Web of Life:  Which matters more, humans or insects?

by Theresa Peluso

What would our planet look like if humans vanished from the face of the earth? Could the rest of nature survive without us?

Millstone photo

Well, in the first day or so, there could be some rather cataclysmic events.  As our power plants ran out of fuel and shut down, all the systems dependent on that power would fail.  Water treatment plants would stop working, causing raw sewage to pour into the rivers, and tunnels and subway systems to flood. Chemical plants would fail as well. All the satellites and other objects now orbiting around the earth would end up crashing back to earth. Nuclear plants would explode, as the water used to cool them stopped flowing, and evaporated. Natural-gas plants would also go up in flames, lights would go out, and billions of cows, pigs and chickens and other livestock, as well as pets, would either starve or have to survive in the wild.

And then Nature would begin the slow process of reclaiming our civilization for its own.  After a couple of decades, most of our streets and sidewalks would be covered in vegetation, habitations on the edge of deserts would be covered in sand, our metal structures and vehicles would corrode and collapse, our houses would rot and fall apart, our dams would crack and crumble, and swamps that once covered vast areas of the world would reappear.  Once the fumes from chemical and nuclear emissions dissipated, our air would become much cleaner as humans stopped emitting chemicals and carbon into the atmosphere. The domestic animals that escaped would either die or find ways to adapt to the wild. The billions of tonnes of plastic we’ve produced in the last century would still be present, though – a tawdry monument to human existence.

Now what if insects disappeared?  Insects, which make up 80 percent of all species on earth, range in size from 0.14 mm (the male Costa Rican fairyfly) to 55.6 cm (the female West Malaysian walking stick).  Spiders, which are, incidentally, estimated to number about 21 quadrillion (21,000,000,000,000,000) are not insects, and not part of this discussion, although their role in our ecosystem is similar to that of insects.

So far, some 900,000 different species of living insects have been identified, and estimates of the actual total number of species range from 2,000,000 to 30,000,000.  Insects probably have the largest biomass of the terrestrial animals.  It is estimated that at any time there are approximately 10 quintillion (10,000,000,000,000,000,000) individual insects alive, which is approximately 1.3 billion insects for every human.  Insects live in just about every habitat on earth, including hot deserts, hot springs, shallow water, up to 50 cm underground, and in the bodies of other animals.  They are found on every continent, even Antarctica (albeit in small numbers).

Insects are one step up from plants and algae, which form the bottom of food chain.  Without insects, the many fish, amphibians, reptiles and birds that depend on them for food would starve.  Eventually, our food chains would collapse, as birds of prey, foxes, bobcats, raccoons, wolves, weasels, bears, and other large mammals lost their sources of food. As a case in point, it’s estimated that 60 percent of birds (and this doesn’t include all the other vertebrate classes) rely on insects for food. In fact, a recent article in the Guardian, titled ‘Catastrophe’ as France’s bird population collapses due to pesticides (https://www.theguardian.com/world/2018/mar/21/catastrophe-as-frances-bird-population-collapses-due-to-pesticides?CMP=share_btn_link) states that “Dozens of species have seen their numbers decline, in some cases by two-thirds, because insects they feed on have disappeared.” Rachel Carson, in her 1962 book Silent Spring, accused the chemical industry of spreading disinformation, and accused government officials of accepting these claims unquestioningly.  Has nothing changed in the last 56 years!?

Plant roots, deprived of the aeration that insects provide by burrowing into the soil and creating air spaces around them, would lack the nutrients they need to grow. Did you know that insects turn more soil than earthworms, and remix nutrients around plant roots as they burrow and nest in the ground?  Did you also know that, without insects like flies and dung beetles, the manure from large animals and the corpses of dead animals would soon accumulate into huge piles, rendering most land unsuitable for agriculture, instead of contributing to the fertility of this land?

The result would be that plants everywhere, except for the very toughest, would get very sickly.  Plant-eating animals, including humans, would struggle to survive, as the disappearance of pollinating insects meant that most of our fruit trees and garden crops would fail to produce fruit and seeds. To show the extent to which we depend on insects for food, it is estimated that 80 percent of wild plants depend on insects for pollination, and that between 25 percent and 50 percent of crop production depends on pollination by wild insects, and a lesser percent by honeybees.

Last, but not least, there would probably be an increase in disease outbreaks, as the accumulating dead matter became impossible to dispose of, and started harbouring all kinds of harmful bacteria and other pathogens.

So what if the very last insect vanished from the face of the earth?  Within 50 years, all life on land would most likely end.  Even if it didn’t, the result would be mass starvation and disease for all terrestrial life.  Marine life might continue, however, since it evolved independently of insects, although here again, it might be affected by events on land. Fish stocks might be further depleted as humans and other animals resorted to ransacking the sea for fish and other protein sources for food.  This could, in turn, trigger a collapse of life in the seas, since fish are responsible for a lot of the nutrient recycling in the oceans that nourishes the organisms at the base of the food chain.

So, given the abundance of insects, there’s no need to fear such a disaster, right?  Actually, there is a real concern that our insects are indeed disappearing.  The journal Yale Environment 360, (https://e360.yale.edu/features/insect_numbers_declining_why_it_matters) cites a 2012 survey by the Zoological Society of London, which concluded that

“many insect populations worldwide are in severe decline, limiting food supplies for larger animals and affecting ecosystem services like pollination. In Europe and the United States, researchers have documented declines in wild and managed bee populations of 30 to 40 percent and more due to so-called colony collapse disorder. Other insect species, such as the monarch butterfly, also have experienced sharp declines.

Another report, published in PLOS/One (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185809), describes a study conducted during a period of 27 years in 63 nature protection areas in Germany to determine the status of all the insects in those habitats – they did not focus on any particular species.  The results were dismaying:  The researchers found a seasonal decline of 76 percent, and a mid-summer decline of 82 percent, in flying insect biomass.  This decline was evident regardless of the type of habitat.  According to these researchers, weather, land use and habitat characteristics couldn’t explain this overall decline.  Remember, these studies were conducted in nature protection areas. The researchers concluded that the causes of this severe decline are large-scale, and they plan to further investigate whether climate change, habitat destruction, and agricultural practices, such as the growing of monoculture crops and the pervasive use of pesticides, may be contributing to this impending disaster.

Scientists cite many factors in the fall-off of the world’s insect populations, but chief among them are the ubiquitous use of pesticides, the spread of monoculture crops such as corn and soybeans, urbanization, and habitat destruction.

As the famous Pogo quote goes:  We have met the enemy, and he is us.  The Yale School of Forestry and Environmental Studies concurs, with this article by Christian Schwägerl titled What’s Causing the Sharp Decline in Insects, and Why It Matters (https://e360.yale.edu/features/insect_numbers_declining_why_it_matters):

It seems indisputable: it is us. It is human activity – more specifically, three generations of industrialised farming with a vast tide of poisons pouring over the land year after year after year, since the end of the second world war. This is the true price of pesticide-based agriculture, which society has for so long blithely accepted.

So what is the future for 21st-century insects? It will be worse still, as we struggle to feed the nine billion people expected to be inhabiting the world by 2050, and the possible 12 billion by 2100, and agriculture intensifies even further to let us do so. You think there will be fewer insecticides sprayed on farmlands around the globe in the years to come? Think again. It is the most uncomfortable of truths, but one which stares us in the face: that even the most successful organisms that have ever existed on earth are now being overwhelmed by the titanic scale of the human enterprise, as indeed, is the whole natural world….

In large parts of Europe, the U.S., and South America, monocultures cover vast areas of the landscape, creating “biological deserts” devoid of hedges or ponds where insects could reproduce. Attempts to make the European Union’s agricultural system more environmentally friendly have largely failed in recent years…. Of particular concern is the widespread use of pesticides and their impact on non-target species….

Yet even environmental campaigners like Miller (Leif Miller, director general of the German chapter of BirdLife International) admit that the root causes and the full dimension of the problem aren’t yet fully understood. “I suspect it is a multiplicity of factors, most likely with habitat destruction, deforestation, fragmentation, urbanization, and agricultural conversion being the leading factors,” says Stanford ecologist Rodolfo Dirzo….

According to conservation organizations like BirdLife International, new attempts are necessary to “green” EU agricultural policy in a substantial way by creating incentives for enriching landscapes with hedgerows, reducing fertilizer and pesticide use, and better rewarding organic agriculture. Previous efforts to do so have largely failed.

“The key question is whether governments view biodiversity as an add-on or as something that is of existential importance for our future,” says Jürgen Deckert. (end of quote)

Another factor contributing to insect deaths is the replacement of traditional warm-spectrum outdoor lights with cool-spectrum LEDs.  According to the article Fatal attraction: moths find modern street lights irresistible (The Telegraph, May 29, 2013)


Researchers found that moths are more attracted by the brighter white lighting that is increasingly being installed on roads around Britain compared to the older traditional orange street lights. They say moths find white light or slightly bluish light irresistible and will exhaust themselves by flying around the lights rather than mating or searching for food. Predators also find it easier to pick the insects off due to the large congregations that gather around modern street lamps.

Professor Richard Ffrench-Constant, a biologist at the University of Exeter who led the study, said: “Just like with butterflies, we have seen moth numbers declining dramatically, but because they are active at night, we are less aware of them. Habitat loss has certainly played a role in the declines of moths, but we have found that they different types of moths are attracted to different wavelengths of light. If you use white light or lamps with a broad spectrum of wavelengths, then it will attract more moths and that completely disrupts their natural behaviour. They are not mating or feeding on flowers. They tend to circle around the light until they get exhausted and fall to the ground.”

There are around 2,000 species of moths in the UK compared to just 52 species of butterfly….Recent research of large, common moths in Britain showed that two thirds have declined by around 28 per cent in the past four decades.

…While habitat loss is thought to be among the main causes for their decline, the switch from traditional orange street lighting to whiter lights has also been blamed.…Professor Ffrench-Constant and PHD student Robin Somers-Yeates, whose work is published in the Royal Society journal Biology Letters, found that more species were attracted to the newer lights. (end of quote)

While it’s true that many insects are considered bothersome – or, in the case of mosquitoes, even fatal – to humans; for example, ants, termites, flies, fleas, bedbugs, lice, cockroaches, and various moths and beetles that attack crops, these insects are only a small fraction of the world’s insect population.  Even these bothersome insects have a use – they are a food source for many animals.

So what can we do, as individuals, to avoid contributing to this tragic decline in insect populations?  We ourselves can refuse to use pesticides in our yards.  We can grow native and pollinator-friendly plants (not just for bees and butterflies, but other pollinators too).  We can use warm-spectrum outdoor lighting. We can teach our children and grandchildren to appreciate the beauty and importance of insects, at the same time that we teach them about the bothersome insects.

At a broader level, we can support our municipality’s use of warm-spectrum street lighting and encourage retailers to do likewise for their outdoor illumination – which, by the way, is better for our own health too.  We can support environmental groups, such as Ontario Nature, the Pesticide Action Network, and the Nature Conservancy of Canada, that advocate against the use of pesticides and promote habitat conservation; we can buy organically grown food whenever possible; and we can oppose the spraying of our roadsides with chemicals.

Insects matter – more than humans.  We need to act now to stem their decline in whatever way we can.