Fireflies around the world are being negatively impacted by human growth and expansion, according to the first comprehensive threat analysis examining threats to the charismatic insect.

Working under the International Union for Conservation of Nature Firefly Specialist Group, Tufts University researchers surveyed 350 members of the Fireflyers International Network, a self-proclaimed group of firefly scientists and enthusiasts. Though the authors of the study published in Bioscience note that their results should be interpreted with caution because they “reflect only expert opinion concerning perceived threats to firefly species persistence,” the findings found the biggest threats facing fireflies are habitat loss, followed closely by artificial light and pesticide use.

By and large, experts believe that the largest threat facing the more than 2,000 global species of fireflies is habitat loss. Furthermore, local extirpations may not be remedied by reintroduction efforts and dwindling populations are “unlikely to be rescued by migration”. For example, the Appalachian blue ghost firefly (Phausis reticulata) is flightless and cannot just move habitats.

"Lots of wildlife species are declining because their habitat is shrinking," said study author Sara Lewis in a statement. "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.”

Pesticide use remains another threat to firefly populations. Fireflies have a unique life history and spend up to 2 years of their larval stage underground or underwater. During this time, insecticide and pesticide leaching may cause unknown health consequences and result in declining populations.

Light pollution has previously been shown to disrupt mating displays and is associated with reduced reproduction success in some species as fireflies rely on bioluminescence to find and attract mates, note the researchers. Over the last century, artificial light has grown globally as human populations continue to increase.

Technically a beetle, fireflies are found in a variety of habitats, from marshes and mangroves to grasslands, agricultural fields, and even urban parks. The enigmatic insects play an important role in both cultures and economies, however, monitoring data is lacking for almost all species. Population declines have been noted in just a handful of species, including Malaysia’s mangrove firefly and the glowworm Lampyris noctiluca in England.

To save this enigmatic insect, the researchers propose four opportunities to limit external pressures, including habitat preservation, controlling light pollution, reducing insecticide use, and developing sustainable tourism guidelines in locations that see large fluxes of ecotourism. The authors note that significant gaps in research exist and further long-term data monitoring trends are needed to understand how fireflies are being impacted.