For billions of years, biology evolved in a world where light and dark was controlled by the length of the day. When the sun went down, celestial sources like the moon, stars, planets and Milky Way lit the sky. Life learned to operate under their glow. Only in the last 100 years or so — with the spread of artificial light — has that cycle largely gone away.

Here are [some] ways researchers say that light pollution influences the world around us:

Spawning Out of Sync

More than 130 different species of coral on the Great Barrier Reef spawn new life by moonlight. Every October or November after the full moon, the reefs spew sperm and eggs into the ocean in what looks like an underwater blizzard. When the two sex cells combine amid the flurry, fertilization begins. Bright urban lights can mask the moon’s phases, throwing the corals’ biological clocks out of sync, according to Oren Levy, of Bar-Ilan University in Israel. This can cause the reefs to release their reproductive cells late or not at all, thwarting their chances of producing offspring.

Beached Babies

Baby sea turtles face a treacherous trek to the ocean after they hatch. The beach abounds with predators like gulls and crabs just waiting to pluck the newborns from the sand. 

At night, beachfront lights can heighten this already herculean undertaking. Sea turtles are drawn to light, and when they emerge from their eggshells they seek out the lowest, shiniest light on the horizon, according to Gregg Verutes, a geographer from Stanford University who has built software to help building developers understand the effects of light pollution and other environmental influences. For the turtles, the moon’s reflection on the ocean waves normally attracts the tiny travelers, but in some cases, bright boardwalk resorts can draw them in the wrong direction. 

“Because they rely on this visual cue,” Mr. Verutes said, “when artificial light is introduced, they have difficulty moving to the ocean because that’s no longer the lowest, brightest horizon.” As a result, the hatchlings can become more vulnerable to hungry predators, dehydration and exhaustion.

When Birds Collide

The allure of beams and bulbs can be a death sentence for migratory birds in cities.

“Those birds will collide with a light tower or find themselves circling in that light until they drop from exhaustion,” said Michael Mesure, the executive director and a co-founder of Fatal Light Awareness Program, or FLAP, a nonprofit organization based in Canada that is focused on safeguarding birds. Between 100 million and 1 billion birds crash into buildings across North America every year, according to FLAP. Some of those deaths are caused by reflective windows during the day and others by bright lights at night.

Not Rising to the Occasion

Light pollution can also meddle with aquatic life in lakes. Zooplankton called Daphnia normally dwell deep below the water in the day and ascend to the surface at night to feast on algae. Darkness triggers their migration. But marine ecologists have found that nighttime lighting can prevent the zooplankton from floating up to their meals, which could lead to algae blooms that overwhelm the other life in the lake.

What's the real solution to light pollution? 

I mean, people need light right?

[Bold is my emphasis] 

"Light pollution is any unintended consequence of our use of artificial light at night,” said John Barentine, an astronomer and program manager at the International Dark-Sky Association, the nonprofit group that helps to promote this week’s events and year-round awareness. Although measuring light pollution can be tricky, Dr. Barentine said it occurs when light is wasted either because no one is using it or because it’s superfluous.

But unlike many environmental issues, light pollution is a problem researchers say could disappear with the flick of a switch. Solutions include turning off unnecessary lights and putting shields on streetlights to direct beams downward."

Okay so basically just make sure there's no wasted light. Got it.