Light pollution is the illumination of the night sky caused by artificial light sources on the ground (streetlights, billboards, etc.). Both the light and the loss of contrast make it difficult to find fainter stars and nebulae. The amount of outdoor lighting increases as a result of increasing population. As cities and suburban areas grow, the number of lights at night also increases. Lights, contrast, and glare all impact the number of stars that are visible in a given location. Only the brightest stars are visible when there is a lot of nighttime lighting.
Outdoor lighting is used for many reasons including security, sporting events, and advertising. Some outdoor lighting is more efficient in its design and/or placement and limits the amount of light shining up or away from the intended purpose. Using lights at night can be helpful, but there are trade-offs in the form of unanticipated effects.
Lights at night can impact both the biology and ecology of species in the wild. Some examples include:
- the disorientation of sea turtle hatchlings by beachfront lighting
- nesting choices and breeding success of birds
- behavioral and physiological changes in salamanders
- disturbances of nocturnal animals
- altered natural light regimes in terrestrial and aquatic ecosystems
Written by Susan Gallagher. Sources consulted:
International Dark-Sky Association's (IDA) Web site, www.darksky.org
The Columbus Astronomical Society’s (CAS) Web site, www.the-cas.org
Longcore, T. and Rich, C., Ecological light pollution, The Ecological Society of America, Ecological Environment 2004; 2(4): 191–198.
Other Light Pollution Campaigns consulted:
IDA - Section Austria,
www.sternhell.at/index.php
StarWatch Program in Canada,
www.redshiftnow.ca/starwatch/default.aspx
Greek Ministry of Education and Religion's Light Pollution Program, www.astrosociety.org/education/publications/tnl/44/lightpoll5.html
U.S. National Park Service, www.nature.nps.gov/air/lightscapes
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