Street Lights Linked to Insect Decline

Five-spot burnet moth, Flamborough Head
Five-spot burnet moth, Flamborough Head

Light pollution from street lights is linked to worrying declines in insect populations.

In a UK study, street lights were found to disrupt the behaviour of nocturnal moths, reducing caterpillar numbers by half, reports the BBC. Modern LED lights have the most damaging impact.

It is hard to separate out the many factors causing insect populations to decline; other than light pollution, there is global heating, habitat loss, and pesticide use.

In the study, scientists compared caterpillar numbers at roadside sites with street lights against nearby roadside sites that were unlit. There were lower caterpillar numbers at the lit sites as follows:

  • 47% fewer caterpillars in hedgerows
  • 33% fewer caterpillars in grass margins

Lights may deter nocturnal moths from laying eggs, and put them at risk of being seen by predators.

40% of insect species are undergoing dramatic rates of decline, and this has consequences for entire ecosystems because they are a food source for birds, amphibians, bats and reptiles.

Practical solutions to the problem of street lights include dimming them in the early hours, fitting motion sensors, or using colour filters to cut out the most harmful wavelengths.

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