Human activities are responsible for the gradual disappearance of fireflies

When night falls and they dot the landscape with their bioluminescence, the fireflies and glow worms offer a truly magnificent spectacle. However, this magic of nature is on hold. The development of urbanization, deforestation, the use of pesticides and light pollution are all factors contributing to the progressive decline of fireflies all over the world. And recently, the alarm signal concerning their extinction was raised by the Group of Specialists of Fireflies of the International Union for the Conservation of Nature (IUCN).

Fireflies are in serious trouble, with many species threatened with extinction due to habitat loss and exposure to pesticides, according to the first major review of their global status. Their natural luminosity is also stifled by artificial light pollution, report researchers in the journal BioScience .

More than 2,000 species of fireflies - which are actually beetles - light up wetlands, marshes, grasslands, forests and city parks around the world. A few, such as Photinus pyralis in the United States, appear to be thriving. "These insects can survive just about anywhere," says Sara Lewis, a biologist at Tufts University in Massachusetts.

But other varieties - glow worms from southern England, synchronous fireflies from Malaysia, and the blue ghost of the Appalachians, both of which attract tourists - are dying out due to human activity. "Some species are particularly affected by the loss of habitat because they need specific conditions to complete their life cycle."

Urbanization: a major factor in the disappearance of fireflies

The Malaysian firefly ( Pteroptyx tener ), for example, lives during its larval phase in the riparian mangroves, many of which have been uprooted to make way for oil palm plantations and fish farms.

The glow-worm ( Lampyris noctiluca ) has another problem: females are unable to fly, which means that they simply cannot move to a new location when their habitat is destroyed by a suburb, crop or road the country.

Deforestation, the construction of new housing and light pollution, in the context of exponential urbanization, are the main factors behind the disappearance of fireflies. Credits: Sara M Lewis et al. 2020

Other species of fireflies, which only eat during their larval phase, have "specialized diets", which means that they survive on one or two types of snails, earthworms or other body prey soft. When orchards in Mediterranean Spain are abandoned or give way to urbanization, like snails consumed by Lampyris iberica , firefly larvae have nothing to eat.

Meanwhile, adult Pteroptyx in Malaysia congregate for nocturnal courtship displays in specific trees along the mangrove rivers. Many of these trees have been felled.

Out of 10 possible extinction factors, experts have identified habitat loss as the main threat worldwide - except in East Asia and South America. In these two regions, artificial light was considered to be the greatest threat to luminescent beetles in the world.

Light pollution, insecticides and tourism: they worsen the overall situation of fireflies

"In addition to disrupting natural biorhythms, light pollution has a negative impact on firefly mating rituals" explains Avalon Owens, biologist. Many species of fireflies depend on their ability to light up to find and attract partners. To make matters worse, this window of opportunity is very narrow: while the larval firefly phase lasts for months or years, adults generally only live a few days.

Around the world, fireflies and glow worms are threatened by habitat loss, insecticides, light pollution and water pollution. Credits: Sara M Lewis et al. 2020

Sparkling beetles are so focused on reproduction that they don't even eat. The investigation found that fireflies are also being wiped out by commonly used insecticides, the third major threat. "Organophosphates and neonicotinoids are designed to kill pests, but they also have non-targeted effects on beneficial insects."

Fireflies light up by triggering a chemical reaction - involving oxygen, calcium and an enzyme called luciferase - inside special organs in their abdomen, a process called bioluminescence. Tourism focused on fireflies (long popular in Japan, Malaysia and Taiwan) is also wreaking havoc, with fragile ecosystems damaged by too much pedestrian traffic.


A Global Perspective on Firefly Extinction Threats

Sara M Lewis, Choong Hay Wong, Avalon C S Owens, Candace Fallon, Sarina Jepsen, Anchana Thancharoen, Chiahsiung Wu, Raphael De Cock, Martin Novák, Tania López-Palafox

BioScience, biz157,

Published: 03 February 2020

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