In my opinion, 2017 will be crunch time for pollinators. In Europe, since December 2013 we have had a moratorium on the use of three types of neonicotinoid insecticides (neonics). A report by European Food Safety Authority (EFSA) scientists due at the end of January 2017, could roll back this ban. The evidence for the damage caused by neonics is controversial. While environmental groups are hopeful that the ban will be made permanent, the agrochemical industry and many in the farming lobby, want to see these products once again made available for general use. While it would be beyond the scope of this short blog entry to review all the evidence concerning the decline of bees, which incidentally is paralleled by declines in the populations of many others insects, I do think it worthwhile pointing out the reasons why the continued use of neonics is such a controversial subject.
I spent many years conducting ‘experiments’ and for seven years I worked on honeybee neurobiology with a view to better understanding the structure and function of their nervous systems. In general, where possible, one sets up experiments to deliver a binary answer. Science deals very effectively with rather simple questions. For example, it can establish that a certain dose of an insecticide will kill 50% of the insects to which it is applied (the so-called LD50). Before elaborating the problems with such a simplistic approach where neonics are concerned, let’s briefly look at just how toxic these compounds are to bees. The results of experiments in which honeybees are fed and dosed through contact with neonics vary a bit due to things like genetic differences or slight methodological variations in the way experiments are carried out. That said, the following statement is roughly correct: neonics kill individual bees when they are dosed with between a few nanograms (ng – 0.000000001 of a gram) and a few tens of nanograms. To put those figures in perspective 1 gram of clothianidin (one type of neonic), if applied uniformly to a population of honeybees will kill 150 million bees. The weight of clothianidin manufactured each year is many, many tonnes. A little calculation shows that the estimated world population of European honeybees (the kind mostly used for honey production) live in ~1 billion hives, both domesticated and wild, with 10,000-50,000 bees/hive – this is 10-50 trillion bees. So, my ‘fun’ calculation shows that between 100 and 300 kilos of this neonic could kill every honeybee in the world. However, the calculation I have just done is truly stupid – fortunately, there is no way that the clothianidin could be spread in such a way as to wipe out bees and the regulation and mode of its use, prevent such catastrophic outcomes. Anyway, it isn’t the dead bees that result from LD50 tests that I want to talk about. What happens to the ones that survive?
LD50 tests are so compelling because they can be carried out in a research laboratory and they are dead simple – no pun intended. You count up the dead bees a fixed time after dosing them. Those that are alive are just that – alive. However, consider a human parallel; suppose volunteers could be found who could be dosed with Sarin (a nerve agent closely related to carbamate inecticides) – once we have cleared away the dead bodies we could subject the survivors to more subtle tests concerning their physical and mental health. It would be pretty surprising not to find that the survivors were in a bad way. We could scale down the dose of Sarin so that everyone survived but I suspect that no one would be surprised to discover that even quite small doses, perhaps a tiny fraction of the LD50, caused long-lasting, measureable impairments. I suppose the most extraordinary thing is that those experiments with Sarin really were conducted! It was done in a controlled fashion at Porton Down (they still managed to kill one poor chap), and in an uncontrolled way during the Iran/Iraq war, and most recently during a terrorist attack on the Tokyo subway. Lasting consequences to those exposed included memory loss, asthenia, sleep disorders and cardiovascular effects – the longest lasting effect was of course, death. Back to the bees.
So, if bees are exposed to sub-lethal levels of neonics we should not be surprised to be able to discover some subtle changes to their behaviour and physiology and that is ‘the rub’. Bayer and Syngenta, the main manufacturers of neonicotinoid insecticides, do not argue the presence of neonics in the bodies of honeybees, nor how toxic these agents are, they dispute that the levels involved have any effect on the survival of those bees and their hives. When insecticides are licensed, the manufacturer carries out detailed experiments to determine whether or not their products can safely be used in the field. However, most of these experiments are simple binary tests like the LD50 tests but may extend to showing that non-target insect species accumulate only a small fraction of the LD50 for their compound. They can’t easily, and did not measure, if they effect things like direction finding, communication between individual bees, drone sperm counts etc. Nor can they, or do they, look at how sub-lethal doses interact with other pressures on bee survival such as other agrochemicals, climate change, parasites etc. It is entirely possible to imagine that in the absence of other pressures, tiny doses of neonics would not affect hive survival while in their presence the same dose could tip the balance. Fortunately, in the interregnum between the ban and now, a number of field studies have been concluded that show that field-realistic concentrations of neonics contribute to the demise of both honey and wild bees and also affect other animals. There is not room to go into all the research papers here but an indication of what they show can be gleaned by reading recent reports from the American EPA (Environmental Protection Agency) and EASAC (European Academies Science Advisory Council).
New research highlights the unsatisfactory nature of the experimental techniques employed during the safety testing of insecticides and other agrochemicals. If we go on with the current regime we will undoubtedly encounter other serious problems. Indeed, we already have, both antibiotics and now, antifungal agents, are being rendered useless through their careless application in agriculture. The agrochemical and pharmaceutical companies do not want us to adopt the precautionary principle. However, if we do not, we will see many other examples of chemicals that turn out to damage our environment. It isn’t simply because the experiments to examine safety are flawed, but also because of pressure to increase the profits of agrochemical companies through the advocacy of blanket/prophylactic application. I am not against the use of insecticides or other biocides in farming, but we should use as little of them as possible and then only when other, less damaging technologies, have not worked. It isn’t simply the effects on the animals and plants that we share the planet with that worries me, but also the fact that we are throwing away the long term potential of so many agrochemicals and pharmaceuticals to do good. I hope that the EFSA report in January 2017 maintains the ban on the use of neonicotinoids in all but the most extreme of circumstances. However, I remain concerned that farmers may make use of those rules that allow exceptional use, to use them when they are not really required. As ever these issues have unexpected outcomes, and I am thus also worried that farming will have turned to older alternatives to the neonicotinoids, such as pyrethroid insecticides, which could prove just as, or even more, damaging! More on this another time!