What could the disappearance of insects mean for the ecosystems that sustain us?

A few days ago, I opened a jar of honey that I hadn’t touched in months. The thick golden molasses was strewn with black spots – ants that had died after gorging on nectar. It was something I hadn’t seen in years. It now seems far away that a forgotten candy bar, a piece of fruit, an uncovered cube of cheese or even a crumb of cake would attract a troop of foraging insects out of nowhere. Their pheromone trails alerted more colony members who would join in the effort to break down the food into tiny particles, which they carried home.

These seemingly pesky creatures are very diverse – there are over 13,000 known varieties of ants and at least 10,000 species yet to be discovered. They outnumber humans by approximately one million to one. Highly organized ant societies are almost everywhere – cities, villages, forests, farms. EO Wilson, arguably the world’s greatest – and sometimes controversial – living naturalist, writes in Tales from the Ant World (Liveright, 2020), “Ants enter every available nest site, take over most available food sources and in doing so create an arthropod hegemony that controls all levels of the land, from the highest canopy to the lowest root mass.

There are over 13,000 known varieties of ants and at least 10,000 species yet to be discovered. They outnumber humans by approximately one million to one. (Source: getty images)

Still, there may be fewer ants than about three decades ago. Last year, a study published in the journal Science reported a 9% loss in the population of insects like ants, grasshoppers and butterflies every decade for the past 30 years.

Good riddance? Ant armies are, after all, notorious for fiercely defending their homelands. In Social Conquest of Earth (Liveright, 2012), Wilson writes that during World War II in the Solomon Islands, snipers “were known to fear weaver ants as much as the Japanese”.

The reality, however, is more disappointing. The decline of ants, butterflies, bees, wasps, grasshoppers, fireflies and dragonflies could have consequences far beyond their own disappearance. Without insects, we wouldn’t have much plant-based food, and without insects, the world would be overrun with decaying matter. Insects are the first recyclers: they digest decaying bodies and dead wood, control the spread of weeds, agricultural pests, disease vectors and other organisms that make life difficult for humans. These are resources for medicines and indicators of the quality of habitat. Much like earthworms, ants are ecosystem engineers who, by tunneling through the earth to form their intricate mounds, redistribute nutrients throughout the soil and improve air and water circulation. .

Point of no return: Human beings throughout history have had an impact on insects and biodiversity networks. (Source: getty images)

Wilson calls insects “the little creatures that run the world.” But apart from certain charismatic varieties – monarch butterflies for example – most species of the insect class are rarely monitored or counted. Beyond the pioneering studies of Wilson and University of Pennsylvania entomologists Daniel Janzen and Winifred Hallwachs, our knowledge of the fate of most ant species is derived from anecdotal accounts. In a landmark speech 34 years ago at the opening of the National Zoological Park in Washington DC, which urged the world to pay more attention to the plight of invertebrates, Wilson said: “If invertebrates were to go extinct, I doubt that the human species could last more than a few months. Most fish, amphibians, birds, and mammals would collapse around the same time. Next would come most of the flowering plants, and with them the physical structure of most of the world’s forests and other terrestrial habitats. The earth will rot. As dead vegetation piled up and dried out, shrinking and closing the channels of nutrient cycles, other complex forms of vegetation died and with them the last vestiges of vertebrates. The remaining mushrooms, after experiencing a population explosion of prodigious proportions, would also perish. In a few decades, the world would revert to a state of a billion years ago, consisting mostly of bacteria, algae, and a few other very simple multicellular plants.

Wilson is among the scientists who believe that the decline of insects is one of the most cataclysmic aspects of the “sixth extinction”. This is something that Janzen and Hallwachs have been warning for at least four decades. “I have observed the gradual and very visible decline in the density and richness of Mexican and Central American insect species since 1953 and Winnie since 1978. The loss is very real…and the reasons are very obvious: Forestry and agricultural simplification intense over very large areas. , massive use of pesticides, habitat fragmentation and, at least since the 1980s, ever greater climate change in temperature… if our terrestrial world remains built by a constant war with the world of arthropods, as well as plants, fungi and nematodes, human society will waste a lot of time. The house is burning. We don’t need a thermometer. We need a fire hose,” Janzen wrote in a 2019 article in the international journal of conservation science, Biological Conservation.

Butterflies, moths and bees are among the most affected. The United States has lost nearly half of its bee colonies over the past 70 years. The creatures’ demise began immediately after the introduction of DDT in the 1940s and continued even after America discontinued the insecticide in 1972.

David Wagner and his co-editors of the seminal issue of the multidisciplinary American scientific journal PNAS on insect decline in January this year believe that “most butterfly declines in Europe are the result of changes in agricultural practices after World War II…when modern tractors and mechanized equipment were employed to hasten the industrialization of agriculture, insecticides became widely available and synthetic fertilizers could be manufactured and applied in prodigious quantities.” Deforestation, primarily for agricultural expansion, is progressing at a rate that is having an alarming impact on insects and other arthropods.The true extent of this crisis is not even known, fear Wagner and his colleagues.

Bumblebee Butterflies, moths and bees are among the most affected. (Source: getty images)

In their contribution to this collection, Janzen and Hallwachs write about the “heterogeneous coverage” of the effects of climate change. Human beings have throughout their history impacted insects and biodiversity networks. But most times in the past, the effects of aggression could be reversed. Due to climate change, Janzen and Hallwachs write, much of this reversal does not occur: “A 200-year-old tree with all its portions of thousands of ecosystem networks, now and during its lifetime, now subject to climate change, no longer has the climate or interactors with which to reproduce as its parents did.Herbivores, pollinators, seed dispersers, mycorrhizae, decomposers, diseases, competitors, commensals, mutualists, parents, parasites and predators are all different from when it was a seed, a seedling and a sapling.” Only minimal recovery is likely, fear the Cassandra d cause of insect decline.

In 2009, French entomologist Nicola Gallai estimated that India had lost almost 40% of its honey bees since the 1980s. of written history, information about other native bee species is sparse and ambiguous,” write Manjishtha Bhattacharya, Sankar Acharya, and Susanta Chakraborty in a 2017 article in an open-access journal, Tropical Conservation Science.

Last year, a study in a village in Andhra – reported in the International Journal of Tropical Insect Science – compared a count of fireflies in the same area in 1996 and found that the population of these beetles had decreased by 80 to 90%. Scientists attribute the decline to the unscientific use of pesticides in rice fields. Research in other parts of the world has attributed the decline of these creatures to light pollution – energy-efficient LEDs, ironically inspired by these glowing insects, are particularly notorious for interfering with firefly courtship rituals, in which males and females use the play of light and color to attract each other’s attention. Lights from houses, buildings and cars disrupt these signals and fewer and fewer larvae are born each year. The International Union for Conservation of Nature’s Firefly Specialist Group says such studies, while valuable, need to be backed up with long-term data. Last year, more than 20 scientists from different parts of the world came together to issue a “Warning to Humanity about Insect Extinctions”. In biological conservation, they said, “when we lose insects, we lose more than species. Such losses lead to a decline in essential ecosystem services on which humanity depends.