Light Pollution

What is Light Pollution?

Although light pollution may intuitively seem to be in a different category from other forms of pollution such as air or water pollution, it is rightly considered a form of pollution, if pollution is understood to mean the presence of something in the environment that is either harmful and/or toxic. Light pollution affects our environments aesthetically, and it also has been demonstrated to have harmful effects on the health of human and nonhuman species and to alter human and nonhuman animal behavior.

What Light Pollution Does

Light pollution has various effects. The most visible effect of light pollution is the reduction of star visibility. This is the result of what has been termed sky glow. Sky glow is what hangs over cities and urban centers. It is said to be the result of artificial light interacting with clouds and other elements in the atmosphere that causes the bright glow common to urban areas that presents a dome-like barrier between the inhabitants of urban areas and the larger cosmos beyond the glow. There are far fewer stars visible to residents of urban, light-polluted areas than to inhabitants of rural, less light-polluted areas. Most of the world's population currently lives under sky glow of greater or lesser severity. Sky glow prevents one-fifth of the world's population from seeing the Milky Way at night; this number is much higher in the most affected areas, such as Europe, Japan, and North America, where the number is set as high as two-thirds.

Light pollution can have severe cultural and physical effects. In terms of health and behavioral effects of light pollution, many species, including our own, are sensitive in our daily routines to the presence and absence of light. Our species is fundamentally [Page 299]diurnal (active by day) as opposed to nocturnal (active by night). To facilitate our activity by night, we need to light up our way. Unfortunately, excess artificial light can severely and detrimentally affect the health and behavior of other species. Light pollution has been cited as disrupting feeding patterns, migration patterns, mating, and so on. There are reported cases of birds being attracted by artificial light from buildings only to collide with them, or to circle the light source until dying of exhaustion. A famous example used in discussions of light pollution is that of the sea turtles that lay eggs on dark beaches; when the hatchlings emerge they gravitate toward the brightness of the sea. With beachfront development and its attendant light pollution, however, the light from the sea is often eclipsed by the light from the beach, thus disorienting the hatchlings, leaving many of them vulnerable and unlikely to ever reach the sea. Another example of the effect of light pollution on animals is the opportunity it provides for creatures to forage for food longer; however, this simultaneously leaves them more vulnerable to predation. The general point is that many species’ health and behavior are closely connected to the cycles of light and day, and as we engineer the darkness into light and obstruct these rhythms, animals and ecosystems are being affected in ways we do not yet fully understand.

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