The Impact of Artificial Lights on Wildlife

This composite image shows the world light use at night. (Credit: Data courtesy Marc Imhoff of NASA GSFC and Christopher Elvidge of NOAA NGDC. Image by Craig Mayhew and Robert Simmon, NASA GSFC.)

As shown by this world map, the night sky is obscured by artificial lights in many parts of the world. These lights are used to illuminate buildings, roadways, stadiums, fields, and other structures. While these lights help humans navigate around their surroundings, they can wreak havoc with the natural movements and functions of other animals. Research indicates that the light pollution caused by artificial lights can disorient wildlife, affect natural circadian rhythms, and disrupt bird migration.

What is Light Pollution?

According to the International Dark-Sky Association (IDA), the term light pollution refers to “any adverse effect of artificial light, including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste.” The IDA further states that light pollution “wastes energy, affects astronomers and scientists, disrupts global wildlife and ecological balance, and has been linked to negative consequences in human health.”

Affects on Wildlife

Research in the field has shown that artificial lights disorient wildlife. For example, research published in the journal Biology by Michael Salmon of Florida Atlantic University indicates that sea turtle hatchlings use a differentiation in light intensities between their nest on the beach and the ocean to navigate toward the sea.

Other research indicates that artificial lights can alter an animal’s normal behavior. For example, research published in the North American Journal of Fisheries Management indicates that the presence of artificial light causes juvenile salmon to stop swimming downstream and instead seek cover from predators in the shallow water near the shoreline. This behavior makes the young salmon more vulnerable to predation.

Research also shows that artificial lights can have an impact on an animal’s circadian rhythms. Such an impact can impair a number of normal behaviors including foraging, migration, and reproductive behaviors by changing when these behaviors begin or end.

Affects on Migration

Perhaps one of the most dramatic impacts of artificial light is its affect on migrating birds. Research indicates that bright lights disorient migrating birds. When flying at night, it is thought that birds use the light from stars to navigate. When there is heavy cloud cover or the stars are obstructed by bad weather, migrating birds are attracted by bright artificial lights. Migrating birds are especially vulnerable to collisions with tall lighted buildings. Researchers have found that birds can become “trapped” in light beams and may die from exhaustion by continually flying in circles, unable to fly out of the light beam’s boundaries.

Research conducted by scientists in the Netherlands indicates that sea birds are attracted by lights on offshore oil platforms in the North Sea. The scientists found that certain wavelengths of light interfere with the bird’s magnetic compass, another method birds use to navigate. Red light (in the visible spectrum) interferes with a bird’s magnetic compass. Blue-green light does not interfere as severely with the bird’s magnetic navigational system. Researchers suggest that the use of blue-green lights on offshore platforms may help to significantly decrease seabird mortality due to navigational interference from artificial light sources.

Possible Solutions

There are a number of possible solutions to the problem of artificial light and its impact on wildlife. Several cities participate in the “Lights Out” program. In this program, building managers either dim or completely turn off the lights in tall buildings such as Chicago’s John Hancock Tower during the spring and fall bird migration seasons. Since this program was first instituted, there has been a dramatic decrease in bird mortality around tall buildings.

Other solutions include replacing bare bulbs or any light pointing directly upward. In many situations, the amount of light used is at a much higher intensity than is necessary. Dimming lights or using a lower-intensity bulb, while still maintaining the proper amount of light to allow humans to see and navigate safely, can also decrease the impact of artificial light on wildlife populations.

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