Kiera Jefferson
Light pollution is the excess or inappropriate use of outdoor artificial light. It occurs when artificial light shines outward and upward into the sky, rather than focusing on the ground where it is needed. This can be caused by street lamps, exterior lights, and illuminated signs, among other sources. Light pollution has various negative effects, including disrupting human health, wildlife behaviour, and our ability to observe stars and other celestial objects. It can also cause light trespass, where light spills into unwanted areas, and glare, which causes visual discomfort. To show night-time light pollution, satellite imagery and ground-based networks of photometers, such as the Sky Quality Meter (SQM), can be used to measure the brightness of the sky and the number and intensity of light sources.
| Characteristics | Values |
|---|---|
| Definition | Excessive or inappropriate use of outdoor artificial light |
| Sources | Street lamps, parking lot/shopping mall lights, exterior lights, neon signs, illuminated signboards, cars, offices, factories, advertising, buildings |
| Effects | Erases stars from the night sky, adverse health effects in humans, disrupts ecosystems, wastes energy, increases impact of climate change, affects wildlife behaviour and migration |
| Solutions | Turn off lights, use fully shielded light fixtures, dim lights, cover lights with hand, use software to reduce stray light |
| Measurement | Night time satellite imagery, ground-based networks of photometers, Sky Quality Meter (SQM) |
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What You'll Learn
Light pollution's impact on human health
Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is caused by the excess or inappropriate use of artificial light outdoors, which shines outward and upward into the sky, where it is not wanted, instead of being focused downward. Common sources of light pollution include street lamps, parking lot lights, exterior lights on homes and businesses, and neon signs.
Light pollution has been shown to have adverse effects on human health. Firstly, it can interfere with the production of the hormone melatonin, which is released in the absence of light and inhibited when light is present. Lowered melatonin production due to light pollution at night can result in sleep deprivation, fatigue, headaches, stress, anxiety, and other health problems. Additionally, light pollution can negatively impact sleep quality, leading to excessive sleepiness, impaired daytime functioning, and an increased risk of obesity.
Moreover, research has suggested a link between light pollution and an increased risk of certain diseases, including diabetes and breast cancer, and potentially Alzheimer's disease. The American Medical Association estimates that white LED lamps have five times the impact on circadian sleep rhythms compared to conventional street lamps. Light pollution can also cause direct glare, affecting vision and nighttime activities, and sky glow, obscuring views of the night sky and diminishing the ability to adapt to darkness, causing blind spots and safety issues.
To address light pollution, it is recommended to turn off unnecessary lights and use fully shielded, light-efficient fixtures that prevent light from escaping upwards into the sky, reducing sky glow and glare. These measures can help restore natural light levels, benefiting human health and well-being.
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Light pollution's effect on wildlife
Light pollution is the excess or inappropriate artificial light outdoors. It occurs mainly due to the upward escape of light from fixtures like street lamps, exterior lights, and illuminated signs. Light pollution has a drastic impact on wildlife, affecting various creatures, including amphibians, birds, mammals, insects, and plants.
Firstly, light pollution disrupts the natural day and night cycle, which is crucial for the biological welfare of all life on Earth. Nocturnal animals, which are active at night, are particularly affected as their night-time environment is altered, making it difficult for them to hunt, feed, and hide from predators. For example, frogs, which are mostly nocturnal, may experience changes in their nesting behaviour and calling patterns due to artificial lighting, impacting their breeding success. Similarly, small mammals, such as mice, tend to eat less in lit areas to avoid attracting predators. In contrast, predators like foxes are drawn to illuminated areas in search of easy prey.
Secondly, artificial lighting can act as a trap for certain organisms, attracting them and leading to their exhaustion or death. Moths, for example, are famously drawn to artificial lights and can end up circling the light source until they are caught by predators or die from exhaustion. This phenomenon is not limited to insects; sea turtles and migratory birds are also attracted to lights, which can disrupt their navigation and feeding habits, leading to fatal collisions with light sources or dehydration.
Additionally, light pollution can lead to habitat loss for some organisms. Certain species may be repelled by artificial lights, excluding them from their natural habitats and forcing them to seek alternative living spaces. This disruption can have a ripple effect on the entire ecosystem, affecting the availability of food sources and the balance between predator and prey species.
The glare from artificial lights can also impact wetland habitats, disrupting the breeding rituals of amphibians like frogs and toads, whose nighttime croaking is an essential part of their reproductive process. Furthermore, light pollution can extend the day for diurnal species, such as songbirds, making them more vulnerable to predators and altering their breeding patterns.
To address these issues, it is crucial to reduce light pollution by employing shielded light fixtures that prevent light from escaping upwards into the sky. Dimming lights, using timers and motion detectors, and adopting seasonal lighting restrictions during critical migratory or mating seasons can also help minimize the disruptive effects of artificial lighting on wildlife.
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Sources of light pollution
Light pollution is a human-made alteration of outdoor light levels from those occurring naturally. There is no single country, group, or industry to blame for light pollution. Instead, it is a result of the entire world's growing reliance on outdoor electrical lights.
The primary cause of light pollution is outdoor lights that emit light upwards or sideways. Any light that escapes upward will scatter throughout the atmosphere and brighten the night sky, thereby diminishing the view. Light fixtures that direct all light downward greatly reduce the amount of light pollution. These are referred to as shielded lights or full cut-off. Light pollution can be further reduced by using a less powerful lamp or bulb.
Outdoor lighting consumes about 3 to 5% of electrical demand in developed countries. Depending on how light pollution is defined and the local lighting practices, the fraction of outdoor lighting that contributes to light pollution can range from 20 to over 50%. In some instances, even a single light can be disruptive to the natural lightscape. Boats, buildings, street lights, and even fireworks contribute to light pollution.
There are three other kinds of light pollution: glare, clutter, and light trespass. Glare is excessive brightness that can cause visual discomfort. Clutter is bright, confusing, and excessive groupings of light sources. Light trespass is when light extends into an area where it is not wanted or needed.
Light pollution can be detrimental to the health of people and animals in the area. It can impact the natural lightscape, causing confusion for birds and sea turtles guided by moonlight during migration, leading them to lose their way and often die. Insects, a primary food source for birds and other animals, are drawn to artificial lights and are killed upon contact with light sources.
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Methods to reduce light pollution
Light pollution is a human-made alteration of outdoor light levels from those occurring naturally. It has harmful effects on humans, wildlife, and the environment. It can be detrimental to human health by disrupting sleep and confusing the circadian rhythm, which can lead to metabolic disorders. It also has negative impacts on wildlife, affecting the migration of birds, the breeding patterns of nocturnal animals, and the mating rituals of frogs and fireflies.
- Use window shades or curtains to keep room lights from escaping your house or hotel room. This also helps with privacy, especially in close quarters such as apartment buildings.
- Avoid driving at night if possible. Using headlights contributes to light pollution and degrades the night sky.
- Turn off lights when they are not needed. Only light what truly needs illumination. This will also help reduce your energy costs.
- Reduce the use of electronic devices in the evening and avoid blue light from devices like phones and laptops. Blue light has been shown to reduce melatonin levels in humans, which can lead to sleep deprivation and other health issues.
- Use dimmers, motion sensors, and timers to reduce average illumination levels and save energy.
- Switch to LED lighting with warm-colored bulbs. LED lighting reduces illuminance without compromising visibility. However, avoid LED lights with blue light, as this creates more light pollution.
- Use outdoor lighting fixtures that shield the light source to minimize glare and light trespass.
- Support organizations like DarkSky International and the International Dark Sky Association (IDA), which work to reduce light pollution and educate the public. Advocate for local legislation to pass lighting ordinances that minimize light pollution.
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The global extent of light pollution
Light pollution is the presence of any unwanted, excessive, or inappropriate artificial lighting. It is a global issue that has been exacerbated by the overuse and misuse of artificial light at night. The brightening of the night sky due to light pollution is not limited to urban areas, as the glow from cities has been observed from distances of over 200 miles away from national parks. Light pollution is increasing globally, in both developed and developing countries, with 83% of the world's population estimated to live under light-polluted skies.
The primary sources of light pollution include street lamps, parking lot and shopping mall lights, exterior lights on homes and businesses, neon signs, illuminated signboards, and advertising. Artificial light from these sources can impact people and wildlife in several ways. Direct glare from light fixtures can affect vision and nighttime experiences, while sky glow from collective sources of artificial light scattered in the atmosphere can obscure views of the night sky. The brightening of the night sky caused by sky glow reduces the contrast between the sky and stars, making it difficult to observe celestial objects.
Light pollution also has ecological and health impacts. It disrupts the natural day-night cycle, affecting the circadian rhythms of humans and animals. Nocturnal light exposure can interfere with melatonin production, leading to sleep deprivation, fatigue, headaches, stress, and potential health issues. Additionally, light pollution affects the behavior and physiology of nocturnal wildlife, impacting migration, reproduction, hunting, and feeding. It can confuse animal navigation, alter competitive interactions, change predator-prey relationships, and cause physiological harm.
The effects of light pollution are not limited to the ground but extend into the sky as well. The glow from cities can enhance sky brightness by up to 1000 times on cloudy nights compared to clear ones, making it challenging to observe the night sky even in remote areas. Light pollution is also influenced by atmospheric conditions, with aerosols from haze, dust, and air pollutants enhancing sky glow. The scattering of light by these particles further brightens the night sky, reducing the visibility of stars and other celestial objects.
While light pollution is a pressing issue, there are efforts to mitigate its impact. Shielding lights to reduce glare, dimming lights, and turning off unnecessary lights can help reduce light pollution. Additionally, implementing lighting regulations and designing lighting fixtures that focus light downward can minimize the unwanted escape of light into the sky. These measures aim to restore the natural darkness of the night sky and alleviate the negative consequences of light pollution on humans, wildlife, and the environment.
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Frequently asked questions
Light pollution is the excessive or inappropriate use of outdoor artificial light.
Light pollution has a wide range of effects, including:
- Disruption of human health, including sleep deprivation, fatigue, headaches, stress, and anxiety.
- Disruption of wildlife behaviour, including migration, reproduction, hunting, and feeding.
- Reduced ability to observe stars and other celestial objects.
- Increased air pollution due to the electricity generation required for artificial lighting.
Common sources of light pollution include street lamps, parking lot lights, exterior lights on homes and businesses, neon signs, and illuminated signboards.
Nighttime satellite imagery is used to measure the brightness of the sky, in combination with physical models of scattering due to air molecules and aerosols. Ground-based networks of photometers, such as the Sky Quality Meter (SQM), are also used to monitor light pollution over time.
To reduce light pollution, it is recommended to turn off unnecessary lights and use fully shielded, light-efficient fixtures that direct light downward where it is needed, rather than upward into the sky.
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