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Start at the Bottom: How Rewilding for Insects Brings Back Everything Above Them

Updated: 2 days ago


If you want more birdsong in your garden, more bats stitching the dusk, a hedgehog snuffling under the hedge, the counterintuitive place to begin is not with the birds, the bats or the hedgehog. It's with the insects; the aphids and caterpillars and beetles and flies that most of us spent years trying to get rid of.

The naturalist E.O. Wilson put it best when he called invertebrates "the little things that run the world."


He meant it almost literally. Insects and their kin are the foundation the rest of the living world is built on; and a garden that gets the bottom of the food web right will, given a little time, find the top of it arriving on its own. Here's how that chain actually works, link by link, and how tending the smallest creatures pulls all the larger ones up behind them.


The base of everything

Nearly every land food chain runs on the same current: plants capture the sun's energy, insects eat the plants, and almost everything else eats the insects. Invertebrates are the great converters, turning leaf into protein and passing it upward. Remove them and the whole structure has nothing to stand on.

Caterpillars deserve a special mention here, because they are the single most important parcel in the whole delivery network. Soft, protein-rich and abundant, they transfer more energy from plants to other animals than almost any other kind of creature — which is why so much of what lives in a healthy garden is, directly or indirectly, living on caterpillars. Get caterpillars right and you've powered the whole system.


Link one: caterpillars become birds

The clearest illustration in any British garden is the blue tit. That tiny, cheerful bird times its entire breeding season; the laying, the hatching, everything; to coincide with a single event: the spring explosion of caterpillars, especially winter moth caterpillars, on freshly unfurling tree leaves. Miss that window and the brood starves.

The quantities are staggering. A single blue tit chick can eat around a hundred caterpillars a day, and a pair may need to find something like ten thousand caterpillars to raise one brood to fledging. Ten thousand!


For one nest, in a few short weeks. That is the true cost of a garden full of blue tits, and it's paid entirely in insects. No caterpillars = no chicks; it really is that direct. And what's true of blue tits is true, in its own way, of robins, wrens, blackbirds, sparrows, warblers and the rest: they may visit your feeder in winter, but in spring they feed their young on invertebrates, because that's where the protein is.


Link two: it all starts with plants (and not just any plants)

Here's the part that hands the gardener real power. Caterpillars don't appear by magic; they hatch on the plants their parents evolved alongside. Most insect herbivores are specialists they can only feed and breed on particular plants they share a deep evolutionary history with which means what you plant decides how much insect life your garden can generate.

And native plants win by a distance. A native English oak supports an astonishing web of life - the Woodland Trust puts it at around 2,300 species across the UK, more than 1,170 of them invertebrates, with 257 found on oak and nothing else. Compare that with the introduced trees we often reach for in gardens: horse chestnut, brought from the Balkans centuries ago, supports only around fifty insect species; an ornamental Japanese cherry, fewer than ten. Native hawthorn supports nearly a hundred and fifty. The pattern is consistent and it's dramatic; a native tree can feed ten, twenty, fifty times the insect life of an exotic one of the same size.

This isn't an abstract preference. In one striking American study, researchers found that a familiar garden bird, the chickadee, simply couldn't sustain its population in gardens dominated by non-native plants: too few caterpillars, so fewer eggs, fewer fledglings, and a local population sliding downhill. The birds needed gardens that were mostly native to hold their own. The lesson travels: choosing a native tree or shrub over an ornamental one isn't gardening for insects at the expense of the birds; it's gardening for the birds by way of the insects.


Link three: up and up the chain

Follow the current upward and it keeps branching.

Bats. All eighteen of Britain's bat species eat nothing but insects. A common pipistrelle -a creature small enough to sit in a matchbox can hoover up as many as three thousand midges, moths and small flies in a single night. Every one of those bats flickering over your garden at dusk is there because the air is full of insects; empty the air and the bats vanish with it.

Hedgehogs, amphibians, small mammals. The hedgehog we all want back is essentially an invertebrate-eating machine, living on beetles, worms, caterpillars and slugs. Frogs, toads, newts, slow-worms, shrews; ALL of them are insectivores or invertebrate hunters, another whole tier of garden life resting on the same foundation.

And the predators above them. The sparrowhawk that scythes through the garden is eating the small birds that ate the insects. The tawny owl is eating the small mammals that ate the insects. The fox takes the beetles and the fledglings alike. Layer upon layer, the entire pyramid, right up to the top predators we think of as the glamorous end of rewilding, is standing on six little legs. Tend the base and you are, quite literally, feeding everything above it.


The proof runs in reverse, too

We know this chain is real because we can watch it break. Insects are disappearing at a frightening rate: the Bugs Matter survey run by Kent Wildlife Trust and Buglife, which counts insects squashed on vehicle number plates, recorded a fall of around 78% in flying-insect abundance across the UK between 2004 and 2023.

Pull the bottom out of the food web and the collapse travels upward, and it is already visible in exactly the animals you'd predict: the insect-eaters. The spotted flycatcher, a bird that lives by snatching flying insects from the air, has declined by around 92% in the UK since the late 1960s. Swifts, swallows, house martins and other aerial insectivores; the birds that feed entirely on the insects overhead, are among the fastest-declining groups we have. They are the canaries in this particular mine, and they are telling us the base of the web is thinning.

That's the sober half of the story. The hopeful half is that the same mechanism runs in both directions. Rebuild the insect life and, in time, the things that eat insects come back to meet it.


What this means for your garden

The single most useful shift in thinking is this: don't garden for birds; garden for insects, and let the birds, bats and hedgehogs follow. Everything below flows from that.

  • Plant native, and plant a tree if you possibly can. This is the biggest lever you have. A native tree, or oak if you have room, or birch, rowan, hawthorn, crab apple or a native willow for smaller gardens, is an insect engine in a way no ornamental can match. Underplant with native shrubs and flowers. Where you're choosing between a native and an exotic, the native almost always feeds more life.

  • Grow the host plants AND let them be eaten. Caterpillars need specific plants to grow on: a patch of nettles for small tortoiseshells, peacocks and red admirals; native grasses for many others. And here's the mindset change that matters MOST a garden that's being nibbled is a garden that's working. Chewed leaves aren't damage; they're the food chain functioning. Learn to read holes in the foliage as a sign of success, not failure.

  • Never spray. Insecticides remove the base of the chain wholesale, and they travel upward into the very birds and hedgehogs you're hoping for. (I've made this case at more length in our ten ways to rewild your garden.)

  • Build structure. Long grass, flowering borders, shrubs, a tree, a log pile, a pond; each layer hosts different insects, and the more layers, the more life. Emergent insects from even a tiny pond will feed the bats directly.

  • Keep the nights dark, and offer homes. Moths are both crucial food and in steep decline, so go easy on outdoor lighting. And put up nest boxes and a bat box so the insectivores, once the insects return, have somewhere to raise the next generation.


None of this asks you to love aphids. It only asks you to see them differently; not as the enemy of a beautiful garden, but as the first course in a very long meal that ends with birdsong (I grow cabbages JUST for cabbage white butterflies - not to eat).


The beautiful inversion

There's a quiet justice in all this. The creatures we've spent longest trying to banish from our gardens; like the caterpillars on my cabbages, the mosquitos and flies at dusk, the beetles under the log, turn out to be the ones holding the whole cathedral of life up. Every hedgehog, every singing blackbird, every bat and owl and darting flycatcher is, when you trace it back, an insect that has climbed up the food chain.

So start at the bottom. Plant the tree, grow the nettles, put away the spray, and let your garden be gently eaten. Tend the little things that run the world, and the larger, louder, more celebrated things will rise up on their backs all the way to the top

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Written by Helena Jevons, AKA The Urban Wildling. Helena spent the first 10 years of her career in 'big food' way before 'ultra processed' food was recognised as the issue it is now, and realised the way we create our food and nurture our land, wildlife and crops needed to change. She is a cultural geographer by training and her dissertation was on 'The cultural, ecological and economic impacts of the common agricultural policy of set aside'.


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