LIGHT POLLUTION 101
Less than 100 years ago, everyone could look up and see a spectacular starry night sky. Today, 80 percent of people can no longer see the Milky Way from where they live.
But light pollution isn’t just erasing our view of the Universe. It’s also terribly impacting our environment, safety, wildlife, and human health.
We’re all familiar with air, water, and land pollution, but artificial light at night can also be a pollutant. The inappropriate or excessive use of artificial light – known as light pollution – can have serious environmental consequences for humans, wildlife, and our climate.
There are different types of light pollution, including:
GLARE
Excessive brightness that causes visual discomfort.
SKYGLOW
Brightening of the night sky over inhabited areas.
LIGHT TRESPASS
Light falling where it is not intended or needed.
CLUTTER
Bright, confusing, and excessive groupings of lights.
Light pollution is a side effect of industrial civilization. Its sources include exterior and interior lighting on buildings, advertising signs, commercial properties, offices, factories, streetlights, and illuminated sporting venues.
While outdoor lighting has improved our lives in many respects, most of it is inefficient, overly bright, poorly targeted, improperly shielded, and, in many cases, completely unnecessary.
Light pollution wastes electricity by spilling light into the sky instead of focusing on what it needs to illuminate.
How Bad is Light Pollution?
According to the 2016 groundbreaking study “World Atlas of Artificial Night Sky Brightness,” 80 percent of the world’s population lives under skyglow. In the United States and Europe, 99 percent of the public can’t experience a natural night!
Here are some fun, interactive ways to check out light pollution from space:
Effects of Light Pollution
For three billion years, life on Earth existed in a rhythm of light and dark that was created solely by the illumination of the sun, moon, and stars. Today, artificial lights overpower the darkness and our cities glow at night, disrupting the natural day-night pattern and shifting the delicate balance of our environment.
The adverse effects of the loss of this natural resource might seem intangible. But a growing body of evidence directly links the brightening night sky to measurable negative impacts.
WILDLIFE & ECOSYSTEMS
Plants and animals depend on Earth’s daily cycle of light and dark rhythms to govern life-sustaining behaviors such as reproduction, nourishment, sleep, and protection from predators. Nocturnal animals sleep during the day and are active at night, and light pollution radically alters their nighttime environment by turning night into day.
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HUMAN HEALTH
Like most life on Earth, humans adhere to a circadian rhythm — our biological clock — a sleep-wake pattern governed by the day-night cycle. Artificial light at night can disrupt that cycle. Research suggests that artificial light at night can negatively affect human health, increasing risks for obesity, depression, sleep disorders, diabetes, breast cancer, and more.
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NIGHT SKY HERITAGE
Until recently, our ancestors, throughout all of human history, experienced a sky brimming with stars. This night sky inspired science, religion, philosophy, art, and literature, including some of Shakespeare’s most famous sonnets. The natural night sky is our common and universal heritage, yet it’s rapidly becoming unknown to the newest generations.
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CRIME & SAFETY
There is no clear scientific evidence that increased outdoor lighting deters crime. It may make us feel safer, but it hasn’t been shown to make us safer. A dark sky does not necessarily mean dark ground. Smart lighting that directs light where it is needed creates a balance between safety and starlight.
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ENERGY WASTE
In an average year in the U.S. alone, outdoor lighting uses about 120 terawatt-hours of energy, mostly to illuminate streets and parking lots. That’s enough energy to meet New York City’s total electricity needs for two years! IDA estimates that at least 30 percent of all outdoor lighting in the U.S. alone is wasted.
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Light pollution affects every creature on Earth. Fortunately, concern about light pollution is rising dramatically. A growing number of scientists, homeowners, environmental groups, and civic leaders are taking action to restore the natural night. We can implement practical solutions to combat light pollution locally, nationally, and internationally.