Lightning bug populations are dimming. Here's what we can do about it

A longtime hallmark of summertime and childhood for many is in danger: fireflies slowly are blinking out as part of a “great insect decline,” scientists say.

Habitat loss, light pollution and pesticide use are driving the lightning bug population down, causing concern for biodiversity and food chain stability. The bugs are just one species affected by a global phenomenon that finds 40% of insects to be threatened with extinction.

“It really is about the biodiversity out there,” said Jim Anderson, the vice president of Citizens for Conservation. “All these insects we might not see on a regular basis or pay attention to, but they're out there. They're playing a role in nature, and some of them are really, really important.”

While it might seem that this year in particular there are more fireflies than usual, that's likely due to accelerated mating cycles as a result of warming temperatures, Anderson said.

Amid a hotter climate, fireflies tend to mate and emerge earlier in the year. In the last century, the average daily temperature in Illinois increased by 1-2 degrees, a recent study found.

While Anderson said earlier mating cycles haven't occurred for long enough to study their potential long-term impact, a 2022 “State of the Fireflies” report lists climate change as one of the main drivers of the species' decline — primarily because global warming contributes to habitat degradation.

“This is something that we talk about a lot, not just firefly decline, but insect decline in general. It's a major concern,” said Marianne Alleyne, a professor of entomology at the University of Illinois Urbana-Champaign. Alleyne also serves as vice president of the Entomological Society of America.

Alleyne said insect cycles go up and down every year, but evidence shows that firefliies and other insects are generally declining over time. However, Alleyne added that scientists need more quality data to continue accurately monitoring such a massive problem.

In terms of solutions, conserving natural areas is one of the core approaches. In 2019, a Biological Conservation study reported that conversion to intensive agriculture is the main driver of waning insect populations.

“Fireflies are going to have a better chance of living and finding a mate in open space areas where there is no major loss of habitat, and there's less impact by pesticides and pollution,” Anderson said. “Providing open space gives them a refuge.”

Anderson said Citizens for Conservation, a volunteer-based group based in Barrington, works to preserve biodiversity and prepare habitats for endangered species. One of the group's goals is to proactively create healthy landscapes.

“If we can prepare habitat, not only on Citizens for Conservation lands and forest preserve land, but in people's back yards, then these opportunities exist for animals to coexist with us,” Anderson said. “It's going to save us money in the long run — and really, the long run is no longer the long run. This is in front of us today.”

Nicole Flowers-Kimmerle, a horticulture educator at UIUC's Illinois Extension program, said there are several steps individuals can take to encourage local firefly activity.

Fireflies rest on tall blades of grass during the day, and their larvae live in the soil, thriving off of snails and other small insects. Mowing too often or using too much pesticide can effectively drive lightning bugs from your yard.

Flowers-Kimmerle recommends letting parts of your lawn overgrow, while maintaining areas that you or your family use often to control pests of concern like ticks.

Fireflies enjoy natural debris such as leaves, and need soil as opposed to mulch. Homeowners can also turn to native plants over typical expansive grass lawns.

To cut down on the impact of pesticides, Flowers-Kimmerle encouraged people to consider using them during only part of the year, on select portions of their lawns, and opting for pest control alternatives such as mosquito discs for standing water.

Light pollution is another challenge for fireflies. The bugs' warm light serves as a form of communication. Different species speak to each other in specific patterns to find mates, but porch and flood lights can make it hard for the bugs to find one another.

People can keep their lights on a motion sensor, dim them or tilt them down and away from their lawns to minimize harm.

Encouraging insect population growth supports the natural food web, Flowers-Kimmerle said. A decline in that base population can lead to reductions in bird and amphibian populations, and continue on to have effects that ripple through the rest of the environment.

Plus, Flowers-Kimmerle said, “fireflies are just amazing.”

“Why are we talking about fireflies? We all love them,” Alleyne said. “They're not a pest. They're pretty, they remind us of when we were kids, they remind us of summer. It would be a loss if we didn't have them anymore.”

• Jenny Whidden is a Report For America corps member covering climate change and the environment for the Daily Herald. To help support her work, click here to make a tax-deductible donation.