It’s no secret that moths have an easy obsession – whether they’re fluttering around the lightbulb on the porch or snuggling up to a street lamp.
But light pollution from these artificial sources is not only a problem when looking at the sky. A study published in Science Advances in August provides new evidence as to why these lights may also damage moth populations, affecting their entire ecosystem.
“Moths are functionally important to terrestrial ecosystems, including as pollinators, prey for both vertebrates (e.g. birds and bats) and invertebrates (e.g. spiders and social wasps), and as hosts for parasitoids,” the authors write the study. “These changes are expected considerable cascading consequences for ecosystems. “
In this study, the researchers looked at the moth’s least agile stage: the caterpillar.
Canary (Ennomos alniaria) populations have declined by two thirds in the last 50 years.Iain Leach / Butterfly Conservation
What’s New – The team studied the overall abundance and size of moths in darkfield locations, those illuminated by LED street lights, or locations illuminated by alternate wavelength light (such as high and low pressure sodium lamps) will.
On Twitter, the study’s lead author, Douglas Boyes, says he spent more than 400 hours collecting the data across different seasons alone.
Although these locations are otherwise identical in terms of flora, the researchers found almost 50 percent fewer moths in illuminated areas, and LED lights in particular had the fewest.
They also found, perhaps nonsensically, that the moths they found in illuminated places were much heavier than their dark-favoring counterparts.
“Caterpillars that were heavier in the illuminated section at the time of sampling may indicate advanced development under stress and investments in earlier pupation,” the authors write. “It is predicted that this will have deleterious effects on adult fitness.”
What makes LED lights different – While non-natural light isn’t good for moths down the line, Boyes says that LED light – which emits “white” or full-spectrum light – are some of the worst culprits simply because they cover the largest area.
“The more wavelengths of light emitted, the greater the variety of species and biological processes that are likely to be affected,” Boyes told Inverse. “The color of white LEDs is also much more similar to daylight than that of sodium lamps, so biological processes that are controlled by daylight are likely to be more easily disrupted.”
All over the world – but especially in the UK – bright white LED lights are increasingly becoming the street lighting standard. Douglas Boyes
Despite these problems, Boyes says, LED street lights are becoming increasingly popular, especially in the UK, where Boyes did this research.
“[LEDs] Save money and CO2 emissions as they are more energy efficient, ”he says. “You are more reliable. In the UK, 55 percent of street lights are now LEDs and almost all of the rest have been contracted to replace them. “
But due to the so-called rebound effect (the idea that replacing old light sources with energy-efficient lights creates an overall higher demand for lights), Boyes says that the energy and cost savings with LEDs will ultimately be less than initially assumed.
Aren’t moths attracted to light?
But let’s rewind: How can artificial light be harmful to moths when they willingly fly towards it as adults? In many ways, this is still an open question for scientists.
When it comes to adult moths flying towards lightbulbs or fire, scientists suspect that these light sources confuse the sense of direction of the otherwise nocturnal insects. Scientists suspect that moths use the parallel light from the stars and the moon to navigate in straight lines, but are confused by artificial light sources that shine in all directions. As a result, they loop around lights instead.
Other researchers have also theorized that moths can mistake these light sources for either sexual partners or food.
But, as with many human vices, what is acceptable in moderation for adult moths seems harmful to them if they are still growing.
And that’s not only going to be a problem for moths, write Boyes and colleagues in their newspaper. As crucial species in these grassy ecosystems, a decline in populations of moths or other nocturnal insect species will also have a negative impact on their predators or benefactors, including songbirds, bats, and other pollinators.
And if we have learned anything from the decline in bees, it is that threats to pollination will spread to humans as well.
Orange sodium vapor lamps could be a good alternative to LEDs, scientists found. Picture alliance / picture alliance / Getty Images
How people can do it better – LEDs aren’t the only thing threatening moths and other insects – habitat loss and climate change also play a big role – but Boyes says there is at least one fairly simple solution to this one problem: reviving the night.
“The nice thing about the subject is that unlike many other threats to wildlife, which can be much more tricky, there are cheap, simple solutions,” says Boyes. “What is important is that LEDs can be modified much more easily than sodium lamps – at a low cost – by reducing the intensity by dimming and using filters to reduce the blue wavelengths of light that are most harmful to insects. We assume that this would help. “
