Light pollution

DEFINITION: Human-caused illumination of areas beyond where light is intended and/or wanted

In addition to its adverse effects on the work of astronomers and the wasted energy it represents, light pollution can have deleterious impact on animals, including humans.

Like most pollution, the most obvious effect of light pollution is aesthetic. Stray light from human-made lighting sources makes the sky bright at night, which makes stars and constellations less easily visible. The field of astronomy is adversely affected by light pollution for this reason; in fact, in many highly populated areas, astronomers are unable to see most galaxies and nebulae, even with the use of telescopes. Because of the impact of this situation on their field of study, astronomers have been among the most vocal critics of light pollution, but environmentalists have increasingly joined in efforts to address the problem, noting that it has negative impacts on the environment as well.

Light pollution is often an unintended consequence of intentional lighting. The light from human-made sources, if not properly directed, often goes beyond the areas that are meant to be illuminated. Many people who install outdoor lighting fixtures do not even think about how the light they generate affects others. In this way, light pollution is much like noise pollution. Light pollution is also like noise pollution in that for many years it was thought of solely as a nuisance issue, a problem without any real consequences for the environment.

Environmental Effects

One of the biggest environmental impacts associated with light pollution is the waste of energy represented by light that goes beyond where it is intended to go. When light shines beyond the area that needs to be illuminated, the light source is using more energy than is really necessary to do the intended job. It has been estimated that the energy used for outdoor lighting could be cut in half if all lighting fixtures were appropriately shielded to direct their light more precisely. Aside from the economic benefits, such a reduction in would have a significant impact on the need for electricity generation, which often has negative environmental effects.

Light pollution has also been found to be detrimental to wildlife. Nocturnal animals are adapted to life in the dark, and the lack of full darkness in areas with high levels of light pollution can influence the activities of such animals. For example, it can affect the relationship between predator and prey, as the prey cannot hide in darkness as they normally would. Some studies have shown that migratory animals, particularly birds, are also affected by light pollution, and other research has found that increased light affects the breeding practices of many animals. Excess nighttime lighting can affect plant growth as well.

Humans also appear to be physically affected by light pollution. An increasing body of evidence indicates that the human circadian rhythm developed to include a certain number of hours of darkness per day. Disruptions of a person’s circadian rhythm can result in serious health problems, ranging from sleeplessness to irritability and depression.

Mitigation

Outdoor lighting is essential for safety and security, but not all outdoor lighting generates the same level of light pollution. Reducing light pollution can be as easy as replacing conventional outdoor lighting fixtures with fixtures that are shielded so that they direct light where it is wanted and limit the amount of light that goes in other directions. Such fixtures can achieve the same level of illumination in intended areas with lower-wattage bulbs than are needed in conventional fixtures, resulting in energy savings in addition to reductions in stray light. Shielded light fixtures tend to cost more than unshielded fixtures, but the savings in electricity costs may offset the greater initial expense over time. Retrofitting existing lights with shielding on a large scale can be prohibitively expensive.

The biggest impediment to the reduction of light pollution is a general lack of awareness and understanding of the effects of light pollution among the public. The deleterious effects of air pollution and water pollution are generally well understood, but the effects of light pollution—other than on astronomy—are often not immediately recognized. Because of this lack of awareness, outdoor lighting is often installed by nonexperts. Municipalities, businesses, and homeowners could reduce light pollution by consulting with lighting engineers who can design lighting plans to ensure sufficient illumination of desired areas with minimal waste of light and energy.

Bibliography

Bakich, Michael E. “Can We Win the War Against Light Pollution?” Astronomy, Feb. 2009, pp. 56–59.

Gallaway, Terrel, Reed N. Olsen, and David M. Mitchell. “The Economics of Global Light Pollution.” Ecological Economics, vol. 69, no. 3, 2010, pp. 658–65.

Klinkenborg, Verlyn. “Our Vanishing Night.” National Geographic, Nov. 2008, pp. 102–23.

"Light Pollution." National Geographic, 1 Apr. 2024, education.nationalgeographic.org/resource/light-pollution/. Accessed 4 Oct. 2024.

"Light Pollution." National Park Service, 17 June 2024, www.nps.gov/subjects/nightskies/lightpollution.htm. Accessed 4 Oct. 2024.

“Light Pollution Harms Wildlife and Ecosystems.” Dark Sky International, 13 Nov. 2023, darksky.org/resources/what-is-light-pollution/effects/wildlife-ecosystems/. Accessed 4 Oct. 2024.

Luginbuhl, Christian B., Constance E. Walker, and Richard J. Wainscoat. “Lighting and Astronomy.” Physics Today, Dec. 2009, pp. 32–37.

Mizon, Bob. Light Pollution: Responses and Remedies. Springer, 2002.

Rich, Catherine, and Travis Longcore, editors. Ecological Consequences of Artificial Night Lighting. Island Press, 2006.