Can banning neonicotinoids bee the solution?
Just last week, the European Commission put a two-year ban on the use of neonicotinoids, the most widely used pesticide group in the world. From December, farmers will be unable to buy or sow treated seeds for crops that entice bees. The ban is precautionary; meaning that over the next two years, additional research will be conducted to determine its efficacy and it could well be lifted if deemed ineffective.
It is estimated that 35% of crops cultivated globally depend on pollinators such as honeybees and bumblebees. We therefore rely heavily on the service that these humble insects provide. However, this also means bees are in close contact with many of our insecticide-treated crops. Unlike many other pesticides which are sprayed onto the plant itself, neonicotinoids are sprayed directly onto the seed. Acting systemically, they diffuse throughout the tissues as the plants develop, resulting in trace quantities being detectable even at the pollen and nectar level.
Neonicotinoids are neuro-active pesticides. They resemble the shape of nicotine, which resembles the shape of a chemical found in the nervous system of both mammals and insects called acetylcholine (ACh). Both ACh and neonicotinoids bind to a spot positioned at the end of nerves called the nicotine acetylcholine receptor (nAChR). Cognitive functions such as learning and memory rely on signals being passed between neurons. This passing of signals is facilitated by ACh and detected by the nAChR. However, because the neonicotinoid is also such a good fit for the nAChR, it can activate the system under false pretences, creating excitatory neurotransmission throughout the nervous system at a level that could be dangerous to bees. Hence, many cognitive functions may be disrupted by prolonged or repeat exposure to neonicotinoids, leading to a loss in learning and memory as well as decreased colony cohesion.
Whilst the ban has generally been celebrated by conservation groups, it has been heavily criticised by crop protection groups and farmers. Pesticides are important in the intensive farming techniques many farmers rely on, and since banning three classes of neonicotinoids is unlikely to turn many farmers organic, this may result in the increased use of older and more toxic pesticides. Bee decline is likely to be due to a collection of issues such as disease, deterioration of habitat and a lack of foraging in addition to pesticide use, so it is important we do not lose sight of these other issues in light of the ban.