Light pollution refers to the excessive, misdirected, or obtrusive artificial outdoor lighting that disturbs the natural darkness of night. Today, over 80% of the global population lives under skyglow—making it difficult to see stars in many cities. The main effects include:
- Disruption of human sleep patterns and health
- Harm to wildlife and ecosystems
- Increased energy waste
- Loss of clear night sky visibility
This growing issue stems mainly from poorly designed outdoor lighting. Fortunately, communities can reverse light pollution through better lighting choices and policies.
Key Takeaways
- Light pollution means too much or badly directed artificial light that brightens the night sky and harms people, animals, and nature.
- Most light pollution comes from poorly designed outdoor lights that send light upward or spill into unwanted areas.
- Light pollution disrupts sleep, increases health risks, and doesen't always improve safety as many believe.
- Artificial light at night confuses wildlife, harms ecosystems, and causes many animals to lose their natural behaviors.
- Cities produce much more light pollution than rural areas, making stars hard to see and changing natural night patterns.
- Using shielded, warm-colored, and motion-controlled lights can reduce light pollution and save energy.
- Communities and governments can fight light pollution by adopting better lighting policies and supporting dark-sky programs.
- Anyone can check local light pollution using online maps and apps, and small changes at home can help protect the night sky.
What Is Light Pollution?
A Brief Description of Light Pollution
Light pollution refers to the presence of excessive or misdirected artificial light in the nighttime environment. Dr. James Lowenthal describes , it is artificial light that brightens the night sky and disrupts natural darkness. This problem affects human health, wildlife behavior, and the ability to see stars. Protecting natural darkness remains important for both ecological balance and cultural heritage.
Over the past 50 years, scientists have studied light pollution and its effects. In 2023, the world marked the 50th anniversary of its first mention in the journal Science. Satellite data shows that artificial light emissions visible from space increased by about 49% over the 25 years leading up to 2017. Today, about 80% of people worldwide live in areas affected by light pollution.
What Causes Light Pollution?
Light pollution has many sources, and scientific research highlights several key contributors:
Urban and city lighting: Cities use unshielded and improperly colored lighting that send light upward.
Outdoor lights: Pathway lights, streetlights, and illuminated signs often waste light by spilling it into the sky.
Streetlights: Many streetlights are not designed to prevent upward light scatter.
Electronic advertising: Bright, unshielded billboards flood light into the night sky.
Parking lots: These areas often remain overlit all night, reflecting unnecessary light upward.
Sports lighting: Poorly designed sports lights cause glare and light trespass, affecting nearby habitats.
Greenhouses: Lighted greenhouses emit bright glows at night and are often unregulated.
Factories and industrial sites: Warehouses and oil and gas production sites emit significant artificial light.
Residential lighting: Outdoor lights from homes add to the problem.
Landscaping and mood lighting: Decorative lights often stay on when not needed.
Rural overlighting: Even rural areas contribute when unshielded lights cause glare and skyglow.
Oil and gas production flares: These flares disrupt wildlife and increase night sky brightness.
Satellites: The growing number of satellites raises night sky brightness and affects astronomical observations.
Most light pollution comes from poorly designed outdoor lighting that emits light where it is not needed.
| Types of Light Pollution | Definition | Examples / Effects |
| Light Trespass | Unwanted light entering a property, causing disturbances such as sleep disruption. | Bright light shining into a neighbor’s window; mitigated by shielded fixtures and limiting light angles. |
| Over-illumination | Excessive and unnecessary use of light, often due to poor design or outdated norms. | High electricity consumption for lighting; solutions include energy-efficient tech and reducing lighting levels. |
| Glare | Excessive brightness causing visual discomfort or temporary vision impairment. | Blinding glare (e.g., sun), disability glare (e.g., headlights), discomfort glare; risks for drivers and pedestrians. |
| Light Clutter | Excessive grouping of lights causing visual confusion and distraction. | Bright advertisements and poorly designed streetlights; increases accident risk. |
| Sky Glow | Bright haze over urban areas from scattered artificial light. | Diminishes star visibility, disrupts wildlife, increases night light levels. |
Glare
Glare happens when a light source is too bright and causes discomfort or even temporary vision loss. For example, high-beam headlights at night can make it hard for drivers to see the road clearly. Glare can also affect pedestrians and wildlife by disrupting natural behaviors.
Light Trespass
Light trespass occurs when unwanted light enters an area where it is not needed or wanted. A common example is a streetlight shining into a bedroom window, making it difficult for people to sleep. Shielded fixtures and careful placement can help reduce light trespass.
Skyglow
Skyglow refers to the bright haze that appears over cities and towns at night. This glow comes from artificial lights scattering in the atmosphere. Skyglow makes it hard to see stars and disrupts the natural night environment for both people and animals.
Sources of Light Pollution
Outdoor Lighting
Outdoor lighting stands as one of the most significant contributors to light pollution. Poorly designed fixtures in residential, commercial, and industrial areas often send light skyward or sideways instead of focusing it on the ground. Unshielded lights waste energy and create unnecessary brightness in the night environment. In fact, only about 40% of outdoor lighting effectively illuminates the ground, while the rest escapes into the sky. Approximately 30% of outdoor lighting gets wasted due to poor design, increasing both energy costs and light pollution.
Common sources include:
Gas station lighting, which causes glare and light trespass, distracting drivers.
Residential lighting that spills beyond property lines, often serving no useful purpose.
Light escaping from building windows, adding to the overall brightness.
Pathway and decorative lights, such as string lights, which contribute to environmental light pollution.
Commercial building lights left on overnight, wasting energy and increasing skyglow.
Note: Shielded fixtures and thoughtful placement can greatly reduce unnecessary light emissions.
Urban Areas
Urban environments produce much higher levels of artificial light compared to rural or remote regions. Dense populations, commercial activity, and extensive infrastructure all contribute to elevated night sky brightness. Both satellite imagery and ground measurements confirm that cities emit intense artificial light, masking the natural lunar cycle and making stars nearly invisible.
| Area Type | Night Sky Brightness (NSB) Range (mpsas) | Notes |
| Urban (e.g., Florence metropolitan area) | ~17.0 - 17.3 | Brighter skies, artificial light dominates, lunar cycle masked |
| Rural/Remote (e.g., Montecristo Island) | ~20.5 - 21.8 | Darker skies, natural lunar effects visible, low light pollution |
Urban areas can have night skies hundreds of times brighter than natural levels, especially under cloudy conditions. In contrast, rural and remote locations maintain darker skies, allowing natural patterns to remain visible.
Bad Lighting Design
Bad lighting design plays a major role in increasing light pollution. Outdated systems and poorly controlled fixtures often emit light in all directions, rather than focusing it where needed. The absence of shields or controls leads to light spillage and glare. Misaligned floodlights shine beyond their intended areas, while overly bright fixtures exceed necessary illumination levels.
Key characteristics of poor lighting design include:
- Inefficient, outdated lighting systems
- Fixtures without shields or controls
- Decorative lights that emit excessive brightness
- Landscape lights placed without consideration for light trespass
- Lights left on in empty parking lots or buildings
- Retail environments with high light levels and excessive signage
These design flaws not only waste energy but also increase operational costs and environmental impact. Communities that adopt modern, shielded lighting can significantly reduce unnecessary light emissions and help restore the natural night sky.
Light Pollution Map
Light Pollution Global Maps
Global light pollution maps help people understand how artificial light affects the night sky around the world. Scientists use several types of data to create these maps. Satellite-based maps, such as those from the Defense Meteorological Satellite Program (DMSP) and the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite, provide detailed images of Earth’s night lights. DMSP data has tracked global lighting since the 1970s, while VIIRS offers sharper images that can show features smaller than one kilometer.
Interactive platforms like Blue Marble and Lightpollution.info use these satellite datasets to let users explore light pollution in different regions. Lightpollution.info even calibrates its maps in physical units, making it easier to compare how much light escapes upward from various places. The New World Atlas of Artificial Sky Brightness combines satellite data with atmospheric models to estimate how much artificial skyglow people experience at ground level.
Projects such as Cities At Night use high-resolution photos taken by astronauts on the International Space Station. These images reveal city lights and changes in lighting technology over time. The Globe at Night project adds ground-based data from citizen scientists who measure sky brightness in their own neighborhoods. Since 2006, Globe at Night has collected tens of thousands of observations, making its interactive map a valuable tool for both researchers and the public.
These global maps show that remote areas, such as parts of the Sahara Desert or the central Pacific Ocean, still have some of the darkest skies on Earth.
Map of US Light Pollution
The United States has some of the most detailed light pollution maps available. Scientists and organizations use VIIRS satellite data to create interactive maps that show the brightness of the night sky across the country. The World Atlas of Artificial Night Sky Brightness highlights regions with severe skyglow, such as the Northeast Corridor, Los Angeles, and Chicago. In contrast, areas like the Colorado Plateau and parts of the western US remain much darker.
Many online tools allow users to zoom in on specific states or cities. These maps help people find dark-sky parks and stargazing spots. They also show how urban development and lighting policies affect sky brightness over time.
Light Pollution Scale
Astronomers use the Bortle Scale to measure and describe the darkness of the night sky. John Bortle created this nine-level system in 2001. The scale ranges from 1 (excellent dark sky) to 9 (bright inner-city sky). Observers rate the sky by counting visible stars and noting features like the Milky Way. A Bortle 1 sky lets people see thousands of stars, while a Bortle 9 sky hides almost all but the brightest.
| Bortle Class | Description | Typical Location |
| 1 | Excellent dark sky | Remote wilderness |
| 5 | Suburban sky | Outskirts of cities |
| 9 | Inner-city sky | Downtown urban centers |
The Bortle Scale helps amateur astronomers and the public compare sky quality without special equipment. By using this scale, anyone can assess light pollution in their area and track changes over time.
How to Check Your Area
People interested in understanding the night sky brightness in their neighborhood have several practical options. Modern technology and citizen science projects make it easier than ever to assess local light pollution. Many tools and resources provide both broad overviews and detailed measurements.
A variety of websites and apps allow users to explore light pollution levels in specific locations:
- lightpollutionmap.info offers interactive maps that display artificial sky brightness and estimated Bortle scale ratings for nearly any spot on Earth. Users can search by address or zoom in on a map to see how their area compares to others. This tool helps identify dark-sky locations for stargazing or photography. However, the map’s estimates sometimes differ from real-world conditions, especially in areas where urban and rural zones meet. The Bortle scale values shown are based on satellite data and atmospheric models, which may not always reflect what people see on the ground.
- Globe at Night encourages individuals to participate in a global citizen science campaign. Participants use smartphones, tablets, or computers to report how many stars they can see in certain constellations. This project collects thousands of observations each year, helping scientists track changes in sky brightness worldwide.
- Dark Sky Meter app uses an iPhone’s camera to measure the brightness of the night sky. This app provides a quick estimate and is popular among amateur astronomers.
- Loss of the Night app guides users through a series of questions about visible stars, using the human eye as a measurement tool. This approach does not require any special equipment and works well for beginners.
- Sky Quality Meter (SQM) devices offer precise, handheld measurements of sky brightness. These instruments are widely used by researchers and serious hobbyists who want accurate, long-term data.
- Cities at Night project involves citizen scientists in mapping light pollution using photographs taken from the International Space Station. Volunteers help classify and analyze these images, contributing to a better understanding of global light pollution patterns.
- MySkyatNight project allows users to analyze their own collected data, providing a personal view of local light pollution trends.
No single map or tool perfectly matches real-world conditions. Satellite-based maps may underestimate light pollution in cities or overestimate it in semi-rural areas. Direct observation remains the most reliable method for assessing sky quality at a specific site.
For the most accurate results, experts recommend combining map data with personal visits. Observers can compare what they see with Bortle scale descriptions or use an SQM device for precise readings. Stargazers often check both digital maps and the actual night sky before planning trips to dark-sky parks or remote locations.
By using these resources, anyone can become more aware of their local night environment. Understanding light pollution levels helps individuals make informed decisions about outdoor lighting and supports efforts to protect the natural night sky.
Light Pollution Effects on Humans
Health Impacts of Light Pollution at Night
Artificial light at night disrupts the natural rhythms of the human body. Scientists have found that exposure to artificial light at night, also known as ALAN, can disturb the circadian clock. This disruption often leads to sleep disorders, such as insomnia, shift-work sleep disorder, and delayed sleep-phase syndrome. A nationwide study in China linked high ALAN exposure to a greater risk of insomnia. Researchers used social media data and spatial models to show that people living in brightly lit areas reported more sleep problems.
ALAN exposure can:
● Disrupt the circadian rhythm, which controls sleep and wake cycles
● Increase the risk of sleep disorders
● Suppress melatonin, a hormone important for sleep
● Affect gene expression related to many body functions
● Raise the risk of mood disorders, including depression
Epidemiological studies, such as the Nurses’ Health Study, have also found that long-term night shift work may increase the risk of certain cancers, including breast and colorectal cancer. The International Agency for Research on Cancer has classified shift work involving circadian disruption as a probable human carcinogen. These findings highlight the need for careful planning and regulation of nighttime lighting to protect public health.
Tip: Limiting exposure to bright lights at night and using blackout curtains can help support healthy sleep patterns.
Light Pollution and Safety
Many people believe that brighter outdoor lighting makes streets safer. However, scientific research tells a different story. Studies in England, Wales, the US, and other countries show no clear link between increased outdoor lighting and reduced crime or traffic accidents. In some cases, excessive or poorly designed lighting can actually make areas less safe.Unshielded lights often cause glare, which impairs vision for drivers and pedestrians. Glare can create deep shadows where criminals may hide, making it harder to spot suspicious activity. For example, a project in Chicago found that brighter alley lighting sometimes led to higher crime rates. Over 25 years of research has shown that more lighting does not always mean better safety. Social factors, such as community engagement, often play a bigger role in reducing crime than lighting alone.
| Lighting Condition | Impact on Safety |
| Excessive/Unshielded | Increases glare,reduces visibility, may increase crime |
| Well-designed/Shielded | Reduces glare, improves visibility, supports safety |
| Reduced lighting | No clear increase in crime or accidents |
Light Pollution and the Silent Disappearance of Cultural Memory
The night sky has inspired people for thousands of years. Artists, scientists, and storytellers have looked to the stars for ideas and meaning. Light pollution now hides most stars from view, especially in cities. This loss affects cultural traditions and shared human experiences.
Many cultures, including indigenous groups, use the night sky for navigation, storytelling, and passing down knowledge. For example, the Kamilaroi people of Australia rely on the Milky Way to teach and preserve their heritage. When skyglow from urban areas blocks the stars, these practices become harder to maintain. Iconic works like Van Gogh’s "The Starry Night" were possible because of a clear, dark sky. Today, many children grow up without ever seeing the Milky Way.
The United Nations and the Starlight Declaration recognize the right to enjoy the night sky as part of cultural heritage. Programs like International Dark Sky Places work to protect this right by promoting responsible lighting and raising awareness.
Environmental Impact Facts or Statistics of Light Pollution
Wildlife
Artificial light at night changes the behavior and survival of many animal species. Birds often become disoriented by city lights, leading to fatal collisions with buildings. Even dim light causes stress in birds and disrupts their natural cycles. Sea turtle hatchlings, guided by moonlight, can become confused by bright beachfront lighting. Many never reach the ocean, facing dehydration or predators instead. Fireflies struggle to find mates because their signals are outshone by artificial lights, which threatens their populations. Bats and insects also face risks. Insects gather around lights, making them easy prey for bats and reducing insect numbers. Tree frogs call less often in lit areas, which lowers their chances of reproduction.
| Species/Group | Effect of Light Pollution | Consequence on Behavior and Survival |
| Insects | Attracted to nocturnal lights | Increased predation risk by bats |
| Migrating Fish | Delayed migration due to illuminated barriers | Increased energy use, reduced reproductive success |
| Glow-worms | Difficulty attracting mates under artificial light | Decreased reproductive success |
| Various Animals | Physiological stress, altered life history traits | Negative impacts on development, survival, reproduction |
Many animals rely on natural darkness for navigation, hunting, and mating. Light pollution interrupts these vital activities and can lead to population declines.
Ecosystems
Ecosystems depend on natural light cycles. Artificial light at night, also called ALAN, disrupts these cycles in both land and water environments. Coral reefs show reduced photosynthesis in their algae and unstable populations when exposed to artificial light. Sandy beach isopods move less and lose their natural rhythms, which lowers their numbers. Fish such as rockfish and salmon change their activity and migration patterns, making them more vulnerable to predators. Terrestrial ecosystems, including grasslands and soil communities, also suffer. Insect communities shrink, and plant growth patterns change. Even low levels of artificial light can disturb food webs and increase extinction risks.
| Ecosystem Type | Observed Effects of ALAN |
| Intertidal sandy shores | Changes in invertebrate communities; some species decline, others increase with more light |
| Coastal zones | Large-scale changes possible as light pollution increases |
Complex ecological networks, such as those found in coral reefs and grasslands, are especially sensitive to changes in natural light.
Environmental Impact Fact
Recent studies show that night skies are getting brighter at an alarming rate. Satellite data from 2012 to 2016 measured an annual increase of about 2% in both the area lit and the brightness of the night sky. However, ground-based observations from over 50,000 volunteers between 2011 and 2022 suggest a much higher global increase—nearly 10% per year. Some regions, such as North America, experience even faster rates. This rapid growth in artificial light threatens biodiversity and the health of entire ecosystems.
The world’s night skies are losing their natural darkness faster than ever before, putting wildlife and ecosystems at risk.
Solutions to Decrease the impacts of Light Pollution
Individual Actions
Individuals can make a significant difference in reducing unwanted artificial light. Experts recommend several practical steps that help restore natural darkness and protect health and wildlife. People can start with simple changes at home and encourage others to do the same.
- Install time and motion sensors so lights turn on only when needed.
- Use dimmable bulbs to control brightness and avoid excessive illumination.
- Choose bulbs with warmer color temperatures (below 3000 K) to reduce blue light and minimize sleep disruption.
- Shield outdoor lights to direct illumination downward and prevent light from escaping into the sky.
- Turn off lights when not in use to save energy and reduce unnecessary glow.
- Use smart lighting systems or timers to automate lighting based on activity or time.
- Draw curtains and close blinds at night to prevent indoor light from leaking outside.
- Educate neighbors and friends about the importance of reducing artificial light at night.
- Small changes in lighting habits can lead to big improvements in night sky visibility and energy savings.
Community Initiatives
Communities play a vital role in addressing light pollution. Many towns and cities have launched successful projects to improve outdoor lighting and raise awareness. These efforts often involve local governments, environmental groups, and residents working together.
| Location | Initiative Description | Outcome/Impact |
| Massachusetts, USA | Street light retrofit organized with guidance from DarkSky International and local chapter advocacy. | Improved lighting infrastructure reducing light pollution. |
| India (Maharashtra) | Conversion of streetlights in four villages to 3000K fully shielded lights after successful design testing. | Reduced light pollution in rural areas, protecting local environment. |
| Oregon, USA | Use of All-sky Light Ratio (ALR) sky glow maps to update county lighting ordinances and promote responsible lighting. | Legislative update and educational programs encouraging responsible outdoor lighting. |
| Missouri, USA | Conservation Federation passed a dark sky resolution to improve lighting infrastructure using Dark Sky principles. | Formal commitment to sustainable lighting practices. |
| California, USA | Shielding of over 100 “acorn” lights near San Lorenzo River to protect endangered fish, after advocacy pressure. | Immediate reduction of light trespass impacting wildlife. |
| Multiple US cities | Proclamations declaring International Dark Sky Week, promoting awareness and community engagement. | Increased public awareness and official recognition of dark sky initiatives. |
| Utah, USA | State proclamation of Dark Sky Month highlighting dark sky certified places and astrotourism benefits. | Promotion of dark sky practices supporting local economy and lifestyle preservation. |
| Colorado, USA | Lights Off for Birds Month proclamation to raise awareness of light pollution's threat to birds. | Community engagement in wildlife protection through lighting awareness. |
| Illinois, USA | Wheaton Park District resolution promoting sustainable outdoor lighting practices. | Local government commitment to reducing light pollution. |
DarkSky International supports communities through its International Dark Sky Places certification program. This program recognizes parks, reserves, and towns that show strong commitment to protecting the night sky. Certified places must improve outdoor lighting, educate the public, and meet strict standards. As of early 2023, more than 200 locations worldwide have earned this recognition. These efforts help communities reduce artificial skyglow, protect wildlife, and promote astrotourism.
Policy and Laws
Governments at local, regional, and national levels have created policies to address light pollution. These laws set standards for outdoor lighting, encourage smart technology, and establish dark-sky preserves. Effective policies include clear rules, enforcement, and public education.
| Country/Region | Policy or Law Enacted |
| Czech Republic | Act on the Protection of the Environment (2002) – strict lighting standards and enforcement to reduce light pollution. |
| France | Loi Grenelle II (2010) – controls outdoor lighting to minimize light pollution. |
| Italy | Regional laws focus on outdoor lighting controls and dark-sky preservation. |
| United States | International Dark-Sky Association Model Lighting Ordinance – promotes shielding, smart lighting, and dark-sky areas. |
Many U.S. states and cities have adopted ordinances based on these models. These laws often require shielded fixtures, limit brightness, and encourage the use of timers or sensors. Public education campaigns help residents understand the benefits of responsible lighting. By following these policies, communities can reverse the effects of excessive artificial light and restore natural night skies.
Light Pollution Example Solution
One of the most effective ways to reduce unwanted artificial light in communities involves installing shielded outdoor lighting. Shielded fixtures direct light downward, focusing illumination only where it is needed. This approach prevents light from scattering into the sky or spilling into neighboring properties.
- Shielded light fixtures improve visibility in outdoor spaces, such as driveways, gardens, and commercial properties.
- Full cut-off fixtures eliminate upward-directed light, which helps reduce glare and sky glow.
- These fixtures also minimize light trespass, making nighttime environments more comfortable for people and less disruptive for wildlife.
- When used in streetlights, parking lot lights, and building exteriors, shielded designs prevent unnecessary brightness and help restore natural darkness.
Communities that combine shielded lighting with smart controls, such as timers and motion sensors, see even greater reductions in wasted light and energy use.
Many cities and towns have adopted shielded lighting as part of their outdoor lighting policies. For example, Tucson, Arizona, replaced thousands of streetlights with fully shielded, energy-efficient models. This change led to a significant drop in sky brightness and energy costs, while still providing safe and effective lighting for residents.
Legislation also plays a key role in promoting shielded lighting. As of 2024, nineteen U.S. states, along with the District of Columbia and Puerto Rico, have enacted laws specifically aimed at reducing light pollution. These laws often require the use of shielded fixtures for new outdoor lighting installations and encourage local governments to follow best practices recommended by organizations like the International Dark-Sky Association.
By choosing shielded outdoor lighting, communities protect the night sky, save energy, and create safer, healthier environments for people and wildlife.
Restoring natural night skies benefits both people and the environment. Everyone can help protect this shared resource for future generations.
FAQ About Light Polltion
How Does Light Pollution Affect Sleep?
Artificial light at night disrupts the body’s natural sleep cycle. Exposure to bright lights can suppress melatonin production. People may experience insomnia or poor-quality sleep as a result.
Can Light Pollution Harm Animals?
Yes. Many animals rely on darkness for navigation, hunting, and reproduction. Birds, sea turtles, insects, and bats often become confused or endangered by artificial lights.
Is Light Pollution Reversible?
Light pollution can be reversed. Communities that use shielded lighting, reduce unnecessary lights, and follow smart lighting practices see quick improvements in night sky visibility.
How Can Someone Check Light Pollution in Their Area?
People can use online maps like lightpollutionmap.info or apps such as Globe at Night. These tools show local sky brightness and help users find dark-sky locations.
What Are Some Simple Ways to Reduce Light Polluti
on at Home?
- Use shielded outdoor fixtures.
- Turn off lights when not needed.
- Choose warm-colored bulbs.
- Install motion sensors or timers.
Small changes at home can help restore the natural night sky.