Light pollution may be driving the decline of moths

Light pollution has evolved in color and severity over the past two decades, resulting in complex impacts on moths and other animals who rely on night vision, according to a new study from the University of Exeter. 

The experts report that artificial lighting can have a subtle yet dramatic influence on the behavior of nocturnal animals. 

To investigate, the researchers analyzed how various types of lighting affect the vision of moths, and the birds that eat them. In particular, the study revealed that elephant hawkmoth vision is enhanced by some types of lighting and disrupted by others. At the same time, the birds that hunt moths were found to see better under almost any type of lighting.

“Modern broad-spectrum lighting allows humans to see color more easily at night,” said Dr. Jolyon Troscianko. “However, it is difficult to know how these modern light sources affect the vision of other animals.”

“Hawkmoth eyes are sensitive to blue, green and ultraviolet, and they use this color vision to help find flowers just like bees, but at incredibly low light levels – even under starlight.”

“Moths are also vitally important pollinators – accounting for a similar proportion of pollination as bees – so we urgently need to investigate how lighting affects them.”

According to Dr. Troscianko, his team used animal vision modeling to calculate the ability of moths to see flower colors, and of birds to see camouflaged moths under a wide range of natural and artificial lighting.

“Artificial lights designed for human vision lack the blue and ultraviolet ranges that are key to moth color vision, and under many conditions will block the moth’s ability to see any colors at all,” said Dr. Troscianko.

“This could make it more difficult for them to find and pollinate wildflowers, and for them to find suitable spots to camouflage them from predators.”

“Conversely, bird vision is much more robust, meaning artificial light will help them to find camouflaged moth prey, and will allow them to hunt later into the evening and earlier in the morning.”

The researchers found that white lights with a greater blue component promote more natural color vision in moths, even though these light sources are known to be harmful to other species.

Moths are declining across Europe, especially nocturnal species, and there is a growing collection of evidence that supports a link with light pollution. The experts are calling for a “nuanced approach” to lighting to limit the amount and intensity of light where possible.

The research was funded by the Natural Environment Research Council.

The study is published in the journal Nature Communications.

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By Chrissy Sexton, Earth.com Staff Writer