Light Pollution

By Lindsay Harrington, Graduate Assistant

In 1879, when Thomas Edison invented the light bulb, he forever altered the way humans would see their world. We as humans are diurnal creatures and enjoy the comfort of daylight as opposed to the unknown darkness of the night. We light up our streets, our buildings, and homes with little thought as to how this unnatural aura can affect the other living things on our planet. Over the past century the effects of the unnatural light produced by humans have begun to negatively affect the ecology and biology of many of the species that live on Earth.

Just as humans can pollute a river or the air, we have the capability of creating light pollution, which can have just as many adverse effects. Technically, light pollution or artificial night lighting can be broken down into two different categories- astronomical and ecological. Astronomical light pollution is the cumulative effects of hundreds of thousands of lights directed towards the sky. When this light is reflected back towards the Earth it is sometimes referred to as “sky glow” and is responsible for poor visibility of the stars in urban and suburban communities. Although obstruction of view of the night sky can be a nuisance to humans interested in viewing the stars and planets, the ecological damages of light pollution are much more alarming.

Ecological light pollution can be caused by a number of different sources such as streetlights, sky glow, buildings, and boats. It is a global phenomenon meaning that there are few places on Earth in which the effects of light pollution are not evident. In fact, about 18 percent of the planet is exposed to artificial night sky brightness and only about 40 percent of Americans live in a region where the human eye makes the complete transition from cones to rod vision. Rods are special light receptor cells within the eye that are designed to work in low light conditions. Scientists traditionally measure light pollution or illumination levels with a unit of measurement called lux. Lux measurements express the brightness of lights as perceived by a human eye and not how other organisms perceive them. Thus, the research on ecological light pollution has been very limited.

Some of the most common effects of light pollution on organisms in their natural environment are changes in orientation, disorientation, attraction, and repulsion. These behavior changes can interfere with foraging, reproduction, migration and communication in several species. Orientation and disorientation are responses to the amount of total light in the area where as attraction and repulsion are responses to the light sources themselves and their individual brightness.

Orientation responses occur when increased artificial illumination can extend organisms daytime behaviors into the night. The light increases the organism’s ability to orient themselves in their environment. For example, diurnal reptiles and birds who continue foraging for food into the evening are able to exploit a niche, which was at one time not accessible by them.

Disorientation occurs when animals accustomed to darkness encounter artificial light. Probably the best-known example of this is baby sea turtles that in normal circumstances would move away from the dark shadows of the dune grasses. With beachfront development, orientation is disrupted and streetlights and houses now illuminate the normally dark dunes. Birds also succumb to disorientation in lighted areas and will often remain “trapped” until daylight. While within the lighted areas such as those around skyscrapers, birds collide with each other, or manmade structures, and often die. The most common species that become trapped by light are insects which are “photopositive” and are attracted to areas of brighter light. As opposed to “photonegative” insects, which avoid lighted areas.

Repulsion away from artificially lighted areas is another common response among organisms. Most notably, reproductive behavior can be greatly altered by the presence of artificial light. Some species of frogs will become less selective of mates, preferring to mate quickly to avoid being eaten in brightly lit areas. Night lighting can also effect the migration of amphibians from breeding grounds as many only do so in the darkness of night.

The effects of light pollution can affect whole ecosystems by fundamentally changing the behaviors of the organisms within them. By altering a species niche or harming population levels, light pollution has the potential to have catastrophic effects when combined with the other pressures we as humans place upon the environment. As we as a society continue to develop the landscape, the influence of artificial light will continue to increase. Light pollution is something that should be considered just as much as water or air pollution because its effects are can be just as detrimental. Not to mention, it prevented me from seeing Jupiter over Thanksgiving break!

The question that remains is what can be done to control light pollution and alleviate some of its effects? Several municipalities have taken steps to minimize the amount of excessive night lighting in their communities through legislation. The United Kingdom has taken the lead in the movement by passing the Clean Neighborhoods and Environment Act, which deems light pollution just as harmful as smoke or noise pollution. Also, recently, the Czech Republic passed the Protection of the Atmosphere Act, which actually fines those who do not follow the guidelines of the law. Several states and municipalities in the United States have passed legislation, which limit the use of outdoor lighting past certain hours. Legislation like this is a step in the right direction and will ensure that communities reduce their impact. Several organizations such as the International Dark Sky Association are at the forefront pushing legislation to control light pollution for the astronomical community.

If you are someone who already takes steps towards minimizing their impacts on the environment, helping to prevent light pollution is something to consider. There are simple steps that can be taken around the home that can help to minimize localized light pollution. These include only using outdoor lights when necessary. Placing lights on timers is a great way to save energy and reduce the amount of light pollution created. If outdoor lights must be used, direct them towards the ground and do not use lights, which are excessively bright. Write to your local government asking them to do their part to control light pollution the community. Overall, educating others about the effects of light pollution is the simplest solution to this growing problem. It would be unfortunate if future generations could not enjoy the beauty of the night sky free from light pollution.


  • Longcore, Travis and Catherine Rich. (2002) Ecological light pollution. Frontiers in Ecology:2(4), 191-198