Buzz
A report from 2001 found that two-thirds of the United States and more than half of Europe can no longer spot the Milky Way with their naked eye. The cause is light pollution—there are so many artificial lights now that they are disturbing various forms of life, including humans. Worse still, some of the proposed solutions may do more harm than good, at least for us.
10. Light Pollution Is Threatening Sea Turtles
Sea turtles spend most of their lives in the ocean but do come ashore to lay their eggs in the sand. When the hatchlings emerge, they must quickly make their way to the water to avoid becoming easy prey for predators. With many beachfront areas being developed for hotels, restaurants, and homes, these turtles are increasingly in danger at both stages of their life.
Female sea turtles searching for a place to nest will avoid areas with excessive lighting. If she cannot find a dark spot after several attempts, she may end up choosing less suitable locations, which significantly reduces the survival chances of her hatchlings. The baby turtles use moonlight as a natural guide to reach the ocean, but artificial lights can confuse them, leading them straight into the path of predators or vehicles. Each year, thousands of young sea turtles are lost in Florida, home to nearly 90 percent of America's sea turtle nests, due to the dangers of artificial lighting.
The Sea Turtle Conservancy (STC) is dedicated to educating the public about the importance of proper lighting on beachfront properties. For those living by the coast, STC recommends using yellow, amber, or red lights to minimize disruption to turtle populations, as well as positioning lights low to the ground and ensuring they are shielded. Since 2014, STC has been collaborating with Florida authorities to enforce new rules requiring property owners to switch off or adjust lighting during turtle nesting seasons.
9. Light Pollution Disrupts Amphibian Breeding Cycles
In areas near wetlands, the nighttime chorus of frogs is one of the most common sounds of spring. However, light pollution could one day silence these calls completely.
Most amphibians are nocturnal and depend on water, with even toads returning to water to breed. Due to their dependence on water, these creatures struggle to adapt when their habitats are disrupted. As nocturnal beings, amphibians rely on photoperiods—how much sunlight they receive in a 24-hour period—to mark changes in their environment. This photoperiod is the primary signal they use to know when to reproduce or enter hibernation, and they are highly sensitive to it.
The introduction of artificial light has led to both physical and behavioral disruptions in many amphibian species, including the loss of their ability to recognize when it’s time to breed or return home. As a result, they miss key opportunities to reproduce. Many amphibian populations are already declining, and light pollution plays a significant role in this problem.
8. Light Pollution Is Devastating for Bats
Bats play a crucial role in controlling insect populations, including those species that bother and infect humans. However, light pollution is having a negative impact on bat populations. While not all bat species are affected, many are extremely sensitive to light and avoid areas lit by streetlights or other artificial sources. Insects are attracted to artificial lighting, but since some bats won’t enter these lit areas, they lose vital feeding opportunities. Additionally, bats that do enter areas with artificial light face fewer insects than they would in naturally dark environments. This disruption can lead to the decline of entire bat colonies. Light pollution can also delay bats’ emergence from their roosts, causing them to miss crucial feeding times after dusk.
A study conducted in Britain, where it is illegal to harm or capture bats due to recent population declines, has revealed that in areas where critical foraging habitats are illuminated by artificial light (especially floodlighting), certain bat species avoid these locations altogether. As a result, roads become barriers to bat movement, and natural spaces like woodland paths, rivers, and streams—where insects gather at night—are inaccessible. The issue is serious enough that using lighting on some properties may even be considered a criminal offense unless consultation with British conservation authorities occurs.
7. Light Pollution Disrupts the Migratory Patterns of Fish
Many fish species migrate to spawn, traveling from oceans to lakes or along rivers. However, studies have shown that streetlights from nearby cities can interfere with these migratory patterns.
In 2012, a study comparing Atlantic salmon smolts in a controlled group with those exposed to simulated artificial lighting found that the control group migrated at sunset. In contrast, the group exposed to artificial light migrated randomly, seemingly disoriented by the lighting. This disruption could negatively affect their fitness. Furthermore, since young salmon typically emerge at night to avoid predators, such random changes in migration timing increase their risk of being preyed upon.
It gets even worse—further research has demonstrated that public lighting, especially during the night, can interfere with essential behaviors like foraging, predation, shoaling, and overall reproductive success. This is detrimental not only to marine ecosystems but also to the fishing industry, which exacerbates the problem by using floodlit boats at night to lure fish from miles away, often catching species they don't intend to. Species likely affected include trout, sea trout, barbel, graylings, eels, and lampreys.
6. Light Pollution Can Harm Trees
Have you ever walked through a city in autumn and noticed a tree with leaves only on the side facing a streetlight? The contrast can be striking, and the reason behind it is concerning. During autumn, many trees enter dormancy to survive the harsh winter months, shedding their leaves to conserve energy. They rely on photoperiods to determine when to start this process. Night lighting, especially in the red to infrared spectrum, artificially extends the day for plants. Since angiosperms (flowering plants, including most trees) base their growth, dormancy, and flowering on uninterrupted periods of darkness, this disruption can lead to problematic periods of non-dormancy.
Photoperiods also affect leaf shape, surface texture (pubescence), pigmentation, and root development, all of which influence plant fitness and can be disrupted by light pollution. Naturally, any disruption to flowering plants also impacts pollinating insects. And as one-third of our food supply depends on pollinators, the effects extend to all of us.
5. Migrating Birds Are Drawn to Their Demise
Apart from the potential health risks to humans, few impacts of light pollution have garnered as much public concern as the struggles of birds. Many bird species are nocturnal and migratory, relying on the setting sun, moon, and night sky for guidance. However, bright artificial lights at night can mislead them, causing them to mistake the lights for their navigational tools, leading them straight into buildings. These collisions often result in the birds' deaths, and even those that survive are vulnerable to predators. Researchers attribute the decline in songbird populations to such collisions, with a parallel rise in scavengers like rats and seagulls, which feed on the carcasses of the fallen birds.
How serious is the problem? Chicago’s Hancock Center recently reduced its lighting at night to prevent nearly 1,500 birds from dying each night when they collide with the building during migration season. In a more striking example, on the first anniversary of the 9/11 attacks, New York commemorated the tragedy by shining two massive beams of light into the sky where the World Trade Center once stood. The resulting cloud of thousands of birds trapped within the lights highlighted the extent of the issue for all to see.
4. The Impact of Artificial Light on Insects
We’ve all seen the common sight of a porch or street light surrounded by a frenzy of insects, so much so that the phrase “like a moth to a flame” has come to symbolize an uncontrollable attraction. For insects, that is precisely the case—many species are irresistibly drawn to artificial lights. Once they enter the light’s domain, escape becomes incredibly difficult, if not impossible. This is because many insects, particularly nocturnal ones, rely on natural light sources like the moon for guidance, and artificial lights disrupt their navigation cues.
Artificial lights not only confuse their navigation but also interfere with normal flight behaviors and migratory routes. As a result, insects are killed in large numbers, either by the intense heat of the lights or by predators taking advantage of the easy prey. The scale of this loss can drastically impact insect diversity, and if a species is unable to reproduce quickly enough, it might completely disappear from the area.
An additional critical issue tied to insects and light pollution is the spread of disease. Some species of disease-carrying insects may have evolved to associate artificial light with human activity. This connection has led researchers to link light pollution to the transmission of diseases carried by mosquitoes (malaria, dengue, West Nile virus), sand flies (leishmaniasis), and kissing bugs (Chagas disease). While mosquitoes are typically not attracted to light, artificial lighting enables people to stay outdoors longer, exposing them to mosquitoes during their most active periods.
3. The Problem With LEDs
Thankfully, more and more individuals are becoming conscious of the diverse issues stemming from light pollution. The good news is that it’s an environmental challenge that can actually be addressed relatively easily. The introduction of energy-efficient LED technology is paving the way to replace outdated street lighting with specialized, glare-free lights that have the potential to significantly reduce harm to local wildlife. While LEDs may have a higher upfront cost, they outlast sodium lights, consume a fraction of the energy, and contain no mercury like fluorescent lights. Additionally, their wavelengths tend to be much less disruptive to wildlife species. What's not to love?
However, the solution for animals may end up creating a more significant problem for us. Blue-rich LEDs increase the amount of light pollution the human eye absorbs, thus heightening the risks already discussed. The blue wavelengths emitted by most LEDs resemble the light of the early morning sun, signaling our brains to wake up (so all those gadgets around us are sending exactly the wrong message at night). Researchers contributing to the Journal of Applied Ecology predict that outdoor LED lighting could worsen light pollution's effects considerably. The consensus is that effective light shielding, rather than the type of lighting used, is our best approach.
2. Light Pollution Can Damage Our Physical Health, Too
Light pollution isn't only affecting our mental well-being; it has become such a significant health concern that the American Medical Association (AMA) has issued a resolution linking it to various physical issues. The resolution highlights that the surge in artificial light, including streetlight glare and ambient light spilling into our homes, is associated with higher rates of breast cancer and weakened immune systems. The effects are not limited to direct health problems—greater glare also reduces visibility, leading to more traffic fatalities during nighttime hours. The AMA estimates that reducing light pollution could save over $10 billion annually in healthcare and related costs.
The Council of Europe has also highlighted that light pollution is associated with a range of health issues, including diabetes, depression, poor academic performance, and concentration difficulties. Additionally, there is a known connection between artificial lighting and obesity. Moreover, artificial lighting has been found to disrupt the development of the circadian rhythm in newborns.
Breast cancer is arguably the most serious health condition linked to light pollution. A study conducted in 2001 uncovered a strong correlation between women who had worked night shifts for over 30 years and an elevated risk of developing breast cancer.
1. It’s Driving Our Minds Insane
In 2011, researchers investigated how artificial light impacts mice, with unsettling results that have significant implications for humans. Mice that were kept outside the natural day-night cycle showed troubling signs of mental and physical decline. Those exposed to a 20-hour light cycle experienced changes in the neurological areas controlling emotion, had difficulty navigating mazes, and became easily startled by unfamiliar surroundings. Their physical health also deteriorated, leading to obesity and altered levels of insulin and leptin, which are crucial metabolic hormones.
Every living being, humans included, possesses an 'internal clock' known as the circadian rhythm, which follows the natural 24-hour day. Light exposure is detected by a pigment called melanopsin, found in the human retina. Interestingly, until the 1980s, many scientists mistakenly believed that humans were immune to the effects of the circadian cycle.
This internal rhythm governs numerous processes in our bodies: when we should be awake, when it's time to rest, when our organs are more active, when to eat, when to digest, and countless other instructions. Our circadian rhythm also greatly influences our mood by regulating hormone production. Similar to the mice in the study, our minds and bodies are negatively affected by artificial lighting, leading to sleep disorders, behavioral issues, and mood disturbances. Additionally, many researchers believe that our diminished connection with the night sky and the stars is damaging our inner well-being.
In 2013, another study indicated that artificial indoor lighting is impacting our melatonin levels (another time-regulating hormone), making us feel sleepy at odd times. In one experiment, groups of 'early birds' and 'night owls' were sent to camp with only sunlight and campfires for illumination. Both groups' circadian rhythms quickly adapted to align with the sun. The researchers concluded that morning drowsiness in many people is likely caused by indoor lighting disrupting this natural rhythm. They recommend maximizing exposure to natural light and reducing unnecessary indoor lighting a few hours before bedtime.
