Darker Summers Ahead? Fireflies Are Facing Extinction, Study Says

MEDFORD/SOMERVILLE, Mass. — Few insects capture children’s imaginations quite like the firefly. These beautiful beetles are well known for their bioluminescent glow, and millions of people look back fondly on summer nights as a child spent chasing and capturing these so-called “lightning bugs.” Now, a new study finds that a variety of factors are endangering the existence of fireflies all over the planet.

Researchers from Tufts University and the International Union for the Conservation of Nature have identified three main threats to the firefly: loss of suitable habitats, widespread use of pesticides, and artificial light. Of those three, habitat loss is the biggest problem facing fireflies in most regions, followed by light pollution and then pesticides. To come to their findings, researchers surveyed firefly experts from all over the world.

“Lots of wildlife species are declining because their habitat is shrinking,” explains study author Sara Lewis, professor of biology at Tufts University, in a release. “So it wasn’t a huge surprise that habitat loss was considered the biggest threat. Some fireflies get hit especially hard when their habitat disappears because they need special conditions to complete their life cycle. For instance, one Malaysian firefly (Pteroptyx tener), famous for its synchronized flash displays, is a mangrove specialist.”

All things considered, it’s fairly easy to guess that loss of habitat would be a major problem for fireflies, but even the study’s authors themselves say they were surprised to find that light pollution is the second greatest threat to lightening bugs existence on a global scale.

Let’s take a moment to unfold why. Over the past 100 years, the rapid expansion and advancement of technology and electricity has caused the amount of artificial light at night to grow at an exponential rate. All of that new artificial light is disrupting human’s natural biorhythms, and wreaking absolute havoc on fireflies mating rituals. Fireflies rely on their trademark glow to find and attract mates. So, when it’s too bright at night due to artificial light, that means countless fireflies aren’t able to find mating partners.

Moreover, extra bright LED lights are making matters even worse. “Brighter isn’t necessarily better,” comments Avalon Owens, a Ph.D. candidate and study co-author.

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Besides light pollution, pesticides are also a major threat to firefly survival. Most fireflies are exposed to pesticides when they are still in their larval stage; young fireflies spend upwards of two years living underground or underwater. Most insecticides, such as organophosphates and neonicotinoids, were never intended to kill off fireflies, but are nonetheless still lethal whenever they make contact.

As far as specific areas and local species, researchers named notable population declines among Malaysian synchronous fireflies and England’s glowworm Lampyris noctiluca. Still, the study’s authors say a great deal of work must still be done in order to formulate long-term data on global firefly population statistics.

On a positive note, researchers are relatively optimistic when it comes U.S. fireflies. “Here in the U.S., we’re fortunate to have some robust species like the Big Dipper fireflies (Photinus pyralis),” Lewis notes. “Those guys can survive pretty much anywhere – and they’re beautiful, too.”

The research team hope their findings can help spread awareness that fireflies are in danger of extinction.

“Our goal is to make this knowledge available for land managers, policy makers, and firefly fans everywhere,” says co-author Sonny Wong of the Malaysian Nature Society. “We want to keep fireflies lighting up our nights for a long, long time.”

The study is published in Bioscience.

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