Insect Populations in Decline are But One other Invitation to Catastrophe – The Connecticut Examiner


In the early 20th century, when asked if anything about “God” could be inferred from a study of natural history, the polymath JBS Haldane replied that “he has an inordinate fondness for beetles.” Currently, more than 380,000 cataloged beetle species make Coleoptera the largest subgroup of the most species-rich and successful animal class on earth ─ insects. This may be the Anthropocene epoch due to our negative impact on the planet, but an estimated 10 trillion insects can inhabit the biosphere at any given time. Indeed, we live in an age of insects, as much as it hurts our human arrogance and causes us to poison and genetically modify crops to combat their numbers. Their realm is not an invisible realm like that of bacteria and other tiny organisms. Before the great dinosaurs, they colonized, adapted, and occupied almost every ecological niche imaginable. Despite their meager dimensions, six-legged, segmented bodies have mastered the skies, freshwater, and soils, synchronizing multiple life cycle stages with the seasonal abundance of plants and prey. These stages are so distinctly different that some insects breathe through the stigmas as full-blown windpipes, as swimming larvae through gills, and in difficult times as pupae crouch to transform. The open oceans alone were a dead end for their millions of species and their vast but fragmentary biomass. On ocean swells, far from any coastline, only the water strider Halobates is on the lookout for undetermined prey. A “real beetle”, like other hemipterans who slide on freshwater lakes and streams, is the only known insect that can gain a foothold seaward.

Insects have evolved on land and in ponds and other freshwater habitats for over 400 million years, digging and building (often elaborately), crawling, hopping, flying and swimming to survive, and even living in terrestrial extremes. Stoneflies have been identified in the Himalayas at an altitude of 18,000 feet and silverfish have been found not only in the damp recesses of our homes but also in caves 3,000 feet below the surface. Alkali flies live in Yellowstone’s hot springs, while other insects survive freezing cold and arid conditions by maintaining a state of numbness for months and even years. Exploits of strength, ferocity, and social organization among insects impress and terrify us. In the dark, a single mosquito, flea or louse hurled around our beds to paraphrase Lao Tzu is “worse than a tiger”. Nevertheless, we marvel at the monarch butterflies’ wandering marathons, calculate the aerodynamic uncertainties of bumblebees in flight and combine our phobias with science fiction, which creates huge insect threats on the screen. For centuries mosquitoes, as carriers of malaria and yellow fever, protected the rainforests from destruction by humans. Due to global warming and climate change, dengue and other insect-borne diseases that were once confined to the tropics are gradually spreading northward. In time, the world’s most venomous moth caterpillar, Lonomia oblique, which lives in the subtropical jungles of the New World and can be fatal to humans, could arrive on America’s doorstep. Invasive species such as fire ants, gypsy moths, Asian hornets and “killer bees” already have it. But the insects are only reluctantly given their rights. Instead, we’ve genetically engineered our plants, made biotechnological insecticides for the bacillus, and increased the use of toxic dusts to deal with insect resistance. Now this comes home to sleep.

Entomologists in Krefeld collected flying insects in identical traps in the same place for two weeks in August 1994 and again in August 2016. Similar studies were carried out in Germany in 63 protected areas over equivalent periods of time. The shocking result: the insect biomass had fallen by 76 percent. When you consider that insects make up an estimated 80 percent of all known animals and conserve the biosphere, their plummeting populations in the wild, farmland, and backyard gardens are alarming. EO Wilson famously came to the conclusion that if humans were to become extinct, the biological world would “return to the rich state of equilibrium that existed 10,000 years ago”. We got a glimpse of this wealth during the “anthropause,” when pandemic lockdowns temporarily led to a reduction in pollution and a resurgence of wildlife. But “if insects went away,” added Wilson. “The environment would be in chaos.” More and more insect Armageddon cases are being made around the world. In New Hampshire, researchers in protective forests found that beetle populations have plummeted 80 percent and their biodiversity has decreased by 40 since the 1970s. A Dutch study of butterflies in the Netherlands found comparable declines in numbers since the end of the 19th century. According to the International Union for Conservation of Nature, reports indicate that almost half of the 2,200 insect species tracked are in decline, with crickets and grasshoppers (order Orthoptera) and odonates (dragonflies and damselfish) being hardest hit.

The cultural diversity of the United States may be a source of pride for many of us, but insects remain the most diverse organisms on earth. Entomologists estimate that the approximately one million insect species classified to date represent only a quarter of the species that have not yet been identified. For example, Ichneumonidae, a taxonomic family of parasitoid wasps that lay eggs on paralyzed spiders and caterpillars, contains more species (about 100,000) than any vertebrate classification combined. Because Charles Darwin used productive parasitism on a philosophical sidebar to disprove Genesis and the existence of “benevolent” deities, members of the Ichneumonidae are commonly called Darwin wasps. While creation myths and possible goodwill of the gods remain a matter of belief and imaginative guesswork, the role of insects in animating this planet is not the case. Dependence on insects for survival is an absolute certainty. Whether their accelerated disappearance is due to climate change, pollution in general, pesticides, or habitat loss for farms and sprawling cities (probably all of the above), we and many other life forms on earth are doomed without them. Insects are a critical link in almost every aquatic food chain on land and in freshwater. Many mammals, from bats and aardvarks to primates and bears, as well as birds, reptiles, amphibians and fish, are insectivorous to some extent. The recent decline in bat and bird populations around the world is almost certainly linked to the disappearance of insects.

Beetles and other insects are also vital decomposers that break down and release nutrients from animal dung, carrion, and rotting vegetation. Anyone who has prepared a skeleton museum specimen like I did for a Siberian tiger that died of gangrenous Clostridium infection knows how invaluable dermestid beetles are in cleaning cadavers for scientific study. Without insect breakers in the wild, plant and animal debris would be left and accumulated, causing plague and delaying the recycling of vital nutrients in ecosystems. Predatory insects, which prey on a wide variety of plant pests, also serve as biological controls against agricultural pests. Blackbird beetles, for example, can eat one million aphids a day on one hectare of arable land. Nationwide, the predation not only saves farmers billions of dollars through better yields, but also reduces the use of toxic pesticides in integrated crop protection. Fewer and fewer insecticide applications not only mean lower exposure to toxic residues on fruit and vegetables for consumers and farm workers, but also limit the pollution of soils and streams from point sources.

Tilling underground colonies of insects, especially ants, termites, and bees, also plays an important role in aerating hard soil, supplying nutrients essential for plant growth, and helping landscapes to retain water. Insects are also critical to seed dispersal. In one of myriad coevolutionary relationships between insects and plants, seeds are often endowed with elaiosomes, tiny lipid-, protein-, and vitamin-filled stimuli to aid in spreading. Ants transport the seeds, eat the elaiosomes and let their undamaged cargo sprout. In addition, insects are the best pollinators. About 90% of flowering plants (75% of cultivated varieties) depend on pollination by animals, mostly insects, for reproduction. Without insect pollination, 30-40% of human food production would be lost. Combined with crop failures due to climate extremes related to global warming (e.g. more frequent floods and droughts), declining insect populations are another invitation to disaster.

Scott Deshefy is a biologist, ecologist and two-time Green Congress candidate.