Kiera Jefferson
Light pollution, the excessive or inappropriate use of outdoor artificial light, has been a growing problem since it was first recognised in the 1970s. It has been estimated that 83% of the world's population lives under light-polluted skies, with around 30% no longer able to see the Milky Way. The night sky is getting brighter, with a global increase in light pollution of 9.6% per year between 2011 and 2022, and some regions experiencing an increase of up to 400% in the last 25 years. This has had significant impacts on human health, wildlife behaviour, and the environment.
| Characteristics | Values |
|---|---|
| Global light pollution increase from 1992 to 2017 | 49% |
| Global light pollution increase from 2011 to 2022 | 9.6% |
| Europe's light pollution increase from 2011 to 2022 | 6.5% |
| North America's light pollution increase from 2011 to 2022 | 10.4% |
| Asia, South America, Oceania, and Africa's light pollution increase | Persistent |
| Impact on humans | Sleep deprivation, fatigue, headaches, stress, anxiety, insomnia, and other health problems |
| Impact on wildlife | Disrupts the migrations of birds, the delicate blossoming of flowers, and the luminous courtship of fireflies. It also affects the behaviour of turtles, bats, and blackbirds |
| Impact on environment | Disrupts ecosystems and spoils aesthetic environments |
| Impact on astronomy | Dims the view of the sky |
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What You'll Learn
Light pollution's impact on human health
Light pollution is a pressing issue that has been accelerating since the 1970s, when astronomers first noticed its effects on their work. Today, artificial lighting continues to brighten the night sky, with the rate of increase differing across the globe. While Europe experiences a slower rate of increase, at around 6.5% per year, North America's night sky is brightening at a rate of 10.5% annually.
This growing issue has sparked a global movement to reduce light pollution, as it is causing significant problems for humans, wildlife, and the environment. Light pollution is the excessive or inappropriate use of outdoor artificial light, and it is affecting human health, wildlife behaviour, and our ability to observe the night sky.
The human body's internal, twenty-four-hour clock, known as the circadian rhythm, is disrupted by nocturnal light. This disruption has a ripple effect on various physiological processes, including 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 artificial light at night can lead to several adverse health consequences, including:
- Sleep deprivation
- Fatigue
- Headaches
- Stress
- Anxiety
- Increased risk of cancer
Recent studies have found a link between reduced melatonin levels and cancer, and the American Medical Association (AMA) is now supporting efforts to control light pollution. Blue light, in particular, has been identified as a significant contributor to reduced melatonin levels in humans, and it is found in cell phones, computer devices, and energy-efficient LED bulbs.
Additionally, research has suggested that artificial light at night can negatively impact human health in other ways, increasing the risks for:
- Obesity
- Depression
- Sleep disorders
- Diabetes
- Breast cancer
Light pollution is a pervasive environmental issue, and its impact on human health cannot be overlooked. The growing awareness of its adverse effects has spurred a global movement to reduce light pollution and protect the health and well-being of people worldwide.
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Its effect on wildlife and ecosystems
Light pollution has been a growing problem since its recognition in the 1970s. The night sky is now estimated to be brightening by 9.6% globally each year, with the rate of increase varying across the world. For example, in Europe, light pollution is increasing at a rate of 6.5% per year, while in North America, it is increasing at a rate of 10.5%.
The excessive and inappropriate use of outdoor artificial light has had detrimental effects on wildlife and ecosystems. Firstly, artificial light can attract certain organisms, such as moths, frogs, and sea turtles, making them an easy target for predators or causing them to become trapped and exhausted. It can also repel other organisms, effectively causing habitat loss.
Secondly, artificial light disrupts the natural day and night cycles that all life on Earth has relied on for billions of years. Nocturnal animals, such as bats and frogs, are particularly affected, with their sleeping patterns and daily routines disrupted. This can lead to sleep deprivation, fatigue, and a lack of downtime for the body to repair itself, impacting their health and reproductive cycles.
Additionally, light pollution can alter the behaviour of migratory birds, amphibians, and marine life. For example, a study found that blackbirds in Germany became active earlier due to artificial night lighting, singing up to five hours before their cousins in natural areas. Underwater artificial lighting may also be altering marine ecosystems, as fewer filter-feeding animals were found near brightly lit panels submerged off the coast of Wales.
Light pollution can also create barriers that fragment habitats. For example, cougars, despite being unfazed by buildings, will not cross brightly lit areas. Similarly, slow-flying bats avoid feeding or passing through illuminated areas to protect themselves from predators like owls.
Overall, light pollution has far-reaching consequences for wildlife and ecosystems, impacting behaviour, health, and the natural balance of ecosystems.
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Light pollution's obstruction of astronomy
Light pollution has been a growing problem for astronomers since the 1970s, when the rapid increase in artificial light began to affect their work. The issue has only worsened since, with the night sky getting brighter by an average of 9.6% globally each year, according to a recent study. This has made it increasingly difficult for astronomers to observe the night sky, compromising scientific discoveries, cultural connections to the stars, and astrotourism opportunities.
The main way light pollution obstructs astronomy is by reducing the contrast between celestial objects and the sky itself, making it harder to see fainter stars and galaxies. This has led to the construction of newer telescopes in increasingly remote areas to escape the effects of light pollution. Even in clear skies, stray light can become visible at longer exposure times in astrophotography, and while software can reduce this, it may also reduce the detail of celestial objects in images.
The skyglow caused by light pollution is particularly problematic for astronomy. This is the scattering of artificial light in the atmosphere at night, which creates a glow that prevents us from getting a clear view of the night sky. The human eye is particularly sensitive to shorter, bluer wavelengths of light pollution, which is more obvious to us than to satellites. This blue light pollution is becoming more common as LEDs, or light-emitting diodes, are increasingly used for lighting.
Light pollution is also a major issue for amateur astronomers, who often have to deal with light pollution from neighbours' lights or streetlights when stargazing from their back gardens. To tackle this, astronomers have advocated for darker skies and a reduction in light pollution, with some even negotiating with neighbours to keep curtains closed at night or installing light pollution filters on their equipment. Dark-sky sites are also being established worldwide, where conditions are purposely maintained to allow anyone to enjoy the night sky and engage in amateur astronomy.
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The rate of increase in different regions
Light pollution is a global issue, with 83% of the world's population living under light-polluted skies. While light pollution is increasing worldwide, the rate of increase varies across different regions.
North America
North America has witnessed the highest increase in light pollution among all regions. Between 2011 and 2022, North America experienced an average annual increase of 10.4% in light pollution, significantly higher than the global average of 9.6%. This trend is particularly evident in cities like Las Vegas, Nevada, which saw an annual increase of 8% from 2002 to 2008, exceeding the population growth rate.
Europe
Europe has also been significantly impacted by light pollution, with an average annual increase of 6.5% between 2011 and 2022. However, there are variations within the region. While some areas, like northern Italy, experienced a notable 10% increase, Eastern Europe showed a different pattern due to economic hardships and government collapse in the 1990s.
Asia, South America, Oceania, and Africa
These regions have persistently increasing light pollution, as observed by satellites. China, specifically the eastern and northern regions, has higher light pollution levels than the western parts, attributed to the concentration of major industrial factories in those areas.
Developing Nations
While the research by Kyba and his team did not extensively cover developing nations, it is evident that these regions also face challenges with light pollution. Many areas in developing countries have insufficient lighting at night, relying on wasteful greenhouse gas-emitting fuels for illumination.
Overall, the rate of increase in light pollution varies across different regions, with some areas experiencing more rapid growth than others. The factors contributing to these variations include economic development, industrial activities, population density, and the implementation of lighting regulations.
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How to reduce light pollution
Light pollution has been increasing since the 1970s, when astronomers first noticed its effects. It has become more widespread and accelerated, with the night sky brightening by an average of 9.6% globally each year. Light pollution is caused by the inefficient and unnecessary use of artificial outdoor lighting, and it has negative impacts on human health, wildlife behaviour, and our ability to observe the stars.
- Use dimmer switches, motion sensors, and timers to reduce illumination levels and save energy.
- Use shielded outdoor lighting fixtures that minimise glare and light trespass to prevent light pollution.
- Use warm-coloured LED bulbs, which are more energy-efficient and environmentally friendly than traditional bulbs, but avoid blue light, which has been linked to reduced melatonin levels in humans.
- Turn off lights when not in use, and avoid over-illumination.
- Use window shades to prevent indoor lighting from escaping and contributing to light pollution outdoors.
- Avoid driving at night, and if necessary, use headlights sparingly and point flashlights and headlights down towards the ground.
- Reduce the use of electronic devices and screens in the evening, and switch to dimmer night settings when possible.
- Advocate for local legislation and join global movements to reduce light pollution, such as the Dark Sky Movement.
- Encourage neighbours and communities to adopt similar practices to reduce light pollution.
By following these steps, individuals can help reduce light pollution, protect the environment, and restore the natural beauty of the night sky.
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Frequently asked questions
Light pollution has increased by 9.6% globally each year on average.
Light pollution has increased by at least 49% from 1992 to 2017.
Light pollution has increased by up to 400% in the last 25 years.
Light pollution has increased by up to 400% in specific regions, with the highest increases in North America.
Detected light pollution in Europe increased until 2010 and then levelled off.
