Firefly population is declining due to climate change
KNOWN FOR THEIR BIOLUMINESCENCE, FIREFLY SPECIES WERE GLOWING INDICATORS OF CHANGING SEASONS. TODAY, THEIR POPULATION IS DECLINING AS CLIMATE CHANGE HAS DESTROYED THEIR HABITATS
IHAVE been staying in Landour in Mussoorie for more than two years, but I never observed any firefly species. Local people told me they too had not seen fireflies for over two decades. This was in line with the global trend of disappearance, or migration, of these fascinating creatures. But in July-August this year, I was witness to a sudden appearance of these lighting insects in Landour. They were seen in pine and oak forest patches near Woodstock School between 6 and 7 pm, and also in the maple trees after midnight. This led me to probe these magical bugs.
Fireflies are unique because they produce their signature glow through light organs located under their abdomen. They take in oxygen within special cells and combine it with a compound called luciferin to produce light with almost no heat. This type of light production is called bioluminescence, and this unique species accounts for 40 per cent of all insect species in the world.
Fireflies are, in fact, beetles— belonging to the Coleoptera order of the Lampyridae family—that have existed in our planet since the dinosaur era, says Sarah Lower, an evolutionary geneticist at Bucknell University, Pennsylvania, USA. There are over 2,000 species of fireflies across the world and they mark their presence in all continents, except Antarctica. In India, fireflies are known as jugnoo in Hindi, jonaki poka in Bengali and jonaki porua in Assamese. These nocturnal insects are winged, which distinguishes them from other luminescent insects of the same family.
Firefly behaviour reveals that each blinking pattern is an optical signal to find potential mates. But when predators such as lizards attack, they produce drops of blood that are filled with poisonous chemicals. Significantly, fireflies are indicators of a healthy environment. They are extremely
sensitive to changing environmental conditions and thrive only in healthy habitats—where water is free from toxic chemicals, land is diverse enough to support different life stages of fireflies, and where there is minimal light pollution. Fireflies, by mainly feeding on pollen and nectar, also play a vital role in pollination and the propagation of many plants.
Their manifold utilities are such that scientists are using their luminesce property to detect cancer and other diseases. For instance, Swiss researchers took the protein that makes fireflies glow and added a chemical tag to it, so when it attaches to another molecule—like on a tumour cell—it will glow. The study was published in Nature Communications in 2015.
LIGHTS OUT
“Everyone is reporting decline in their populations,” says Eric Lee-Mäder, co-director of the pollinator program, Xerces Society for Invertebrate Conservation, a US-based non-profit. “I have observed a drastic decline in firefly population in the campus of the Wildlife Institute of India (WII),
Dehradun, since 1999,” says
V P Uniyal, senior scientist, WII.
Though the exact extent of the decline is not known, reports suggest that their numbers have either shrunk or disappeared in many places, or they are migrating to find new habitats—moist, humid, wet or damp regions.
Population decline of fireflies is due to various factors, including loss of habitat due to rapid urbanisation and deforestation and light pollution that prevent fireflies from seeing each other’s flashes, thus indirectly affecting their biological cycles as they are unable to find their mates. A study published in Ecology and Evolution in 2018 says light can make fireflies lose track of time or their position or even blind them. Then there is the threat of pesticides—a large part of a firefly’s life is spent as a larva, on or under the ground, or underwater where they are exposed to pesticides.
CLIMATE CHIMES
Fireflies are also signalling the impacts of a changing climate. A number of reports suggest that with changes in the global climatic conditions, the ecological habitat and distribution of the fireflies are also changing. That could be the reason for the appearance in Landour, where fireflies have extended their duration of stay. Here, summers have become comparatively warmer along with extreme rainfall—from April to
September. The changing climatic conditions may have driven fireflies to migrate and extend their distribution to this part of the lesser Himalayas.
A 12-year study published in
Science in 2016 found that warmer springs caused by climate change would mean an earlier firefly peak, but only if rainfall remains the same. On the flip side, the seemingly increase in the number of firefly in other regions may be due to wet springs—a trend occurring with climate change in the northeastern USA, says Michael Hoffman, professor emeritus, entomology, Cornell University.
I have come across many studies that have focused on the biology and luminescence of fireflies, but there is little research on the global effects of climate change on firefly ecology and habitat. The disappearance of fireflies comes amid a larger decline in insect populations globally. This will leave the world with more pests and fewer pollinators and less luminance and wonder.
WARMER SPRINGS CAUSED BY CLIMATE CHANGE WOULD LEAD TO EARLY FIREFLY PEAK. ON THE FLIP SIDE, THE SEEMINGLY INCREASE IN THE NUMBER OF FIREFLY MAY BE DUE TO WET SPRINGS