Starting in 1970, the Game & Wildlife Conservation Trust's (GWCT) ongoing Sussex Study is the world's longest running scientific study on the cereal ecosystem, providing a robust indication of the national picture. The data collected up until 2019 has shown that insect abundance declined by 37%.

It is unique in that it samples invertebrates on the same area of farmland, at the same time of year, using the same methods. It also maps changes in farming practices, such as cropping, field size, and pesticide use, which, together with climate change, are major drivers of variations in invertebrate abundance. 

As well as identifying the problem, the GWCT has used the results of the Sussex Study and other research projects to find practical solutions to conservation challenges. A new Guide to Insect-Rich Farmland Habitats published by the Trust details what measures farmers can take to increase invertebrate numbers, improving biodiversity while still remaining as productive as before.

During the period 1970-2019 a total of 4,757 samples containing 2.98million invertebrates were collected from cereal fields across the study area. A newly published scientific paper, analysing the results of sampling in this 50-year period, showed a drop in overall abundance of 37% with varying levels of decline in different invertebrate groups. Beneficial predators including ground beetles (-80%) and ladybirds (-78%) fell significantly and aphids, which are food for a wide range of invertebrates, dropped 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.

The results from 2020-2024 samples have yet to be analysed, but indications are that in the past four years invertebrate abundance has remained fairly constant on average.

Another key discovery was a decline of between 50-80% in several groups that provide food for farmland bird chicks. National data shows that since 1970 the UK has lost 73 million wild birds, and farmland species have shown the biggest overall decline of 60%. In the first few weeks of life many of these farmland species are dependent on insects including sawflies, ground beetles, and weevils, which in turn depend on arable flora in cereal fields.

Steve Moreby GWCT senior entomologist joined the Sussex Study team collecting and analysing samples in 1983, a role he continues to this day. He 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 with a knock-on effect on red-listed species such as partridge, skylark and yellowhammer."

'Farmers are not to blame'

The GWCT has worked with farmers and land managers to develop agri-environment scheme measures, including 30 out of 36 arable options currently available to farmers through the new ELM schemes. Creating and refining such schemes will be key to achieving national nature recovery on the 72% of the UK land mass which is farmed.

By following GWCT guidelines farms have shown they can double their songbird numbers and remain just as productive as before.

Dr Julie Ewald who co-authored the recently published peer-reviewed paper said: "We are grateful to the farmers in the study area for allowing us to survey their land over so many decades and they are keen to learn from the results of the research.

"Farmers cannot be blamed for the impact of the intensification of agriculture. Since the Second World War they have been tasked with producing more and cheaper food in a global marketplace against a backdrop of rising costs.

"The Sussex Study farmers have used agri-environment options such as conservation headlands and grass margins developed by GWCT creatively, and reduced their insecticide use in cereal crops. It is vital that the Government continues to properly fund these measures, so more farmers take them up."

GWCT has been at the forefront of the evolution of Integrated Pest Management (IPM), an approach which enables farmers to reduce pesticide use through a variety of measures including adopting more efficient methods of insecticide use and creating habitats for beneficial invertebrates like ladybirds and spiders, which prey on the species that damage crops. These options can reduce costs for the farmer delivering a win-win solution.

The new Guide to Insect-Rich Farmland Habitats, details the various agri-environment options available to farmers interested in increasing invertebrate populations on their land. Many of the measures are based on research by the Allerton Project, the GWCT's demonstration farm at Loddington in Leicestershire. Allerton Project director Alastair Leake said:

"The new guide is based on years of groundbreaking research by the GWCT. Here at the Allerton Project 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."