We often hear that insects are declining, and broadly there is good reason for concern. But as someone who works with crops and biological control, I always find myself asking a second question: which insects are we talking about?
Are we losing pollinators? The predators and parasitoids that help keep pests in check? Are crop pests declining as well? And what happens when an invasive insect arrives while some of our native species are struggling?
There isn’t one answer that fits every insect.
The UK’s pollinator indicator shows that bees and hoverflies have become less widespread overall. In 2024, their measured distribution was 23% below its 1980 level. That tells us something important about where these species are found, although it doesn’t mean there are exactly 23% fewer individual insects. Some species have expanded their range; more have contracted. (jncc.gov.uk)
We see a similar split with butterflies. Habitat specialists have declined substantially over the long term, while the overall trend for generalist species is much less clear. An insect that depends on particular plants or habitats may be far more vulnerable than one that can use a range of places. (jncc.gov.uk)
For me, the decline in beneficial insects matters just as much as the decline in pollinators. A hoverfly can pollinate flowers as an adult, while the larvae of many species feed on aphids. Ladybirds, ground beetles and other natural enemies also help control pests before we even notice there is a problem. Research into British invertebrates has found continuing declines across groups that include bees, hoverflies, ground beetles and ladybirds, particularly in intensively farmed landscapes. (ceh.ac.uk)
So what about the pests? Surely if insects are declining, aphids and other crop pests must be declining too?
It would be nice if it were that simple. Rothamsted’s long-running insect survey found a decline in larger moth catches between 1969 and 2016, but aphid catches told a different story: overall numbers were broadly stable, with considerable differences between species. More recently, AHDB has drawn attention to changes in aphid activity and the risk of earlier flights as the climate changes. That doesn’t mean every aphid species is increasing, or that every crop faces more damage. It means we cannot assume a general decline in insects will take care of pest pressure for us. (rothamsted.ac.uk, ahdb.org.uk)
There is another part of the picture: new arrivals. The yellow-legged hornet is an invasive predator of bees and other insects. Confirmed nests in the UK rose sharply in 2025, though the authorities have been finding and destroying them. Its presence is a reminder that an insect can become a growing concern here at the same time as other insects are declining. (gov.uk, aphascience.blog.gov.uk)
From a grower’s point of view, what matters is the balance within the crop and around it. If a pest can build quickly but its natural enemies are scarce or arrive too late, the crop can still suffer, even in a countryside with fewer insects overall. That is why I think we need to look beyond the headline and ask what is happening locally: which species are present, when do they appear, and what conditions are helping or hindering them?
This isn’t an argument to protect crop pests. It is an argument for paying closer attention. We need good monitoring, sensible decisions about when intervention is necessary, and habitats that give naturally occurring beneficial insects somewhere to feed, breed and survive between crops.
“Insects are declining” is an important warning. For practical crop management, the next question is the useful one: which insects are disappearing, which are holding their own, and which are becoming our next problem?