Evenings may look a little duller this summer than they have in previous years. As Popular Science reports, firefly species around the world are at risk of extinction. They're vulnerable to many of the same threats as other bugs, but there's one human-made problem that poses a unique threat to the insects: light pollution.

A research team led by Tufts University biology professor Sara Lewis shared its findings on the causes of firefly decline in a new paper in the journal BioScience. To identify the biggest threats, they surveyed scientists, conservationists, and other firefly experts working in different parts of the globe about their observations.

Most subjects pointed to habitat loss—a factor that's put pressure on species spanning the animal kingdom in recent decades. Fireflies have also fallen victim to insecticides, as have many insects, whether they're considered pests or not. But light pollution was the most surprising concern brought up by firefly experts.

A firefly's light show isn't just pretty to look at—it's essential for the beetles' survival. The blinking caused by bioluminescence is part of the insect's courtship rituals. Like the stars over a city sky, a firefly's flashes can be washed out by light from human-made sources. If fireflies can't see each other's light signals, they can't get together to mate, and populations suffer as a result. According to the study, experts ranked artificial light at night as the second highest threat to fireflies, with more than 23 percent of the planet's land experiencing some degree of light pollution.

This report shows that curbing land development and insecticide use may not be enough to save fireflies from extinction. Moving forward, the study authors recommend regulating the usage of artificial outdoor lights to make them more suitable for firefly courtship. In doing so, conservationists may inadvertently help other species that evolved to thrive in darkness. The study's authors write, "Reducing artificial light—both its extent and its duration—should, in contrast, benefit a wide range of culturally and economically important nocturnal animals."

[h/t Popular Science]