Two new bee papers were published just a few days ago. Below I will take a closer look at one of them, the larger European study, partly funded by pesticide companies but performed by an independent research lab, and it was was aimed to be a more comprehensive test of neonicotinoids. The other one was five month field study in Canada, completed with a year-long lab study where they observed some negative health effects under field-similar but constant exposure conditions, especially when combined with a fungicide. More about the Canadian study can be read in an analysis by The Mad Virologist.
The European study went on for two years in three countries, spanning over 33 sites. A whooping 88 variables were measured (different health measures, different bees, etc). but only eight of them came out with a statistically significant difference. Three variables actually showed a significant beneficial correlation between neonicotinoid treatments and bee health, whereas five correlated with more harmful results. However, 18 results had to be dismissed altogether because the Varroa mite killed off many UK hives. But the study did not choose to track disease rates as variables.
This Arstechnica piece by a long time biology researcher gives a succinct coverage of these science news (which are reflected in all kinds of headlines in the media already): Study paints a confusing picture of how insecticides are affecting bees:
a team of independent researchers purportedly tied neonicotinoids to bee colony health. But a quick look at the underlying data shows that the situation is far more complex. And a second paper, with more robust results, supports the idea that these insecticides are merely one of a number of factors contributing to bees’ problems
The researchers themselves indeed put their results in a rather peculiar way. They say their study supports the harmful effects of neonicotinoids, but in ‘a country-specific way’. As they found statistically significant beneficial effects mainly in Germany (though one was in the UK), they argue that this may be explained by other factors, because the bees were found to be in generally better health in Germany. For UK and Hungary, however, where bee pests were more of a problem, and the sources of nutrition were more limited, they say the five significant findings can be interpreted as an interaction-effect of neonicotinoids. They write:
The country-specific responses of honey bees and bumble bees strongly suggest that the effects of neonicotinoids are a product of interacting factors (20–23). This study has identified between-country differences in the use of oilseed rape crop as a forage resource for bees (affecting exposure to crop residues) and incidence of disease within hives. Both factors were higher for Hungarian and U.K. honey bees (tables S10 and S11).
The study presents the presence of neonicotinoid treatment significantly correlating with a negative effect on worker numbers (UK), storage cell number (UK, clothiadinin), and one species of wild bee drone numbers (UK), as well as egg cells (Hungary) and worker numbers (Hungary).
Whereas they also find that neonicotinoid treatments significantly correlate with egg cells (Germany), drone numbers (Germany) and storage cells (UK, thiametoxam) but in a positive direction.
So in UK, storage cell numbers were diminished by clothiadinin but boosted by thiametoxam…? Sounds peculiar. At what point would a beneficial correlation also suggest a causative relationship? When measuring correlations, it is good to be watchful for factors that may either have no real connection, or have a more complicated relationship than a simple cause and effect – as en example, both may follow from another variable so they correlate without a causal relationship with regard to each other.
What seems problematic in the logic of the authors, is that if the three observed beneficial effects can be considered the result of factors other than neonicotinoids, then the same could be said about the five cases where they detected harmful effects. If you consider that significant effects in either direction represent a very minor portion of the results, it seems like an awful lot of weight is being put on these five out of 88 findings.
A look at the raw data
The small number of findings becomes particularly clear when we look at the summary of all the measured endpoints – raw data which for some reason was not included in the supplemental material of the study, but was released from the study’s partial funder, Syngenta, instead. The inclusion of the total data table in this piece in Slate is quite illuminating: Do Neonics Hurt Bees? Researchers and the Media Say Yes. The Data Do Not. Light green cells show no significant difference between beehives near treated fields and controls, red cells point to a significant difference for the worse, and dark green shows the beneficial correlations (my apologies to the red-green colour-blind, I don’t have the original so can’t change the colours easily).
Out of these 258 data points, only 9 were negative and 7 were positive, 3.5 and 2.7 % of cases respectively. Four colonies gave no data (I assume these cells are for the colonies where controls and treatment groups were wiped out by Varroa mites and diseases). Almost all negative data points came from clothianidin (7 of 9), whereas thiametoxam had 6 out of the 7 positive findings, and two negative findings. If these results truly are to be taken as suggestive of causation, should we take them to mean thiametoxam treatment is beneficial for bees? Somehow I wouldn’t be ready to easily assign such predictive power to these results one way or another, when so many data points found no difference at all.
The inconsistency is also problematic if you consider statistics of bee health and winter losses in general, which are the product of many factors, several not tracked by this study, and that show great variability. The scientists themselves hint at as much in their supplemental materials:
Other potential covariates showed strong systematic variation with either country or seed treatment and as such could not be directly tested within this framework without violated underlying model assumptions (e.g. the proportion of oilseed rape making up the diet of pollen (Table S10), disease (Table S11) and starting colony size (Table S2)).
Bee losses are known to vary a great deal across countries and years in Europe. From the COLOSS bee surveillance project on 2015 and 2016 numbers:
These loss rates vary considerably between countries. In this year’s survey the highest losses were found in Ireland and Northern Ireland, followed by Wales and Spain. The pattern of loss rates differs from last year, when higher mortality and loss rates were found in central Europe and countries to the east. This year the higher loss rates tend to be in the west and northern countries, although Spain had high rates of loss in both years.
The losses have generally been lower in Europe than in the US in the last decade or so, and a recent Pan-European epidemiological study found that honey bee colony survival depended on beekeeper education and disease control – it was first and foremost hobby beekeepers who had trouble with epidemics, whereas professional beekeepers in Europe had very little problems with diseases and Varroa (more on that in my piece: Treatment-free beekeepers give Varroa mite free rein). It is unfortunate, in this context, that the study lost entire colonies to Varroa, and it raises questions about the presence of diseases in the study colonies in general.
As a side note, the partial ban of neonicotinoids by the European Commission on three chemicals: clothianidin, imidacloprid and thiamethoxam, came in effect December 2013 and as such, would have been unlikely to have had even a potential effect on the statistics above before winter 2014-2015. The scope of the suspension only applied to “the treatment of seeds or soils for crops that are attractive to bees (except greenhouse crops and winter cereals) and the spraying of crops that attract the pollinators (except post-flowering and greenhouse crops).”
UPDATE: The Mad Virologist confirms in his analysis what I also suspected, but did not quite dare to point out without reading up on statistical corrections when measuring so many variables at once: it is a serious statistical flaw not to make the appropriate corrections. Without them, random findings will pop up as significant. He writes:
This looks like the type of result you would see if there were false positives in the study from not correcting for multiple comparisons. Because of the lack of correction for multiple comparisons, which is commonly done in cases even when the measurements are semi-independent, we can’t draw conclusions from the statistical tests that were run for this data set.
More questions – what is the role of fungicides?
Another factor with regard to the European study, pointed out by a piece by pollinator researcher David Pattemore, is an inconsistency in the fungicide applied together with the neonicotinoids at different sites. From More evidence on the effects of neonicotinoids on honey bees…maybe?:
But all three treatments (the control and the two different neonicotinoid treatments), had different fungicide treatments applied with them, violating the basic scientific rule to control all variables apart from the one you are interested in, or at least account for these other variables. This study, unfortunately, has confounded neonicotinoid treatment with fungicide treatment, so it is not really possible to draw many conclusions on neonicotinoids alone. So my personal opinion is that the effect on honey bees in this study is ambiguous at best.
He also puts these studies in the context of earlier research:
So in terms of the number of studies evaluating the hypothesis that real-world use of neonicotinoids have colony-level effects on honey bees, the score in my calculation now stands at 2 for, 4 against. This is how science proceeds: we are likely to continue to see scientific tussles back and forth while we narrow in on the actual suite of factors that affect honey bee health.
While many headlines have hurried to report on these studies as a confirmation of neonicotinoids’ role in bee health, several news outlets have also handled the topic with admirable nuance. Consider this Washington Post headline: Controversial pesticides may threaten queen bees. Alternatives could be worse. Insecticides are indeed likely to have some negative effects on bees , even though it is hard to pinpoint the realistic degree of the effect. Nevertheless, what is clear is that we can’t properly address bee problems if we ignore the larger issues of pests, disease, and habitat loss. From the Washington Post piece:
The differences between bees in treated or untreated fields were largely insignificant, and many of the bees in both groups died before they could be counted.
Christopher Cutler, who studies insect toxicology at Nova Scotia’s Dalhousie University, echoed Carreck’s concerns, pointing out that “when many different analyses are conducted” (42 in this case), “a small number of statistically significant effects are bound to emerge by chance.
An approach popular with activists would be to ban neonicotinoids altogether, but many experts worry this would cause farmers to turn to older and potentially more harmful methods of pest control. “Things are better for honey bees since neonics replaced more harmful insecticides,” said beekeeper and science blogger Randy Oliver.
In other words: if you care about bees, look past neonicotinoids. No, we should not ignore their effects, we should welcome more solid research, and we should definitely try to find optimal ways of using them with minimal harm to non-target insects, while maximizing their effect in helping keep down resource use like land, fuel, and other inputs, that goes into growing crops.
The European partial ban, based on the information so far, might have even had some net negative effects for the environment: some farmers are simply narrowing their rotation to crops that are not as sensitive to the relevant pests. From Foodinsight:
Yields are down and the area sown is falling as some farmers are switching to other crops because they do not want to take the risk. This means rapeseed is being dropped from crop rotations which has a negative environmental impact,” Max Schulman, of Copa & Cocega said.
It is great to get more research about the effects of neonicotinoids. But what about the effects of other pesticides? Before we jump into a ban, we should compare the situation to the alternatives. What realistic solutions do farmers have? How would those alternatives affect the health of bees, other non-target insects, carbon emissions, soil health, or any number of other important factors? In the words of the agricultural researcher Andrew Kniss, Everything in Agriculture is a Trade-Off.
More of my articles on the the topic of Environment and Agriculture. If you would like to have a discussion in the comments below, please take note of my Commenting policy. Sometimes it may take some time before I find the time to sort through and accept comments, especially if they make long arguments without evidence. In a nutshell:
- Be respectful.
- Back up your claims with evidence.
It is unclear whether only corellations were established or differences between means. In the latter case what were the effect sizes? And how was error rate controlled/adjusted considerin the large number of tests?
The authors state this (it’s in the Supp materials): “We did not apply Bonferroni corrections as the lack of independence for the majority of the response variables (e.g. different life stages of honey bee) meant that there was no valid level for the correction.”
A lame explanation, IMO, but they did consider it. Effect sizes for some (not all) responses were shown in a figure.
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Thanks for the detailed and thoughtful post. I have been writing on this topic, too, for many years. The various players are pretty firmly entrenched in their positions and beliefs. Somehow, middle ground has to be found.
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Middle ground? What is the middle ground here? Would it be to take equivocal evidence and suggest somehow that it is not equivocal? Some of the players are not firmly entrenched, they are following the evidence and are properly interpreting the data. The opinions of those players should be considered and those who see only see more grist for their advocacy mill should be ignored.
The risk is unclear and not large but this does not need to be an excuse for inaction. There are issues: use in OSR and cereals in the UK only generates a response on around 20% of occasions – but that response pays for the excess treatment. In contrast, the chance of a return in sugar beet is around 60% of occasions. Does it matter? Perhaps since increased use means that the chance of resistance developing is increased and there is at least some environmental damage (the jury is out on how much). I understand that in UK conditions neonicotinoids break down in the soil more slowly than anticipated so annual use is to be avoided if there is a risk of leakage or damage.
But we can do more. Our pesticide approval scheme can be improved. The easiest solution would be to make establishment of a complementary pollen nectar barrier or refuge area part of the condition of use so that even the slight risk is minimised and might even be enhanced. This might also help reduce risk of resistance by ensuring a genetically diverse insect population. Of greater benefit to the industry would be a policy of limiting supply, and auctioning that available, so those growers most at risk paid the most and there was value applied to those developing better risk assessments. This could not have been done even 10 years ago – it is now easy to implement.
A ban is not sound. Universal use is not sound. Peter Borst is correct
Julian Little from Bayer was spot on in ‘Country File’ when he said that the industry needs to identify the reasons for the variation in order to improve use. And Guy Smith of the NFU gave his support for the value of pollen and nectar mixes. Both intelligent responses looking towards something more than the status quo.
So …. Where is this raw data? I didn’t see a link either here or in the Slate piece.
It is from a researcher at Syngenta. Also presented at a talk according to Henry Miller: “Here’s what this mass of data looks like laid out in a matrix that was provided to the public by Dr. Campbell during his talk.”
Work done in the US, published earlier this year, showed that despite Ag chemicals, bees did better in farmland than elsewhere.
Sixteen honey bee (Apis mellifera L.) colonies were placed in four different agricultural landscapes to study the effects of agricultural landscape and exposure to pesticides on honey bee health. Colonies were located in three different agricultural areas with varying levels of agricultural intensity (AG areas) and one nonagricultural area (NAG area).
Colony weight and brood production were significantly greater in AG areas compared to the NAG area. Better colony thermoregulation in AG areas’ colonies was also observed. The quantities of pesticides measured in the trapped pollen were relatively low compared to their acute toxicity. Our study indicates that agricultural crops provide a valuable resource for honey bee colonies, but there is a trade-off with an increased risk of exposure to pesticides.
In conclusion, honey bee colonies foraging in moderate and high AG areas were clearly able to grow faster and to a larger size as a result of better access to sustainable nutrition sources than bees foraging in NAG area and a low AG area with urban activity.
Agricultural Landscape and Pesticide Effects on Honey Bee (Hymenoptera: Apidae) Biological Traits
Journal of Economic Entomology, 2017, 1–13
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Thanks! I read about the study, but didn’t include it yet in my collection of bee articles. Nice of you to post about it.
I wish people would understand that human habitation and grassy lawns are also a major factor in habitat loss for bees, and having large fields of flowering crops is an important source of nutrition (optimally with a mix of wild habitats near with plants of different timing of flowering as well), and that these agricultural sources of nutrition appear quite rarely to be a threat to bees due to pesticides. Another example of recent research, discussed in my earlier bee health article:
“Although neonicotinoid insecticide residues were detectable, the amounts were substantially smaller than levels shown in other studies to not have effects on honey bee colonies. The WSU researchers referenced 13 studies to identify no observable adverse effect concentrations for bee populations, which they used to perform a risk assessment based on detected residues.”
Appreciate your input!
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The study I referenced hits home with me, since I have about 20 beehives and they are in a non-agriculture landscape. All the honey and pollen comes from natural forage; wildflowers and flowering trees. Honey production is extremely unpredictable and varied. The most reliable source of nectar is Japanese knotweed, an invasive weed.
Most commercial honey producers move their bees to agriculture areas where honey producing crops are grown. These are things like alfalfa, clover, canola, etc. The role of pesticides in these crops is to control plant pests, which means without controlling pests, the production of these crops would not be profitable and * they would not get planted *. The growers would plant something else, like corn, which is useless for bees.
The idea that moving bees into natural areas is better for them depends entirely on what is growing in those natural areas. If it is predominantly forest or grassland, it may provide very little to sustain bees or other pollinators. Finally, many of the best sources of nectar and pollen are in fact invasive weeds. That’s one of the reasons they are so successful.
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Is this study publicly available?
I’m afraid it’s paywalled. https://doi.org/10.1093/jee/tox111
Press release here:
“The study, “Agricultural Landscape and Pesticide Effects on Honey Bee Biological Traits,” which was published in a recent issue of the Journal of Economic Entomology, evaluated the impacts of row-crop agriculture, including the traditional use of pesticides, on honey bee health. Results indicated that hive health was positively correlated to the presence of agriculture. According to the study, colonies in a non-agricultural area struggled to find adequate food resources and produced fewer offspring.” https://ag.tennessee.edu/news/Pages/NR-2017-05-AgGoodForBees.aspx
It’s pay-walled. I have access through my employment at Cornell University.
thanks – the press release will have to suffice
For those new to the subject there is a good primer and plenty of references to primary studies at http://rspb.royalsocietypublishing.org/content/royprsb/281/1786/20140558.full.pdf
The important thing is not just a Trump exclamation of fake news but to realise that the evidence is mixed. Habitat loss and varroa are clearly more of a problem for bees and pollinators but the extra burden can be reduced without agronomic loss it is worthwhile trying. For farmers the risk of developing resistance, as is almost universal for pyrethroid insecticides, through greater use than necessary is a worthwhile action. . UK use is on cereals and sugar beet neither of which are renowned for their supply of pollen and nectar but there is at least some evidence of uptake through neighbouring margins as a result of soil persistence. Long term studies such as the Buzz project have demonstrated that environmental enhancement is relatively straightforward to achieve.
Yes, aiming for the minimum necessary pesticide use is absolutely a worthwhile goal, and as far as I understand, exposure to many pyrethroids is potentially a bigger threat to bees than neonicotinoids. Reducing pesticide use is not only a good idea because of pollinators – there are also input costs (monetary and emission-wise), fuel use, farmer health hazards, etc, to consider. Europe has been behind US generally in reductions of pesticide use, and France, for instance, is the top pesticide user in EU. I most certainly hope that they could reduce their pesticide use without compromising yields, and there is at least one recent paper that suggests as much (for insecticides, specifically).
You’ve kindled my curiosity, what kind of environmental enhancement might you be referring to?
The EU v USA for pesticide use will keep you going for a long time. The trouble is that our climate tends to be wetter than most of the US in the summer, and our winter mild, so pests and disease levels are high. Our interval between harvest and planting wheat or canola is about 2 months so carry over of pest and particularly disease is almost inevitable despite being grown in rotation. Wheat yield is not generally limited by say moisture or temperature but by disease and pest so return on pesticide investment is high.
One big problem is that the cost of insecticides is well below that of herbicides or fungicides and the economically correct action is to spray routinely and make no attempt to develop better risk systems (the cost of developing them and any residual risk would result in a very small cost saving if any). Acceptability is a legitimate – treated eyes shut we use neonicotinoids in situations where we are only expecting a return in about 20% of occasions used -BUT that return pays for the other four occasions. I make no value judgement and can supply no cost for any collateral affects.
I have not checked but suspect EU pesticide per tonne of wheat is probably less than the US. It is probably also true that 8000 years of growing wheat has a legacy in terms of pest and disease. We have no major pests in maize (corn). However, without doubt glyphosate tolerant crops would reduce our pesticide use particularly in sugar beet – but as far as I know even in the US there is no commercial glyphosate tolerant wheat – our major crop.
The UK environment is relative fragile compared with many countries because we do not have much in the way of large areas of wilderness so rely on a fairly integrated farm and environmental habitat.
Pyrethroids can certainly be damaging to bees although they lack persistence and now don’t effectively control aphids or even cabbage stem flea beetle any more. I must agree that the focus on neonicotinoids has meant that the collateral damage of pyrethroids is even less understood . We have weeds, diseases and insects that are no longer controlled by our established crop protection materials. Loss of effective active agreements is one of our biggest threats and we are doing very little to minimise the risk of loss – but we could do a lot more with more imagination.
The Buzz project was largely organised by Syngenta and really was the first replicated work in this country looking in detail at arthropod numbers (CEH and Defra were also collaborators). It even resulted in an increase in particular bumble bee species that had been in decline. https://data.gov.uk/harvest/gemini-object/beef5f7c-5a84-4cf1-bfc3-a260e21fb4ae. I could probably find the detailed papers if my arm were twisted. However, I leave you to decide how important loss of wildlife is…
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This may be of interest
Worth listening to http://www.bbc.co.uk/programmes/b08wmk5x for both sides. It does look to me as though there is some deliberate misunderstanding of statistical analysis (and perhaps an over strong introductory sentence to the paper). Bayer remain correct- more understanding of the circumstances is needed. Neither unfettered use or zero use is supported by the data
Unfettered use, I believe, has never had supporters, however.
Very limited fettering is argued quite strongly!
I was under the impression that the label strictly directs use so as to avoid contact with pollinators… surely people do not argue against that?
This is why the issue is complex. We are discussing seed treatments and until recently virtually all crops could be treated and wheat and canola (our major crops by area) were almost universally treated. These crops are planted between August – November and canola flowers at least 6 months after sowing, and wheat is not insect pollinated, so there should be a very low risk to pollinators (they can also be used on spring planted crops with a short interval and still believed to be safe). However, i) the cost was so low that it was economically worth deskilling and treating all crops with many producing a return on only about 20% occasions used (the return in those years paid back enough to cover the other years) 2) There is at least some evidence that use in this way builds up residues in soil (the break down in the laboratory appears faster and more consistent than in the field in our specific conditions). Similarly there is some trials work showing neighbouring vegetation and water course become contaminated with the seed treatment at low but arguable lethal levels 3) The risk of the pest developing resistance is enhanced. There is a sequence of unforeseen circumstances.
The legislators and users do aim to protect pollinators but knowledge is imperfect and just occasionally the system fails. I have in the past used herbicides (e.g. a sulphonyl urea) that were approved but subsequently found to have a longer residual life than had been believed killing the following crop. The herbicide was withdrawn almost immediately (arguable an over reaction and effort should have been expended looking into identifying the circumstance). We ALL occasionally get things wrong, and better to accept this than ban anything new, albeit with a sensible assessment of whether risk is contained and rectifiable if the unforeseen happened. But we should try to improve knowledge to reduce risk rather than protect the status quo.
To me, having followed it up and delved more deeply, the CEH work appears more robust than the Syngenta interpretation – it is statistically. No one is saying that there is decimation, and there are clearly a number of interrelated factors. I would still argue that Bayer are correct – we need to put more effort into identifying those circumstances when there is a risk so the pesticide can be used most effectively with least collateral damage. We know that wheat is vastly more damaging to pollinators than a flower rich meadow and we are prepared to accept this damage.
Hi – quite many statements that on the face of it seem hard to reconcile with my past experience. Do you have references? Is there an integrated evaluation available anywhere?
Did they really perform power analysis for all the variables in the study?
I dont remember having seen a detailed design plan – are the replicates true replicates?
Are other possible influential factors the same for all experimental units eg varroa, nosema etc.
Why not contact the authors? (I bore all sorts of authors silly with incessant questions) The paper is not a small or lightweight study. As you know the elements you describe were considered significant factors (as well) and not held constant. These confounding factors were taken into account in the design. It did after all cost £2.8m, probably more than any other party has invested in a study on the subject.
The binomial (increase or decrease) reported in the coloured table above is not legitimate analysis since data is lost. The paper (as against some of the reporting) does not condemn neonicotinoids and reports a mixed result but with some significant impacts and relationships with the factors you mention. There is no impact in the German trials (and as stated a positive impact initially) although not the case in the UK and Hungary. However, I understand OSR pollen was a small proportion of the diet in Germany begging the question of what were the other feed sources at that time of year. (I am trying to find out (back to boring authors with questions). I suspect that OSR is a very positive influence on bees providing a threshold of contaminant is not exceeded but this might prove nonsense).
As far as I can tell the authors do not have an agenda (hence the involvement of Syngenta and Bayer and the supply of the detailed data to them). I suspect other less professional researchers would have been more selective in the information supplied to those selling the product but I suppose there maybe some sort of Machiavellian double bluff. Bayer and CEH appear more or less in agreement -i.e. let’s find the situations when damage is minimal so we can continue use.
It is I believe clear that the impact over all trials is small but negative in some situations. Varroa, for example, is far more important. However just because it is small does not mean we should not try to be more targeted in our use – if for no other reason than reducing the risk of resistance to this important group developing.
Simon – Thanks for elaborating. Rather than debating with the authors I prefer a critical dialogue with competent readers. Based on previous experience: whether or not power analysis was performed (for all variables) I think that when testing such a large number of variables a number of significant results are bound to appear spuriously. Some significant effects are indeed seen – both positive and negative in almost the same number. This needs to be detailed explained as other than spurious cases of significance. I am not in a position to pay for access to the study hence my questions to people who have.
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Rather annoyingly just lost my work so a shortened version (perhaps just as well).
To summarise this paper is a good start: http://pubs.acs.org/doi/pdf/10.1021/acs.est.5b03459. I am sceptical of anything connected with Professor Goulson (he has made, or been reported to have made, some seriously unscientific and unjustifiable statements in the main stream press) but I spoke to the lead author and I am convinced as far as I can be that the trial is sound. Just because someone has an agenda does not necessarily mean that the trials are not sound. I also saw the following while looking for above which looked worth a glance: https://www.sussex.ac.uk/webteam/gateway/file.php?name=goulson-2013-jae.pdf&site=411. See also the summary and references in the Royal Society paper along way above.
As you will know healthy pollinators and diverse food sources are the way to remove the negative impacts.
My agenda is to maintain use and effectiveness of all pesticides through better use with a decision made on the appropriate balance (wheat production is damaging for pollinators but rather necessary). I do not think it is reasonable or even possible for farmers to do this working individually. I have considerable experience of pesticide trials and agronomic practice in the UK. Feel free to ask if you would like detail of any of the other points.
just discovered the Pingback above:
Highly interesting and relevant to this discussion.
What is a Pingback by the way?
Pingback is a link to another (wordpress) blog that has linked to the piece above. Re: your earlier questions, sorry I am on a holiday and only respond sporadically.
The Power analysis they present in the supplemental material appears to be a sort of analysis of each country and its blocks separately. Several entomologists have remarked on the problems with the number of measurements and the small number of significant results (or even results significant in any one direction) or the lack of consistent effects – one would preferably expect for a pattern to emerge from the data.
What they say about their power analysis in the supplements:
Figures S2A-C presents a power analysis used to assess the capacity of the experimental design to detect overall additive neonicotinoid seed treatment effects that were consistent across all countries (i.e. y ~ seed treatment + block/country). Figure A
(honey bee response metrics recorded during the oilseed rape flowering period), B (honey bee population metrics following the overwinter period) and C (wild bee population metrics) provides the power (1-β) of the experimental design to detect effect size
reductions from 7 – 50 % under different levels of replication (3, 4, 5, 10 or 20 replicate blocks within each country). To perform the power analysis we simulated data to determine how the number of replicate blocks within each country (where a block
represents a control, clothianidin and thiamethoxam treated site) affects the power (1-β) of the study to detect a given effect size difference between the control and a single neonicotinoid seed treatment. This reflects the key experimental goal of identifying
consistent cross-country effects of neonicotinoid seed treatments. To perform the power analysis we used a simple country only null model to derived estimates for univariate distributions, e.g. mean and standard deviation for normal distribution or theta for
Negative binomial. From this we simulated data sets where effect size difference was altered between the control and a single neonicotinoid seed treatment. This was done by generating random outcomes from either a negative binomial, normal or binomial
distribution depending on the response variable (Table S4 and S5). For each combination of effect size and number of blocks 10,000 simulations were run. Power (1-β) was defined to be the proportion of these simulations (for each effect size and block number
combination) that had a probability of detecting an additive seed treatment effect.”
They have figures for distributions, adding one note from figure text: “These data provide the power (1-β) of the experimental design to detect effect size reductions from 7 – 50 % under different levels of replication (3, 4, 5, 10 or 20 replicate blocks within each country).” It does not appear to me that they looked at the power taking the entire study setting into consideration as a whole. I believe there are statistical ways to correct for this (Bonferroni and others), but they choose not to.
You might also be interested in the reddit Ask Me Anything with the study author, where they seem quite evasive and make rather convoluted arguments against any corrections for the large number of measurements as a response to my question, making strange parallels to correcting for whole journal-fulls of data or entire research careers… Here: https://www.reddit.com/r/science/comments/6me05a/science_ama_series_hi_reddit_im_richard_pywell/
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