Bronte Wells
Light pollution is the presence of unwanted, inappropriate, or excessive artificial lighting, which has adverse effects on human health, ecosystems, and stargazing. It is a major side effect of urbanization, with bright city lights changing nightscapes around the world, making it harder to spot stars with the naked eye. The night sky is estimated to be getting brighter by 8% every year, with 83% of people globally living under light-polluted skies. Light pollution is also linked to the Sustainable Development Goals, with a revision proposed to include Quality of the sky and access to starlight (SDG 18). To combat this, areas with protected dark skies, known as dark sky oases or Starlight Reserves, have been established, with over 200,000 km2 of such areas in more than 30 countries.
| Characteristics | Values |
|---|---|
| Definition | The presence of any unwanted, inappropriate, or excessive artificial lighting |
| Effects | Competes with starlight, interferes with astronomical observatories, disrupts ecosystems, and has adverse health effects |
| Impact on stargazing | Makes it difficult to observe the night sky, drowning out the stars |
| Impact on the environment | Disrupts ecosystems, compromises health, and spoils aesthetic environments |
| Impact on energy | Represents wasted energy, leading to additional financial and climate emission costs |
| Forms | Skyglow, Glare, Light Trespass |
| Measurement tools | The Bortle scale, Globe at Night project |
| Magnitude | 83% of the world's people live under light-polluted skies, 23% of the world's land area is affected by skyglow |
| Protected areas | Starlight Reserves, Dark Sky Oases, Starlight Tourist Destinations |
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What You'll Learn
Light pollution hides the stars
Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It is a major side effect of urbanisation, and its effects are magnified at night, compromising human health, disrupting ecosystems, and spoiling aesthetic environments.
The night sky is getting brighter every year as light pollution becomes more prevalent. Nights are becoming around 10% lighter each year, with the sky brightness doubling roughly every seven or eight years. This has implications for the health of both humans and wildlife. The stars are vanishing before our eyes, as increasing levels of light pollution mean that fewer stars are visible in the night sky. A global community science project found that around 30% of people worldwide can no longer see the Milky Way, rising to 80% in North America.
The issue of light pollution was first recognised in the 1970s when astronomers began to see the impact of the rapid increase in artificial light on their work. Light pollution competes with starlight, washes out the stars, and makes it increasingly difficult to see the night sky. As Dr Ashley King, a Future Leaders Fellow at the Natural History Museum, notes, 'The first humans could look up at the sky and use it in so many parts of their lives. Now, we don't have that same experience as there's much more light pollution.'
Light pollution is not just an issue for astronomers, but for anyone who appreciates the beauty of the night sky. It is also a concern for those worried about the well-being of plants, animals, and humans, all of whom are negatively impacted by light pollution. To preserve stargazing opportunities and mitigate the adverse effects of light pollution, it is essential to reduce artificial lighting and direct existing lighting downward to minimise the amount of light escaping into the sky.
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Health, ecosystem, and environmental impacts
Starlight pollution, or light pollution, refers to the presence of any unwanted, inappropriate, or excessive artificial lighting. It is a rapidly increasing type of environmental degradation, with levels growing exponentially over the natural nocturnal lighting provided by starlight and moonlight.
Starlight pollution has significant impacts on human health, ecosystems, and the environment. Here are some of the key effects:
Human Health Impacts:
- Sleep Deprivation: Unwanted light entering homes, such as light shining over fences or through windows, can cause sleep deprivation for residents.
- Melatonin Suppression: Exposure to certain types of artificial light, particularly those with strong blue emissions like metal halide and white LEDs, can lead to melatonin suppression in humans. This can potentially impact sleep and other biological processes regulated by melatonin.
Ecosystem and Environmental Impacts:
- Migration and Navigation Disruption: Artificial light can disrupt the migration and navigation of nocturnal animals, such as birds, that rely on moonlight and starlight. This can lead them to wander off course, collide with illuminated structures, and alter their migratory timing, affecting nesting and foraging behaviors.
- Insect Population Decline: Insects, including ecologically important species like fireflies, are attracted to artificial lights. This can result in fatal consequences, contributing to the decline of insect populations. This decline then impacts other species that rely on insects for food or pollination.
- Reproduction Interference: Artificial lighting can disrupt the nocturnal activities and breeding rituals of amphibians, such as frogs and toads, affecting their reproduction and population levels.
- Altered Nocturnal Ecology: The introduction of artificial light drastically alters the nighttime environment, impacting the predator-prey dynamics. Predators may use light to their advantage for hunting, while prey species that rely on darkness as cover become more vulnerable.
It is important to note that the impacts of starlight pollution are not limited to the points mentioned above, and there may be unknown consequences that are yet to be fully understood.
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Urbanization and satellite overcrowding
Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It is a growing environmental problem that is especially pronounced in urban environments. Urbanization and satellite overcrowding are major contributors to this issue.
Urbanization, the expansion of urban land, is expected to increase by 2-6 fold over the 21st century, exposing more organisms to artificial light at night (ALAN). Urban areas are more at risk of light pollution due to inefficient or unnecessary use of artificial light. This includes unshielded and improperly directed lights, such as those used in warehouses, distribution hubs, and oil and gas production sites, as well as excessive residential lighting. The light from these sources scatters in the atmosphere, creating a bright haze known as "sky glow" that can be seen from space. Sky glow washes out the stars, making it difficult to observe celestial objects even in professional and amateur astronomical observatories.
The growing number of satellites, particularly mega-constellations like Starlink, is also a significant contributor to light pollution. The astronomical community fears that the increasing number of satellites will significantly increase light pollution, as they already contribute to sky glow by reflecting artificial light from the Earth. This has led to public discourse and petitions by astronomers and citizen scientists regarding the continuing deployment of satellite constellations and the regulatory bodies that hold jurisdiction over human actions that obscure starlight.
Light pollution has adverse effects on both humans and the environment. It competes with starlight, interfering with astronomy and spoiling aesthetic environments. It also disrupts ecosystems, fragments habitats, and alters the diversity and spatiotemporal distribution of species, impacting both nocturnal wildlife and human health. The effects of light pollution are magnified at night, and it has been estimated that 83% of the world's people live under light-polluted skies, with global light pollution increasing by at least 49% from 1992 to 2017.
To address light pollution, it is essential to advocate for robust policies and innovative lighting designs that reduce light trespass, over-illumination, glare, light clutter, and skyglow. By working together, we can cut down on light pollution and preserve stargazing opportunities for future generations.
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Measurement and detection methods
Starlight pollution, also known as light pollution, refers to the presence of unwanted, inappropriate, or excessive artificial lighting. This phenomenon is a major side effect of urbanization and can interfere with stargazing, astronomy, and the natural environment. To combat this issue, various methods are available to measure and detect starlight pollution, allowing for better observation and mitigation strategies.
The Bortle Scale
The Bortle Scale is a widely used method to measure the darkness of the night sky, ranging from Class 1 (pitch black) to Class 9 (heavily light-polluted). It provides a standard way to assess the impact of light pollution on stargazing conditions. The scale takes into account factors such as the visibility of the Milky Way, the dimmest stars visible to the naked eye, and the overall sky glow. While it offers a rough estimate, it is a useful tool for astronomers and stargazers to understand the level of light pollution in a given area.
Sky Quality Meter (SQM)
The Sky Quality Meter (SQM) is a device used to quantitatively measure the brightness of the night sky. It provides precise measurements in magnitudes per square arcsecond, indicating the luminance of the sky as observed by an individual. SQM readings help distinguish between darker skies and those impacted by light pollution. SQMs are employed by both professional observatories and citizen scientists, contributing valuable data to the study of light pollution over time.
Satellite Imagery and Photometers
Satellite-based observations play a crucial role in measuring light pollution on a global scale. Satellite imagery captures the number and intensity of light sources, which are then fed into physical models to calculate cumulative sky brightness. In addition, ground-based networks of photometers supplement the data by monitoring light pollution over extended periods. Together, these tools provide comprehensive insights into the extent and changes in light pollution worldwide.
Ground-Level Observations
Simple actions can be taken to detect and mitigate starlight pollution at the ground level. This includes turning off unnecessary lights, shielding lights to direct them downward, and using blackout curtains to minimize indoor light pollution. By reducing light trespass and the amount of light escaping into the sky, these measures help preserve the darkness of the night sky and improve stargazing conditions.
By utilizing these measurement and detection methods, individuals, astronomers, and communities can gain a better understanding of starlight pollution and take appropriate steps to reduce its impact on the environment and our ability to observe the stars.
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Conservation efforts and dark sky oases
Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It competes with starlight, interfering with observatories, disrupting ecosystems, and adversely affecting human health.
The conservation of dark skies is essential to mitigate the adverse effects of light pollution. Dark Sky International, founded in 1988, leads the way in this regard. The organization works to reserve public or private land for nocturnal territories and starry night skies. Dark sky preserves are conserved for their cultural, scientific, natural, or educational value and public enjoyment. These areas have strict lighting protocols to ensure natural darkness, benefiting nocturnal wildlife.
As of January 2023, there are 201 certified Dark Sky Places globally, including communities, parks, reserves, sanctuaries, and urban night sky places. Dark Sky Communities are legally organized cities and towns that adopt quality outdoor lighting ordinances and educate residents about the importance of dark skies. Dark Sky Parks are spaces protected for natural conservation, implementing good outdoor lighting, and providing dark sky programs for visitors. Dark Sky Reserves consist of a dark "core" zone surrounded by a populated periphery where policies are enacted to protect the core's darkness. Dark Sky Sanctuaries are the most remote and often the darkest places globally, with a fragile conservation state. Urban Night Sky Places are recognized for their efforts to educate the public about proper outdoor lighting, ensuring safety while minimizing harm to the natural nighttime environment.
Dark Sky International also works with communities and professionals to establish codes and statutes that reduce light pollution. They inform the public about the harmful effects of excessive artificial light on humans, wildlife, and the climate. Additionally, they certify lighting products, designs, and installations that minimize light pollution.
Other conservation efforts include partnerships with universities, nonprofits, community groups, and businesses. Guidance documents promote quality lighting designs, and some examples are the Towards a Dark Sky Standard in the U.K. and a County Development Plan to upgrade roadway lighting in Ireland. The Insect Diversity Protection Act in Germany also helps reduce light pollution for sensitive nocturnal species. These initiatives demonstrate a commitment to protecting dark skies and expanding the movement to new audiences.
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Frequently asked questions
Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It is a major side effect of urbanization and is caused by light sources that are poorly implemented.
Light pollution has multiple adverse consequences. It competes with starlight, making it difficult to observe the night sky, interferes with astronomical observatories, disrupts ecosystems, and has adverse health effects. It also represents wasted energy, leading to additional costs and climate emissions.
Light pollution is a global issue. It has been estimated that 83% of the world's people live under light-polluted skies, and this number is projected to increase to nearly 7 in 10 people by 2050. The rate of increase varies across the world, with Europe experiencing a slower rate of increase compared to North America.
There are efforts to reduce light pollution and preserve stargazing opportunities. Areas with protected dark night skies, known as "dark sky oases" or "Starlight Reserves", are established to ensure access to starlight. Additionally, there are proposals to include sky conservation in the United Nations Sustainable Development Goals, recognizing the impact of light pollution on various areas such as environmental degradation and climate.
