonious nocturnal landscape also means brighter, starrier skies — and the chance to reconnect city dwellers with a beauty our ancestors once took for granted.