It’s sometimes easy to forget quite how much of the living world depends upon insects.

That might seem an odd thing for someone who has spent much of his career studying insects and their relationships with plants to say. But conservation, ecological research, and public interest are still disproportionately focused on vertebrates: the birds, mammals, reptiles, amphibians and fishes that most people think of when they hear the word “wildlife”.

Yet those animals exist within ecological networks in which insects are frequently central players, not walk-on extras. A new review that I’ve co-authored with Rob Cooke, Eliza Grames, Chris Elphick and 18 other colleagues, published in Nature Reviews Biodiversity, tries to bring together what we know about those relationships – if you follow this link it’s free to read:

Cooke, R., Grames, E.M., Ollerton, J. et al. (2026) The importance of insect biodiversity for vertebrates. Nature Reviews Biodiversity DOI: 10.1038/s44358-026-00201-w.

The starting point is food, and the numbers are striking. We assembled diet information for 19,750 species of terrestrial and freshwater vertebrates. Of those for which data are available, 73% eat invertebrates and 44% eat them exclusively. That alone ought to give us pause when thinking about the consequences of insect declines.

But one of the things that I particularly enjoyed about writing this review is exploring with colleagues how food is only the beginning of the story. All of us involved in it, I think, learned just as much as we contributed.

Much more than something to eat

The relationships between insects and vertebrates are extraordinarily varied, and some are wonderfully unexpected. Termite mounds and ant nests provide nesting sites, refuges and places to lay eggs for mammals, birds, reptiles and amphibians. Some bats use cavities created by beetle larvae. Birds incorporate insect and spider silk into their nests. Other birds deliberately nest close to wasps or ants, apparently gaining protection from predators.

Then there are the chemical relationships. Poison frogs obtain many of their defensive alkaloids from the insects and other arthropods that they eat. Some snakes acquire defensive toxins from fireflies. Birds, mammals, reptiles and amphibians engage in various forms of “anting” or anointing, applying ants and other invertebrates to their bodies, probably for a variety of functions including parasite control.

Insects can even provide sanitation services. Beetles remove vertebrate dung and can thereby reduce the survival of parasites, while moths living in the nests of some birds consume faeces and other organic debris. There is fossil evidence that similar relationships involving feather-feeding beetles occurred in dinosaur nests during the Cretaceous.

One of the figures in the paper brings together examples from around the world, and is worth spending some time exploring. There are chimpanzees applying insects to wounds, parrots nesting in termite mounds, geckos “milking” honeydew from planthoppers, frogs sheltering in ant nests, herons using insects as fishing bait, and much more. Ecological interactions are rarely dull!

Insects connect ecosystems

There is also a much bigger ecological story within this review, because insect relationships with vertebrates move enormous quantities of energy and nutrients through ecosystems. Aquatic insects emerge from streams and lakes and become food for terrestrial animals; terrestrial insects fall into rivers and feed fishes. In some forest birds, aquatic insects can provide more than a quarter of their energy budget, rising seasonally to 50–90%. Conversely, terrestrial invertebrates can provide approximately half of the annual energy budget of freshwater fishes.

And then there are the indirect effects. As readers of this blog will know, a lot of my research and writing is related to plant pollination, but insect pollination doesn’t just matter to plants. When an insect pollinates a plant whose fruits or seeds are subsequently eaten by a bird or mammal, the insect is indirectly supporting that vertebrate too.

One striking example concerns figs. Fig trees depend upon their tiny agaonid wasp pollinators, while figs themselves are eaten by at least 1,274 species of birds and mammals. Remove the wasps and the consequences potentially propagate far beyond the insects and plants themselves.

This is something I’ve discussed from a different direction in my book Birds & Flowers, where the focus is largely on birds as pollinators rather than insects supporting birds, though all nectar-feeding birds also consume insects. But the broader lesson is the same: species do not exist independently of the ecological relationships that sustain them. I’ve written previously about some of the extraordinary diversity of these pollination relationships on this blog, including in my post on the limits to pollinator diversity.

What happens if the insects disappear?

This brings us to the more difficult question addressed by the review. There is now substantial evidence that insect abundance, biomass and diversity are changing, although, as I’ve argued on this blog before, the magnitude, geography and taxonomic extent of those changes need to be discussed carefully rather than reduced to simplistic claims of an impending “insect apocalypse”.

Nevertheless, widespread changes in insect populations inevitably raise the question of what happens to the vertebrates that depend upon them. Here the evidence becomes surprisingly patchy.

There are good reasons to expect effects: a meta-analysis of 125 studies, for example, found strong positive relationships between insect prey availability and bird reproductive success and chick condition. European insectivorous birds declined by 13% between 1990 and 2015 while omnivorous bird populations remained stable. There are also examples involving bats, small mammals and other groups.

But demonstrating that declining insects actually caused a particular vertebrate population to decline is much harder. Insects and vertebrates can respond simultaneously to habitat destruction, pesticides, climate change and other pressures, making cause and effect difficult to disentangle.

That’s an important distinction. Ecology is full of plausible stories; demonstrating the causal links is another matter. There are nevertheless cases where dependence on particular insects is difficult to ignore. The Critically Endangered Mountain Pygmy Possum in Australia depends heavily on Bogong Moths, whose numbers have crashed. The probable extinction of the Eskimo Curlew has likewise been linked partly to the disappearance of the Rocky Mountain Locust, formerly an important component of its diet.

A surprisingly large gap in our knowledge

Perhaps the thing that surprised me most while working on this review was how poorly documented many insect–vertebrate interactions remain. Even something as apparently straightforward as “what insects does this bird eat?” often turns out not to have a satisfactory answer. Studies may report prey simply as “invertebrates”, “arthropods”, or “insects”, with little or no taxonomic resolution. Birds are much better studied than most other vertebrates, yet detailed quantitative diet information is still available for only a small fraction of species.

Non-feeding relationships are even more scattered through the literature. This is part of what ecologists call the “Eltonian Shortfall“: our incomplete knowledge of who interacts with whom in nature.

One conclusion of the review is therefore that we need much better ways of recording these interactions: common data standards, better taxonomic resolution, long-term monitoring, experiments, larger databases, and greater collaboration between entomologists and vertebrate ecologists. Citizen science, computer vision, metabarcoding and environmental DNA all have potentially important roles to play.

There is also a plea here for something rather unfashionable: natural history. Observations of animals eating, nesting, sheltering, grooming and otherwise interacting with insects are not trivial anecdotes. Properly documented and brought together, they are the raw material from which larger ecological patterns emerge.

Conserving relationships, not just species

For me, one of the broader messages from this review is that conservation needs to pay much more attention to what I’ve referred to in the past as the “biodiversity of species interactions“.

We naturally talk about conserving species and habitats. But an ecosystem is not merely a list of species occupying the same place. It is also the vast network of feeding, pollination, seed dispersal, decomposition, competition, parasitism, facilitation and other interactions connecting those species.

Lose enough of those connections and an ecosystem can change profoundly even before many species have disappeared. That has a very practical implication: insect conservation is also vertebrate conservation. If we want landscapes that support healthy populations of birds, bats, amphibians, fishes and other vertebrates, maintaining abundant and diverse insect communities is not an optional extra. It is part of the ecological infrastructure upon which those animals depend. And, as our review makes abundantly clear, we have probably only begun to understand the full extent of that dependence. That’s why nature conservation policies and regulations, such as Biodiversity Net Gain (BNG) in England for instance, need to look carefully at their implications for insects and other invertebrates.

Finally, I’d like to thank all of the contributors to this paper for working so diligently on the review. It’s an output from the Vertebrates and Insects Working Group, which was formed by the Status of Insects Research Coordination Network – check out the website and get involved!