“Thus hath the candle songs the moath”
-Shakespeare, The Merchant of Venice
Just like the quote above, more commonly known today as the phrase “like a moth drawn to a flame”, light pollution can result in increased mortality for moths as these nocturnal creatures often fly into urban light sources. Through direct burning or increased exposure to predators, their attraction to light can be fatal. Take a look at the video below to understand why moths are so attracted to light.
On the other hand, research has shown that ‘urban moths’ in areas with high light pollution tend to have a reduced flight-to-light behaviour which may counteract the negative impacts of artificial night light (Altermatt, 2016).
From the figure above, we see that the flight-to-light behaviour of small ermine moths (Yponomeuta cagnagella) are less attracted to light compared to their counterparts in natural dark-sky conditions. According to the study, there was a 30% mean reduction in flight-to-light behaviour between moths in heavily light polluted versus areas which are less light polluted. Because of reduced flight-to-light behaviour moths may benefit from less direct mortality as well as reduced susceptibility to predators.
However, not all is bright as there are costs associated with reduced flight-to-light behaviour. Closer look at the behaviour of these moths point to the fact that these moths might be behaviourally or physiologically impaired to react and perceive light. Because of light pollution in urban areas, the light receptors in the eyes of moths are altered, causing information processing of light to be affected.
Additionally, reduced flight-to-light behaviour is associated with a drop in the overall mobility of these moths. This is detrimental to the moth community in the long term because reduced mobility means that moth habitats will likely be more fragmented and dispersed. There are also wider implications to other organisms in the ecosystem when it becomes increasingly challenging for insectivores such as bats and spiders to feed on moths because of their reduced mobility in the sky.
Moths are valuable creatures for us humans as they aid in the overall wellbeing of our ecosystem through pollination, pest control and improving the quality of soils. A decline of these creatures can have knock on effects on not only the moth population, but other organisms in our ecosystem that rely heavily on moths for their growth.
The good news is that to help reduce the impact of light pollution on moths, there are relatively easy and concrete steps that we can take. We can start small by making a conscious effort to switch off the lights when not in use. Additionally, we can make the switch from blue-white lights to red or amber lights that are proven to be more insect-friendly.
Stay tuned for more!
Jean
References:
Altermatt, F., Ebert, D. (2016). Reduced flight-to-light behaviour of moth populations exposed to long-term urban light pollution. Biology Letters, 12, 1-4.
Nature Conservation Canada. (2020). Reducing light pollution is a simple way to help insects. Retrieved from https://www.natureconservancy.ca/en/blog/light-pollution-insect-conservation.html