This coverage is made possible through a partnership between BPR and Grist, a nonprofit environmental media organization.
It’s firefly season in the Blue Ridge. This time of year, their lights can be found by the water, high up in the tree canopy, and out in open fields, drawing onlookers of all ages to one of nature’s loveliest light shows. Fireflies are a beloved, essential feature of a Southern summer - but their habitat is fragile.
There are about 100 firefly species in the continental United States, and the Smoky Mountains are home to about 20% of them. From the rare synchronous fireflies and “blue ghosts,” to the common Photuris lightning bugs that are probably in your front yard, these glowing insects light up the sky after dusk.
However, recent studies have shown that habitat challenges, increasing temperatures, light pollution, and drought could pose serious threats to these bugs - and some populations are already in decline, including about 18 species in the U.S. and Canada.
Darin J. McNeil, associate professor at the University of Kentucky Department of Forestry & Natural Resources, and Sarah Lower, an associate professor of biology at Bucknell University, recently contributed to a study on firefly population patterns last summer, using citizen science data about firefly species collected across the U.S. to connect larger populations with environmental factors like heat, light pollution, and land use.
"We've been hearing anecdotal reports of fireflies population is declining for years," Lower said. "Every time I would go out and give a scientific talk somewhere, somebody would raise their hand and say, 'I've been out in my yard and when I'm with a kid I remember they're being fireflies everywhere now I don't see them.'"
McNeil said changes in the weather have a big impact on the insects.
“We see that they're very, very sensitive to temperature and weather and things like that,” McNeil said. "In southern areas where we expect it to get quite warm - and maybe get outside the comfort zone of fireflies - we might expect the fireflies are going to do poorly."
McNeil said this means the expected impacts of climate change in the Southeast - like heat and drought - could impact fireflies, though as other areas get wetter the populations could move with the changing weather.
McNeil and the research team also studied how different habitats impact the fireflies. Fireflies thrive in woodland areas but when those areas become more urban the populations decline.
“We have this effect of fragmentation where people are chopping up the forest into little chunks and then the forest that's left behind doesn't get managed in any way,” McNeil said.
He found that fireflies also do well on farm land, despite herbicides.
The connection to forests and fields for fireflies is important because that’s where they find their food.
Fireflies are technically carnivorous beetles. They spend two years of their short lives as larvae, living in the soil and eating slugs and other moisture-loving critters. This remains their diet throughout their lives.
“You disrupt that access to the soil, and fireflies disappear very quickly,” he said.
McNeil hopes that in the future researchers study how forest management including prescribed burning impacts fireflies.
In the meantime, there’s a lot that community members can do to help the firefly populations thrive.
How you can save your local fireflies
Jill Jacobs and Brannen Basham own Spriggly’s Beescaping, a local native plant nursery in Waynesville. Their love of local bugs extends beyond bees to include fireflies.
The pair are also full of endless fun facts about lightning bugs. “One random interesting fact is that these animals never stop glowing,” Jacobs added. “They're glowing as little eggs even.” And one of the most common front yard species, Photuris, use their glow to lure males nearby - and then eat them.
But they’re serious about firefly conservation, too. They host regular workshops about landscaping for an ideal pollinator habitat at their business and at the Asheville Botanical Gardens, and often use portions of their workshops to discuss planting ideal gardens for fireflies to shelter in, particularly as climate change disrupts growing seasons.
“Fireflies might enter into their adult form and find themselves emerging into a world in which which their favorite plants have either already bloomed or they haven't bloomed yet,” Basham said. “By increasing the diversity of native plants in your space, you can help ensure that there's something in bloom at all times of the growing season.”
Here are some tips from Spriggly’s Beescaping to help support fireflies in your yard this summer:
- Turn your porch lights off when you don’t need them. Fireflies are incredibly sensitive to artificial light and it can confuse them.
- Instead of a carefully mowed lawn, consider native plants - they take less care and effort because they’re suited to our local environment. Native plants conserve more water than grass, because their roots reach deeper into the soil.
- When raking your leaves in the fall, consider leaving some leaves in your yard so fireflies can find food, stay cool, and lay their eggs.
- Some shrubs, tufting grasses, and other, larger plants can also shelter fireflies in the event of severe weather, like heavy rain or flooding.
- You can take notes on the appearance and location of your local fireflies, and upload your observations to citizen science databases like iNaturalist, Firefly Watch or Firefly Atlas to help scientists collect data.
