September 23, 2021

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Decline of caterpillars emphasized by streetlights (study)

Released on Wednesday, August 25, 2021 at 9:05 p.m.

Street lights are not good for insects. In addition to disrupting their behavior, it could go as far as directly reducing their numbers, according to a study conducted in the south of England and published in the journal Science Progress on Wednesday.

The researchers studied caterpillars, especially moths. They only move a few meters around the hatchery, so their population can be read very easily locally.

A total of 26 sites were illuminated at night – roadside hedges or lawns. They were each compared to a dim and very distant site, presenting the same characteristics (plants, urban planning, etc.).

Samples of caterpillars were taken.

As a result, caterpillars averaged 47% less in hedges and 33% less in grasses.

“We were all amazed that this was so amazing,” Douglas Boise, lead author and researcher at the UK Center for Environment and Aquatic Resources, told AFP. In contrast, a reduction of about 10% is expected.

“The explanation is mostly that women don’t lay eggs in these areas,” he explains. “It’s not the behavior they have in the light.”

These nocturnal animals have been used in the dark for “millions of years”, so “this light is extraordinary, it’s new,” he says.

It also disrupts their life cycle: each caterpillar was weighed and the ones taken from the burning areas were heavy.

As they “accelerate their growth” and eat faster, the condition appears to them to be “dangerous or abnormal,” explains Douglas Boys.

The researchers also found that using LED lights – similar to white lights and daylight – reduced the number of caterpillars under streetlights more than conventional sodium bulbs (HPS).

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However, LEDs are becoming more and more used due to their excellent energy efficiency.

“Street lights may have provided only a small path to the long-term decline of moths nationwide,” the study agrees.

But this light has “only one very important local effect.” Layering effects: Less caterpillars means less food for birds or bats.

However, there are “more accessible solutions” that underscore the Douglas Boys. For example, by installing color filters or screens that direct light only on roads.