The Hidden Cost of Light Pollution
After midnight at the Megler Bridge, near the mouth of the Columbia River, Astoria, Oregon. Photo: Jeffrey St. Clair.
The night sky—the silent dark between stars—is a living commons bridging Earth, life, and spirit. As the 13th‑century Zen master Eihei Dōgen taught in Keisei Sanshokuor “The Sound of the Streams, the Shape of the Mountains,” rivers, forests, mountains, and night are not mere backdrops but the body and speech of the Buddha—sacred, alive, and deserving reverence.
Imagine stepping outside on a clear night, looking up at the stars, only to find the heavens dimmed to a faint, featureless glow. Where once the Milky Way stretched across the sky, now only a handful of stars remain visible to the naked eye. This creeping veil is light pollution—the quiet theft of night’s natural darkness. It spills from streetlights, billboards, and high-rise windows, casting cities in a permanent, artificial twilight.
While it leaves no residue in air or water, its effects ripple through life on Earth, confusing migrating birds, misleading sea turtle hatchlings, and disorienting nocturnal animals. The same lights also negatively impact humans, disrupting sleep, altering hormone cycles, and affecting overall health. Also, access to natural darkness is not equally experienced: communities differ in how light—or the lack of it—shapes public safety, cultural life, and ecological exposure.
An international team of researchers notes that “[m]any of the behavioral and physiological processes of life on Earth are connected to daily and seasonal cycles. For example, visual predation requires sufficient light, and predator-prey interactions are therefore expected to be affected by sky glow.” In response, groups like DarkSky International have emerged as advocates for protecting natural darkness, safeguarding both our view of the stars and the countless species whose survival depends on nighttime.
Mažeika S.P. Sullivan, director of the Wilma H. Schiermeier Olentangy River Wetland Research Park and lead author of a 2018 research published in Ecological Applications, said, “We are experiencing this pollution that we don’t think about, but it’s all around us and it’s chronic and it’s happening everywhere—from newly lit villages in rural Africa to streams alongside the highway in Columbus, Ohio. It’s also unprecedented in Earth’s history.”
Taylor Stone, a scholar in environmental ethics, argues that natural darkness has intrinsic moral value and should be considered alongside clean air and water while making decisions about urban lighting and biodiversity protection.
The Growing Problem of Light Pollution
Light pollution refers to any excessive, misdirected, or intrusive artificial lighting that disrupts natural darkness. Scientists identify four primary forms of light pollution: glare from overly bright lights; sky glow, the diffuse brightening of the night sky in inhabited spaces; light trespass, where unwanted light spills where it “is not intended or needed”; and clutter, the visual confusion created by dense, competing light sources.
Urban growth intensifies all four components. Streetlights, signage, stadiums, and architectural lighting cast a constant haze over cities.
Since 1992, global artificial light at night has grown substantially, with satellite‑based measurements showing at least a roughly 50 percent increase in detectable light emissions over 25 years and indications that total light output may have risen several times more than that when accounting for emissions satellites miss.
Citizen science data collected between 2011 and 2022 reinforce the rapid growth of light pollution. Volunteers around the world have documented steadily dimming night skies, with an estimated annual increase in sky brightness of roughly 9.6 percent—a rate faster than satellite measurements suggest. These observations highlight how even areas with policies meant to limit artificial light are still experiencing a marked decline in darkness. In practical terms, a child born today in a region where 250 stars were once visible might see fewer than 100 stars by the time they reach adulthood, illustrating just how dramatically our view of the cosmos can fade in a single generation.
Researchers warn that “Artificial light at night is significantly correlated for all forms of cancer, as well as lung, breast, colorectal, and prostate cancers individually. Immediate measures should be taken to limit artificial light at night in the main cities around the world and also inside houses.”
Dana Zartner, assistant professor in the International Studies Program and adjunct professor in the School of Law at the University of San Francisco, highlights that the global spread of artificial light and the resulting loss of natural darkness are having significant impacts on nearly all living things, including human health, animal behavior, and cultural and spiritual practices—a reality she and her co‑authors argue must be addressed through new legal and policy strategies to protect the night.
The most visible impact of light pollution is the erasure of the Milky Way. Sky glow washes out faint stars, leaving urban residents with a dim, impoverished sky. The Bortle Scale, which measures the brightness of the night sky in a specific location, shows that many cities now fall into the brightest categories, where the Milky Way is invisible. A 2016 study revealed that the Milky Way is not visible to more than one-third of the human population. “[M]ore than 80 percent of the world and more than 99 percent of the U.S. and European populations live under light-polluted skies,” the study published in Science Advances stated. In urban centers like New York, Beijing, and Mumbai, entire generations have grown up without experiencing a true night sky.
The cultural and psychological loss is profound. Philosopher Ivan Illich argued that environmental commons—silence, darkness, and natural space—can be destroyed through unchecked technological intrusion, constituting “the most fundamental form of environmental degradation.” Modern researchers echo this sentiment, noting that artificial night lighting disrupts ecological cycles and human perception. Losing natural darkness diminishes imagination, culture, and shared frameworks shaped by the night, even as artificial lighting creates new kinds of cultural and creative expression.
Impacts on Wildlife and Human Health
Artificial light destabilizes natural behaviors that nocturnal species rely on, including hunting, mating, and migration. Birds navigating by moonlight and starlight often collide with buildings, while sea turtle hatchlings, drawn to the brightest horizon, may head inland instead of the ocean. Plants and pollinators are affected as well: artificial lighting alters flowering schedules, interferes with insect activity, and weakens the delicate balance between plants and the species that sustain them. “About 30 percent–40 percent of insects that approach street lamps die soon thereafter… as a result of collision, overheating, dehydration, or predation,” stated a 2018 study published in Ecology and Evolution.
Researchers Davide M. Dominoni and Randy J. Nelson highlight how blue-enriched artificial lighting shifts activity patterns, hormone cycles, and energy use across species. These effects occur not only in cities but also along roads, industrial installations, and other lit areas, showing that artificial illumination impacts life far beyond urban centers.
Nocturnal insects—from moths to beetles—are exquisitely tuned to the rhythms of darkness. Artificial lighting disrupts navigation, feeding, and mating behaviors, drawing many to luminous traps where they perish or become easy prey. These declines ripple through ecosystems: birds, bats, reptiles, and amphibians lose vital food sources, while plants lose essential pollinators. Scientists reviewing more than 150 studies concluded that artificial light at night, combined with habitat loss, pollution, invasive species, and climate change, is “another important—but often overlooked—bringer of the insect apocalypse.”
Research shows that artificial light shifts the timing of activity in nocturnal, crepuscular, and diurnal species, rewiring food webs and destabilizing ecological networks. “Nighttime light is having profound impacts that extend to the entire ecosystem,” said Sullivan.
Humans, like all life, evolved under predictable cycles of light and dark. Artificial light at night (ALAN) suppresses melatonin, disrupts sleep, and raises risks of insomnia, anxiety, obesity, and diabetes, and has been linked to increased risks of cancers in sites such as the breast and colorectum. Blue-enriched LEDs, screens, and nighttime signage magnify these effects, particularly in children.
“Blue wavelengths of light are damaging to many forms of life, and glare from unshielded light compromises road safety and infiltrates bedrooms, suppressing melatonin production, undermining sleep quality and duration, and exacerbating susceptibility to many kinds of illness,” explains an article in the AMA Journal of Ethics.
Lighting, Safety, and Equity After Dark
Decisions about nighttime lighting are never neutral. They reflect whose safety is prioritized, whose presence in public space is welcomed or discouraged, and which communities bear the costs of either over- or under-illumination. In many cities, low-income neighborhoods and communities of color are exposed to harsher, more intrusive lighting—often justified in the name of crime prevention—while wealthier areas benefit from subtler, better-designed illumination or protected dark skies. At the same time, inadequate lighting in under-resourced areas can limit nighttime mobility, restrict access to public space, and heighten real or perceived risks for residents.
These tradeoffs raise critical questions of environmental justice. Excessive lighting contributes to health harms, disrupts sleep, and degrades local ecosystems, impacts that are not evenly distributed. Who lives under glaring streetlights that shine into bedrooms all night? Who loses access to darkness as a cultural, spiritual, or restorative experience? And who has a voice in deciding how the night is shaped? Initiatives like Light Justice emphasize that equitable nighttime lighting requires engaging historically neglected communities in the design process, ensuring that all neighborhoods benefit from safe, culturally vibrant, and ecologically responsible illumination.
Equitable nighttime design requires moving beyond one-size-fits-all approaches. It means engaging communities directly, recognizing different cultural uses of night, and designing lighting that supports safety and social life without turning public space into zones of constant surveillance or ecological disruption. When lighting policy accounts for equity, it becomes possible to protect both human well-being and the shared nighttime environment—ensuring that darkness and light alike are treated as common goods, not privileges.
Designing the Night: Balancing Safety, Health, and Ecology
Fortunately, communities can design night lighting that meets human needs—providing safety, visibility, and public enjoyment—while minimizing harm to wildlife, ecosystems, and human health. For example, Groveland, Florida, achieved International Dark Sky Community status in 2023 by implementing shielded, warm‑colored, and context‑sensitive lighting across streets and public spaces to reduce sky glow and enhance safety and nighttime experience.
Flagstaff, Arizona, has long maintained dark‑sky‑friendly lighting codes that balance urban illumination with sky preservation; zoning regulations restricting outdoor lighting per acre were approved by the city and county in 1989, and on October 24, 2001, Flagstaff was recognized as the world’s “first International Dark Sky City” by the International Dark Sky Association (IDA) for its pioneering work in protecting dark skies while addressing public safety and community needs.
Shielded, downward-facing lights minimize glare while maintaining visibility; warm-colored bulbs reduce blue-light emissions that disrupt wildlife and human circadian rhythms; and motion sensors or dimmers ensure lighting is only switched on when needed, supporting both safety and energy efficiency. Supporting local dark sky ordinances to protect the night skies helps entire neighborhoods and cities transition to healthier, more sustainable lighting, protecting nightscapes without compromising nighttime activity or security. The U.S. National Park Service provides outdoor lighting principlesthat demonstrate how shielded, targeted fixtures can reduce light pollution without compromising visibility.
Global Solutions and Dark Sky Sanctuaries
By certifying preserves, supporting community lighting policies, and raising awareness, DarkSky International provides practical solutions to reclaim the night. It protects and certifies dark sky preserves, advocates for responsible lighting, and equips communities to reduce glare and sky glow. Certified preserves—found on almost every continent—demonstrate that intentional lighting policies can restore star-filled skies. DarkSky has certified more than 200 dark sky places since 2001, spread across 22 countries.
For those seeking to experience the night sky in its natural glory, DarkSky International recognizes sanctuaries worldwide, including Big Bend National Park in Texas, Aoraki Mackenzie in New Zealand, NamibRand Nature Reserve in Namibia, and Exmoor National Park in the UK, while Jasper National Park in Canada was designated a Dark Sky Preserve by the Royal Astronomical Society of Canada in partnership with Parks Canada. These preserved landscapes show what is possible when lighting is carefully managed, offering a glimpse of the sky as it once was—and as it can be again.
Paul Bogard, author of The End of Night, writes: “Tonight, wherever you are, go outside and look at the sky. Can you see the wonders? … This was the darkness in which all life evolved and which our body and spirit still crave.” Chad Moore, a former wildlife biologist with the U.S. National Park Service, states: “When we add light to the environment, that has the potential to disrupt habitat, just like running a bulldozer over the landscape can.”
Light pollution is more than an aesthetic loss. It disrupts ecosystems, endangers wildlife, threatens pollinators, and affects human health. By shielding lights, reducing glare, advocating for dark sky policies, and supporting dark sky preserves, communities and individuals alike can reclaim the night. The night belongs to all life. Ensuring that future generations can see the stars also means addressing who benefits from thoughtfully designed lighting and who bears the burdens of over- or under-illumination, making equity central to reclaiming the night. Preserving darkness ensures that future generations can still look up and see the stars—a shared inheritance worth protecting.
This article was produced by Earth • Food • Life, a project of the Independent Media Institute, with research support from Meghan Grady.
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