The world's insect population is in decline — and that's bad news for humans

Habitat loss, pesticides and climate change are threatening insect populations worldwide. In 2019, Biological Conservation reported that 40% of all insects species are declining globally and that a third of them are endangered.

And while it may sound nice to live in a world with fewer roaches, environmental writer Oliver Milman says that human beings would be in big trouble without insects. That's because insects play critical roles in pollinating plants we eat, breaking down waste in forest soil and forming the base of a food chain that other, larger animals — including humans — rely upon.

"It would be an extremely dire place to live in — and certainly not something we should ever aim for," Milman says of an insect-free existence. "You would certainly have mass starvation [and] societal unrest ..... It'd be a place where there would be rotting feces and corpses everywhere because dung beetles and other insects that break down those materials would be gone."

Milman charts the troubling decline of insects in his new book, The Insect Crisis: The Fall of the Tiny Empires That Run the World. He says that while it's impossible to know exactly what's happening with every insect species in the world, the overall trends are not good: The monarch butterfly population in North America has plummeted in the past 40 years, for instance, and a U.N. assessment done in 2019 found that half a million insect species are under threat of extinction, some in the coming decades.

"The world, our surroundings, would be far quieter, far duller, far drabber without insects," he says. "When you start kind of digging down into these figures looking at the research, it's clear that there's something seriously amiss. ... There is a consistent decline in most insect populations, and that spells major trouble for them but also for us."

Interview highlights

On what the loss of pollinators means

You've got some places in China where the loss of insects is so great that armies of people have been told to ... fan out and go through orchards with ... paint brushes and feathers on sticks to pollinate crops by hand — a hugely ... labor intensive operation that obviously isn't really sustainable long-term. We need the insects around to do these jobs as they've done them for millions of years.

So there is this growing ... rumble of concern about food insecurity, especially when you think about what's happening with the overall trends. I mean, the world's population is growing. There's been a ... 300% increase in the volume of agricultural production dependent on animal pollination in the last 50 years. So we're losing pollinators at a time when we're demanding more and more pollination. We have more mouths to feed. We need more farmland. We need more intensively farmed farmland. At this kind of crucial moment, we're losing the pollinators that do that for us.

On the variety of insects that serve as pollinators

Bees get a lot of the focus and the attention when it comes to pollination, but there's a whole array of insects that provide that pollination service. In fact, three-quarters of the world's flowering plants and about a third of the world's food crops depend on pollinators at some stage. And so it's not just bees .... Flies are huge pollinators. That includes the midges that pollinate the cocoa crop that chocolate comes from. And there are wasps as well. Wasps are major pollinators. Again, another insect that's widely disliked but actually crucial for our environment.

Without these creatures, we would be without apples, cranberries, melons, almonds, broccoli, blueberries, cherries, I mean, the list goes on and on. We'd even be without ice cream, because alfalfa ... that is fed to cows ... is [pollinated by insects]. So we'd be without many of the kind of staples of our lives, many of the luxuries of our lives. Curries would become a historical dish, because cardamom would not be there, cumin would not be there. Many spices — many of the things that make our diets kind of colorful, interesting and nutritious — would be stripped from our lives without insects. That's a really important thing to think about when we're thinking about pollinator declines because many of the world's poor rely upon agriculture that's directly pollinated in their immediate surroundings, and without that, all of the nutrition is stripped from their diets. Malnutrition rates start to climb. ...The U.N. has warned that this is going to become a food security issue, something that the world needs to focus on quite acutely.

On the importance of the insects at the base of the food chain

Once you kind of yank insects out of the base of the food chain, everything kind of starts toppling away from above them, really. They're crucial in terms of just the basic foundations of forests and grassland ecosystems. We think about the placement of soil as a cycling of nitrogen through the soils that ensures that plants grow.

We may hate mosquitoes, but they provide a huge amount of food to frogs and then also birds. Once you start climbing up the food chain, you start affecting things that we really do value. So, as well as these declines that have been documented in insects, bird numbers have been reported to be down in several countries, and the birds that eat insects are faring far worse than the birds that are omnivorous, such as crows, for example. They provide a really important base to the food pyramid, and they provide a really crucial part of our overall environment.

On some extraordinary things that insects can do

I'm a very big fan of the caterpillars that can generate their own antifreeze to ward off the cold. That seems like an incredible ability to me. There's the water beetle that, once it's eaten by a frog, can actually escape from the frogs' rear end, to actually escape being eaten by the frog. Even insects that we revile are extremely impressive when you think about them objectively. Cockroaches can last two weeks after being beheaded. They can run at incredible speeds. They can survive huge amounts of poison and radiation, even.

Bees themselves are just incredible creatures just in terms of their logistical work, their ability to organize socially. Honeybees can understand the concept of zero and can add and subtract numbers. You have bumblebees that researchers have found can play soccer. They can learn to play soccer with food rewards, and there are bees that can detect landmines as well. There's all kinds of incredible things that they can do with their minds, for such small creatures. And so the more you learn about, I think, the more you're enamored with them and the warmer you feel by insects, the more you discover how incredible they really are.

On insect habitat loss

When we think about habitat loss, we think about the idea of the Amazon rainforest being burned down or chopped down. But a lot of the habitat loss is far more mundane. It's the conversion of a barren piece of land or seemingly barren piece of land into a Starbucks. It's the conversion of a field where wildflowers will grow into a field of soy or corn or another single crop. It's largely driven by agriculture. Some of it is also driven by urban sprawl. These are the laying down of highways, heavy industry and so on. So it's obviously a model that's exploded in Europe and North America, and that model is being transported elsewhere. You're seeing other countries adopt this method of farming large fields of single crops, dousing them with insecticides and other chemicals in order to boost their yields. So a lot of what we consider unproductive grounds, messy land, the kind of stuff the place is filled with wildflowers, with scrub, with kind of brambles and weeds, we call them weeds when they're in fact actually really important food providers for insects.

Lauren Krenzel and Seth Kelley produced and edited this interview for broadcast. Bridget Bentz, Molly Seavy-Nesper and Marc Silver adapted it for the web.