LED street lights contribute to decline in insect populations: study

Street lights, especially those that use white light-emitting diodes (LEDs), not only disrupt the behavior of insects, but are also responsible for the decline in their numbers, a new study in the south of England showed on Wednesday.

Man-made nocturnal lights had been identified as a possible factor in the decline of insect populations around the world, but the subject had been under-studied.

To answer the question, the scientists compared 26 roadside sites that were either hedges or grassy edges lit by lampposts, to an equal number of nearly identical sites that were unlit.

They also examined a site with one unlit section and two lit sections, all similar in their vegetation.

The team chose moth caterpillars as a surrogate for the nocturnal insects at large, as they stay a few meters from where they hatched during the larval stage of their life, before acquiring the ability to fly.

The team either hit the hedges with sticks to make the caterpillars fall or swept the grass with netting to collect them.

The results were revealing, with a 47 percent reduction in the insect population in hedgerows and 37 percent in grassy roadside areas.

“We were really surprised at the gravity of the situation,” senior author Douglas Boyes, of the UK Center for Ecology and Hydrology, told AFP, adding that the team expected more decline. modest about 10%.

“We consider it very likely that this is due to the fact that the females, the mothers, do not lay eggs in these areas,” he said.

The lighting also disrupted their feeding behavior: when the team weighed the caterpillars, they found that those in the lit areas were heavier.

Boyes said the team interpreted this as the fact that the caterpillars don’t know how to react to the unfamiliar situation that goes against the conditions they’ve evolved over millions of years, and feed more to rush into their development.

The team found that the disturbance was more pronounced in areas lit by LED lights as opposed to high pressure sodium (HPS) or older low pressure sodium (LPS) lights, both of which produce a yellow glow- orange that looks less like sunlight.

LED lamps have become more popular in recent years due to their superior energy efficiency.

The document recognized that the effect of street lighting is localized and that it is a “minor contributor” to the decline in insect numbers, along with other important factors such as urbanization and destruction of their habitats. , intensive agriculture, pollution and climate change.

But even localized reductions can have cascading consequences for the wider ecosystem, resulting in less food for birds and bats that prey on insects.

Plus, “there really are quite accessible solutions,” Boyes said, like applying filters to change the color of lamps or adding shields so the light only shines on the road, not on the road. insect habitats.

The study is published in Scientists progress.

© 2021 AFP