Toxic pesticides in widespread use by farmers around the world are gradually killing neurons in the brains of bees and causing “slow death by poison”, scientists are warning.
Nicotine-based chemicals used to protect crops from insects could also be harming butterflies, hoverflies and other insects essential for pollinating flowers, they say – and could threaten food production.
The warning has prompted renewed calls by wildlife campaigners for the Scottish Government to impose a permanent ban on some pesticides. The pesticide industry, however, has insisted a ban would do “very little” to help bees.
Scientists from the University of Sydney in Australia and the French National Institute for Agricultural Research have investigated the dangers of neonicotinoid pesticides. They make up a quarter of the global insecticide market, and are used on potatoes, wheat, barley and oats in Scotland.
In an expert review in the latest issue of the scientific journal Bee World, Francisco Sánchez-Bayo and Nicolas Desneux point out that central European countries lost 25 per cent of their honeybee colonies between 1985 and 2005. In North America 59 per cent of colonies have gone over 60 years.
Neonicotinoids are amongst the most toxic pesticides on the market for bees, they argue. They bind to receptors in bee brain neurons, kill off the neurons and eventually kill the bees.
“It is literally a slow death by small but constant inputs of poison,” they say. The pesticides also weaken bees’ immune systems “leaving them defenseless against virus proliferation”, they argue.
Neonicotinoids seem to be “one of the main drivers behind the widespread propagation of parasites and diseases in the last two decades,” they continue. “These systemic insecticides are the ultimate cause of this complex crisis of honey bee health.”
The pesticides may also be endangering butterflies, hoverflies and other insects, the scientists conclude. “The impact that these systemic insecticides are having on the ecosystems built upon these myriad insects may thus compromise the sustainability of our agricultural production.”
The conclusions of this new report should make the Scottish Government think again about imposing a permanent ban. Dr Maggie Keegan, Scottish Wildlife Trust
According to Dr Penelope Whitehorn, a bee researcher at the University of Stirling, there was now a great deal of evidence that neonicotinoids were “at least in part” responsible for declines in wild and honeybee populations.
She said: “Studies have shown that the chemicals cause immune suppression in honeybees, a decreased ability to navigate and forage successfully in both honeybees and bumblebees and, crucially, a loss of reproductive success in bumblebees.”
The Scottish Wildlife Trust has been campaigning for years to get three neonicotinoids permanently banned from use in Scotland. The European Union has limited their application, but this has not stopped them from being used on several crops.
The trust’s head of policy, Dr Maggie Keegan, said: “The Scottish Government has told us that there is not enough evidence to know if the effects of neonicotinoids are strong enough to affect honeybee colony health, but the conclusions of this new report should make them think again about imposing a permanent ban.”
She was backed by Matt Shardlow, chief executive of the insect conservation group, Buglife. “There is good evidence that neonicotinoid and other pesticides severely damage the immune systems of honeybees,” he said.
“Most pollination is done by wild bees, moths and hoverflies that are also vulnerable to pesticides and disease. For the sake of the health of the countryside we would like to see a complete ban in Scotland.”
The Crop Protection Association, which represents pesticide manufacturers, argued that pesticides were just one of many factors that put pressure on pollinators. “For managed honeybees disease is by far and away the most significant problem,” said the association’s chief executive, Nick von Westenholz.
“Modern agriculture relies on crop protection products, such as insecticides, to maintain a safe and affordable supply of food. It also recognises that they are, by design, intended to control pests such as insects.”
He added: “Restricting the use of neonicotinoids without addressing the other factors affecting bee health will not only damage the ability of farmers to produce a healthy, sustainable crop, but will do very little to improve the viability of bee populations.”
Julian Little, a spokesman for Bayer, which makes neonicotinoids, dismissed the new review. “Blaming the nearest chemical might seem appropriate but it is often a big distraction from the real issue, in this case the lack of options for beekeepers to control the ever present danger of the Varroa mite,” he said.
The Scottish Government declined to comment on future plans because of the election.
The scientific review in full
A version of the article was published in the Sunday Herald on 17 April 2016.