Brian Barton
Light pollution, caused by the excess or inappropriate use of outdoor artificial light, is a pressing issue that affects human health, wildlife behaviour, and our ability to observe the stars. The night sky, once a source of wonder and inspiration for humans, is now obscured by the glow of city lights, making it increasingly difficult to spot stars with the naked eye. This phenomenon, known as sky glow, is particularly prevalent in urban areas, where street lamps, storefronts, and advertising lights illuminate the night, washing out the stars. The impact of light pollution is not limited to the obstruction of our view of the stars but also extends to disrupting ecosystems, wasting energy, and contributing to climate change. While light pollution has received less attention compared to other forms of pollution, it is a growing concern as urbanization increases and more people reside in cities, further reducing access to dark skies.
| Characteristics | Values |
|---|---|
| Type of pollution | Light pollution |
| Cause | Excessive or inappropriate use of outdoor artificial light |
| Sources | Street lamps, billboards, neon signs, car headlights, storefronts, offices, factories, buildings |
| Impact | Disrupts ecosystems, wastes energy, increases impact of climate change, affects human health, affects wildlife behaviour, interferes with the atmosphere, reduces air quality, affects plant growth |
| Global impact | Light pollution increased by 9.6% a year over the study period |
| Regions affected | North America, Europe, the Middle East, Asia |
| Measurement | Bortle Scale, where a high number is bad |
| Solutions | Use fully shielded, light-efficient fixtures, enhancing lighting efficiency, minimizing light waste, adopting the five principles for responsible outdoor lighting by DarkSky International and the Illuminating Engineering Society |
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What You'll Learn
- Light pollution, caused by artificial light, is the primary reason why stars are not visible in many places
- Sources of light pollution include street lamps, billboards, cars, offices, factories, and buildings
- Light pollution has negative health effects on humans, such as sleep deprivation, fatigue, and headaches
- Light pollution affects wildlife, disrupting ecosystems and the behaviour of migratory birds, bats, and cougars
- Light pollution can be reduced by using fully shielded, light-efficient fixtures that prevent light from escaping
Light pollution, caused by artificial light, is the primary reason why stars are not visible in many places
Light pollution has received less attention than other types of pollution, but it is a growing concern. Nearly 70% of people worldwide are expected to live in cities by 2050, and light pollution is most acute in urban areas. It also has ecological effects and can influence human circadian rhythms. Light pollution disrupts ecosystems, wastes energy, exacerbates climate change, and has adverse health consequences. It can disorient migratory birds and expose nocturnal predators such as bats and cougars. Research has also shown that it impacts plant growth, altering their ability to respond to natural light and disrupting seasonal cycles.
The brightness of the night sky due to light pollution is measured using the Bortle Scale, with a high number indicating more light pollution. Times Square in New York City, for example, would be a 9 on the scale, where it is nearly impossible to see any stars. Even national parks, which are meant to provide protected natural habitats, are impacted by light pollution. Shenandoah National Park, for example, has a Bortle Scale rating of 4, which is better than nearby cities but still not as dark as it was just two generations ago.
Light pollution can be reduced by using fully shielded, light-efficient fixtures that prevent light from escaping into the sky. Replacing current fixtures with fully shielded ones could reduce sky brightness by up to 75%. Additionally, turning off outdoor lighting at night and raising awareness about light pollution can help mitigate its effects. Some cities in the U.S. and other countries have been designated Dark Sky Communities, recognising their dedication to preserving the night sky by discouraging wasteful lighting practices.
Overall, light pollution caused by artificial light is the main reason why stars are not visible in many places. It has far-reaching consequences for humans, wildlife, and the environment, and addressing it is crucial for reclaiming dark skies and restoring natural darkness.
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Sources of light pollution include street lamps, billboards, cars, offices, factories, and buildings
Light pollution is the excess or inappropriate use of outdoor artificial light, which affects human health, wildlife behaviour, and our ability to observe stars and other celestial objects. Sources of light pollution include street lamps, billboards, cars, offices, factories, and buildings.
Street lamps are a significant contributor to light pollution, as their bright lights can illuminate large areas, causing glare and light trespass. Light trespass occurs when light from street lamps spills over into areas where it is not wanted or needed, such as residential neighbourhoods, disrupting the natural patterns of darkness and sleep patterns of nearby residents.
Billboards and advertising displays also contribute to light pollution, particularly in urban areas. The bright lights used to illuminate these displays can be a source of glare and clutter, causing visual discomfort and confusion.
Cars are another source of light pollution, especially in densely populated cities with heavy traffic. The headlights and internal lighting of vehicles can contribute to the overall brightness of the night sky, making it harder to see the stars.
Offices and factories often have bright lighting to illuminate large spaces and ensure the safety of their occupants. However, the excessive use of artificial light in these settings can result in light trespass and sky glow, impacting nearby areas and the surrounding night sky.
Buildings with external lighting, such as security lights or illuminated signage, can also contribute to light pollution. Inefficient or poorly designed lighting fixtures can allow light to escape upwards, wasting electricity and contributing to sky glow, which washes out the stars.
While artificial lighting has brought numerous benefits to society, the excessive and inappropriate use of outdoor lighting has led to light pollution, impacting our ability to observe the stars and affecting the well-being of humans, plants, and animals. Addressing light pollution requires a combination of awareness, responsible lighting practices, and the adoption of energy-efficient lighting technologies.
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Light pollution has negative health effects on humans, such as sleep deprivation, fatigue, and headaches
Light pollution, caused by the excessive or inappropriate use of outdoor artificial light, is a growing global issue that affects human health, wildlife behaviour, and our ability to observe stars and other celestial bodies. It is estimated that more than 80% of people worldwide are affected by light pollution, with only the most remote regions of the world, such as Siberia, the Sahara, and the Amazon, remaining in total darkness.
Light pollution has been linked to various negative health effects on humans, including sleep deprivation, fatigue, and headaches. Research suggests that artificial light at night can disrupt the production of melatonin, a hormone released in the dark that is inhibited in the presence of light. Lowered melatonin production has been associated with sleep deprivation, fatigue, headaches, stress, anxiety, and other health issues. Additionally, studies have found a correlation between reduced melatonin levels and certain types of cancer.
The American Medical Association (AMA) has recognised the potential risks of exposure to light at night, particularly blue light from electronic devices and energy-efficient LED bulbs, which can reduce melatonin levels. Bright outdoor artificial lights have also been linked to an increased risk of developing breast cancer, with studies showing a statistically significant correlation between light pollution and cancer cases.
The impact of light pollution on human health is an emerging field of study, with researchers investigating the connection between light exposure and various health issues. For example, a study in Israel found a correlation between outdoor artificial light at night and breast cancer cases, even when controlling for other factors. Additionally, research has suggested a link between night work and colorectal cancer, although more evidence is needed to establish a causal relationship.
To mitigate the negative health effects of light pollution, organisations like the International Dark-Sky Association (IDA) and DarkSky International provide guidance on reducing light pollution. This includes recommending fully shielded, light-efficient fixtures that prevent light from escaping into unwanted areas and reducing glare by dimming light levels to what is necessary. These efforts not only help protect human health but also preserve the night sky and the ability to observe stars.
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Light pollution affects wildlife, disrupting ecosystems and the behaviour of migratory birds, bats, and cougars
Light pollution, caused by excessive or inappropriate use of outdoor artificial light, is a pressing issue that affects not only our ability to observe the stars but also has detrimental effects on wildlife and ecosystems. It disrupts the natural rhythm of day and night that all life on Earth has relied on for billions of years, encoded in the DNA of plants and animals. This disruption has consequences for the behaviour and survival of migratory birds, bats, and cougars, among other species.
Migratory birds that navigate by moonlight and starlight can be disoriented by artificial light, causing them to veer off course and collide with illuminated buildings and towers. Millions of birds die each year due to this issue. Light pollution also affects the timing of migration and the daily and seasonal movements of birds and other animals, as they rely on cues from the natural light cycle.
Bats are another species affected by light pollution. Lights near their roosts can delay their emergence at dusk, when their insect prey is most abundant. In some cases, bats may become entombed in their roosts, starving to death as they wait for darkness that never comes.
Even large predators such as cougars are impacted by light pollution. Cougars roam freely through developed areas but are often stopped short by lights at night, particularly in areas like Los Angeles, where their habitats are already fragmented and inbred.
Light pollution can also be a fatal lure for wildlife, such as sea turtle hatchlings. Instead of heading towards the ocean, they are drawn to artificial lights, leading to their deaths. This phenomenon has also been observed in juvenile salmon, which are attracted to lit patches of water where they become vulnerable to predators.
Addressing light pollution is crucial for mitigating these harmful effects on wildlife and ecosystems. Some cities have implemented "Lights Out" policies during migratory seasons, turning off outdoor lights at night. Simple solutions, such as using fully shielded light fixtures, can also help reduce light pollution and its impact on the natural world.
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Light pollution can be reduced by using fully shielded, light-efficient fixtures that prevent light from escaping
Light pollution is the excessive or inappropriate use of outdoor artificial light. It affects human health, wildlife behaviour, and our ability to observe stars and other celestial objects. One of the main causes of light pollution is poorly designed light fixtures that produce light trespass, glare, sky glow, and light clutter. Light trespass occurs when light escapes from one property into adjacent properties, while glare is excessive brightness that can cause visual discomfort. Sky glow is the collective light pollution found over big cities, and light clutter is redundant clusters of lighting in urban centres.
To reduce light pollution, it is recommended to use fully shielded, light-efficient fixtures that prevent light from escaping. These fixtures are designed to minimise glare, light spill, and sky glow. Dark-sky approved light fixtures are available in a variety of designs and can be used indoors and outdoors. They are fully shielded and do not emit illumination above a horizontal plane, preventing light from escaping directly into the sky. Research shows that 75% of artificial sky brightness comes from light escaping directly from fixtures, so replacing current fixtures with fully shielded ones would significantly reduce sky brightness and light pollution.
The Illuminating Engineering Society of North America (IESNA) provides classifications for cutoff lighting, which emits illumination downwards to the ground where it is most needed and improves visibility. Full cutoff lighting means no light is distributed at or above an angle of 90 degrees from the nadir, preventing light from escaping upwards.
In addition to using fully shielded, light-efficient fixtures, there are other ways to reduce light pollution. The Dark Sky Movement, led by professional and amateur astronomers, aims to reduce light pollution by raising awareness about the effects of photopollution and the benefits of reducing energy usage. The International Dark-Sky Association (IDA) offers advice on contacting local authorities to install better fixtures and create ordinances to reduce pollution. They also provide a searchable database of DarkSky Approved light fixtures and devices that are environmentally friendly and reduce light pollution.
By using fully shielded, light-efficient fixtures that prevent light from escaping, we can reduce light pollution and its negative impacts on human health, wildlife, and our ability to observe the stars. This simple solution can help restore the natural darkness of the night sky and improve the well-being of many living things.
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Frequently asked questions
Light pollution.
Light pollution is the excess or inappropriate use of outdoor artificial light. It is caused by light that is wasted or sent upwards into the sky.
Light pollution has a number of effects on humans, wildlife, and the environment. It can cause sleep deprivation, fatigue, headaches, stress, anxiety, and other health problems in humans. It also disrupts ecosystems, wastes energy, increases the impacts of climate change, and affects the ability of humans and animals to see stars.
Light pollution can be reduced by using fully shielded, light-efficient fixtures that prevent light from escaping into the sky. It is also recommended to turn off outdoor lighting when it is not needed and to advocate for better lighting practices in your community.
