Will fireflies light up summer skies? Here’s why they’re fading

Raphaël De Cock was 9 years old the day he caught his first firefly, the glowing insect he’d read about with great interest in his grandfather’s nature books. While exploring the Belgian countryside, he lifted a stone and found a treasure: the larvae of a common glow-worm, a firefly species widespread in Europe, Africa, and Asia. 

While running back to his grandparents’ house with the critter, he tripped and lost it in the grass. The insect was gone. But days later, while taking a walk on a humid summer night, De Cock and his grandmother returned to the spot where he lost the firefly and were greeted by a breathtaking sight: Hundreds of little lights were re-creating a starry sky on earth. 

Yet if De Cock returns to this childhood spot in the countryside, something is missing. “There are no [fireflies] anymore,” he says. “They constructed houses and industries, and so they are gone.” 

De Cock, now a firefly researcher who wrote his PhD thesis on larvae like the one he found as a child, knows that many people have nostalgic childhood memories of catching fireflies. Anecdotally, many of those people also report seeing fewer fireflies—or lightning bugs, as they’re called in some places—every summer. Experts say there’s scientific merit to that observation, as firefly species around the world are declining. 

Most fireflies are a mystery to scientists 

There are more than 2,600 firefly species across all continents, except for Antarctica, yet scientists have assessed the conservation status of only 150 species (or fewer than 7 percent). Of those 150 firefly species, 20 percent are already threatened with extinction, which is a concerning number, says firefly scientist Wan Faridah Akmal Jusoh, co-chair at the IUCN Firefly Specialist Group. 

Yet, while a few species are well-studied—and scientists know that some of them are declining globally—researchers still lack the most basic information about most fireflies, and new ones are still being discovered today. “We only know up to species name [for most fireflies],” says Jusoh. Oftentimes it’s only due to specimens that were collected in a museum. What most species eat, where and how they live, and, in some cases, whether they are extinct, remains a mystery. 

This knowledge gap is a huge problem for conservation. “In order to be able to protect the fireflies, we need to build a ‘profile’ of the species to better inform policymakers,” says Jusoh. “We lack people actually studying their behavior, studying their ecology: What do they eat? Where can they be found?”

To fill this gap, scientists in the Firefly Specialist Group began studying just that. Their work officially began in 2018, and they’re monitoring fireflies globally, says Jusoh. “Currently, we’re slowly building a species list and, at the same time, assessing their conservation status.” 

What’s threatening fireflies?

While some species are more stable than others, scientists have identified key factors that are fueling fireflies’ decline, a trend that probably began a few decades ago. However, researchers admit that it’s hard to say when the decline actually started, due to the lack of historical data, though Southeast Asia and Europe have larger data sets than North America due to a decade or more of monitoring, says Candace Fallon, the firefly program lead at the Xerces Society for Invertebrate Conservation.

Still, scientists are aware that these insects experience different levels of threats, depending on location, according to Jusoh. Common problems include light pollution, habitat loss, pesticide overuse, and unsustainable tourism. 

“Our night skies are just getting brighter every year,” says Fallon. She calls light pollution “a growing threat,” explaining that most fireflies “need dark nights in order to communicate.” Artificial light can impact courtship as well, and pesticides can harm fireflies at all life stages and decrease their food sources. 

Climate change also plays a key role, as extended droughts make some areas inhabitable for fireflies, while rising sea levels and more severe storms may affect species inhabiting coastal areas, by flooding and submerging their habitat.  

In fact, habitat decline is a key strategy in determining which species of fireflies are threatened, says Fallon. If a wild area where researchers know a firefly population used to live now has been urbanized, they can now assume that population is declining or gone. 

The glimmers of hope for firefly conservation

Even though threats against fireflies are growing, many experts are hopeful that we will continue to see them lighting up the night skies.

“There is always in the darkness a flash of hope,” says De Cock. “But I think we have to be quite fast.”  

In the United States, firefly season tends to be from late spring to early summer, though researchers say it can vary due to species and location. The Great Smoky Mountains National Park in Tennessee is a particularly well-known viewing spot that’s so popular you must win a lottery to attend a viewing session in early June. However, fireflies are found across the U.S. and in Canada, particularly near ponds, streams, rivers, marshes, and lakes—but it may be as easy as looking in your backyard.  

Speaking for European populations, De Cock says many appear beginning in June or early July, but that it wholly varies on region and species, as well as global warming. 

To ensure that we keep seeing them, scientists around the world continue to plan efforts aimed at helping conservation. The Firefly Atlas, for instance, launched in 2022, studies species across the U.S. and Canada. The IUCN is working on global assessments in the U.S., Europe, and Southeast Asia.

But anyone can play a role in saving fireflies by giving them a comfortable habitat. You can re-create conditions in your backyard by leaving out woody debris, for example, or simply reducing light pollution. 

“Compared to 30 years ago, we are on the right track,” says Jusoh. “I’m very hopeful about the future.”