ABOUT LIGHT POLLUTION
“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
Artificial light at night (ALAN) may be one of the main drivers of firefly decline in the US and worldwide. Rapid technological changes in lighting sources over the last century have contributed to an increasingly brighter sky at night. 80% of people in North America can no longer see the milky way under even the clearest conditions, because it is obscured by skyglow.
Current evidence suggests that ALAN does have a demonstrable impact on firefly reproduction. Artificial light impairs their unique use of light signals to communicate and male’s ability to track female flashes. It essentially gets in the way of them being able to see each other and if they can’t see each other, they can’t reproduce.
Recommendations for combating light pollution
Light Color
– Use warm yellow, amber or red colored LED lights. Amber colored lights with a yellow/orange hue occur in the 600nm-700nm range and do not interfere with fireflies light as much as other sources. Extended wavelength colors (yellow and orange) are less visible to insects, and most of them can’t see the red light at all. Scientists have discovered these lights also have the benefit of attracting less “other” bugs to outdoor lights as well.
– It’s good to remember that bright bluish white LED lights emit a spectrum of light (430-700nm) that washes out most colors of light, including the spectrum of light used by fireflies in the yellow-green spectrum (475nm – 670nm) to signal to one another.
– Avoid using incandescent light bulbs, CFL, halogen globes, and cool-coloured LEDs directly in your firefly habitat.
Best Practices
1. Turn out lights you are not using!
2. Turn off as many outdoor lights as you can.
3. Remove lights that are only for decoration, such as tree lighting and facade lighting.
4. Install motion sensors to switch off your lights when no one is nearby.
5. Install timers to turn off your lights when you are not likely to be around or when fireflies are active, which is from dusk to several hours later.
6. Install shielding around your lights to keep light from escaping into the sky or away from firefly areas with native plants and vegetation.
7. Dim your lights and install lighting fixtures that point downward.
8. Close your curtains at night so light doesn’t escape in the surrounding areas
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 DarkSky.org. Let’s save our dark skies and pass them off onto our future generations to enjoy!
References
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.