Night Pollution

Examining the consequences of artificial lights

When people first arrived in Hawaiʻi, the moon was the brightest light in the night sky. The landscape at night was dark and the sea, reflecting the light of the moon and stars, would have been bright. These certainties were not just facts of natural history—they were woven into the daily life of the mammals, reptiles, birds, and insects that lived on the island and the sealife that surrounded it.  

With the arrival of humans, the rules changed, literally overnight.  The previously reliable beacon of the moon was eclipsed by the light of fires in some areas. For night-flying insects, a navigation system that had evolved and worked just fine for millions of years was suddenly less reliable. 

The Milky Way over Maui. Light pollution quickly erases the Milky Way from view. Courtesy Patrick Langwallner / Unsplash

While the moon is moving at about 2,500 miles an hour relative to Earth, to you, me, or a moth, it is holding still. As an unmoving object, it is possible to orient to the moon and move in a straight line. However, if we do this to a nearby light and try to always keep the light on our right, we start to circle it, getting ever closer and closer, until…bam!

For newly hatched sea turtles, instinct is screaming, “Crawl toward the light!” On a dark beach this means moving toward the bright arc of the sea that will provide relative safety for a baby turtle and its nestmates. Artificial lights are not part of turtle traditions. In areas with night lighting, the young turtles’ instinct to move toward the brightest light can steer them away from the sea—across roads, into parking lots, and toward other unfriendly environments.

Adult seabirds seem to have done a better job of finding their way despite artificial lights. Baby seabirds, however, specifically the ‘ua’u kani (wedge-tailed shearwater) here on Maui run into trouble when lights are near their nest at night. Though the why is less certain than with insects and turtles, bright lights confuse the young birds as they first leave the nest to head out to sea. They may be disoriented by the lights, like moths, or they may be attracted to the lights as sea turtles are. The end result, regardless of cause, is that they can fly into things or just get tired out as they fly circles around a light, eventually falling to the ground injured or exhausted.

These are just a few examples of how ALAN (artificial light at night) causes trouble for wildlife. But the truth is most every species that has been studied in respect to ALAN has been shown to be affected: bugs, snails, corals, plants…and even us.

Artificial lights are not just a wildlife problem.

Even though firelight has been a companion for much longer than other forms of artificial lighting, we did not evolve with light. Continuing research on ALAN and people makes it clear that it is harmful. The main takeaway is that artificial light at night (even that little nightlight, the glow from an electric clock, or the light squeaking around the edge of your blinds) messes with our circadian rhythm—the daily and monthly cycles of changes in light and dark that were our clocks before the cellphone—and this messes with our health.

Even a little ALAN has been shown to reduce our melatonin production. Melatonin is a sleep-related hormone produced when we sleep. This change has other physiological effects such as how deep we sleep, our heart rate during sleep, and even our response to insulin when we wake up. Light at night has been linked to obesity (it may be as bad as junk food), diabetes, and breast cancer; correlates with the rates of tumor growth (more light at night, faster tumor growth); and is linked to a number of other chronic diseases.

But wait, what about lights for our safety?

As we begin to understand the health consequences for humans and wildlife, it is important to start considering if every light is really needed and if the lights we have now aren’t actually causing more harm than good. One of the big reasons to light things up is supposed to be for safety. However, while this seems to be a common-sense reason to turn night into day, it is not well-supported by research.

The research on public safety and lighting is not on the side of more light is good to deter crime. Review studies since at least 2015 have shown that more light might actually increase crime. One study of different types of street lighting—bright, dim, none, LED—showed no difference in accident rates. Another recent study of partial lighting (turning off street lights around midnight) showed that darker streets actually reduced the rate of break-ins in automobiles.

The explanations for these results are not entirely clear. Some researchers propose that a dark street makes it hard for potential thieves to see what is in cars or whether the person coming down the street is worth robbing. It may make illegal activity easier to spot as someone looking into cars along a dark street suddenly becomes obviously up to no good.  Regardless, it’s clear that we need to check our assumptions before continuing to go all in on “more light is better.”

Bad lighting is something we can solve

Not all ALAN is bad, but light that is not doing a job is light pollution. Along with the negative effects, it wastes money. It’s estimated that in the U.S., three billion dollars are spent pointlessly shining light into the sky. That is light that is shining up into space and not serving any useful purpose. We are certainly spending as much shining light on our neighbors yard, streets, empty buildings, and more. 

Fortunately, unlike some environmental problems, light pollution is something any of us can start to fix. Astronomer Kelsey Johnson suggests five simple ways to help in her TED talk about light pollution: don’t use lights if they aren’t needed; only use lights as bright as needed; shield lights and point them down; use warm white bulbs; and advocate—tell others about the issue of light pollution.

At a governmental level, Maui County is taking action to reduce light pollution. The county council recently passed an ordinance “protecting wildlife from outdoor lighting and preserving dark skies.” While the bill’s primary intention was to protect young seabirds and sea turtles, it is a step in the right direction to curb light pollution as a whole. 

Everyone on Maui—people and wildlife—will benefit from less light and more dark at night. Reducing light pollution can save you, your neighbors, businesses, and the county cold hard cash if we all work to solve it. What are you waiting for? Go make a difference. 


Maui County Lighting Ordinance

Light, Crime, and Safety

Kelsey Johnson’s TED talk on light pollution

Globe at Night Community Science to measure light pollution

Find a grounded seabird?

John Starmer