HomeNatureGuest blog – New paper, same old… – Mark Avery

Guest blog – New paper, same old… – Mark Avery

Dominic Woodfield is the Managing Director of Bioscan, a long established and well-respected consultancy specialising in applied ecology.

He is a life-long birder, a specialist in botany, habitat restoration and creation and in protected fauna including bats, herpetofauna and other species. He is also a highly experienced practitioner in Environmental Impact Assessment and Habitats Regulations Assessment. Most of his work is for the development sector, but he has also undertaken commissions for Natural England, the RSPB, Wildlife Trusts and campaign groups. He once mounted an independent legal challenge in defence of an important site for butterflies in Bicester, Oxfordshire, which resulted in planning permission for a five-hundred unit housing development being overturned. He lives in Oxford with his partner and family.

Breeding Bird Survey (BBS) data, badger culls, Natural England and the British Trust for Ornithology: New paper, same old.

Most readers would, I imagine, concur that an increase in fox populations in places where there are vulnerable ground nesting waders and waterfowl might be a matter worthy of conservation concern and attention. Especially where such increases are substantial (as much as a doubling of numbers), and arise as a consequence of a specific controllable human intervention, such as culling up to 95% of badgers across large swathes of English countryside.

Natural England (NE), which issues the licences to cull badgers, is obliged by statute to assess the potential side effects of badger culling on other species. When it comes to designated sites – SACs, SPAs, Ramsar Sites and SSSIs – NE do (now) acknowledge that a ‘predator release’ effect (where foxes and other mammalian predators increase in number via backfilling the ecological niche vacated by culled badgers) is an impact risk. Under pressure from legal challenges since 2017, NE has developed detailed guidelines for such assessments, amended their assessment procedures and added restrictions onto licences to better take this risk into account and/or mitigate potential effects on such sites. But outside these sites and across the larger part of the countryside in cull zones, the same birds, as far as NE are concerned, are on their own. There are no procedures for assessment or protection.

The small group within NE that processes and issues cull licences describes the ecological risks associated with ‘predator release effect’ as a consequence of badger culling as “theoretical”. This is despite their being flagged as a risk worthy of further investigation in the wake of the Randomised Badger Culling Trial (RBCT) in 2007 (Defra 2007) and again in 2011 (Fera 2011). This loose end did not trouble the masterminds behind the current badger cull, which commenced in 2013, nor those responsible for cull licensing within NE. At least it didn’t until relatively recently. Ultimately, it took the pressure of tribunals and legal challenge and the scrutiny of the courts in 2018, five years after the cull had started and with tens of thousands of badgers already removed, to force the agency charged with protecting our wildlife to finally promise a High Court judge they’d look more closely at this issue.

It’s conceivable that NE then asked the Government, through Defra, to fund a proper study and the Government refused. We don’t know. But in any event the outcome was that instead of a properly designed and controlled investigation, NE elected to go ‘cheap and cheerful’. Behind a wall of secrecy, they commissioned the British Trust for Ornithology (BTO) to conduct a simple desk study, extracting subsets of volunteer data from the Breeding Birds Survey (BBS) for cull and non-cull areas, and comparing them to see if there were any patterns to be found that might be attributable to badger removal. When, in 2018, the BTO unsurprisingly reported to NE that nothing conclusive could be gotten from such a coarse approach (Kettel and Siriwardena 2018), NE chose to interpret that as indicative that there was no issue to be concerned about, and advised Ministers and the Courts the same.

This is all old news of course, especially for readers of my previous guest blog, kindly published by Mark on 18th June (see here). In it I criticised the methodology and utility of these desk-top analyses of BBS data, the secrecy around them, and how NE’s chosen ‘absence of evidence is evidence of absence’ interpretation was used to inform badger culling policy decisions at Government level, without the benefit of such ‘science’ being through independent peer review or subject to any public scrutiny.

One of the BTO scientists involved was piqued into responding (his remarks can be found in the comments section under the blog, again here). Amongst a somewhat prickly defence of the study’s approach and methodology, he conceded two of the central premises underpinning mine and others’ concerns. One: that the study did little to answer questions about the wider ecological side effects of removing as much as 95% of the population of an apex predator across large areas of English countryside. And two:  that ecological side-effects from removing badgers from the ecosystem were, to use his word, “certain”. Notwithstanding what those two concessions, when read together, say about the worth of this form of study, he said that he stood by it and furthermore that the BTO had been commissioned to repeat it in 2022.

The results of this repeat exercise have just been published in the Journal of Zoology. The paper is titled Ward et al. 2022 “Breeding bird population trends during 2013-2019 inside and outside of European badger control areas in England”. The abstract can be accessed here (but the full paper is behind a paywall). I encourage interested minds to read the full thing. Does it represent a robust way of finding out whether localised predator increases as a consequence of removal of badgers are having any impact on local populations of sensitive ground nesting species, such as lapwing, redshank, snipe or curlew?

My own thoughts on this question are below. Ward et al. 2022 essentially repeats the exercise carried out in 2018 and modified in Kettel et al. 2021, albeit with a slightly bigger data input. For me, the biggest difference is a much-improved discussion. Indeed, anyone who read my previous blog will observe that despite neither myself or any of the other more vocal critics of the 2021 paper (and its suppressed 2018 predecessor) being part of the peer review process, the discussion within the new paper rather reads as if we were! It attempts, at least, to respond directly to some of the criticisms of the methodology of analysis, the utility of the results and the inherent problems of bias, that were levelled at both Kettel et al. 2021 and Kettel and Siriwardena 2018.

In consequence, the authors are now more openly cognisant of the fact that studies this coarse-grained, data-limited and with such little statistical power, are never likely to detect impacts anything short of catastrophic for any individual bird species. It now also appears to be recognised by the authors that this sort of high-level approach inherently militates against the prospect of arriving at any conclusive answers to the fundamental question – is badger culling having a collateral ecological effect of relevance in conservation terms on any individual bird species?

All of which means NE have frittered away a further four years and paid the BTO an unknown quantity of public money to conclude, as Ward et al. 2022 does, that it’s not clear whether there is an effect or not and that answering the question would need better, more targeted investigation. The same conclusion reached fifteen years ago following the RBCT, again by Fera in 2011 and further reiterated by the Godfray Review of 2018 (Godfray et al. 2018). That a proper study is necessary and important. Not exactly revelatory – indeed it is no more than critics of NE’s lackadaisical approach to assessing the collateral ecological impacts from badger culling have been urging for years.

Although the authors’ discussion of the results in Ward et al. 2022 is an improvement on previous iterations, the continued application of a flawed methodological approach renders the study only marginally less worthless than its predecessors. The 2022 version remains, in particular, compromised by the decision to lump species at high risk of predation effects together with those at inherently lower risk, and by the inescapable fact that the BBS dataset is too coarse grained to provide a sufficient platform for sensible analysis for precisely the scarcer species – such as ground nesting waders – that should be a focus of concern. Instead, and in common with its 2018 and 2021 predecessors, the study contrives an ecologically nonsensical guild of “ground nesting” species on the basis of a single common parameter – that they construct nests generally within 0.5m of the ground. Thus, ecologically disparate species such as chiffchaff, herring gull and coot are homogenised into a single receptor with a standardised susceptibility to mammalian predation. The continued failure of the authors to properly explain, qualify or acknowledge the deficiencies of this approach is glaring. They either genuinely believe that vulnerable species such as lapwing, nesting on the ground, in open uncluttered environments such as arable fields, are at the same risk of predation from larger mammalian predators as a whitethroat in a bramble thicket, or they are wilfully building a massive source of obfuscation and bias into the methodology. Either way, it muddies the waters and fatally undermines the study.

Sadly, predetermined bias is not just restricted to the methodological design. It also infects the syntax of the discussion and conclusions of the paper. Most glaring perhaps is the abstract – the bit one can read for free – concluding with a wholly unsupported premise – that “this predator removal has not affected bird populations”. That might be the conclusion the authors from Natural England (and Defra) wish casual readers to take from the study, but for those who read the full paper, it’s not actually a conclusion supported by the analyses. I am surprised this statement survived the peer review process and that the BTO authors (at least) would allow such an unevidenced leap of logic. In contrast, the all-important last line of the conclusions calling for a landscape-scale quasi-experimental approach: “to provide stronger inference about the complex potential ecological effects of culling predators such as the badger” didn’t make it into the abstract. Strange that.

So, beyond the authors’ clearer acknowledgement of the fundamental limitations of the exercise, Ward et al. 2022 merely perpetuates the uncertainty that has presided over this question since the end of the Randomised Badger Control Trial, fifteen years ago. In other words, it does nothing to progress Defra’s, the Secretary of State’s, Natural England’s, conservationists or the wider public’s understanding of collateral ecological effects from badger culling any further forward from the position prior to the current cull starting in 2013. At all the junctures in time cited above, independent review has indicated that further investigation into the ecological side effects from badger culling was merited. All NE have actually done in the wake of their promise to a High Court judge in 2018 is commission a spectacularly coarse analysis which was never likely to deliver anything close to a useful answer, suppress the results for three years and now repeat it. A cynic might conclude that this is deliberate – a means to be seen to be doing something in the face of repeated legal challenges that exposed systemic failures by NE to properly assess impacts – whilst actually kicking the can down the road.

There is one paragraph worthy of note in the discussion of the results. Despite the continued determination of the authors to muddy the waters by casting the analytical net to include species of inherent low-vulnerability to predation by ground-based mammalian predators – such as nuthatch and green woodpecker (really, guys?), the authors do for the first time note and discuss separately the negative trends indicated for two of the species which actually ought to be the critical focus – lapwing and curlew. It is worthy of remark, at least, that such trends as there are for these species appear more or less consistently negative across all three iterations of BTO analysis. Finally, this has been remarked upon in Ward et al 2022. The problem of course is that this potential cause for concern should have triggered further targeted investigation – along the lines that the paper now suggests – much, much earlier. Not now, nearly ten years too late.

Repeating a near-pointless study again and again is, in my view, a poorly disguised exercise in obfuscation and delay. An excuse to do nothing more meaningful, just in case that gives you an awkward answer. But don’t listen to my cynicism and take my word for it. Read Ward et al. 2022 and ask yourself whether this is valuable and robust science being commissioned by Natural England and/or a good use of the time and resources of the BTO and of the data that it receives from volunteers. Do you think this type of data analysis exercise has any conceivable prospect of determining whether curlew in Somerset, redshank in Gloucestershire or stone curlew in Wiltshire are experiencing increased predation pressure as a consequence of badger removal? Do you agree with NE that ‘absence of evidence is evidence of absence’? Or alternatively, ‘if you can’t see the wood for the trees, it means there is no wood’.

References: Defra (2007) The ecological consequences of removing badgers from the ecosystem. Defra Project Report ZF0531. (http://webarchive.nationalarchives.gov.uk/20071104143302/http://www.defra.gov.uk/animalh/tb/research/summary/zf0531.htm.) Food and Environment Research Agency (Fera) (2011). Evaluation of the Potential Consequences for Wildlife of a Badger Control Policy in England. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/182478/badger-control-consequences.pdf Professor Sir Charles Godfray FRS (Chair); Professor Christl Donnelly FRS; Professor Glyn Hewinson; Professor Michael winter OBE; Professor James Wood. (October 2018) Bovine TB strategy review. Report to Rt Hon Michael Gove MP, Secretary of State, Defra. https://www.gov.uk/government/news/review-of-governments-bovine-tb-strategy-published Esther F. Kettel, Ivan Lakin, Matthew J. Heydon & Gavin M. Siriwardena (2020) A comparison of breeding bird populations inside and outside of European Badger Meles meles control areas, Bird Study, 67:3, 279-291, DOI: https://www.tandfonline.com/doi/full/10.1080/00063657.2021.1889460 Kettel, E.F. and G. M. Siriwardena 2018. Comparisons of breeding bird population and abundance trends within and outside two specified areas located in SW England. Unpublished (confidential) Report to Natural England. British Trust for Ornithology, Thetford, Norfolk, UK. V. Ward, M. Heydon, I. Lakin, A. J. Sullivan, G. M. Siriwardena. (2022) Breeding bird population trends during 2013–2019 inside and outside of European badger control areas in England. Journal of Zoology 108. https://zslpublications.onlinelibrary.wiley.com/doi/10.1111/jzo.13010




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