Nocturnal moths as pollinators -- and effects of light pollution

Most pollinator studies have focused on insects that are active during daytime, largely ignoring nocturnal insects.  Many nocturnal insects have suffered significant declines.  For example, the populations of two-thirds of the widespread large moth species in Great Britain have significantly declined over the last 40 years.  In addition to bats, beetles, and flies, moths are important nocturnal pollinators; particularly the nectar-feeding species from the moth families Sphingidae, Noctuidae, Geometridae, and Erebidae.  A great diversity of plants, in a wide range of ecosystems, benefit from pollination by moths.

Long-term trends reveal that moth populations have declined, and distributions have narrowed, in Great Britain, the Netherlands, and Finland.  Surely this has been a widespread occurrence elsewhere, though long-term trend data is not necessarily widely-available.  It is likely that habitat degradation and climate change are causing much of these declines, as is the case for diurnal (daytime) pollinators.  Additionally, artificial lighting during nighttime has also been proposed as a cause of nocturnal moth declines.

Moths are well-known to be attracted to artificial lights, often in large numbers.  Shorter wavelengths are generally more attreactive to moths, attractiveness peaking around wavelengths of 400 nm (violet light).  Males of some species have been significantly more-frequently observed at light traps than females, but it is unclear whether this is due to males having a higher attraction to lights, or males being more active and therefore more likely to move into an artificial light's area of influence.  Other than this flight-to-light behavior, moths may be affected by increased ambient light at night, or altered perception of photoperiod in the vicinity of artificial lights.  Additionally, hot components of lamps, or radiant energy from bright lights, can kill insects or damage their wings, legs, and antennae.

Moth reproduction may also be negatively affected by artificial night lighting.  Artificial light can prevent egg-laying, as well as the release of sex pheromones (disrupting mating activity), in some nocturnal moth species.  Artificial lighting could also distract males from female pheromone signals.  In fact, artificial lights have been observed to redirect dispersing- or migrating moths to locations that are unsuitable for breeding, creating an ecological trap for the moths.

Aside from the fact that nocturnal moths are an important food item for numerous other organisms, the loss of these pollinators would certainly lead to the loss of plant diversity, since many plants are reliant on a single- or a few species of moths in order for the plant to sexually reproduce.

LINK to Macgregor et al.'s 2015 article in Ecological Entomology.