How much did white LED light reduce moth activity at night?

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Artificial lighting can harm nocturnal insects through effects ranging from harmful attraction to light to disruption of feeding and reproduction. Changes in activity are comparatively poorly explored but could be associated with many detrimental outcomes.

Researchers experimentally investigated how different types of light-emitting diode (LED) lighting affected activity in wild-caught moth species from three families. Behaviour under natural conditions varied among species, but artificial lighting strongly and largely consistently suppressed activity.

In the main experiment, involving 843 moths of 23 species, white LEDs at 10 lx reduced activity by an average of 85% relative to natural night-time illumination; amber lighting, purportedly less harmful, had a similar effect at the same intensity. The effects did not differ between broad-spectrum LEDs and combinations of narrowband LEDs that produce equivalent light for human vision. Collection method—using light traps or hand-catching with nets—affected activity in some species, with implications for future research.

Further experiments found significant suppression of activity overall under lighting at 1 lx, especially with white LEDs; some species were affected even by skyglow levels of white light. The substantial inhibition under multiple LEDs relevant to street lighting suggests potential for widespread impacts on moth populations.