New research from Tufts University and the International Union for the Conservation of Nature found that habitat loss, pesticides, and artificial light pollution are posing serious threats to firefly species around the world.

Fireflies are an iconic type of soft-bodied beetle. We know of over 2,000 different species of these glow-in-the-dark insects around the world, and they all have important parts to play in their local ecosystems (as pollinators, predators, or prey) and ecotourism. A team led by Sara Lewis, Professor of Biology at Tufts University and lead author, performed a survey of firefly experts across the world to understand the most pressing threats their local species are experiencing.

According to respondents of the survey, habitat loss is the most pressing threat against fireflies in the wild across geographical regions. Light pollution and pesticide use were the second- and third-most-common threats reported on by experts.

Fires fade

“Lots of wildlife species are declining because their habitat is shrinking,” said Lewis.

“So it wasn’t a huge surprise that habitat loss was considered the biggest threat. Some fireflies get hit especially hard when their habitat disappears because they need special conditions to complete their life cycle. For instance, one Malaysian firefly [Pteroptyx tener], famous for its synchronized flash displays, is a mangrove specialist.”

Previous research has shown that conversion of mangrove habitats to farms — palm oil plantations and aquaculture farms respectively — has led to a drastic decline in Malaysian firefly numbers. This showcases how powerful an impact habitat destruction can have on a species’ success.

However, one surprising finding of the study was that light pollution was, on a global level, considered to be the second most serious threat to fireflies. Artificial light can disrupt the natural wake-sleep cycles for all sorts of organisms, including humans. For fireflies this is especially problematic as it interferes with their courtship rituals — they rely on their bioluminescence to woo potential mates. The high-efficiency, ultra-bright LEDs of today are only making the problem worse, explains Avalon Owens, Ph.D. candidate in biology at Tufts and a co-author on the study.

“Brighter isn’t necessarily better,” says Owens.

Wide-scale pesticide use is also seen as a major threat to the insects’ survival. The first part of a firefly’s life is spent as a larva (this stage can last up to two years) below ground or under water. It’s at this stage that pesticides such as organophosphates and neonicotinoids come into contact with and negatively impact fireflies, which are considered a beneficial species for agriculture. The team explains that targeted research is needed into different types of common insecticides to see exactly which are harmful to fireflies.

Additionally, they say we need more and more reliable data on how populations of fireflies are faring. There is some literature that quantifies declines in the numbers of certain species of fireflies, and numerous anecdotal reports of population decline in a wide range of habitats.

“However,” Lewis points out, “we really need better long-term data about firefly population trends — this is a place where citizen science efforts like Massachusetts Audubon’s Firefly Watch project can really help.”

Certain species are more exposed to threats than others: the team explains that females of the Appalachian blue ghost firefly (Phausis reticulata) are flightless, so habitat damage will affect them more severely as they can’t just fly to a new area. Still, the team hopes that their findings will help us better protect these glowing insects for future generations to enjoy as well.

“Our goal is to make this knowledge available for land managers, policy makers, and firefly fans everywhere,” says co-author Sonny Wong of the Malaysian Nature Society. “We want to keep fireflies lighting up our nights for a long, long time.”

The paper “A Global Perspective on Firefly Extinction Threats” has been published in the journal Bioscience.