Kiera Jefferson
Light pollution is the human-made alteration of outdoor light levels from those occurring naturally, and it's having a detrimental impact on the environment, wildlife, and human health. It is caused by the overuse and misuse of artificial light at night, such as street lamps, exterior lights, and illuminated signs, which shine outward and upward into the sky. This has various adverse effects, including disrupting the natural rhythms of plants and animals, interfering with astronomical observations, wasting energy, and compromising human health. The good news is that light pollution is reversible, and individuals, institutions, and governments can all take steps to reduce it.
| Characteristics | Values |
|---|---|
| Definition | The human-made alteration of outdoor light levels from those occurring naturally |
| Sources | Street lamps, parking lot/shopping mall lights, exterior lights on homes/businesses, neon signs, illuminated signboards, cars, offices, factories, advertising, buildings |
| Impact on humans | Sleep disorders, insomnia, delayed sleep-phase syndrome, depression, hypertension, attention deficit disorder, obesity, diabetes, heart disease, headaches, worker fatigue, stress, decreased sexual function, increased anxiety |
| Impact on wildlife | Disrupts nocturnal ecosystems, affects migration patterns, wake-sleep habits, habitat formation, mating, feeding, predator-prey relations, plant phenology, plant pollination and reproduction, amphibian foraging and reproduction |
| Environmental impact | Wastes energy, mars landscape beauty, disrupts ecosystems, impacts climate |
| Economic impact | The International Dark-Sky Association estimates that 1/3 of all lighting is wasted at an annual cost of $2.2 billion |
| Reversibility | Unlike many other forms of pollution, light pollution is reversible |
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What You'll Learn
Light pollution impacts human health and well-being
Light pollution, caused by the excessive or unnecessary use of artificial outdoor lighting, is having a detrimental impact on human health and well-being. This form of pollution is a relatively modern phenomenon, brought about by urbanization and industrialization, and is now considered one of the most pervasive forms of environmental pollution.
The primary way in which light pollution affects human health is by disrupting the natural circadian rhythm, or the 24-hour sleep-wake cycle, which is governed by the day/night light cycle. Nocturnal light exposure has been linked to reduced levels of melatonin, a hormone that is released in the dark and inhibited by light. This disruption can lead to a range of health issues, including sleep deprivation, fatigue, stress, anxiety, and an increased risk of certain cancers, particularly hormone-related cancers such as breast and prostate cancer.
In addition to the physical health impacts, light pollution has also been associated with mental health issues. Research has suggested a link between light pollution and an increased risk of mental disorders, depression, and obesity. A 2023 paper published in GeroScience also highlighted the potential connection between light pollution and Alzheimer's disease, although more research is needed to fully understand this relationship.
The impact of light pollution on human health is not limited to direct exposure to outdoor lighting. Indoor artificial lighting can also contribute to health issues, particularly when it reaches people inside at night and affects hormone production. Blue light, in particular, is of concern as it is found in many electronic devices such as computers, TVs, and cell phones, and is known to reduce melatonin levels. The American Medical Association has expressed concern about exposure to blue light, recommending shielding light fixtures and using lighting with a lower correlated color temperature.
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It disrupts the natural rhythms of wildlife
Light pollution has a significant impact on wildlife, disrupting the natural rhythms of various species and affecting their behaviour, health, and survival.
Nocturnal animals, in particular, have evolved to depend on the cover of darkness to carry out essential activities such as breeding, foraging, and migrating. The introduction of artificial light radically alters their nighttime environment, making it harder for them to hide from predators. According to research scientist Christopher Kyba, artificial light "probably represents the most drastic change human beings have made to their [nocturnal animals'] environment."
One well-known example of this is the impact of light pollution on sea turtles. Female turtles nest on beaches, and after about two months, the hatchlings emerge and instinctively scramble towards the brightest horizon—usually the moon and starlight glimmering off the water. However, artificial lights disorientate them, leading them away from the safety of the ocean and towards potential dangers such as dehydration, predators, and roads.
Light pollution also affects bird migration. Birds that navigate by starlight can become confused and lose their way, and they may collide with brightly lit buildings. Even a brief flash of headlights can disrupt fireflies' mating signals, and the light from street lamps can cause insects to gather and be instantly killed. Insects are a primary food source for many birds and other animals, so declining insect populations due to light pollution can have a ripple effect on the entire food web.
Some predators exploit the attraction of their prey to artificial light, affecting food webs in unanticipated ways. For example, moths, frogs, and sea turtles are all attracted to light, which can make them an easy target for predators. In addition, artificial light can alter the sleep patterns of animals, affecting their health and reproductive cycles.
Addressing light pollution can have immediate positive effects on wildlife. Simple solutions include turning off unnecessary lights, using darker finishes and non-reflective materials for outdoor lighting, and choosing amber, red, or orange-coloured lights, which wildlife is generally less sensitive to.
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Light pollution affects ecosystems and food webs
Light pollution, defined as the presence of unwanted, excessive, or inappropriate artificial lighting, has detrimental impacts on ecosystems and food webs. It disrupts the natural balance of ecosystems, affecting the behavior and physiology of plants and animals.
One example of how light pollution impacts ecosystems is by favouring certain species over others. Lamp posts, for instance, attract flying insects, benefiting those spiders that build their webs directly on them while disadvantaging spider species that avoid lit areas. This simple example demonstrates how artificial light can alter species frequencies and food webs.
Light pollution poses a serious threat to nocturnal wildlife, disrupting their natural behaviours and patterns. It can confuse animal navigation, alter competitive interactions, and change predator-prey relationships. For example, bats tend to avoid lit-up areas to remain hidden from predators such as owls. Fish also adapt their behaviour in response to light, moving to deeper waters.
The impact of light pollution on wildlife extends to their health and well-being. Research has shown a connection between light pollution and adverse health effects in animals. For instance, sea turtles and birds that rely on moonlight during migration get confused by artificial light, lose their way, and often die.
Additionally, light pollution contributes to the degradation of environmental quality. It is considered a form of waste energy, often generated by the combustion of fossil fuels, which leads to increased air pollution and environmental harm. The reduction in night sky visibility due to "skyglow" from poorly designed lamps and security floodlights is a significant concern for astronomers and casual observers of the night sky.
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It is a driver of insect declines
Insects are attracted to light, and artificial light can create a fatal attraction for them. Insects have, for all evolutionary time, adapted to the daily cycle of light and dark, the lunar cycle, and the annual cycle of the seasons. However, artificial light at night (ALAN) has disrupted this cycle, and insects have not evolved adaptations to ALAN. Some species retreat from artificial light, while others are attracted to it, circling it until claimed by injury, exhaustion, or predation. The light output of most common fixtures is more than enough to disturb the entire habitat of small-bodied animals such as insects.
ALAN impacts the vital biological functions of nocturnal and diurnal insects, affecting their behaviour and physiology. ALAN can also interact with other anthropogenic disturbances such as climate change or noise pollution in complex ways. For example, pollinator insects pushed from agricultural fields to road verges by pesticides will be more exposed to streetlights and vehicle headlights. Impacts on single species will have downstream effects on other members of the food web, and the outcome can be extremely difficult to predict.
The impacts of ALAN vary between insect orders. Excess light makes it difficult for some species, like fireflies, that rely on bioluminescent cues to find mates. Some insects use polarized light to find bodies of water where they breed, and reflections from outdoor fixtures confuse their sense of direction. For instance, mayflies, which only live and breed for a day, can be confused by light bouncing off asphalt and lay their eggs in the street instead of a lake or stream. A mistake like that can wipe out an entire population overnight.
Artificial light also interferes with the way some insects hunt at night and can hinder their ability to navigate. Insects are attracted to the headlights of moving cars, with an estimated 100 billion meeting their end on German highways each summer. ALAN also affects the flowering plants that bees rely on for their food source. Research has shown that light pollution reduces nocturnal pollinator visits to flowers by 62% in some areas.
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Light pollution obscures the night sky
Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is caused by the overuse and misuse of artificial light at night, which shines outward and upward into the sky. This can include light from street lamps, parking lots, shopping malls, exterior lights on homes and businesses, and illuminated signs.
Sky glow, a type of light pollution, is the brightening of the night sky, mostly over urban areas, due to the electric lights of cars, streetlamps, offices, factories, outdoor advertising, and buildings. This turns night into day for people who work and play long after sunset. People living in cities with high levels of sky glow have a hard time seeing more than a few stars at night. According to a 2023 study, the number of stars visible in the night sky decreased by 7-10% per year from 2011 to 2022. This means that in a decade, a location with 250 visible stars in 2011 would have only 100 visible stars.
Light pollution competes with starlight, reducing the ability of astronomers to view celestial objects. It also mars the wilderness experience and landscape beauty. The Bortle scale is a nine-level measuring system used to track how much light pollution there is in the sky. A Bortle scale of four or less is required to see the Milky Way, while a rating of one indicates a "pristine," or the darkest possible, night sky.
Light pollution has also been shown to have adverse effects on human health and well-being. Nocturnal light interrupts sleep and confuses the circadian rhythm, the internal 24-hour clock that guides day and night activities and affects physiological processes. Disruption of the circadian rhythm has been linked to sleep disorders, depression, hypertension, attention deficit disorder, obesity, diabetes, and heart disease.
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Frequently asked questions
Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is caused by the whole world's ever-expanding reliance on artificial light.
Light pollution has negative impacts on wildlife, human health, and ecosystem functions. It disrupts nocturnal ecosystems, interferes with the natural rhythms of plants and animals, mars the wilderness experience, and wastes energy.
Light pollution can confuse animal navigation, alter competitive interactions, change predator-prey relations, and cause physiological harm. It also impacts animal behaviours such as migration patterns, wake-sleep habits, and habitat formation.
Light pollution can interfere with human health and safety. It can disrupt the circadian rhythm, the internal 24-hour clock that guides day and night activities, and affect physiological processes. This disruption has been linked to sleep disorders, depression, hypertension, attention deficit disorder, obesity, diabetes, and heart disease.
Solutions to light pollution include adjusting light fixtures, using more appropriate light bulbs, and educating the public to push for legislative change. Individuals, institutions, and governments should work together to adopt nature-friendly outdoor lighting and establish lawful requirements for outdoor lighting.
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