Imagine — a world without head-lice, bed-bugs and mosquitoes, no malaria or yellow fever, no clothes-moths, no deathwatch beetles bringing the rafters down, no wasp stings, no lily beetles shredding the turk’s-caps, and no ravaging locust plagues of biblical proportions.
What would happen if insects disappeared?
An idyllic world perhaps? No, far from it. An environment without insects would be a drab pale shadow of the bustling vibrant natural world we have today — it would lack all vitality and diversity, and would soon spiral into crushing monotony.
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It’s not just that a few pretty butterflies, dragonflies and brightly coloured beetles would be sadly missed. Without insects whole ecosystems would collapse.
Though they are very small, insects are so diverse and so numerous that they wield a power far beyond their diminutive size — they dominate the centre ground of all terrestrial and freshwater food webs, feeding on everything (including each other) and being fed upon.
Without their vast biomass in the middle, there would be nothing to eat for those above — no insect-eating birds, fish, or mammals, with drastic knock-on effects higher up the food chain.
For hundreds of millions of years, insects have been the small cogs that run the planet — providing, what in the technical jargon are called ‘ecological services’. Simply — they keep nature in balance.
With no caterpillars keeping plant growth in check, a few vigorous ‘weed’ species would soon overwhelm the world, over-shadowing and squeezing out anything more delicate. And without scavengers recycling them, dwindling nutrients would be permanently locked up in amassed leaf litter, dead trees and logs, dung, carrion, and all the other byproducts (or end-products) of life on Earth.
We’ve already dodged a bullet on one continent-wide ecological near-disaster caused by the absence of particular insects. When European settlers took their domesticated stock animals to the new colony of Australia in the late 18th century, the native dung beetles, evolved to feed only on hard dry marsupial nodules, could not cope with the copious wet droppings of cows, sheep and horses, so it lay around for months or years, slowly smothering the pasture, or providing breeding grounds for clouds of disease-ridden flies.
It took a massive international effort a century and a half later to breed and release millions of African and Eurasian dung beetles to provide the necessary clear-up squad — to try and re-establish some of that natural balance.
But it would be the absence of that best-known insect behaviour, flower-visiting, that would spell the worst disaster for the world. Without pollination most flowering plants would not set seed or, more importantly for humans, set fruit. Claims vary, but there are estimates that between 35% and 75% of the world’s crops are insect pollinated.
No more beans or petits pois — figs, strawberries, apples, pears and peaches would be things of the past. Things are already near breaking point — the vast monoculture orchards of southern California are only kept in harvest by the artificial transport of millions of domesticated honeybees to pollinate the industrial swathes of trees. Wild flowers, with their often very specialist individual pollinators, would soon fade away, so plant diversity would shrivel up too.
Insect diversity is mind-numbingly complex. About 1 million insect species (90% of all animals) are recorded at the moment, but extrapolated estimates of 10 million to 30 million are quite plausible.
The interconnectedness of these mostly still unknown insect species with their food-stuffs, prey, predators and parasites, and their effect on their habitats largely remain a mystery to us. But it’s clear that if aliens landed on Earth, and with limited time and limited resources they wanted to try and understand the biosphere, all they need do is study beetles, and just dismiss everything else as sampling error. Insects are, by far, the most important animals on the planet, even if, at the moment, we don’t know by quite how much. If they disappeared it would be catastrophic.
What would the world be like if there had never been insects?
These apocalyptic scenarios, with the sudden vanishment of moderately well-understood insects, can at least be guessed at. But what if insects had never evolved in the first place? How would the world work today? What other small-cog organisms could have evolved in insects’ stead.
No other invertebrates can fly and it is certainly wings that gave insects the ability to colonize the globe — to migrate, find food, find each other, hunt, avoid being hunted, and pollinate flowers.
Maybe woodlice would have stepped up to the mark, and taken to pollen and nectar, rather than just leaf litter. Maybe spiders would have evolved herbivory or become aquatic. Maybe worms might fly. None of these imaginary options quite ring true, so we should be thankful that we have insects already in place — keeping the world running, keeping the world fresh and alive. We should value and try to better understand the life that we already have here on this planet — our home. And their home too.
