The case of the missing butterflies, fireflies and dragonflies | Technology News

In India, too, their numbers are dwindling, with researchers pointing to a combination of factors such as climate change, habitat loss, the ubiquitous use of pesticides, and artificial light pollution.

A 2020 study by the Zoological Survey of India (ZSI) showed that higher temperatures in the Himalayan region have driven several dozen species of butterflies and moths to habitats higher up the mountains. (File)

Sanjay Sane, Dean of Faculty at the National Centre for Biological Sciences (NCBS) in Bengaluru, says, “I’m absolutely certain that we are seeing massive drops in the insect population in India. You can talk to anyone who observes insects and they will tell you the same… no more insect splatter on your car windshield, the number of beehives or dragonflies that we used to catch as children… we don’t see as many of them anymore.”

An insect apocalypse?

Unlike in the US and European nations, India lacks comprehensive long-term data that captures this decline in insect population. Entomologists (those who study insects) are, however, certain that India isn’t untouched by the global phenomenon of vanishing insects.

A survey conducted in October in seven biodiversity parks of Delhi found that in four out of seven parks, the count of damselflies had dipped in comparison to last year. (File)

A survey conducted in October in seven biodiversity parks of Delhi found that in four out of seven parks, the count of dragonflies and damselflies had dipped in comparison to last year. As per the survey, the number of dragonfly species fell from 16 last year to eight this year at Kalindi Biodiversity Park, near Okhla; and to 21 from 23 last year at the Yamuna Biodiversity Park, near Wazirabad. The number of dragonflies counted as part of the survey dipped to 256 from 323 last year at Neela Hauz Biodiversity Park in Vasant Kunj and to 344 from 555 last year at Aravalli Biodiversity Park in Vasant Vihar. Both insects belong to the order Odonata — bugs characterised by minute antennae, extremely large eyes that fill most of the head, and two pairs of veined wings.

Experts say recent extreme weather events may have affected their population. Dragonflies and damselflies require marshy water bodies to breed and lay eggs, but excess rainfall in June-July this year followed by a dry spell in August-September thwarted the creation of ideal breeding conditions, leading to a drop in their numbers.

Pankaj Koparde of MIT World Peace University in Pune says several dragonfly species have disappeared due to the construction of dams and roads. (File)

Extreme weather events are just one impact of climate change. Soaring temperatures have also severely affected insects. For instance, a 2020 study by the Zoological Survey of India (ZSI) showed that higher temperatures in the Himalayan region have driven several dozen species of butterflies and moths to habitats higher up the mountains.

Reports suggest that with the world heading for a 3.2 degree Celsius global temperature rise over pre-industrial levels by 2100, half of all insect species are set to lose more than half of their current habitable range.

Entomologists and ecologists say that more than climate change, it’s the current rate of habitat loss in India that is a bigger threat to the insect population.

“Climate change is like slow poison. It’s going to kill them, but that is a process that will perhaps take some 20-30 years. On the other hand, as soon as the habitat is cleared, the insect species are instantly lost,” says Pankaj Koparde, an evolutionary ecologist and assistant professor at MIT World Peace University in Pune. He has been mapping dragonflies across the Western Ghats for several years now and has found a decrease in their numbers in the region.

(Credit: Abhishek Mitra)

Koparde points out that several dragonfly species have disappeared due to the construction of dams and roads. “Damming streams and rivers has a much bigger impact on dragonflies than climate change. Many of their species require a free-flowing water stream and their breeding biology depends on the dissolved oxygen levels in that stream. If you dam the stream, it will change the water flow and their habitat for breeding. This will either force dragonflies to move out of the area or they will go locally extinct,” he says.

In Himachal Pradesh’s Kullu Valley, the excessive use of pesticides in apple orchards have kept away natural insect pollinators, leading to a dip in fruit production, says V P Uniyal, scientist at the Wildlife Institute of India in Dehradun.

“The overuse of pesticides has killed pollinators like bees and butterflies in Himachal Pradesh. Without them, you can’t get the fruits. These insects are a crucial part of the pollination process,” he says.

Bengaluru has also witnessed a decline in bugs, especially fireflies — a type of beetle that naturally produces light. A 2022 study carried out by Karnataka’s Environmental Management and Policy Research Institute (EMPR) noted the dwindling firefly count as they were restricted to just 12 areas in and around the city.

Bengaluru has witnessed a decline in bugs, especially fireflies. (File)

The study attributed their disappearance to two main factors. One, rapid urbanisation has led to Bengaluru losing most of its wetlands, where a large number of these bugs thrived. Two, harsh artificial lights across the city pushed these bugs to 12 identified pockets. Fireflies use their bioluminescence, a chemical reaction that produces light, to exhibit courtship behaviour. Adults of one or both sexes (depending on species) emit particular flash patterns which are received by the other sex. High levels of artificial light can hinder this signalling activity.

Another study done in 2020, published by the journal Proceedings of the National Academy of Sciences (PNAS), showed that the Giant Honey Bee — a key pollinator in South Asia that is almost twice as big as the western honey bee — is at risk in several parts of Bengaluru due to rising air pollution.

As part of a three-year-long analysis, researchers collected 1,800 Giant honey bees from different parts of the city and found that four out of five bees collected from the most polluted areas died a day later — twice as many as those collected from the less polluted areas. Moreover, bees covered in toxic dust visited flowers only half as many times as their cousins in less polluted parts, potentially reducing the chances of successful pollination, the study found.

A world without insects

The plummeting insect population has set off alarm bells among scientists and experts. These tiny creatures are the most diverse group of animals on Earth — there are around 5.5 million species of insects.

Pollination is just one among many jobs that insects perform. They are also a crucial part of the food chain.

Neha Mujumdar, a researcher at the Conservation Department, Bombay Natural History Society in Mumbai, describes this role of bugs: “Insects are excellent food for higher organisms like birds and foxes — the latter typically live in open grassland areas and feed on beetles and big-sized grasshoppers. During their breeding cycle, birds go out in search of caterpillars as they are a rich source of protein for their chicks.”

Another essential role that bugs play is that of decomposers. Insects such as dung beetles break down and bury animal waste, reducing overall methane emissions on dairy and beef farms.

“In addition, these six-legged ‘garbage collectors’ reduce disease, aerate the soil, disperse seeds, and promote plant growth,” said a report by the World Wildlife Fund.

The critters are also natural pest controllers. For example, dragonflies are vociferous eaters of mosquitoes, with some species consuming hundreds of them in a single day.

While there’s little debate on why insects need to survive and thrive, researchers say that given the lack of data, most conservation plans in India runs into a wall

Dearth of data

“In India, there are only anecdotal observations to suggest that the insect population is declining,” says Sane, who has been researching insects for around 30 years. He explains that during British rule, there was fairly expansive data on insects — in the late 1930s, they published a scientific book known as The Fauna of British India, which documented insects in India — and post-Independence, the country continued to do well in terms of identifying and discovering new species. However, long-term surveys on insects didn’t take place in India.

According to Sane, there are three broad reasons for this scarcity. “One, the research funding cycle (a grant given to researchers for a fixed number of years) runs for only three years, which isn’t conducive for years-long research that such studies demand. Two, the popularity of molecular taxonomy — that involves studying genetic and hereditary molecular differences, predominantly in DNA sequences — has stopped taxonomists from going into the field. Lastly, there aren’t any incentives for carrying out a long-term survey of an insect. Unlike when a new species is discovered, a published paper, for instance, on the rise and fall of the population of a particular hawk moth in a habitat over the years isn’t a flashy bit of news,” he says.

Pointing out that researchers abroad have tracked insect specimens over decades, recording, in some cases, weekly data or even daily data on insects. “The researchers use this data to observe insect numbers during different seasons… They correlate the numbers with weather patterns or with the level of urbanisation… Those data are absolutely pivotal in allowing us to determine what is and is not good for the health of insects, and therefore of our ecosystems,” Sane adds.