The regulatory system for pesticides - which does not take into account sublethal effects, chronic effects, or simultaneous exposure to multiple pesticides and other stressors - is woefully inadequate in capturing what actually happens in the real world.
In spring 2012, my postdoc Penelope Whitehorn and I published a paper in Science on the effects of neonicotinoid pesticides on bumblebee colonies.
It appeared to show that field-realistic doses of these chemicals, such as bees would be exposed to if they fed on a treated oilseed rape crop, are enough to cause greatly reduced colony growth and an 85% drop in production of new queens.
The work appeared alongside another paper from a French group showing that exposure to the same chemicals impaired honeybee navigation, possibly leading to colony collapse if sufficient worker bees became lost.
This was our first foray into the world of pesticide research, and at the time we naively had no idea of the bumpy ride ahead of us. These chemicals are the world's most widely used insecticides, with global annual sales worth about $3 billion, and their manufacturers did not like what we were saying.
Our research, alongside the French study, both of which built on a background of much previous work, suggested that neonicotinoids had somehow got through the regulatory process without the threat they posed to bees being properly evaluated.
The EU asked the European Food Safety Authority to conduct a review of their safety, and six months later in January 2013 EFSA announced their findings: neonicotinoids pose "an unacceptable risk" to bees.
Against ferocious lobbying, a European moratorium
As a direct result of EFSA's findings, a moratorium on the use of neonicotinoids was proposed, and approved by the European Parliament. There was fierce lobbying against the moratorium, a lot of spurious criticism of the science, and wild claims that crop yields would plummet without neonicotinoids.
The UK government voted against the moratorium, with the then-Secretary of State for the Environment, Owen Patterson, pledging his support to Syngenta, a Swiss company that manufactures neonicotinoids. Nonetheless in April 2013 the moratorium was voted through, and it came into effect in December 2013, for two years.
It prohibits the use of three commonly used neonicotinoids on flowering crops such as oilseed rape, or the sowing of treated seeds during the spring or summer, when bees are foraging.
But it allows the continued use of neonicotinoids on crops such as winter wheat, on horticultural crops, in gardens, and on domestic pets - if you have a dog or cat, you probably apply drops of neonicotinoids to the back of its neck to kill its fleas.
At some point soon a decision will need to be taken as to whether the moratorium should continue, or be allowed to lapse. Considerably more scientific evidence has accumulated to inform this decision.
And yes, they really do harm bees - wild bees most of all
A number of new studies on bumblebees suggest that field-realistic doses of neonicotinoids adversely affect fecundity, mortality, pollen collection, susceptibility to disease, and overall colony performance, corroborating our 2012 study.
The evidence for honeybees is less clear, with the agrochemical industry having funded some field trials that have failed to find negative effects at the colony level, generating yet more controversy as to whether it is appropriate for industry to fund and/or conduct its own studies of the safety of its products.
Perhaps the best study so far, performed by Maj Rundlöf and her team in Sweden and recently published in Nature, is a large one year field study comparing the effects on solitary bees (Osmia), bumblebees and honeybees of being near a flowering field of treated or untreated oilseed rape.
The honeybees were not significantly affected, but the bumblebee colonies fared poorly and produced few queens when next to treated fields, just as we had found. The solitary bees showed zero reproduction next to treated fields.
It thus seems that wild bees, and particularly solitary bees, may be much more strongly affected than domestic honeybees.
Pesticide regulation is woefully inadequate
One point that is widely agreed among scientists is that the current regulatory system for pesticides - which does not take into account sublethal effects, chronic effects, or simultaneous exposure to multiple pesticides and other stressors - is woefully inadequate in capturing what actually happens to organisms in the real world.
More broadly, new work suggests that bees may be the canary in the coal mine, and that the environmental impacts of neonicotinoids go far beyond bees - the pesticides accumulate and persist in soils for many years, routinely turn up in freshwater systems, and are also found in wild plants growing in field margins.
Aquatic insects, insectivorous birds, and butterfly declines have all now been linked to neonicotinoid pollution, as described in a major series of reviews on the subject published by a large group of scientists in Environmental Science & Pollution Research in 2014.
This view is independently supported by a recent report from the European Academy of Sciences (2015). These broader issues should be of deep concern to all of us. I for one very much hope that the current moratorium is not allowed to lapse.
One might well ask, have bee populations improved since the moratorium came into effect? Unfortunately, there is at present no systematic monitoring of wild bee populations, so we do not know the answer.
Monitoring wild pollinators at a nationwide scale in challenging, and one of the most promising ways forwards is to enlist the aid of the public in collecting data. I am involved in a new initiative, The Buzz Club, that will be attempting to do just that - if you are interested in taking part, please register your interest.
All ages are welcome (including school groups), and no previous experience is needed.
The only real answer - a whole new model of food production?
Even if we did have good data on how our bees are doing, my guess is that it is too soon to expect a positive effect of the moratorium: neonicotinoids are highly persistent in the environment, and quite a lot are still being used, so it would be very surprising if bee health had significantly improved.
In any case, those of us who study bees are agreed that bees face many problems, of which neonicotinoids are just one. There are few flowers, new bee diseases and parasites have invaded from abroad, and they are exposed to cocktails of many different pesticides throughout their lives.
We need to work on improving all of these things if we want to ensure healthy, diverse population of wild pollinators.
The neonicoitinoids and bees debate has raised some broader issues about food production and sustainability. How do we feed people without wiping much biodiversity from the planet, degrading soils and polluting natural habitats?
Is the current model of food production, based on intensive monocultures dependent on very high levels of agrochemical inputs - and, in the EU, on enormous subsidies from the taxpayer - the best way forwards?
Bees epitomise this debate: if modern farmland cannot sustain bees, can it really sustain us in the long term?
Action: Join the Buzz Club - as first step, register your interest.
Dave Goulson is Professor of Biological Sciences at the University of Sussex. He has spent the last 20 years studying bumblebees, and has published over 200 scientific articles on their biology. He founded the Bumblebee Conservation Trust in 2006. A Sting in the Tale was published by Jonathan Cape in 2013 and was shortlisted for the Samuel Johnson Prize.