By Elizabeth Pennisi May. 4, 2021
Each summer, on bridges across the world, mayfly massacres occur. First, warm weather prompts the transformation of the insects’ aquatic larvae. Within hours, the short-lived, flying adults pop out of streams, rivers, and lakes, eager to mate and lay eggs by the millions.
But bridges illuminated with artificial light can lure the newly emerged adults away from the water to a futile death before breeding. Others, fooled by the sheen of reflective pavement, drop their eggs on the bridge road instead of the water. Because mayflies control the growth of algae and are food for fish, the fate of these humble insects may reverberate through ecosystems, says Ádám Egri, a biological physicist at the Centre for Ecological Research in Budapest, Hungary, who is working to save endangered mayflies there.
Mayflies aren’t alone in their fatal attraction to what researchers refer to as ALAN: artificial light at night. Studies from around the globe are finding worrisome impacts on insect mating and abundance, says Stéphanie Vaz, an entomologist at the Federal University of Rio de Janeiro’s main campus. In the past year, researchers have published the first experimental and regional studies of the problem, and in March, Insect Conservation and Diversity devoted a special issue to the topic.
Some researchers think brighter nights may be a factor in recently documented insect declines, says Stephen Ferguson, a physiological ecologist at the College of Wooster. With insect numbers dropping by 80% in some places and 40% of insect species headed for extinction by some estimates, “Some researchers have started to make more noise about the ‘insect apocalypse,’” Ferguson says. “ALAN is almost certainly one of the drivers.”
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