Impact of ecological light pollution on nocturnal Lepidoptera

Nearly half of the world’s human population lives in urban areas with artificial night lighting,

which degrades night skies. Artificial lights can create ecological traps for species that use the

moon as a cue for important behaviors. The number of moth species is rapidly declining due to

anthropogenic changes in the environment, but the cause is not readily apparent. Whether light

pollution causes an ecological trap for moths and/or causes changes in community structure has

not been studied yet and is of critical importance because Lepidoptera provide essential

ecosystem services as pollinators and prey. By using artificial lights instead of the moon,

individuals often suffer increased predation and limited access to resources. These negative

impacts illustrate the potential fitness consequences of streetlight attraction for moths and lead us

to posit that artificial light may act as an ecological trap. Over time, the alteration of moth

behavior by light pollution may result in differing communities in areas of high and low light

pollution. We sampled moth communities in 22 sites surrounded by human development five

times in the summers of 2011-2012 to look for community responses to light pollution while

controlling for habitat size and vegetation cover. We found no relationship between area, vegetation cover, and light pollution, which allowed us

to independently test these effects on moth abundance and species richness. Using multiple

regression, we found that neither habitat size or vegetation cover affected moth abundance and

species richness. Two light pollution measures had contrasting effects; more illuminance led to

higher abundance and richness while higher luminance decreased abundance and richness.

Additionally, we performed three experiments at both larval and adult life stages to look for

mechanisms driving changes in moth communities across this gradient.