Why Are Fireflies Disappearing?

fireflies in a forest at twilight

Hristo Svinarov / Shutterstock

Do you have a summer memory about fireflies? I have many, having grown up next to a wetland. I knew it was finally summer when I would be outside playing after dinner and those little flying lights appeared. I imagined each light was a fairy with trailing long blonde hair like my own at the time.

But like bees, amphibians and butterflies, fireflies are disappearing. While the exact reason isn't known, three main factors are suspected: Habitat loss, toxic chemicals (which tend to linger in aquatic environments where fireflies start their lives) and light pollution.

According to Firefly.org:

"Most species of fireflies thrive as larvae in rotting wood and forest litter at the margins of ponds and streams. And as they grow, they more or less stay where they were born. Some species are more aquatic than others, and a few are found in more arid areas — but most are found in fields, forests and marshes. Their environment of choice is warm, humid and near standing water of some kind — ponds, streams and rivers, or even shallow depressions that retain water longer than the surrounding ground."

As the human population continues to grow, more and more wild habitat will be developed for our use. As long as we keep interrupting forest land with houses, turning meadows into lawns and paving over wetlands, the fewer fireflies there will be — unless we start living in some radically different ways.

Light pollution and fireflies

Catching a firefly in a jar is summer tradition for many kids.

Suzanne Tucker / Shutterstock

The other part of the problem is light pollution.

Both female and male fireflies use their glowing lights to communicate with one another, to find mates, to keep interlopers away and to establish territory. Depending on the species, those flashy messages are coordinated, often across huge groups of thousands of bugs. Research has shown that lights — both stationary, like streetlights or lights from a house, and temporary, like car headlights — make it harder for fireflies to communicate. If mom and dad firefly can't find each other to mate because they're thrown off by car headlights, young fireflies never get created.

The most recent report says this is happening far too often. A 2020 study published in BioScience is a comprehensive review of the status of firefly populations and how the three main factors mentioned above are hurting them. In short, the scientists say we've done a lot to raise awareness of the problem, but now we need to create better monitoring systems to know exactly which human behaviors are causing their numbers to plummet.

The human curiosity factor

One of the human behaviors the researchers wondered about was sheer curiosity. Fireflies are becoming an attraction in some areas of the world, and the researchers say it's time to create guidelines for best practices. In China, firefly pupae were brought into an urban park to re-establish a colony of the beetles there. "Entrepreneurs are trying to revive the population of bioluminescent insects in special firefly parks," writes Josh Lew. "One of the first of these parks, in the city of Wuhan in Hubei province, opened in 2015. The response was so positive that the park plans to open annually (from May through early October each year)."

And in the Smoky Mountain National Forest, people come from far and wide every May and June to experience synchronous fireflies.

Kids who grow up without fireflies will never know what they're missing. The bioluminescent bugs are a magical addition to the landscape, but if we lose them, they'll exist only in the summertime memories of older people. If you'd like to keep fireflies around in real life and not just as a memory, you can create a firefly habitat around your house. The Xerces Society for Invertebrate Conservation offers an in-depth guide for protecting these "jewels of the night."