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How light pollution causes more harm than realized

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APRIL 26, 2023

Standing at the top of the Golden Gate Bridge overlooking San Francisco late at night, it almost feels as if there is a glow encasing your surroundings for miles. While at the top of the Lawrence Hall of Science, the ambient glow stretching into the far reaches of south San Francisco and Oakland fills the sky with a grayish hue. It may only be 11 p.m., but you can see the steady cascade of cars moving along I-680 into San Francisco or the East Bay. For city dwellers who may have not experienced true darkness, there is quite a contrast.

The most notable difference I feel between this heavy layer of light and true darkness is when I go backpacking in the summer. At night, the only form of light available is from stars, which, depending on the location, can be more or less pronounced. In Lake Tahoe, the sky color is truly different than in any city. There lies a feeling of greater solitude, peace and connection to the rhythm of the rotation of the sun.  

When traveling to even larger cities, like New York City, Athens or Barcelona, the effects of light are far greater, where you may feel encompassed in a magnitude of humans much greater than yourself. Not only is the feeling of this never-ending light enclosing for some, but it has many environmental impacts that people are not aware of.

The technical term for this “nighttime glow” I have described is known as light pollution. When we typically think about pollution, of any form, this sparks thoughts of oil spills, trash on the sidewalk or toxins in the atmosphere. Light pollution doesn’t typically come to mind when someone is describing the effects of industrialization or climate change. However, it has just as many impacts on the natural world, almost acting as a silent character in this never-ending battle against balancing development and environmental concerns.

Light pollution is defined as the excessive use of artificial light that affects wildlife and human health. The most light-polluted countries across the globe include Singapore, Qatar and Kuwait. When light continues at night, this affects one’s circadian rhythm, which encompasses physical, mental and behavioral patterns that rely on a 24 hour cycle. Specifically, scientists have found a disruption of the production of melatonin in the body associated with artificial light. Melatonin is released in the dark, but with constant excessive light, this process is inhibited resulting in negative effects such as sleep deprivation, fatigue, and headaches. 

Melatonin has many beneficial antioxidant properties. It has the ability to induce sleep, activate the immune system, decrease cholesterol and assist in the function of many important organs. This constant exposure to light pollution at night, which many living in cities face, suppresses the benefits of melatonin having long-term effects on human health. About 56% of the human population today live in cities, around 4.4 billion people. With so many facing the effects of light pollution, from a public health lens, this is quite worrisome. 

Not only are humans facing the effects of light pollution, but wildlife are as well. Animals are mainly disrupted through an alteration of migration patterns, sleeping habits and habitat formation. For example, turtles are guided by moonlight when they are migrating. Because of light pollution, turtles are unable to follow their typical migration patterns, often leading to death. Many animals are naturally drawn towards light, such as birds, which has resulted in large numbers of deaths in large cities. 

Especially harmful are the impacts of light pollution on marine ecosystems. Boats can often have underlight panels on their bottom side, which light up the water underneath. As a result, many marine species will move further away from the light areas, disrupting where they find shelter and form habitats. Prolonged exposure to light pollution among any form of wildlife can affect their hormones, skin coloration, thermoregulation and reproduction.

Not only are animals needing to adapt to habitat degradation and climatic changes, but the unfortunate effects of light pollution are also disrupting daily behaviors that they rely upon for survival. We humans, who may not realize the harmful extent of such an issue, will find that their short and long term health will become greatly affected. 

Organizations such as the International Dark-Sky Association and Saving Our Stars are currently working to suppress the effects of light pollution. Important in this movement is first general awareness amongst the public on the unrealized implications of this seemingly unnoticed situation. Many may have noticed the effects of “city lights” once the sun goes down, but do not truly understand the intrinsic relationship it has with human, wildlife and overall ecosystem health. As climate change continues to intensify, hopefully more situations that have been often overlooked will come on display in public discourse. For now, all we can do is recognize the heightened severity of the issue and work to not only raise awareness, but find innovative ways to combat this. 

Contact Ashley Carter at 


APRIL 26, 2023