Light pollution

Author: Johan Smit - Dark Sky Director, Astronomical Society of Southern Africa.

( Article Type: Explanation )

Light pollution is a widely accepted term for adverse effects of artificial light on nature and humans. Nearly all living organisms, including human beings, have evolved under a natural rhythm of day and night. The artificial disturbance of the natural day/night cycle may, as a result, have serious psycho-physiological and even medical consequences for humans, along with ecological and evolutionary implications for animals, plants, and even entire ecosystems.
Light pollution is caused by improper lighting installations.

The most obvious effects are:
• Light trespass – Light shining where it is not needed.
• Glare - excessive contrast between bright and dark areas in the field of view

All these contribute to the sky glow that can be seen over populated areas, and destroys the night-time ambience. Contrary to popular belief, light does not deter crime or improve security. Improperly implemented, it can do more harm than good. Lighting consumes about a quarter of all energy produced worldwide. Light that shines where, and when, it is not needed is wasted energy.

Significant savings can be achieved with responsible and intelligent lighting practices, for example, a low wattage lamp in a well-designed light fixture can achieve the same effect as a higher wattage lamp in a badly-designed fixture. Light pollution is the only pollution that costs more to perpetuate than to eliminate.