Light Pollution


map of light pollution growth in the united states

“Darkness is as essential to our biological welfare, to our internal clockwork, as light itself.” – Verlyn Klinkenborg, National Geographic, Nov. 2008

Fireflies communicate in a language of light.

They flash to signal for mates. Scientists believe they may flash to drive away predators, claim territory, and communicate with others of their species as well—although the finer points of their language have never been studied extensively. One thing’s for sure, though: without those flashing lights, there could be no fireflies.

And we may be getting there sooner than you’d think. Anecdotal evidence suggests firefly populations are dwindling; in some areas they’ve crashed dramatically. Loss of habitat, poisonous pesticides and fertilizers, and suburban sprawl are all likely culprits.

Another is light pollution.

Along with increased development comes increased artificial illumination at night. In rural areas where the only night lights once came from the moon and stars, suburban sprawl has brought extensive exterior lighting along roads, in private yards, and in commercial centers. It can be so bright that residents can no longer see the stars at night.

When an earthquake hit Los Angeles in 1994 knocking out power to the entire city, many anxious residents called 911 to report seeing a strange “giant, silvery cloud” in the dark night sky. What they really saw – for the first time – was the Milky Way, long obliterated by the urban sky glow and light pollution.

Scientists aren’t completely sure how this is affecting fireflies—extensive studies on the effects of light pollution on firefly populations haven’t been completed yet. But firefly behavior has been observed to be affected by bright lights at night [1]. Fireflies typically won’t make an appearance where there are bright ambient lights, such as full moon evenings [2]. If artificial light interrupts fireflies’ ability to signal each other, it could disrupt mating—meaning fewer fireflies will be born each year.

Turn off your exterior lights at night

If you keep lights on outside your house and in your garden or yard at night, you may be unknowingly contributing to the decline in firefly populations in your area. Luckily, it isn’t difficult to be part of the solution instead. All you need to do is turn off exterior lights in the evenings when fireflies are active. This may help firefly populations increase in your area.

For more information about light pollution and finding ways to help your community reduce the amount of excess lighting it uses, visit or Let’s save our dark skies and pass them off onto our future generations to enjoy!


1. J. Costin, Kevin & Boulton, April. (2016). A Field Experiment on the Effect of Introduced Light Pollution on Fireflies (Coleoptera: Lampyridae) in the Piedmont Region of Maryland. The Coleopterists Bulletin. 70. 84-86. 10.1649/072.070.0110.

2. Picchi, Malayka Samantha & Avolio, Lerina & Azzani, Laura & Brombin, Orietta & Camerini, Giuseppe. (2013). Fireflies and land use in an urban landscape: The case of Luciola italica L. (Coleoptera: Lampyridae) in the city of Turin. Journal of Insect Conservation. 17. . 10.1007/s10841-013-9562-z.

3. Lloyd, J. E. 2000. On research and entomological education IV: quantifying mate search in a perfect insect-seeking true facts and insight (Coleoptera: Lampyridae, Photinus). Florida Entomologist 83: 211–228. Crossref

4. Lloyd, J. E. 2006. Stray light, fireflies, and fireflyers [pp. 345–364]. In: Ecological Consequences of Artificial Night Lighting ( C. Rich and T. Longcore , editors). Island Press, Washington, DC.