Understanding Light Pollution

Lighting areas at night can provide safety and security, illuminating dark spots and shadowy recesses. However, excessive night lighting can have a negative impact on the environment, on living species, and on the view of the night sky. Light trespass happens when night lighting spreads out from a light source into other areas where the light is not needed or wanted. An example of light trespass could be if a neighbor's night lighting spreads to other adjacent properties. Over-illumination happens when nighttime lighting provides excessive illumination beyond what is needed for safety and security. Over-illumination is typical in parking lots. Skyglow is a third type of light pollution; it refers to the glow that often hangs over large cities and densely populated areas.

Light pollution can impact human health because it may disrupt the body's circadian rhythm. The circadian rhythm is the internal body clock in humans that requires regular times of light and dark. With disruptions in circadian rhythm, melatonin levels may decrease, which can further compound problems with sleep and overall health. Nocturnal animals and insects can experience disorientation and disruptions due to light pollution. These species may have trouble finding food, and they can be more visible to predators, so population levels may decline. The excessive use of lights at night increases carbon waste, which contributes to global warming. Skyglow may also disrupt the natural ozone, which may contribute to higher pollution levels. With excessive night lighting, it frequently becomes difficult to view stars and constellations in the sky, too.

Cities can play a significant role in reducing light pollution by changing night lighting practices. Individuals can also make lighting changes to reduce light pollution. Using motion detectors for outdoor lights will reduce night lighting so it's on only when necessary. Installing shields over exterior light fixtures can point the light down where it's needed, thereby reducing the amount of light that shines out and up into the sky. Reduce the amount of indoor lighting that shines out of windows, too, by using light-blocking window coverings.

Explore light pollution and steps you can take to reduce your contribution to this problem by visiting these websites:

  • Missing the Dark: Health Effects of Light Pollution : The first incandescent light bulb chased away the dark in 1879. Explore how artificial lighting could be affecting the environment and human health in this report.
  • Light Pollution : The National Park Service explains two forms of light pollution, skyglow and glare, and their impact on the night sky.
  • The Fading Milky Way : The night sky and its twinkling stars are fading due to the prevalence of artificial lighting that floods the darkness.
  • Skyglow/Light Pollution : View images of skyglow in these maps, which show the concentrations of artificial lighting in the United States.
  • View of the Nighttime Sky : The Wisconsin Department of Natural Resources explains light pollution to kids, offering suggestions for reducing your personal impact on light pollution.
  • Ecological Light Pollution : Light pollution has a significant impact on how the night sky appears from Earth. Ecological impacts are also occurring from light pollution, including disruptions to animal biorhythms and changes in their behavior.
  • Night Lights: Too Much of a Good Thing? The New York State Conservationist explores artificial lighting and its impact on insects, birds, and air pollution levels.
  • Task Force to Study Lighting Efficiency and Light Pollution in Maryland : A light pollution task force in Maryland has published information about how to provide outdoor night lighting that maximizes safety while minimizing its impact on the environment.
  • Outdoor Lighting Tips to Avoid Light Pollution : Learn how to reduce your contribution to light pollution with these tips provided by the Pennsylvania Outdoor Lighting Council.
  • Outdoor Light Pollution Standards : Arizona State University is active in research performed in conjunction with NASA. Consequently, the Arizona legislature is taking steps to reduce light pollution to ensure that ASU can continue its research.
  • Light Pollution : View images of nighttime lighting between 1950 and 1997 with a projected image of nighttime lighting in 2025.
  • Are Artificial Night Lights Among Threats to Declining Reptiles? The U.S. Geological Survey provides information about the connection between light pollution and declining numbers of reptiles.
  • Preserving Dark Skies : Explore ways that municipalities can reduce light pollution by instituting ordinances about the types of lights used at night.
  • Lights Out for Loggerheads : Loggerhead sea turtle hatchlings can become disoriented by night lighting as they leave their nests to make their way to the sea, causing them to move inland instead.
  • Guidelines for Good Exterior Lighting Plans : The Dark Sky Society provides information to help individuals and municipalities use night lighting responsibly.
  • The Heart of Darkness : An article published in Montana Outdoors explains scotobiology, which is the study of the effects of light pollution on living species and the environment.