There’s been a lot of coverage recently (August 2013) of the badger cull in Somerset and Devon. Campaigners such as the League Against Cruel Sports (here) are upset at the decision by DEFRA and Natural England to proceed with the controversial cull, and state that the decision to cull goes against scientific consensus. Indeed, proceeding with the cull is against the recommendations of the Independent Scientific Group (ISG) on Cattle TB. In their final report (here) they state:
“[W]hile badgers are clearly a source of cattle TB, careful evaluation of our own and others’ data indicates that badger culling can make no meaningful contribution to cattle TB control in Britain” (p5)
That’s a pretty unequivocal statement from the body that was set up to investigate the issue over the course of ten years, and spent over £50 million doing so. Unless something has changed significantly since 2007 when the report was published, it’s hard to see how a cull is now a meaningful intervention.
Other studies have reached similar conclusions to the ISG. For example, Smith et al (2007) found that most of the scenarios for trapping and gassing showed an overall cost (rather than benefit) to society. The only scenario where culling was effective was where there was “a high culling efficacy and no social perturbation” – in other words, assuming badgers could be gassed and wouldn’t run away. More recently, Karolemeas et al (2012) stated:
“[T]he RBCT badger culling strategies are unlikely to reduce either the prolongation or recurrence of breakdowns in the long term, and… reactive strategies (such as employed during the RBCT) are, if anything, likely to impact detrimentally on breakdown persistence.”
Given that the cost of bovine TB is significant – over £100 million in 2012 – and rising year on year, we do have to look for solutions. The government claim that the cull could reduce the increase in incidence of BtB in cattle by up to 16% (here), based on the Krebs trial which showed such a reduction under a particular culling scenario (although Lord Krebs does not himself agree with this claim)..
A relevant document to us is the Impact Assessment (IA) that DEFRA have published in their assessment of the policy pilot (see here), which makes interesting reading. An Impact Assessment is carried out “to help policy makers to fully think through the reasons for government intervention, to weigh up various options for achieving an objective and to understand the consequences of a proposed intervention” – see here.
The cost-benefit analysis undertaken in the IA is based on valuing the BTb outbreaks avoided as a result of carrying out the pilot. The average cost of a Confirmed New Incident (CNI) is assumed to be £30,423, most of which is taken up by government-incurred costs of testing and slaughtering, which are well understood. The Assessment also assumes that the culling and vaccination programme (designated as Option 6) would yield a net effect of 136 fewer CNIs than under the ‘do-nothing’ scenario.
The first thing apparent on the IA is that it shows a policy NPV (Net Present Value) of -£0.88 million. There is no clear explanation within the IA of why a policy with a negative NPV would be accepted. Furthermore, item 7.7, P18 of the IA states “[c]hanges in any one assumption mostly leave a negative NPV”. In other words, the entire scenario tends to still be of negative value when assumptions are proven to be incorrect.
What makes this all the more concerning is that the negative NPV is shown even without building in any consideration of the non-market costs borne by wider society from the loss of badgers. The normal Treasury guidance in the Green Book is that non-market costs and benefits should be considered as part of policy appraisal, and DEFRA’s IA attempts to do so at item 6.32/6.33. Yet, because of the difficulty of making such an assessment, no value of avoiding badger deaths is included in the calculations. This seems like a serious omission, especially given the badger’s status as a charismatic and popular animal, and the emblem of the UK’s Wildlife Trusts who represent some 800,000 members nationally!
The most confusing part of the entire story is that the objectives of the most recent (August 2013) cull are still unclear. DEFRA’s own statement is that the cull is a pilot of the badger control policy (here) in order to test “assumptions about the effectiveness, humaneness and safety of controlled shooting”. But that’s inconsistant with the published IA, which considers the pilot as a discrete project with its own (albeit negative!) NPV. So is the cull a fact-finding exercise or a strategy to reduce BTb? And should it have gone ahead either way?
Smith, GC, Bennett, R, Wilkinson, D, & Cooke, R, A cost-benefit analysis of culling badgers to control bovine tuberculosis, The Veterinary Journal 173 (2007) 302–310
Karolemeas K, Donnelly CA, Conlan AJK, Mitchell AP, Clifton-Hadley RS, et al. (2012) The Effect of Badger Culling on Breakdown Prolongation and Recurrence of Bovine Tuberculosis in Cattle Herds in Great Britain. PLoS ONE 7(12): e51342.
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