Prof. Lynn Dicks has had her hands in the soil for almost thirty years – and she has watched it slowly being stripped of invertebrate life.
“I have seen the decline in my lifetime,” said Dicks, professor of ecology at the University of Cambridge. She knows from the data: “The data we have on long-term trends in insect abundance over time shows that the decline is on average about 1% per year.
But she also sees it every day. “There are fewer insects flying around. If you leave the window open at night and the lights on, you won’t be flooded with it like you used to.”
Dicks has spent her life trying to find out exactly why Britain’s insect populations are plummeting before it is too late to prevent species from being lost forever. And the use of pesticides – the pesticides that farmers have been using on crops for decades – is one of the key factors.
While farming groups say the weight of pesticides used in Britain has halved since 1990, scientists and campaign groups say this is not an accurate measure of chemical use. This is because the types of chemicals used have become more toxic and the area treated with pesticides has increased.
Pesticide Action Network says some modern pesticides are 10,000 times more toxic than DDT, a notoriously harmful chemical that was banned because of its impact on human health and the environment.
And we still don’t know what effects these cocktails of chemicals have on insect ecosystems, says Nick Mole, policy officer at Pesticide Action Network UK. “Hundreds of different pesticides are used to grow food in Britain. As a result, pesticides appear in millions of different combinations and in varying concentrations across our landscape. However, safety assessments are only conducted for one chemical at a time. There is little to no understanding of how these pesticides interact with each other and affect soil, water and biodiversity. Much more research is needed to fully understand this.”
Dicks said: “The wild insects are exposed to a very wide range of pesticides during their lives. And it’s fungicides, herbicides, molluscs, insecticides, a whole cocktail of different things. In fact, a recent European study on bumblebees shows that there are on average eight different chemicals in the pollen stores collected by bumblebees, and up to 27 different pesticides are collected.”
Governments also don’t legislate for combinations of toxic chemicals, she explains, adding: “We don’t really know how this affects insects on a larger scale. I would say it affects them. In that European study on bumblebees, they were able to measure exposure. They call this pesticide risk, but it’s actually a measure of exposure to pesticides weighted by their toxicity. That measure predicted the number of bumblebee queens that could be produced, the number of bees in the colonies and the way the colonies lived. grew. In fact, the most exposed colonies produced 47% fewer queens than the least exposed colonies.”
The State of Nature report, conducted in 2023, showed that insect numbers were declining. “Pollinating insects (bees, hoverflies and moths), which play a crucial role in food production, have shown an average decline in distribution of 18% since 1970. Crop pest predators (ants, carabids, rove and ladybirds, hoverflies, dragonflies and wasps) showed an average reduction in distribution of 34%”.
Max Barclay, the curator of beetles at the Natural History Museum in London, said he had also noticed a decline: “I examined horse manure over the weekend in Sussex and found it was completely devoid of dung beetles and their larvae and was simply lying around.” . in its original form on the pasture for weeks instead of being broken down in the ground. This has potential long-term consequences for soil health and fertility. I never experienced intact piles of manure everywhere in a pasture when I started doing beetle research in the 1980s and 1990s, but now it is an everyday occurrence.”
He said the pesticides used in livestock farming are decimating beetle populations: “Ivermectin and related dewormers routinely used on sheep, cattle and horses can have a devastating effect on the dung beetle fauna, which are important for recycling nutrients in the soil and by their entrenchment. for soil aeration.”
And unlike crop pesticides, the problem is getting worse and dewormers are being used more often. “Ivermectin has been available since the 1970s, but recently there has been a cultural change from deworming animals when necessary to administering regular deworming doses regardless of whether there is evidence of worms. This means that the manure and pasture are permanently contaminated with toxic chemicals.”
Ali Karley, Jenni Stockan and Cathy Hawes, an agroecologist, an invertebrate specialist and an ecologist working on arable biodiversity at the James Hutton Institute respectively, said they had also noticed the beetle’s decline.
They said: “From our Environmental Change Network data at our Glensaugh research farm, a hill farm in the north east of Scotland, we have seen a reduction of around 70% in ground beetle abundance over 30 years, although this number varies depending on the habitat. The largest declines are seen in heathlands and the smallest in grasslands.”
They said pesticide use can be reduced with a technique known as integrated pest management, which “attempts to use natural predators or parasites to control pests, with selective pesticides used only as a backup if pests are not available.” can be combated naturally. It is important to take an integrated approach to enable pesticide reduction without increasing risk.”
Some farmers are already doing this. Dicks said she was optimistic about the future, as many farmers will stop using insecticides.
“I’m quite optimistic that we can change and that we can reduce the use of pesticides on all our agricultural lands,” she said. a positive effect of that transition on insects in the real environment.”