Green Cities

Light Pollution: Everyone Sees It, But Nobody Knows About It

Imagine you are in a major city, like New York or Los Angeles, and you want to see what the stars look like from where you are. You go outside, look up at the sky, and to your disappointment, nothing is there. 

This actually isn’t that uncommon. As more Americans move to urban towns and cities, it is becoming more and more customary to look up at the night sky and see absolutely nothing. In fact, according to a study conducted in 2021, 99% of the people living in the United States and Europe look up to see starless skies, and even further, 80% of Americans are prevented from seeing the Milky Way. 

This isn’t just your average cloudy night: the impacts of light pollution are being felt by many throughout the world. But, while we’re struggling to see the stars in the galaxy, other critters are struggling to survive.

What is light pollution? 

Light pollution is the misdirected or excessive use of artificial light caused by industrial areas, such as large cities or towns. Specific sources include exterior and interior building lighting, advertising and billboards, commercial properties, office buildings, factories, streetlights, and sporting venues, such as stadiums. In fact, the International Dark Sky Association concluded that of the 30% of lighting that is used strictly for outdoor purposes, nearly all of it is wasted.  

There are several types of light pollution, including skyglow, glare, light trespass, and clutter. Each of these four types of light pollution can have serious consequences and may be disorienting for those who experience it. 

  1. Skyglow is the combination of reflected light and unshielded light up into the sky, causing it to “glow.” 
  2. Glare is one of the more well-known forms of light pollution, which typically occurs with unshielded lighting when driving at night.
  3. Light trespass is exactly that: unwanted light. A common example of light trespass would be light peeking through a window when you are trying to sleep. 
  4. Finally, clutter is the grouping of bright and excessive light sources causing confusion. 

Impact on Ecosystems

Chances are, most of us have experienced at least one of these forms of light pollution at one point or another. Research has suggested that the increase of artificial light has led to negative impacts on human health, including fluctuated melatonin levels, hunger, hormone production, body temperature, sleep cycle disturbances, and mood disorders. In fact, studies show that even a small amount of exposure to dim light — equivalent to that produced by bedside lamps — can lead to a 50% reduction in melatonin levels in the human body

While light pollution has significant impacts on human health and wellness, the influence is much more dire on our ecosystems. Many animals are dependent on the daily cycle of light and dark to maintain life-sustaining practices, including sleep habits, when to wake, when to migrate, when to feed, and when to reproduce. Human development, specifically the increased usage of artificial light, disrupts the balance of these cycles and throws wildlife out of step with nature’s rhythms. Animals that use the night to migrate or hunt, such as sea turtles and birds, are particularly vulnerable.

Many birds use the night to hunt for food, but increased artificial lighting of landscapes and cities can disorient them, causing them to wander off course. Those disoriented by lights collide with human structures like buildings, get hit by cars, and even become more vulnerable to starvation and predation. In fact, millions of birds per year die colliding with buildings that are illuminated with artificial lighting. And, researchers at Indiana University found that in addition to problems with hunting and migration, the reproductive cycles of birds exposed to artificial light at night are thrown off. 

Sea turtles are another animal dependent on the night for survival. While they live in the ocean, sea turtle eggs are laid on the beach, and they typically hatch at night. In the early hours of the morning, the young turtles use the horizon to navigate their way to the sea. But, artificial light is confusing the turtles, causing them to set out in different directions, ultimately exposing themselves to other dangers. In Florida, millions of turtle hatchlings die every year due to the confusion caused by artificial lighting. 

What can we do? 

According to researchers, there is little awareness regarding light pollution, which is a main obstacle we must address. A study revealed that artificial outdoor lighting grew approximately 2.2% each year between 2012 and 2016, while already lit areas brightened at a relatively similar rate. 

EARTHDAY.ORG’s Invest in our Planet campaign encourages communities and governments to fight the climate crisis to ensure a habitable planet for future generations to come — part of that mission involves learning about underlying problems that may not be well recognized. With America’s growing artificial light usage continuing to impact our ecosystems, it is imperative that we educate ourselves on the topic and its influence on ourselves as well as our ecosystems.