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Why Dark Skies are the New Climate Change Frontier

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A man camping enjoying the brilliance of a starry sky
A man camping enjoying the brilliance of a starry sky

By Sarah Currie-Halpern, Co-Founder and Partner


For most people, light pollution is more annoying than concerning. Even describing it as ‘pollution’ sounds a little severe. Water or soil pollution, for instance, require concentrated decontamination measures. Light pollution is frustrating for stargazers, but really just a matter of flipping a switch. Right?


Not exactly. We’re reminded of the environmental dangers of filling the skies with artificial light (and sound) every New Year’s Eve, when fireworks cause birds to abandon their nests en masse and die in huge numbers from stress. The other 364 nights of the year, however, offer little respite. A January 2023 study found that light pollution increased 9.6% globally each year between 2011 and 2022, and it’s only getting worse in North America, where light pollution has reached an annual increase of 10.6%. According to National Geographic, some 99% of Americans and Europeans live under “sky glow,” a term for the brightened night sky caused by manmade light scattering in the atmosphere.


The U.S. seen at night from space, revealing many heavy concentrations of light pollution across the country
The U.S. seen at night from space, revealing many heavy concentrations of light pollution across the country

This isn’t just bad news for those amateur stargazers. Light pollution contributes to climate change, harms animals on every tier of the food chain, and makes habitats—including human ones—unhealthy and even unlivable. Here’s what’s really hiding in the shadows:


Light pollution is visibly wasted energy

A street light scattering light upward contributing to "sky glow"
A street light scattering light upward contributing to "sky glow"

In simplest terms, light pollution is caused by light scattering into the atmosphere and space. If electric light is beaming into the sky, then it’s not doing what it was designed to do: light something on the ground for human use. That makes it wasted light, and wasted light is wasted energy. The Department of Energy estimates that outdoor lighting in the U.S. consumes about 1.3 quadrillion British thermal units annually. It’s impossible to say exactly how much of that energy is being wasted lighting empty parking lots and office buildings, but anyone who has driven around late at night knows it’s not a small percentage. DarkSky International estimates that light emissions account for at least 1% of global greenhouse gas emissions, and every night we send a huge proportion of those nearly 250,000 annual gigawatts directly into space.


Light pollution harms wildlife and natural habitats

A baby bat, bats are nocturnal animals
A baby bat, bats are nocturnal animals

Around 70% of all mammals are nocturnal. Another 80% of North American birds migrate primarily at night. For these animals, light pollution is not just a disruptive phenomenon but a dangerous one, meaning entire ecosystems are now at the mercy of human light pollution. Reproduction, hunting, and basic survival are compromised. Newly hatched sea turtles need the brighter horizon that occurs naturally over the ocean to see where they’re going and can be led further ashore by streetlights. Insects that form the basis of the food chain are attracted to and killed by light sources, threatening the bird populations that rely on them as food sources. Disrupting the darkness is disrupting the life cycle itself.


Light pollution makes humans sicker


Humans may not be nocturnal, but we need darkness as much as any other species. For thousands of years, our biological clocks evolved in tandem with the natural cycles of sunrise and sundown. LED lights in particular have wreaked havoc on our circadian rhythms. Over time, not sleeping enough (and not sleeping deeply enough) contributes to a host of serious health problems—hypertension, heart disease, obesity, and diabetes among them. The American Medical Association has already issued warnings about melatonin-suppressing LED lights, warning communities against using the technology as street lights. The brighter our cities, the worse we sleep. And the worse we sleep, the shorter our life expectancies. Unfortunately LED lights have been a major contributor to increasing levels of light pollution around the world.


There’s a kernel of truth to the idea that we can just flip a switch on light pollution. Fixing light pollution is indeed possible through existing solutions like dimmers, lighting curfews, spill-reducing fixtures, smart regional lighting ordinances, and by buying from lighting manufacturers who offer dark-skies friendly lighting solutions, which is especially important for municipalities purchasing on a large-scale. Doing so will make us sleep better at night—in more ways than one.

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