Light pollution is the disruption of a natural night environment by the presence of manmade light. The effects of light pollution are harmful to human health, the surrounding ecosystem, and can also ruin a good view. Think of how you can see so many more stars when you’re in the countryside, than when you are in or near a city – this is just one effect of light pollution.
What is light pollution?
Light pollution, sometimes called photopollution, is a detrimental and all too common side-effect of urbanization. When humans introduce artificial light to an environment, it compromises the natural cycle of the ecosystem. The night phase does not become as dark and this is harmful for both those plants and animals who rest at night, and the nocturnal ones who thrive in the night’s darkness.
What are the effects of light pollution?
Light pollution affects a range of subjects in a variety of ways. Plants and animals – including humans – experience adverse physical and mental effects. Overexposure to artificial light can have the following effects on humans: headaches, fatigue, stress, increased anxiety, and a decrease in sexual functions. Negative effects on alertness and mood have been observed in both diurnal animals (those active during the day) and nocturnal animals (those active during the night). Light pollution also disrupts migratory and breeding patterns and behaviors of many animals.
Most life on Earth follows a circadian rhythm. Plants, insects, your dog, and you all operate on circadian rhythms. The circadian rhythm is sometimes referred to as the “body clock” and it is just that. The circadian rhythm regulates much of our physiological processes. It lets us know when we should sleep, awaken, and even eat. Elements of the environment including light and temperature affect our circadian rhythms.
As part of the circadian rhythm, our bodies produce melatonin. Melatonin is an important hormone. Not only does it induce sleep, it also helps boost our immune system, lower cholesterol, and keep our thyroid, pancreas, adrenal glands, ovaries, and tests functioning smoothly. Melatonin also has antioxidant properties. Exposure to light at night or overexposure to certain types of light during the day will suppress melatonin production.
What are the types of light pollution?
There are five different types of light pollution: over-illumination, trespass, light clutter, glare, and skyglow. Usually, an artificial light source will fit into a few of these categories.
Over-illumunation happens when more artificial light is supplied than is needed or appropriate for the subject. It’s literally over-lighting. You’ve experienced this anytime that you’ve had to squint or hold your hand up to shade your eyes from a bright artificial light. A good example is a ballpark.
Light trespass is light pollution that occurs when an artificial light illuminates a subject nearby that is not the intended subject. An example of light trespass is if your neighbor has a security light on his garage that illuminates your yard as well. Another example is a streetlamp shining into your window.
Light clutter refers to an excessive amount of lights grouped together that results in a confusing and bright environment.
Glare describes excessive brightness that either causes visual discomfort or decreases visibility. If you’ve ever experienced difficulty driving at night due to another car’s headlights or a bright light shining into your car, this is glare.
Skyglow is the brightening of the night sky. Skyglow occurs around inhabited areas and is the result of urban lighting. This is what prevents you from seeing stars as visibly near cities and towns.
How can we prevent light pollution?
On an individual level, use only what you need and when you need it. Use timers and motion detectors on outdoor lights so that they are not left on all night long. Otherwise, leave your lights off.
If you do install outdoor lighting, make sure the fixture is low glare and highly efficient. You can find a list of approved fixtures here: the International Dark-Sky Association.