Thomas Edison’s first light bulb illuminated New York City in 1879, and humanity rapidly connected the dots between towns and cities with streetlights, illuminated billboards, and economic growth. Lights paved the way for bigger business, more usable time and entertainment late into the night. They also made us safer. Criminal elements often use darkness as a means to strike and disappear, so the emergence of lighted pathways and street corners has also had a deterrent effect on crime.
As with any technology, though, Edison’s lightbulb indeed has a dark side–light pollution. And it affects us physically, economically and ecologically.
So what is light pollution?
When scientists talk about light pollution they’re referring to artificial light that is excessive, obtrusive or misdirected. If the Earth could tell you about it, it would likely say that it messes with nocturnal animals, interrupts circadian rhythms and is another example of humans trying to conquer nature.
Glare, trespass, skyglow and over-illumination might sound like a funk band from the 1970s, but they’re actually types of light pollution. Lights that shine horizontally create glare and can cause temporary blindness as the light scatters in the eye, especially in aging eyes.
Light trespass occurs when light crosses property boundaries and lights up an area that would otherwise be dark, like that neighbor with the floodlight that points to nowhere.
Skyglow is the haze that floats over urban developments like a halo blocking out starlight and planets. In large cities, its light can emanate for hundreds of miles, making it difficult to find true darkness, which scientists are discovering is a necessary component of health.
Over-illumination is the use of lights when they aren’t necessary. You’ve seen this; it’s the house with every light on like Studio ’54, even though it’s 2015. This is why in Hong Kong, people sleep with eye masks on.
How does it affect our planet?
The ecological impacts of artificial light have been well documented. Long-term exposure to artificial lights can prevent trees from adjusting to seasonal changes, which has an impact on wildlife that depend on trees for food or shelter. Artificial lights also have a devastating impact on birds.
There are over 200 bird species that follow nocturnal migratory patterns across North America, but their highway in the sky is lined with treacherous communication towers and skyscrapers.
Lights on these (sky)road hazards confuse the birds and cause them to crash, head-on, into buildings. The New York skyline kills 10,000 birds per year, and one billion die from collisions across North America alone.
Turtles are also impacted by artificial lights. For thousands of years, chelonian hatchlings born at night would follow the moon’s reflection on the water to find the ocean. Now, big cities along coastlines confuse them and they head inland, often dehydrating in the process, which is exceedingly troublesome for species that are already endangered.