Light pollution poses a more severe threat than previously thought: Moths not only struggle to navigate beneath streetlights but also experience disrupted flight patterns beyond the light’s reach.
The rise in artificial nighttime lighting represents one of the most significant alterations caused by humans on our planet. Streetlights and bright buildings are greatly altering the habitats of nighttime wildlife.
Researchers have pointed to light pollution as a key factor behind the considerable drop in insect populations in recent years. Many night-active insects are attracted to artificial lights, where they often fly in circles and eventually become easy targets for bats and other predators or collapse from exhaustion.
Moths, a crucial group of nocturnal insects, are facing a notable decline. Their reduction is concerning as they are vital for food chains and the pollination of various plants.
A recent study reveals that moths’ behavior is affected not just in the immediate vicinity of street lighting but also in the darker areas surrounding it. This research was conducted by a team from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, alongside researchers from Berlin and Providence (USA), and the findings were published in the scientific journal PNAS.
“Through radar tracking, we discovered that moths’ orientation is disrupted even outside the light cone: the flight paths of three species of hawkmoths and one type of lappet moth showed significantly more curvature than normal. This indicates there is a barrier effect from streetlights,” explains Dr. Jacqueline Degen, who leads a junior research group at the JMU Biocentre.
“We were surprised to find that our initial assumption—that the majority of individuals would fly towards the streetlights—was incorrect; only about four percent did. This indicates that the impact of light pollution extends beyond mere attraction to light sources and is likely more extensive and complex than we previously imagined.”
Flight Tracking Using a Radar System Near Marburg
The studies were conducted at a radar system in Großseelheim near Marburg, Germany. This harmonic radar is currently unique in its ability to track small insects over distances of several hundred meters. Researchers monitored the flight of 95 moths up to one kilometer from the release point, which was within 85 meters of six street lamps.
To track the moths via radar, a tiny transponder was attached to each one. Weighing just 10.5 milligrams and measuring twelve millimeters long, the antenna did not impact the moths’ flight behavior, as demonstrated through rigorous control tests conducted by the researchers.
Interaction With the Moon
The experiments also revealed a relationship between the disorientation caused by artificial lighting and the position of the moon, depending on whether it is above or below the horizon. “We currently don’t fully understand this interaction,” says Jacqueline Degen. However, further research is expected to shed light on this phenomenon.
