light pollution
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What is light pollution?
Light pollution refers to unwanted or excessive artificial light that disrupts the natural environment. Similar to noise pollution, it is a form of wasted energy that degrades environmental quality.
Light pollution manifests in several ways, including skyglow, glare, and light trespass. Skyglow reduces the visibility of stars and celestial objects. Glare from various sources causes discomfort and distraction. Light trespass occurs when unwanted light intrudes onto properties.
Fortunately, reducing light pollution is often simpler than reducing other forms of pollution. Solutions range from turning off unnecessary lights to installing shielding fixtures that focus light where it is needed.
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What are some common sources of light pollution?
Common sources of light pollution include upward-directed light from lamps and security floodlights, road lamps, commercial security lights and signs, and bright yard lighting. Light pollution, defined as unwanted or excessive artificial light, affects visibility and disrupts the environment. The wasted light, known as "skyglow," reduces the visibility of stars and celestial objects because the light scatters off particles in the atmosphere. Light pollution can also interfere with sleep cycles and circadian rhythms in humans and other animals. Fortunately, it can be reduced by turning off unnecessary lights or adding shielding fixtures to focus the light where it is needed.
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How does light pollution affect our ability to see stars at night?
Light pollution impairs the visibility of stars and celestial objects due to skyglow, which is upward-directed light from poorly designed lamps and floodlights. This light scatters off particles in the atmosphere and returns to the ground, obscuring the night sky. Even small towns can cause noticeable sky degradation several miles away. Light pollution not only affects astronomers but also disrupts sleep cycles and disorients nocturnal animals. Fortunately, reducing light pollution is achievable through better lighting designs and regulations.
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What are the main types of light pollution?
Light pollution, a form of wasted energy, includes unwanted or excessive artificial light that disrupts the environment.
The primary types are:
* Skyglow Upward-directed light from poorly designed lamps and floodlights scatters off atmospheric particles, reducing night sky visibility, even far from the source.
* Glare Light from road lamps, security lights, and signs causes discomfort, distraction, and impaired vision.
* Light trespass Unwanted light that disrupts sleep cycles and circadian rhythms of animals.3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does light pollution impact animals and the environment?
Light pollution, a form of wasted energy, occurs when artificial light is unwanted or excessive. This pollution impacts animals and the environment by disrupting animal circadian rhythms, especially in nocturnal animals. Migratory birds become disoriented by sky glow, leading to collisions with illuminated structures; over four million birds die this way each year in the United States alone. Sea turtle conservation is also threatened, as bright lights deter females from nesting on beaches, and hatchlings head inland instead of towards the ocean, resulting in tens of thousands of deaths annually. Light pollution also interferes with insect bioluminescence and reduces moth caterpillar abundance.
To reduce light pollution, governments can enforce light-control laws, and people can minimize their use of outdoor lighting.
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What actions can people and communities take to reduce light pollution?
Light pollution, a form of wasted energy, has far-reaching impacts on humans and wildlife. Fortunately, communities and individuals can take action to mitigate it.
People can minimize light pollution by using outdoor lighting only when needed and by closing curtains or blinds at night. They can also use well-designed light fixtures that direct light downward and use the lowest necessary wattage.
Communities can implement light-control laws and ordinances. These may include requiring shields on outdoor fixtures to prevent light from extending above the horizontal. Coastal communities can also regulate lighting near beaches to protect the nesting habitats of sea turtles.
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light pollution, unwanted or excessive artificial light. Like noise pollution, light pollution is a form of waste energy that can cause adverse effects and degrade environmental quality. Moreover, because light (transmitted as electromagnetic waves) is typically generated by electricity, which itself is usually generated by the combustion of fossil fuels, it can be said that there is a connection between light pollution and air pollution (from fossil-fueled power plant emissions). Control of light pollution therefore will help to conserve fuel (and money) and reduce air pollution as well as mitigate the more immediate problems caused by excessive light. Although light pollution may not appear to be as harmful to public health and welfare as pollution of water resources or the atmosphere, it is an environmental quality issue of no small significance.
(Read Britannica’s essay “Is Light Pollution Really Pollution?”)
The quantity of light pollution from a given area depends on the number and brightness of light sources on the ground, the fraction of light that escapes above the horizontal, the reflectivity of surfaces near the light sources (e.g., roads, pavements, walls, windows), and the prevailing atmospheric conditions. Empirical formulas allow the calculation of skyglow as a function of population and distance from the observer. When skyglow levels are more than 10 percent above the natural background levels, significant sky degradation has begun. Even lights from a fairly small town with a population of only 3,000 people can cause significant night sky degradation for an observer as far as 10 km (6 miles) away.
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Impact on humans
Light pollution adversely affects professional and amateur astronomers, as well as casual observers of the night sky, because it severely reduces the visibility of stars and other celestial objects. The reduction in night sky visibility is a result of “skyglow,” upward-directed light emanating from poorly designed or directed lamps and security floodlights. This wasted light is scattered and reflected by solid or liquid particles in the atmosphere and then returned to the eyes of people on the ground, obliterating their view of the night sky. The effect of skyglow from a town or city is not necessarily localized; it can be observed far from the main source.
Light pollution is a problem not only for astronomers and people who simply want to enjoy the beauty of a starry night. Glare from road lamps, commercial security lights and signs, or even from a neighbor’s bright and misdirected yard lighting can cause discomfort and distraction and adversely affect the quality of life of many people.
Impact on animals
Light pollution has adverse impacts on birds and other animals. Many migratory birds, for example, fly by night, when light from the stars and Moon helps them navigate. These birds are disoriented by the glare of artificial light as they fly over urban and suburban areas. It has been estimated by the American Bird Conservatory that more than four million migratory birds perish each year in the United States by colliding with brightly illuminated towers and buildings. Light pollution is considered to be one of the contributing factors in the dramatic decline of certain migratory songbird populations over the past several decades.
Sea turtles are also particularly vulnerable to the effects of light pollution. Although the females of such species as loggerhead sea turtles typically return to the beach on which they were born, bright lights can deter gravid females, forcing them to seek a less familiar or less suitable alternative. Hatchlings emerging from their nests can become disoriented by artificial lighting and, instead of heading toward the ocean, head inland, where they frequently die from exhaustion, dehydration, predation by other animals, or being hit by vehicles. A considerable challenge to sea turtle conservation, light pollution is estimated to be responsible for many tens of thousands of hatchling deaths each year in the United States alone.
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Experiments have demonstrated that street lighting reduces moth caterpillar abundance, when compared with unlighted areas, and is linked to slowed caterpillar development. In addition, studies have shown that these disruptions were more evident when streetlights were outfitted with LEDs (light-emitting diodes) than yellow sodium-vapor lamps. The declines in firefly populations have also been linked to light pollution, which likely interferes with the insects’ bioluminescent mating signals.
Control
Light pollution can be reduced by using well-designed light fixtures with modern optical controls to direct the light downward and also by using the minimum amount of wattage for the area to be illuminated. Residents can reduce light pollution by closing their curtains or blinds at night and by minimizing the use of outdoor lighting.
National and local government agencies can help by passing and enforcing appropriate light-control laws and ordinances. In 2002 the Czech Republic became the first country to enact a law to address light pollution: all outdoor fixtures were required to have a shield to prevent light from extending above the horizontal. In the United States and elsewhere, many coastal municipalities have regulations to reduce light pollution near beaches to preserve the nesting habitats of sea turtles.