How to reverse insect decline and preserve food output

A new free guide for farmers has been produced by the Game and Wildlife Conservation Trust (GWCT), outlining the measures they can take to increase insect numbers and improve biodiversity, without damaging productivity.

The Guide to Insect-rich Farmland Habitats builds on the findings of the GWCT’s Sussex study – the world’s longest running scientific study of cereal ecosystems, having started in 1970.

See also: How arable farms can support farmland bird populations

Monitoring the same farmland, at the same time of year, using the same methods has revealed a 37% decline in insect abundance.

A newly published paper shows that, over 50 years, beneficial predators such as ground beetles and ladybirds dropped in number by about 80%, while aphids (which are a food source for many invertebrates), were down by 90%.

“There was no detectable change in the number of pollinators, but many groups, such as bees, are not normally associated with cereal fields,” says the report.

Farmland birds

A lack of insects is also blamed for a 60% decline in farmland bird numbers over the 1970-2020 period.

Steve Moreby, GWCT senior entomologist, said: “While we have seen a decrease in insecticide use in the past 15 years, herbicide usage continues to increase and this has resulted in a decline of what we call ‘chick food’ insects.”

The GWCT says that farmers are not to blame, as since the Second World War, they have been incentivised to intensify, to produce cheaper, more plentiful food.

But it is confident that, by engaging in agri-environment schemes and following advice contained in the new guide, farmers can reverse some of these trends without impacting food output.

Options

Sensitive crop rotation, growing pest-resistant varieties, selecting appropriate sites and sowing dates, and reduced tillage practices can all help.

Adopting more efficient methods of insecticide use and creating habitats for beneficial invertebrates like ladybirds and spiders through an integrated pest management approach are also recommended.

“These options can reduce costs for the farmer, delivering a win-win solution,” it says.

Many of the measures are based on research by the Allerton Project, the GWCT’s demonstration farm at Loddington in Leicestershire.

Its director Alastair Leake said: “Here, we have been able to show how simple management techniques such as beetle banks, hedgerow restoration, and pollinator mixes can reverse insect declines and increase farmland bird numbers, without affecting crop yields.”