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 red colored LED lights. Red LED’s or Red incandescent bulbs do not interfere with firefly light as much as other sources. Extended wavelength colors (amber, yellow and orange) are less visible to insects but still do impact fireflies. Scientists has done testing to confirm that red light does not affect fireflies mating and flashing behavior [5]. Scientists have discovered these lights also have the benefit of attracting less “other” bugs to outdoor lights as well.

– Avoid bluish white LEDs. 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. A good rule of thumb, is that the cheaper the LED bulb, the more prone it is to cause glare and be bad for wildlife. Avoid low-quality LED bulbs if you can. If the light from the bulb causes glare to your eye, it will definitely cause it for fireflies and other animals.

– Avoid using high-wattage incandescent light bulbs, CFL, and halogen globes directly in your firefly habitat.

– Fix those street lights. Street lights with high intensity purplish-blue light are bad for fireflies. Request your city change these bulbs if you have these in your neighborhood. Rebates are available from the manufacturer to do this. These types of lights have emerged in recent years and are starting to be seen in many urban and suburban areas. The color of these bulbs originate from a manufacturer who did not produce the bulbs coating correctly. The protective coating has failed and instead of white light it now broadcasts in all spectrums of bluish light.

– Blue light is bad for fireflies. Blue light disrupts the delicate communication system that fireflies use to find mates. Their flashes evolved to be seen at twilight and in natural darkness, and blue-rich light easily drowns out those signals. Research has shown that exposure to blue wavelengths can also trigger the production of reactive oxygen species (ROS), which are unstable molecules that cause cellular stress and tissue damage – shortening lifespan and reducing reproductive success [6]. Some blue wavelengths (400-500nm) are more toxic than others to insects. Blue-heavy light not only overwhelms their communication but also makes them more visible to predators – so minimizing light in the blue spectrum is a key part of keeping firefly habitat healthy.