The Butterfly Effect in Delhi: How Climate Change is Silencing Insects

Paradoxically, there's a surge in mosquitoes as many other insects are quietly vanishing, reports Sakshi Srivastava.

(Photo: Vibhushita Singh/The Quint)

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On a cold February evening in Delhi, mosquitoes hum uninvited. Once silenced by winter, they now thrive year-round, a clear sign of climate change.

With shorter winters and rising temperatures, mosquito breeding cycles are speeding up, aided by erratic rainfall and urban heat islands.

Paradoxically, this surge in mosquitoes comes as many other insects are quietly vanishing.

A 2022 Nature study reports a 2 percent annual drop in global insect numbers, with species like bees, butterflies, and dragonflies at risk.

A Delhi Development Authority (DDA) survey from October 2023 found a slight dip in dragonfly and damselfly counts across seven biodiversity parks, citing disrupted breeding cycles from erratic monsoons.

Four parks reported reduced species diversity of which Kamala Nehru Park recorded the most (25 species).

Experts attribute the alarming ecological shift to rising temperatures, extreme weather, and shrinking green spaces.

Why Insects Matter

Insects silently perform vital roles in ecosystems, making them essential for pollination, pest control, and nutrient recycling. Yet, they are vanishing at an alarming rate.

“Insects are the most speciose (comprising many species) organisms on earth, comprising 70 percent of all species and thriving in almost every environment,” says Mohammad Faisal, an entomologist at Yamuna Biodiversity Park.

He explains that most flowering plants depend on insects for pollination, while frogs, lizards, fish, birds, and small mammals rely on them for food.

Grasshopper at Yamuna Biodiversity Park, Delhi.

(Photo Credit: Mohan Singh)

Dr Faiyaz Khudsar, Senior Scientist at the Biodiversity Parks Programme, Centre for Environmental Management of Degraded Ecosystems (CEMDE), University of Delhi, adds that insects maintain the health, complexity, and resilience of ecosystems.

From butterflies pollinating flowers to termites aerating soil and wasps hunting prey, their roles drive crucial processes like nutrient cycling, energy flow, and biotic interactions.

With over 10 million estimated species, insects form the backbone of ecosystems.

In his 2019 paper “The insect apocalypse, and why it matters”, Dave Goulson links this decline to intensive agriculture—marked by habitat loss, pesticide use, and monocultures—along with climate change and pollution. He warns that insects are key to ecosystem stability and food security.

Their decline threatens water purification, air quality, plant reproduction, and food chains—destabilising nature’s delicate balance.

Blister Bee at Yamuna Biodiversity Park, Delhi.

(Photo Credit: Mohan Singh)

The Link Between Climate Change and Insect Decline

A 2022 study published in the Nature Climate Change revealed that insect abundance drops by nearly 50 percent in areas facing both rising temperatures and habitat loss.

In Delhi, erratic monsoons, heatwaves, and relentless urbanisation have fragmented natural habitats, making it harder for insect populations to survive.

Faisal calls this a “deadly anthropogenic cocktail,” forcing insects to adapt, migrate, or perish.

Once known for their evolutionary success—thanks to their versatile body structure and high reproductive potential—insects now face limited mobility due to shrinking green corridors in urban landscapes.

“They survived past extinctions by relocating to favourable conditions,” Faisal notes, “but that movement is no longer feasible in today’s fragmented world.”

Dr Khudsar explains that, as ectothermic organisms, insects depend heavily on ambient temperatures to regulate metabolic functions. Even minor climate shifts can disrupt breeding, hatching, and migration.

If pollinators emerge before flowers bloom, or if prey vanish before predators hatch, food chains collapse. Rising temperatures are pushing many insects to cooler areas like Dehradun or Shimla, leaving ecosystems in cities like Delhi vulnerable and unbalanced.

Khudsar warns this is a dangerous feedback loop—climate change accelerates insect loss, which in turn destabilises ecosystems, making them more susceptible to further climate impacts.

Climate change, especially in mountainous regions, coupled with habitat destruction, pesticides, invasive species, and disease, is driving these losses. Dr Shashank PR from the Entomological Society of India confirms India is facing similar trends.

Beekeeper Apoorva BV, director of The Hive Trust, notes that 92 percent of vegetation relies on insect pollination, with honeybees playing a central role. Native bee species like Apis cerana indica are under stress from climate-induced changes in flowering, which affect nectar availability and colony development.

The loss of beneficial insects disrupts ecosystem balance, letting pests like aphids and termites thrive, leading to pesticide overuse. This harms biodiversity and causes resistance in pests.

“Pesticide overuse eliminates wild plants, extending pollinators’ starvation time. Neonicotinoid pesticides also disorient bees, leading to large-scale colony losses."

Dr Shashank PR

Ground beetles aid decomposition and soil health, while declining predators like Trichogramma allow invasive species to spread. Dr Khudsar warned that falling pollinator numbers could reduce crop yields and trigger broader biodiversity collapse.

Several studies have also suggested that the absence of insects in densely populated areas might be a critical factor in the decline of house sparrows.

“Sparrows need insect caterpillars to feed their young, and declining insect numbers during the breeding season may contribute to their drop,” noted Faisal. He added that sparrows still thrive in areas like the Yamuna and Aravalli Biodiversity Parks, where insect populations remain stable.

Apis cerana (Asiatic honeybee) colony in a bathroom at Banashankari, Bengaluru.

(Photo Credit: Apoorva BV)

Insects Are Vanishing, but Who’s Watching?

“In India, pest control services list bees as pests and charge to kill them,” notes Apoorva, a beekeeper, highlighting the lack of awareness around insect importance.

Result for a Google search for “beehive removal Delhi”.

Quantitative ecologist Mansi Mungee, who has worked extensively in the Eastern Himalayas, points out that while insects account for almost 70 percent of the terrestrial biomass, the country lacks long-term datasets needed to understand how they’re being affected by climate change.

Moths photographed against a gridded cloth to estimate body size.

(Photo Credit: Mansi Mungee)

“Insects are hyper-diverse and hyper-abundant. Monitoring them requires continuous, standardised tracking, ideally for 15-20 years,” she says, adding, “But most research grants in India last only 3-5 years. You can’t study long-term shifts if your funding dries up halfway.”

Mungee’s own study in Arunachal Pradesh involved setting up light screens to photograph hawk moths across 13 elevation levels—from 200 m to 2,800 m. Surprisingly, she found that the moths got larger at higher elevations, a trend with unclear causes.

She explains,

“We saw a strong correlation between body size and elevation, that is, the moths were bigger as we went higher. The change in body size is probably their way of adapting to something else that’s changing. This could be due to lower air density affecting flight efficiency, or due to fewer resources at high altitudes, requiring them to bulk up and store energy.”

Identifying such changes—and understanding whether they are adaptive or distress signals—needs expertise that is currently in short supply.

“The UK has about 300 moth species. India could have 2,000, many still unknown to science. The kind of taxonomic knowledge we need is immense,” Mungee adds.

Mansi Mungee with a local Bugun community boy, Biki Marphew, at Eaglenest Wildlife Sanctuary, Arunachal Pradesh. He has been working with her over 10 years and helps with all field work.

(Photo Credit: Satya Rai Nagpaul)

She also explains why we need years of data to detect real trends: insect populations fluctuate wildly by day or season.

“You might see 100 moths one night and just 10 the next. That doesn’t mean there’s been a decline. It could be weather or life cycle timing. To separate noise from signal, you need 20 years of data."

Mansi Mungee

Commenting on the same, Dr Shashank PR notes that Delhi’s insect monitoring is hindered by short funding cycles, few experts, and inconsistent methods. “We need standard protocols, sustained investment, and global collaboration,” he says.

“Long-term ecological monitoring (LTEM) is vital to track species responses to climate change and habitat loss. Without continuous data, the decline of pollinators risks agricultural sustainability and informs climate-resilient conservation policies,” he further adds.

Act Before It’s Too Late

Dr Khudsar emphasised that the first step toward insect conservation is simple yet powerful: we must start by “respecting these tiny creatures.”

Apoorva teaching beekeeping to the tribals of Chhattisgarh with his four-year-old son.

(Photo Credit: Apoorva BV)

While Apoorva stresses that sustainable conservation starts with awareness and policy intervention, suggesting a shift in how urban spaces treat bees.

Instead of calling pest control when colonies settle in balconies, he advocates for training professionals to relocate them. He also calls for incentives for farmers to adopt pollinator-friendly practices.

Dr Shashank highlights the importance of citizen science and community involvement in insect monitoring, citing projects like the Great Pollinator Project and Butterfly Monitoring Schemes.

He notes that reducing air pollution, especially particulate matter, is crucial for protecting pollinators. Platforms like iNaturalist, Moths of India and  ifound butterflies enable people to document insect sightings, aiding conservation efforts.

In 2024, Sharma & Ramamurthy’s paper emphasises the discrepancies in the Indian Wildlife (Protection) Act’s insect listings, urging updates to reflect current species status. Out of 493 species listed, 9 Lepidoptera species are not found in India, and 2 are recognised agricultural pests.

Insects, vital to Delhi's ecosystems, now signal an ecological emergency. The question remains: will we act before it’s too late?

(The reporter is a Delhi-based multimedia journalist covering politics, environment, and culture.)