The European Academies Science Advisory Council (EASAC)は、イミダクロリプドなどのネオニコチノイド系農薬が、花粉を媒介する昆虫の生態や生物多様性に悪影響を及ぼすとの報告書をまとめました。この件に関する、海外専門家のコメントをお送りします。
Neonicotinoids: European Science Academies call for debate that expands beyond bees
Dr Christopher Connolly
Reader in Neuroscience, University of Dundee and Member of the Expert Assessment Group for Pollinator Conservation Delivery Group (Cambridge)
“This report is a very interesting assessment of the issues surrounding the need for, and risks from, neonicotinoids. Of course, further evidence has accumulated since the cut-off date (January 2015) for this report. Importantly, one of these tracks field-relevant dietary exposure of neonicotinoids (2.5 parts per billion) into the brain, where damaging levels are reached within 3 days and impairs colony growth in field experiments (Moffat 2015).
“Of particular importance, this report highlights the enormous commercial value of beneficial insects (annually €153 billion for insect pollination and another €100 billion for natural pest control services). So it is not a choice between economics and the environment. Insects more than pay their way!
“The report makes the excellent point that prophylactic use of neonicotinoids is inconsistent with the basic principles of integrated pest management. This is important as it is not possible to consider the risk/benefit of a compound as both the risk and benefit is unknown. Therefore, no scientific assessment of the value is possible.
“The variability of honeybee colony losses by country is interesting, but the fact is that losses are higher in areas of intensive agriculture, where the pesticide load is high and native forage is low. It is not possible to answer whether this is an association with neonicotinoids as we use hundreds of chemicals in agriculture. Although EU regulations demand their use is recorded, the UK government does not collect this information. Therefore, we cannot learn from any past mistakes. There are also clear impacts from lack of habitat and changing weather. This makes a ‘model’ field experiment impossible to extrapolate to all field conditions.
“Although fair balance is achieved, the report fails to emphasise the importance of laboratory studies that can prove a causal relationship. In contrast, field studies are only realistic to the actual environment tested. Whilst neither lab nor field studies are field realistic to all situations, lab studies can prove that X does Y. In contrast, field studies do not know what the complexity of the environment is (which chemicals/diseases are present and how good the natural forage is). For example, well-nourished insects would be stronger and more able to withstand stress. In contrast, insects weakened by disease or other chemicals may be more vulnerable. Moreover, when bees are removed to pristine locations after a ‘field trial’ this destroys the argument for being field-realistic. In field trials, bees are places on the experimental site for a limited period (say during the flowering of Oil Seed Rape). Before and afterwards, the bees are kept in perfect conditions, away from pesticides. Therefore, healthy bees are exposed transiently. In a real arable environment, the bees would have to cope with limited wild forage and exposure to many pesticides throughout the trial. The outcome will only be the same in both scenarios if the toxic effects are fast acting or permanent. Chronic effects are unlikely to be detected. The problem is that in a real environment, you can’t distinguish between the test compound and all other variables that might contribute to the effect. A realistic field experiment can’t be done unless the scale is enormous. Most insects cannot escape the complex challenges of intensive agriculture (high pesticide load and low natural forage).
“Laboratory studies tell us how to conduct field trials. Bees must be challenged when foraging if the deficits caused by neonicotinoids are to be revealed and this must be included in future studies. Bees struggle to forage efficiently when exposed to neonicotinoids because they can’t learn to associate floral scent with food reward (nectar and pollen) and so become poor foragers of the pollen required to feed their brood. Slowly the colony weakens. As stated in this report the effects are likely to be more extreme in small colonies (e.g. bumblebees) or solitary insects. Sadly, the report does not highlight the fact that the field trials are not realistic. Currently, bees are not challenged to perform in the difficult intensively farmed arable areas but are whisked away to pristine habitats to recover from a transient exposure to neonicotinoids. Real bees can’t escape their arable environment, where prolonged neonicotinoid exposure and a depleted landscape is a permanent life style forced on them.
“A point that seems to have been missed in this report is that collectively, laboratory and semi-field studies demonstrate a connected strength of knowledge: field-relevant doses of neonicotinoids reach the bee brain and cause dysfunction in the bee learning centre, impairing the ability for bees to learn and foraging in the field, leading to reduced colony growth. Together, the message is strong and clear, current neonicotinoid use is not safe for the beneficial insects we need.”
Dr Peter Campbell
Senior Environmental Specialist: Head of Product Safety Research Collaborations, Syngenta
“This is a highly selective and biased view of the published literature reviewed, similar to the frequently cited IUCN (Worldwide Integrated Assessment) Systemic Pesticides Task Force Reviews, which some believe to be a deliberate anti-neonicotinoid campaign rather than a balanced review of the literature: http://www.forbes.com/sites/paulrodgers/2014/12/04/leaked-memo-raises-questions-about-pesticide-ban/.
“Whilst this report starts off by pointing out quite elegantly the limitations of laboratory versus field-based evidence it then goes on to virtually completely disregard all the published field evidence. For example, even though it references field studies such as our PLOS One Field study on Cruiser treated Oil Seed Rape (Pilling et al 2013), the more recent Clothianadin treated Canola field study (Cutler et al 2014) and also the balanced review of the neonicotinoid literature carried out by Godfray et al 2014, it does not actually describe or significantly discuss the results of those studies but instead either quotes rather minor points or dismisses the results entirely.
“The report claims that the neonicotinoid mode of action involves irreversible binding at target site, which may result in cumulative and long term effects being likely and of concern. However, this review ignores other published papers (e.g. Maus & Nauen, 2010; Kimura-Kuroda et al, 2012 and Lopez & Fernandez-Bolanus 2011) that show that target site binding in both insects and vertebrates in in fact reversible and thus contradicts what is being proposed.
“The authors report long soil-persistence values of neonicotinoids. However, most of these values are taken from laboratory conditions where persistence of neonics is much longer than from studies carried out under field realistic conditions. In addition, this report quotes the wrong laboratory half-life for thiamethoxam (i.e. 3001 days) which was an error in the original Goulson 2013 reference and was subsequently corrected by the journal to the correct value of 301 days. Again, no mention is made of the referenced Pilling et al 2013 field study, which investigated potential soil-persistence under field conditions and reported no elevation or accumulation of pollen and nectar residues from succeeding treated crops in rotation. An additional problem with this report is that it continually groups the neonicotinoids together (e.g. in their conclusions and calls for policy action) even though their own data (e.g. the soil DT50 degradation data mentioned earlier) show them to be quite different in certain areas of their environmental profile.
“For soil persistence, birds, aquatic and predator of pest sections, these are heavily reliant on the unbalanced IUCN (WIA) review papers with only a very small number of new papers which all suffer from either unrealistic exposure or are correlative approach (no causative evidence!) studies. No recognition is given to the large volume of regulatory studies and risk assessments that have been conducted in these areas and submitted to regulatory authorities for assessment, prior to getting an approval. Also where there is a published rebuttal paper challenging the IUCN (WIA) review paper conclusions e.g. Vijver & van der Brink, 2014 who challenged the Van Dijk et al 2013 IUCN/WIA aquatic review paper, this is not referenced.
The report also claims there were 21 neonicotinoid-related bee poisoning incidents reported in the UK Wild Life Incident Investigation Scheme in 2012. However, none of these were confirmed as due to the approved agricultural use of the products concerned. In fact later in the report, when pointing out that honeybees are not a good model for assessing safety to other pollinator species, the report actually admits that honeybee colonies are probably not affected due to the strong buffering capacity of such colonies.
“In its call for policy action against the neonicotinoids, this report states that prophylactic use of neonicotinoid seed treatments directly contravenes the principles of Integrated Pest Management (IPM). However, for some crops e.g. Oil Seed Rape, you cannot use a typical IPM pest threshold approach for flea beetles or aphid virus vectors since once a farmer has identified the pest in his crop it is too late and the damage is done. For example, the Oil Seed Rape establishment damages reported this year, following the neonicotinoid ban, were substantial (>50%) in some English counties and in also in Germany. Also for Oil Seed Rape flea beetle attacks, it is not possible for a farmer to predict where the pest pressure is going to be high, therefore a seed treatment is the best option. Furthermore, for protecting other crops e.g. maize from soil-borne pests such as corn root worm, seed treatments are by far the most effective way of achieving control and protecting yields. So seed treatments are absolutely a key tool for the farmer within IPM. This report then challenges the need/efficacy of neonicotinoid seed treatments e.g. using both a US EPA Soya Bean Statement and the rather biased IUCN (WIA) associated review by Simon-Delso et al 2015, but gives no reference to a much more detailed review of the value of soya seed treatment technology reported in an AgInformatics report, which rebutted this EPA statement with a much more substantial data evidence base.
“Considering this was meant to be an ecosystem service approach, no analysis of the environmental impact of alternative pesticides is carried out as a comparison and the key question would be whether any pesticide (and certainly any insecticide) could meet the standards being used in this report to call for policy action against the neonicotinoids (i.e. ignoring field data and using laboratory or unrealistic exposure based data on which to make conclusions).”
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