When fireflies wait forever but night never comes: Light pollution is slowly killing the planet

While many species of fireflies have adapted quite well to light pollution, some of their other relatives are struggling to reproduce and are in serious danger.

When the setting sun gradually covered the dark shadows on the edge of the forest, a tiny light source glimmered into the quiet space. Very soon, the twilight will be filled with light from such "lamps" gliding back and forth, flashing to transmit a special signal.

This light show is the mating call of the family Lampyridae or, colloquially, fireflies. However, the darkness they enjoyed in order to maintain their species was severely damaged by artificial light. Humanity's love of luminous objects has caused most of the habitable area on the Earth's surface to be affected by light pollution.

In recent years, firefly scientists have heard concerns from many sources that the species is on the decline, according to Avalon Owens, an entomologist at Tufts University.

"There's a sense of destruction. They're not where they used to be," she said.

Artificial light - enemies with many species of fireflies

Dr Owens said little is known about how fireflies live so it's difficult to judge if they are endangered - and if so, why, she said. But in a study published earlier this month in the journal Royal Society Open Science, she and Sara Lewis, professor of biology at Tufts University, shed some light on how fireflies respond to artificial light.

Dr. Owens in a field study session at dusk.

Experiments in forests and fields as well as in the laboratory show that while some North American fireflies will enthusiastically reproduce, regardless of the light environment, others will not. Artificial light.

Fireflies seem to rely heavily on each other's flickering light to find mates, so artificial light interferes with that behavior. Of the four common species studied, the female fireflies would hide on the ground to watch as the male fireflies "searched" in the sky. When a female firefly "answers" a male with its blinking light, the two communicate and possibly reproduce.

Fireflies rely on flickering light to find each other and reproduce.

In previous research, Dr Owens and Dr Lewis found that shining light on female fireflies of the species Photinus obsllus made them less likely to respond to male calls.

In a forest west of Boston, US, scientists impersonated female fireflies and responded to male Photinus greeni fireflies with green LEDs. Lights are left in the dark or an illuminated area simulates a street light.

Scientists found that more than 96% of males prefer the dark. Then, in laboratory experiments with Photinus obsllus, they observed that although dim light did not interfere with successful mating, in brighter light no pair of fireflies mates. . The insects found each other, and some even crawled past each other, but something stopped them from going any further.

Dr. Owens said this is important and worth noting because if we don't control light pollution, it is useless to help the fireflies find each other, because they will not mate.

The "strips" of fireflies are lighting up the edge of the forest.

She speculated that the fireflies were interpreting the artificial light as day and were waiting to mate in darker conditions - essentially waiting for a night that never came.

In a field in Tionesta, Pennsylvania, Dr. Owens saw something complicating the death and gloom of lab experiments. Bruce Parkhurst, a firefly enthusiast who lives in the area, alerted her to the introduction of outdoor lights in the tourist center, so Dr. Owens and her colleagues studied the behavior of fireflies. locality in the adjoining area.

Over the course of several July nights, they captured and marked the females of two species - P. pyralis and P. marginellus - and placed them in areas of the field on a spectrum from very light to complete darkness. Females in bright areas tended to appear later and further into the dark, suggesting that if the insects found the light uncomfortable, they would simply move into the dark.

But even though the light was almost blinding to the researchers, somehow the fireflies of both species found each other and successfully mated.

According to Dr. Owens, by that time they were blindly mating and didn't care anymore.

Unpredictable consequences of light pollution

In a family as large and diverse as fireflies - more than 2,000 species worldwide - adapting to different levels of darkness could mean different responses to light, the researchers speculate. light pollution. Of the four species in the study, P. obsllus, an insect that never mates in bright light, is also the least active at dusk, preferring the deep night. However, an agent that has no effect on one species can destroy another.

The question now is, could there be an all-firefly-friendly version of artificial light - a wavelength of light suitable for humans and light-sensitive insects? Dr. Owens has been pursuing this idea for some time, but a harmless option for all remains elusive.

The best solution might be something simpler and more radical: raise awareness about outdoor lights and use them more sparingly. Although research shows that fireflies can flee from light pollution to shelter in the dark, if there is no longer a dark place for them, the nightly symphony of tiny rays can become into the past.