Nighttime is when the effect of humans on the environment is especially pronounced. Outside of wildfire, most nighttime lighting is from artificial sources such as street lights.
Satellites and photographs taken from the International Space Station now are able to captured illumination of the Earth’s surface and in some areas, the contrast is significant.
As artificial lights cover more and more of the Earth, nighttime darkness is becoming increasingly rare.
What is light pollution?
Light pollution, defined as the “inappropriate or excessive use of artificial light” is increasing worldwide. Light pollution doesn’t just affect urban areas.
Sky glow is the brightness of the night sky as a result of nearby artificial light pollution. Sky glow affects an estimated 80% of the world’s population. Glare, from the direct shining of artificial lights is another problem area.
Light pollution can have deleterious effects on both human and wildlife populations by affecting diurnal rhythms. The disruption of the circadian rhythm has been shown to impact wildlife migration as well as impacting sleep patterns, feeding schedules, and reproductive cycles.
Some of the ecological effects of light pollution:
- Birds: Many species of birds that migrate or hunt at night can become disoriented by artificial lights, leading them astray from their traditional routes or causing them to collide with illuminated buildings.
- Insects: Artificial lights attract nocturnal insects, leading to reduced populations due to increased predation and energy exhaustion. This has a cascading effect on the food chain and disrupts pollination patterns.
- Sea Turtles: Hatchlings have an instinct to move towards the brightest horizon — traditionally the moonlit ocean. However, with coastal developments and their accompanying lights, these young turtles often head inland, where they face numerous dangers.
Nighttime lights can image human health
Light pollution also impacts human quality of life.
- Sleep Patterns: The human body operates on a circadian rhythm, which is heavily influenced by natural light. The intrusion of artificial light, especially the blue light emitted by LEDs, can suppress melatonin production, leading to sleep disorders.
- Mental Health: There is growing evidence to suggest that prolonged exposure to artificial light at night can exacerbate symptoms of depression and other mental health disorders.
Light pollution makes it hard to see the night sky
- Stargazing: In many urban areas, the glow from artificial lights obscures all but the brightest celestial objects. Many children growing up in cities today have never witnessed the Milky Way.
- Astronomical Research: Observatories require dark skies to study celestial bodies. With the encroachment of light pollution, it’s becoming increasingly challenging to find suitable locations for these facilities.
Mitigating Light Pollution
There are efforts to combat excessive nighttime lighting. For example, some cities are swapping out light fixtures that angle lights down instead of shining up into the night sky.
Addressing the issue of night pollution requires a multifaceted approach:
- Better Design: Adopting lighting fixtures that minimize upward and outward spill of light can substantially reduce skyglow. Shielded fixtures that direct light downward, where it’s needed, are a simple solution.
- Dimming and Sensors: Modern lighting technology allows for lights to be dimmed during off-peak hours, reducing unnecessary brightness. Motion sensors can also ensure lights are only on when needed.
- Public Awareness: As with many environmental issues, raising awareness is crucial. The more people understand the implications of light pollution, the more they can push for regulations and adopt better practices in their communities.
The International Dark-Sky Association works with nations and organizations to create dark sky sanctuaries. These areas have prioritized access to night time views. Niue was the first nation to receive the Dark Sky Nation status.
Satellite imagery and photographs of the Earth at night
The growth of night lights is most visible in satellite pictures of the Earth and in photos taken from the International Space Station (ISS). High-resolution nighttime photos of Earth taken by astronauts onboard the ISS frequently serve as research tools for studying light pollution and urban growth.
Satellites also capture more wider but lower resolution views of the Earth at night. Remotely sensed data from satellite imagery is also used to study the growth of night lights.
Black Marble – World view of the Earth at night
United States at night
This composite image of the United States at night was created in 2012 by NASA.
The level of light pollution varies across the United States, depending on the density of the area.
According to a study done in 2016, 99 percent of the population of the United States lives under light-polluted skies, which means that the vast majority of Americans do not have access to a really natural view of the night sky. Furthermore, 80% of Americans are unable to see the Milky Way from where they live.
Night lights over New York
The northeastern part of the United States is very densely populated. New York City is home to almost nine million residents. This night time view of major cities along the northeastern coast of the United States was taken aboard the International Space Station.
The cities of New York (NY), Newark (NJ), Philadelphia (PA), New Haven (CT), and Hartford (CT) are visible in this photo. The thin line of lights of 1-95 is also visible. The dense urban area spans 200 miles (300 kilometers) from Hartford to Philadelphia.
Holiday lights over Texas and Louisiana
Nighttime lighting increases significantly in the United States around the Christmas and New Year’s holiday season. A 2015 study on holiday lights found that, when compared to the rest of the year, evening lights in many major U.S. cities shine 20 to 50 percent brighter between Christmas and New Year’s.
NASA researchers analyzed the change in light intensity in the period between Thanksgiving and New Year’s as compared to other times of the years. This satellite image has the mapped results of changes in light intensity over parts of Texas during the month of December (for the years 2012 and 2013) compared to the monthly average from 2012 to 2014 excluding those months.
Green coloring indicates locations where light usage grew in December, yellow indicates areas where light usage remained unchanged, and red indicates areas where light usage decreased.
The researchers also found that holiday-light related increases were more pronounced in suburban areas compared to urban areas.
South America’s Atlantic Coast
Night lights from the South American cities of Rio de Janeiro, São Paulo, and Buenos Aires can be seen in this satellite image taken in 2012. Small dots over the Atlantic Ocean are lights from fishing boats.
Rail Station Legacy Influences Argentina’s Night Lights
A view of Argentina’s night lights reveals an interesting pattern. Argentina’s night lights are evenly space out in lines across the country. This formation is a legacy from when these towns sprung up around railway stations.
These stations were established about every 20 to 30 miles (30 to 50 kilometers). Developments rose around these stations, which explains the regularly and linearly spaced lights visible on satellite imagery of Argentina today. Also visible is a segment of the Pan-American Highway around San Luis.
This Suomi satellite image shows the night lights of the Northern Europe countries of Finland, Sweden, Norway, Denmark, and Russia.
Volcanic eruption at night on the Canary Islands
There are some sources of natural nighttime light. The flowing lava from the Cumbre Vieja volcanic eruption on La Palma in the Canary Islands was visible at night from the International Space Station. Lights from nearby Los Llanos and El Paso can also be seen in the photo.
Night lights in Antalya, Türkiye
This night time photograph taken from the ISS of the coastal Mediterranean city of Antalya, Türkiye shows the contrast between urban and rural areas. Within the urban areas, the total darkness of Zeytinpark, a city park of olive trees, stands out in contrast the the brightly lit surrounding areas. The illuminated strip of the airport can also be clearly seen. Agriculture along the Aksu River and the Taurus mountains that sit to the north and
Bangkok, Thailand night lights
This oblique photo from the International Space Station shows Thailand at night. Bangkok’s urban lights dominate the area, with neighboring cities’ lights along the Gulf of Thailand.
Green lights from fishing boats can be seen out in the ocean. The green lights draw plankton and fish to the surface which in turn attracts squid which the fishing boats then capture.
Night lights at the India – Pakistan border
In the Indo-Gangetic Plain, a line of orange-hued lights marks the border between northern India and northern Pakistan. The floodlights, as well as fencing, were constructed by the Indian government to deter smuggling and arms trafficking.
The border’s brightness is so bright that it can be seen from the International Space Station, where this image was taken in August of 2011.
North Korea at night
One country that stands out for its lacks of night time lights is North Korea. On maps depicting nighttime lights, North Korea’s whole country is a large black area.
Due to the collapse of the Soviet Union in the early 1990s, a cheap source of fuel was no longer available, and the country now descends into darkness with the sunset, with the exception of an island of light where Pyongyang, the capital, is located. According to the U.S. Energy Information Administration, North Korean’s electricity consumption dropped from 33 billion kilowatthours (BkWh) in 1990 to 16 BkWh by 2000.
The satellite image below shows the stark difference between night time lights in North Korea compared to South Korea. Only a small amount of lighting, mostly centered on the capital of Pyongyang can be seen in North Korea. South Korea is gleaming with artificial lights across the country.
Lights from fishing boats can be seen in the Yellow Sea and the Sea of Japan.
Falchi, F., Cinzano, P., Duriscoe, D., Kyba, C. C., Elvidge, C. D., Baugh, K., … & Furgoni, R. (2016). The new world atlas of artificial night sky brightness. Science advances, 2(6), e1600377. DOI: 10.1126/sciadv.1600377
Light pollution – Night skies. (n.d.). NPS.gov (U.S. National Park Service). https://www.nps.gov/subjects/nightskies/lightpollution.htm
Román, M. O., & Stokes, E. C. (2015). Holidays in lights: Tracking cultural patterns in demand for energy services. Earth’s future, 3(6), 182-205. https://doi.org/10.1002/2014EF000285
Schmidt, S. (2023, July 30). Nighttime in Antalya, Türkiye. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/151643/nighttime-in-antalya-turkiye
This article was originally written on June 11, 2022 and has since been updated.