Artificial lights are shrinking firefly habitats in India and beyond

Insects act in coordination with natural light regimes and are sensitive to changes in light intensity, wavelengths, sources and other factors. Nocturnal insects perform various activities such as searching for food, reacting to predators, or navigating using the stars and the moon. For family insects Lampyridaecommonly known as fireflies, low light is required for reproduction.

June is considered the best time to spot these bioluminescent creatures, as it is an important breeding season.

Maharashtra hosts firefly festivals in May and June, which are celebrated by local communities and wildlife enthusiasts as well as photographers from different parts of the country. However, this congregation of Lampyridae is affected by increasing urban lighting, impacting their number.

Artificial light effect

Fireflies use their bioluminescence, a chemical reaction that produces light, for mating communication. Adults of one or both sexes (depending on the species) emit specific flash patterns which are received by the other sex. During mating season, fireflies flash late in the day, shortly after sunset, when light levels are low. High levels of artificial light can inhibit this signaling activity.

In the presence of artificial light, fireflies are forced to expend more energy trying to blink louder and get their signals noticed by potential mates, although the effects vary among species that are receptive to different wavelengths. .

According to a 2018 study on Aquatic ficta fireflies, commonly found in Taiwan and parts of China, the intervals between flashes become much higher as the fireflies try to flash harder to compete with artificial light. This reduces their chances of finding a mate and negatively affects reproduction rates.

Fireflies are very sensitive to ambient light cues since their courtship activities are restricted to specific times of the day. Nocturnal insects are generally adapted to natural light regimes, so they are extremely sensitive to artificial light which can disorient, attract, repel or blind them.

Although there is little data available on the populations of nocturnal and bioluminescent insects, researchers around the world have observed the decreasing presence of insects such as fireflies. Light pollution then becomes a matter of ecological concern.

Fireflies are found in temperate and tropical regions in wetlands and swamps near forested areas. Adult fireflies are short-lived, with lifespans ranging from a week to a few months.

Lack of studies

Compared to other countries, fireflies have not been well studied in India. There are very few data on the exact occurrences of the population. In one study, a researcher, Ramesh Chatragadda, from the National Coastal Research Center attempted to record the population of Abcondita chinensis species of fireflies in a specific area of ​​Andhra Pradesh.

In the study village, Barrankula, fireflies within a 10 meter area have fallen from 500 in 1996 to 10-20 in 2019. The exact reasons for this drop are difficult to determine, given that only two counts have been recorded , 23 years apart. Local communities, however, confirm that they have witnessed a steep decline in the firefly population.

Visualization by Shreya Sharma/ Mongabay

According to another survey in 2020, which attempted to understand the global perspective on firefly extinction threats, the most serious threats to fireflies noted by experts are habitat loss, light pollution from artificial light, night and pesticides – in that order.

The researchers surveyed experts from various geographic regions to identify the most significant perceived threats and only two of the 49 experts who responded were from South Asia – but they admitted that habitat loss and pesticides are the biggest threats.

Light pollution

Although pesticides are thought to be a central factor in the decline of fireflies, light pollution is a major contributor, as evidenced by a separate study on the species. Photinus sp1, conducted in Brazil. The researchers in this study found that the occurrences of fireflies (as observed by their flash patterns) depend on the proximity of light.

They studied three transects of different areas, 60 meters, 150 meters and 280 meters from the main source of artificial light: four spotlights with three multi-metal vapor lamps each. They observed a significant difference in the number of fireflies. The closer you got to a light source, the fewer fireflies there were.

Visualization by Shreya Sharma/ Mongabay

These results from the Brazilian study are significant, as they highlight the direct correlation between the number of active fireflies and the distance to artificial light. With dark areas shrinking around the world, fireflies are facing increasing habitat loss, making light pollution a significant threat to their population.

As firefly populations dwindle, they could be on the verge of extinction, with several species on the brink of extinction or even already extinct. Studies and monitoring efforts have been sparse, particularly in India. One of the main reasons for this lack of research is that photo pollution or light pollution is difficult to measure.

The precise way it affects different populations, especially nocturnal and bioluminescent species, is also difficult to study. Further research is needed to document the species and their behavioral changes under artificial light.

Visualization by Shreya Sharma/ Mongabay

Role of fireflies

The luminescent genes of fireflies have several applications in medicine, food safety testing and forensics. More importantly, however, an ecosystem is made up of interconnected parts. Each link in the chain depends on the other and the loss of each species weakens the links.

Plants and animals perform different processes that directly or indirectly affect other species. Firefly larvae feed on snails, slugs, mites and earthworms, controlling their population. An excess of these invertebrates harms the growth of vegetation. This affects the fauna that feed on this vegetation. The snowball effect is a vast environmental damage. Fireflies, like other species, maintain a delicate balance in the ecosystem.

This article first appeared on Mongabay.

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