Helena Joyce
Light pollution, caused by the excessive or inappropriate use of outdoor artificial light, is a global issue that affects human health, wildlife behaviour, and our ability to observe the night sky. It is estimated that 83% of the world's population lives under light-polluted skies, with 23% of the world's land area affected by skyglow. The night sky is getting brighter every year, with an average increase in brightness of 10% annually, and this has detrimental effects on both humans and wildlife. Light pollution has been linked to various health issues, including sleep deprivation, fatigue, headaches, stress, anxiety, and potentially, cancer. It also disrupts ecosystems, wastes energy, and increases the impacts of climate change. While there are efforts to reduce light pollution, such as the International Dark Sky Places Program and legislative actions, it continues to be a pressing environmental concern.
| Characteristics | Values |
|---|---|
| Sky brightness in densely populated areas | 17 magnitude/sq. arcsecond, 100 times brighter than natural levels |
| Sky brightness with a full moon | 18 magnitude/sq. arcsecond, 40 times brighter than the darkest sky |
| Darkest possible sky brightness | 22 magnitude/sq. arcsecond |
| Sky brightness in Southern England, Netherlands, Belgium, West Germany, and Northern France | 2-4 times normal |
| Sky brightness in the Yangtze River delta, Pearl River delta, and Beijing-Tianjin area | Of particular concern |
| Percentage of lighting wasted | 1/3 |
| Annual cost of wasted lighting | $2.2 billion |
| Percentage of carbon dioxide pollution caused by electricity generation for lighting | 15 million tons |
| Equivalent number of cars that would need to be removed from roads to achieve the same reduction in carbon dioxide pollution | 9.5 million |
| Percentage of the world's population living under sky glow | 80% |
| Percentage of Americans and Europeans living under sky glow | 99% |
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What You'll Learn
Light pollution's environmental and economic impact
Light pollution is a pressing issue that has severe environmental and economic impacts. It refers to the human-made alteration of outdoor light levels from those occurring naturally, caused by artificial light sources such as street lamps, advertising, commercial properties, and offices. The environmental effects of light pollution are far-reaching, affecting both humans and wildlife.
Environmental Impact
Light pollution disrupts the natural day/night cycle, which is essential to our biological welfare. It affects the human body's internal, twenty-four-hour clock, or circadian rhythm, which guides day and night activities and affects physiological processes in nearly all living organisms. Disruption of this rhythm has been linked to various health issues, including sleep disorders, depression, hypertension, attention deficit disorder, obesity, diabetes, and heart disease. It also inhibits the production of melatonin, a hormone released in the dark that is crucial for regulating sleep and other biological processes.
Additionally, light pollution has detrimental effects on wildlife. It impacts animal behaviours such as migration patterns, wake-sleep habits, and habitat formation. For example, sea turtles and birds guided by moonlight during migration get disoriented and lose their way due to the altered light conditions. Insects, a primary food source for many species, are attracted to artificial lights and are killed upon contact. Even underwater ecosystems may be affected by artificial lighting.
Light pollution also poses challenges for astronomy. Skyglow, the collective light pollution over cities, reduces the contrast between celestial objects and the night sky, making it harder to observe faint stars and galaxies. This has led to the construction of telescopes in remote areas.
Economic Impact
The economic consequences of light pollution are also significant. The International Dark-Sky Association estimates that one-third of all lighting is wasted, resulting in an annual cost of $2.2 billion. The generation of electricity to power excessive lighting contributes to air pollution, with coal-fueled power plants releasing around 15 million tons of carbon dioxide into the atmosphere annually. Addressing light pollution would be equivalent to removing 9.5 million cars from the roads in terms of reducing air pollution.
In conclusion, light pollution has far-reaching consequences for both the environment and the economy. It disrupts natural cycles, affects human health, harms wildlife, hinders astronomical observations, and results in substantial economic and resource waste, as well as contributing to air pollution. Addressing light pollution requires a combination of improved lighting design, regulations, and public awareness to reduce its environmental and economic impacts.
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The Bortle scale
Light pollution is a growing concern for astronomers, both amateur and professional. The Bortle scale is a nine-level scale that measures the amount of light pollution in a given location. It was created by John E. Bortle in 2001 and published in Sky & Telescope magazine. The scale is based on Bortle's nearly 50 years of observing experience.
There are several ways to measure light pollution and determine one's location on the Bortle scale. Specialized tools such as sky quality meters can measure sky brightness from a localized area. Online resources such as light pollution maps can also provide an approximate reading for any location. Additionally, smartphone apps like "Clear Outside" can use GPS to present an accurate reading of where one's night sky falls on the Bortle scale.
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Light pollution sources
Light pollution is a human-made alteration of outdoor light levels from those occurring naturally. It is caused by the whole world's ever-expanding 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 of it.
There are various sources of light pollution, including street lamps, parking lot/shopping mall lights, exterior lights found on most homes/businesses, neon signs, and illuminated signboards. Even a single light can be disruptive to the natural lightscape. In addition, light pollution can be caused by boats, buildings, fireworks, and even a full moon.
The type of lights used can also affect the amount of light pollution. For example, mercury, metal halide, and first-generation blue-light LED road luminaires are much more polluting than sodium lamps. The use of full cutoff lighting fixtures is advocated by most campaigners for the reduction of light pollution.
Light pollution has harmful effects on both humans and animals. Disruption of the natural day/night cycle has been linked to sleep disorders, depression, hypertension, attention deficit disorder, obesity, diabetes, and heart disease. It can also confuse nocturnal animals, migrating birds, and insects, causing them to lose their way and often die.
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Light pollution's effect on astronomy
Light pollution is the presence of any unwanted, excessive, or inappropriate artificial lighting. It is a side effect of industrialization and urbanization, with sources ranging from building exterior and interior lighting to streetlights and illuminated sporting venues. Light pollution is increasing globally, affecting both developed and developing nations, with some of the most light-polluted countries being Singapore, Qatar, Kuwait, and China.
The effects of light pollution are far-reaching and detrimental, impacting human health, wildlife behavior, and the environment. It disrupts ecosystems, wastes energy, exacerbates climate change, and negatively affects human well-being by interfering with circadian rhythms and potentially triggering insomnia and other health issues.
The impact of light pollution on astronomy is significant. Astronomers are particularly concerned with sky glow pollution, which is the brightening of the night sky due to artificial light sources. Sky glow reduces the ability of astronomers to observe celestial objects and study the night sky. In highly light-polluted areas, it becomes challenging to see beyond a handful of stars, obscuring our view of the universe and diminishing the beauty and connection to nature that the night sky offers.
The issue of light pollution in astronomy is not limited to professional astronomers. Stargazing and observing celestial events such as meteor showers or lunar eclipses are enjoyable activities for many people, enhancing their appreciation of nature. Light pollution takes away these opportunities and experiences, affecting individuals' well-being and sense of wonder.
To address light pollution's effects on astronomy, efforts are being made worldwide to reduce artificial lighting and preserve dark skies. Organizations like the International Dark-Sky Association (IDA) advocate for dark sky places and educate the public about the importance of reducing light emissions. Additionally, individuals can contribute by turning off unnecessary lights, using downward-facing fixtures, and supporting legislation aimed at controlling outdoor lighting. These collective efforts are crucial to restoring the natural night sky and ensuring that astronomy can be enjoyed by all.
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Light pollution's impact on human health
Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It is a major side effect of urbanization and industrialization, with 83% of the world's population living under light-polluted skies. The impact of light pollution on human health is significant and wide-ranging.
One of the primary ways light pollution affects human health is by disrupting the natural body rhythms and the internal, twenty-four-hour circadian clock that guides day and night activities. Artificial light, especially at night, can inhibit the production of the hormone melatonin, which is released in the absence of light. Reduced melatonin levels can lead to various health issues, including sleep deprivation, fatigue, headaches, stress, anxiety, and potentially, an increased risk of cancer.
Research has also linked light pollution to adverse health effects such as obesity, depression, sleep disorders, and diabetes. A study by the American Medical Association found that brighter residential nighttime lighting was associated with reduced sleep times, poor sleep quality, excessive sleepiness, and impaired daytime functioning. Additionally, blue light, commonly found in cell phones, computer devices, and LED bulbs, has been shown to reduce melatonin levels in humans, further emphasizing the impact of light pollution on sleep and overall health.
The excessive use of artificial light at night can also have indirect health effects. For example, light pollution from sources such as streetlights, buildings, and advertising can alter the behavior of wildlife, including migration patterns and habitat formation. This can lead to potential safety issues and conflicts between humans and wildlife, impacting the health and well-being of both.
While light pollution has negative consequences, it is important to recognize that artificial light has benefited society by extending the productive day and providing lighting for recreational activities. However, the growing awareness of the harmful effects of light pollution has led to a global movement to reduce it. Organizations like the International Dark-Sky Association (IDA) are working to preserve the natural night sky and educate the public about the importance of reducing light pollution for the benefit of human health and the environment.
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Frequently asked questions
Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It has four main types: glare, clutter, light trespass and night glow/sky glow.
Common sources of light pollution include street lamps, parking lot/shopping mall lights, exterior lights found on most homes/businesses, neon signs and illuminated signboards.
Light pollution has been shown to harm wildlife, including birds, sea turtles, insects, and plants. For example, it disrupts the mating patterns, sleep, and hunting behaviors of nocturnal animals.
Light pollution can be reduced by adjusting the types of lights used, evaluating existing lighting plans, and redesigning lighting plans. It is also recommended to use full cutoff lighting fixtures, space lights appropriately, and match the number of luminaires and wattage to what is needed.
