PENNSYLVANIA (WHTM) — Fireflies are a beloved sign of summer and Pennsylvania’s state insect, but along with other insects around the globe, experts worry that their populations are declining due to factors like habitat loss and light pollution.
Although there are still fairly few long-term monitoring studies of fireflies, anecdotal and observational reports have been drawing attention to their decline, and the research that does exist seems to support this concern.
Hoping to expand the body of research surrounding fireflies, the Xerces Society for Invertebrate Conservation, along with two other organizations, published a study in March 2021 that investigated the extinction risk of 128 species of North American fireflies.
The study found that 11% of assessed species are threatened with extinction, while over half of the assessed species are “Data Deficient,” meaning that there is not enough information known about them to determine whether they are at risk or not.
While monitoring studies of fireflies may still be in short supply, experts agree that insect populations are declining globally, and fireflies are likely among those insects with diminishing numbers.
“We’re losing a lot of the insects that not only are an integral part of our natural world, but also are important for things like pollinating our food,” Stephanie Wein, clean water and conservation advocate at PennEnvironment, said, “and one of those types of insects that we’re seeing losses [in] are our fireflies, and that loss is happening across the country and in Pennsylvania.”
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Why fireflies are declining
Several factors contribute to the decline of fireflies and other insects, including habitat loss, light pollution, and pesticide use.
Habitat loss can be the result of clear-cutting forests or constructing neighborhood developments that split up firefly habitats, explains Kim Schubert, environmental education specialist at Kings Gap Environmental Education Center.
Habitat loss can even be related to maintaining a well-mowed lawn with short grass, minimal plant debris, and minimal foliage because fireflies like tall grass and their larva like to live in leaf litter, Schubert explains.
Light pollution also impacts fireflies’ numbers. Lightning bugs use their bioluminescence to communicate, attract mates, and defend their territory, says Schubert. When humans brighten the night with their artificial lights, fireflies have trouble seeing one another.
For the insects, “[It’s] like shining a flashlight during the day,” Schubert says.
Pesticides, especially neonicotinoid insecticides, can also harm fireflies and other native insects, says Wein. The Xerces Society explains that neonicotinoids were originally thought to be less harmful pesticides, but research has since shown that they negatively affect beneficial insects and pollinators.
While it brings people together to appreciate nature, firefly tourism can negatively impact fireflies, as well. Large numbers of people gathering in one place can lead to habitat damage, Schubert says. It can be too much love for the lightning bugs.
What can be done to stop firefly decline
The good news is, there are several steps individuals can take to help protect fireflies. “There’s so much people can do to make their own space really great habitat for fireflies,” Wein says.
The even better news is that some of those steps actually involve doing less work.
“In order to help protect their habitats, something people can do at home is just be a little bit lazy,” says Schubert. Allowing the grass to grow a little taller or leaving some leaf litter in the garden can help create a habitat for fireflies.
Eliminating or reducing the use of pesticides, especially neonicotinoids, is another way individuals can help protect firefly populations, Wein explains. This flyer from the Xerces Society offers information about neonicotinoid pesticide brands.
Additionally, planting some wildflowers or native plants can help create a habitat for fireflies, says Wein. “A plain, golf-course lawn is not good habitat for fireflies,” Wein says. “What I’ve found is when I let more native plants grow in my yard, I found a lot more fireflies the following summer.”
Adding a water feature may also attract fireflies, as their larva eat things like snails and worms, which like humid, wet areas, says Schubert.
Turning off unneeded lights at night, especially around June and July when fireflies are most active, can help protect their populations, as well. For lights individuals want to leave on, Schubert suggests adding motion detectors or angling the lights straight down so they contribute less to light pollution.
People can also get involved with citizen science projects like Firefly Watch to help increase monitoring data about fireflies. The goal of Firefly Watch is to “learn about the geographic distribution of fireflies and what environmental factors impact their abundance,” according to the initiative’s website.
Encouraging elected officials and companies to take steps to protect fireflies and other insects and to eliminate the factors contributing to their decline is another thing people can do to help lightning bugs, Wein says.
Why firefly decline matters
“To me, it’s not July in Pennsylvania if when I walk through a field or am hanging out in my backyard at night, if I don’t see all the little fireflies lighting up and glowing. It’s like the fireworks that last all month,” Wein says.
Besides being an integral part of summer for many, fireflies and other insects play an important role in the food chain. Birds and other animals eat insects like fireflies, and then larger animals eat those animals. If insects were to disappear, the effects would ripple through the rest of the food chain, Schubert explains.
“We can also think of fireflies and insects in general as a clue to how the environment is doing or how a specific habitat is doing,” Schubert says. If insects are disappearing, it could be an indication that something is wrong in their environment, whether that’s pollution or the loss of too many trees or something else.
“We need to make sure that we’re protecting them, not just because we enjoy them — we all love fireflies — but they’re also just a critical part of the whole ecosystem we’re a part of,” Wein says.