I was thinking of posting some thoughts on the talk that Christl Donnelly gave yesterday at the Symposium (in fact I briefly commented on a previous post here). As it happens this is one of the main news in today’s papers and so I’m spending a bit of time on this.
The very, very, very quick background to this story is that bovine tuberculosis (bTB) is an increasingly important problem; to put things in perspective, Christl said in her talk that over 26,000 cattle were compulsorily slaughtered after testing positive for the disease, last year. Clearly a huge problem in terms of animal welfare and, incidentally, for the British food industry.
I have to admit that I don’t know enough to judge whether this is the only theory, or some other biological mechanism could be out there to explain things off. However, one theory (in fact, the theory, it appears) is that badgers living in and around farming areas are the main responsible for the epidemics of bTB. In the late 1990s, the government commissioned a study (which Christl led and described in her talk), to investigate whether “badger culling” (or, more appropriately, “killing”; that’s effectively what it is…) would be effective in reducing the level of bTB. The study was complicated to even set up, but, as far as I understand, there is not much controversy on the high quality of the trial, which went on for nearly 10 years (and data are, in theory, continuously monitored $-$ apparently, DEFRA have changed their IT supplier, which has screwed things up and so the data for the last year are still not available).
The problem is that the results are not so clear cut as one would hope; according to Christl, badger culling seems to be effective within the “culling area”, but also to produce higher rates of bTB just outside of it. Based on these results, the then Labour government didn’t implement the policy; Tories and LibDems, on the other hand, were always in favour of culling and, once they happily got married in coalition government, they started plans to actually go for it.
But, and I’m coming to today’s news, there is now an apparent U-turn, due to the high cost of implementation of the policy. In fact, in order to be effective, at least 70% of the badgers in a given area need to be culled; but because there was a very large uncertainty in the estimation of the badger population stocks, this has turned out to be a more complicated and expensive enterprise than expected (as the absolute numbers have gone up from previous estimations).
Now: to my mind this was always going to be a decision-making problem, where the cost components would play a major role. Christl said in her talk that, when they were setting up the trial and even later when presenting the results, some commentators pointed out that cost considerations should not enter the science, and they were criticised for actually taking them into account in their recommendations (in some way; I don’t know the details here, but I’m guessing not in a formal, health-economics-like way). To me, this is nonsense and quite hypocritical too!
First, there’s an underlying assumption that a cow is worth (considerably) more than a badger; if this weren’t the case, then why killing an animal to save another one, instead of leaving Nature alone? Of course, to humans the value of a cow is quantifiable in terms of its market in the food industry, and thus is quite high. So, by definition of the problem, the very reason why the government bothered with the trial is economic. Second, if a policy is ever to be implemented, and if science is there to help decide the best course of action, how can the costs attached to a) gathering the relevant data; and b) eventually doing something not be relevant?
I think in this case the evidence is just not clear enough $-$ and that’s not because of how the trial was run or the stats computed and presented. Things are just not clear. So perhaps the value of information (either on badger culling or implementing alternative or additional strategies) is clearly very high $-$ and possibly still affordable.