In 2024, International Dark Sky Week, April 2-8, ends with an extraordinary astronomical event passing over a large swath of North America: a total solar eclipse. Many U.S. residents are traveling to locations in the “path of totality” to experience the eclipse. Whether or not you are making such a journey, International Dark Sky Week presents an opportunity to revisit why the campaign to curb light pollution is important—and much misunderstood.
In the United States and Europe, 99% of people live under a light-polluted sky. The damage of artificial light at night goes far beyond blocking our view of the stars and disrupting wildlife migratory patterns. Scientists have linked light pollution to global insect decline, the death of millions of migrating birds, increased carbon emissions, and increased human disease.
The Dark Sky movement, however, has a branding problem. Many people are understandably afraid of darkness. When our eyes have not adjusted to the dark, we cannot see to walk or drive safely, we think lots of artifi cial outdoor light is the answer. Dark Sky advocates merely point out that too much light can be a huge hazard.
The lighting industry has for too long played on fear of crime as the reason to sell businesses, municipal governments, and property owners on an overabundance of lighting, much of which results in wasted energy as it casts a glare out to the human eye and up into the sky where is does not add to our safety. The key to safety is to have the right amount of light, the right color (or “temperature”) of light, aimed in the right direction-down at the ground where we need it to see and move safely.
More than three billion dollars is wasted annually on energy to power our artificial outdoor lights. This cost is borne by all of us, and if we produce that energy by burning fossil fuels like coal and gas, excess outdoor light contributes to our dangerous level of climate change.
Thoughtful lighting installations limit light to where it is needed, and only in the amounts necessary. This approach eliminates unnecessary lighting and light going up into the sky, and reduces over-lighting, glare, and lighting that spills out past its intended area.
The Illuminating Engineering Society and Dark Sky International have published Five Lighting Principles for Responsible Outdoor Lighting.
The engineers recommend lighting that is (1) Useful for a clear purpose, (2) Targeted exactly where it is needed to achieve the purpose, (3) Low level no brighter than needed, (4) Controlled by timers or motion sensors, and (5) Warm-colored (yellow not blue) to ease impact on human eyes.
Take some time this spring to do your own home outdoor light inventory, or assess the lights in your community and help locate improved lighting options. International Dark Sky Week helps raise awareness of the benefi ts of community-friendly lighting and our heritage of dark skies—even darkness at midday on Monday, April 8.
About the author: Anne L. Harper, Ph.D. Leelanau Dark Sky, a chapter of Leelanau Energy
