Severe and widespread reductions in nighttime activity of nocturnal moths under modern artificial lighting spectra

Artificial lighting has many negative impacts on nocturnal insects, from
harmful phototaxis to disruption of feeding and reproduction. Although
comparatively poorly-explored, many detrimental outcomes could be
associated with changes in activity. We investigated the effects of
different types of light-emitting diode (LED) lighting on activity in
multiple wild-caught moth species in three different families. While
behaviour under natural conditions varied among species, artificial
lighting strongly and largely consistently suppressed activity. In our
main experiment, testing 843 moths of 23 species, we found that white LEDs
at 10 lx illuminance depressed activity by 85% on average relative to
natural nighttime illumination, and even purportedly less harmful amber
lighting had similar impacts at the same intensity. There were no
differences between the effects of broad-spectrum LEDs and combinations of
narrowband LEDs that produce equivalent light for human vision. Collection
methods, using light traps or hand-catching with nets, did affect activity
in some species, with implications for future research. Finally, further
experiments found significant activity suppression overall under lighting
at 1 lx, for white LEDs especially, with some species affected even by
skyglow levels of white light. Substantial inhibition of activity under
multiple streetlight-relevant LEDs suggests potential for widespread
impacts on moth populations.