Since December 2013 farmers have been unable to sow seeds treated with these active chemicals for crops known to attract bees and the European Food Safety Authority is now reviewing the risk that neonicotinoids pose.
Scientific consultants and farming leaders want decision makers to take a “holistic approach” to that assessment for a variety of reasons set out in a new study by Berlin-based scientific consultancy HFFA.
It found 17 separate studies and academic papers had documented a yield decrease in oilseed rape crops since the ban, in some cases by more than 20 per cent.
On average, yields are thought to be down by four per cent across the EU and in total the loss is estimated to amount to nearly one million tonnes a year.
The study found that the absence of the insecticides has meant smaller seeds and lower oil content, occurring on average in 6.3 per cent of the harvest volume and accounting for a price cut of 36.50 euros per affected ton.
Without the ban, another 912,000 tons of oilseed rape would have been produced in the EU each year - lost production the equivalent size of the crop produced in the whole of Romania.
The study claims that the annual revenue losses since the ban total around 400 million euros.
As well as causing “massive economic disruption”, Steffen Noleppa, the report’s author, said the environment was also being damaged, stating: “Banning neonicotinoids has increased global land conversion towards agricultural uses by 533,000 hectares.
“All this now agriculturally used land had sequestered carbon both above and below the ground before it was converted into farmland... consequently, a tremendous part of this carbon has been released into the atmosphere.”
More than 80 million tones of carbon dioxide equivalents have been released into the atmosphere as a result, he said - equal to what Austria emits in a year.
The vice president of the National Farmers’ Union, Guy Smith, said: “There is clear emerging evidence that farmers both in Britain and in the EU are finding it more difficult to grow profitable crops of oilseeds because of increasing insect damage to crops. This in effect is increasing the amount of oilseed and protein crop imports from other parts of the world such as the Americas, the Ukraine and Australia where neonicotonoids banned in the UK and the EU remain widely used. This gives farmers elsewhere in the world competitive advantage over home producers.”
Mr Smith wants evidence on the impact the neonicotinoids ban has had on pollinators, saying farmers are the first to want to understand the impacts their practices make.
“At the moment the evidence base is woefully lacking,” he said, adding: “If farmers continue to walk away from growing pollen rich crops such as oilseed rape then one of the victims will be bees who enjoy an early springfeed in farmed fields of gold.”
Mr Noleppa said all risks related to neonicotinoids need to be holistically assessed.