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Badgered to death - but not by statistics.

SIGNIFICANCE MAGAZINE - Statistics making sense
22 July 2011 by Julian Champkin

The UK’s Minister for the Environment, Food and Rural Affairs, Caroline Spelman, has announced that she is ‘strongly minded’ to allow a cull of badgers in Britain. This is in order to reduce the spread of TB in cattle.

She is quoted as saying that her decision is ‘based on scientific research.’ 

With any due respect to the Minister, her statement is factually incorrect. The scientific research shows very clearly that a cull of badgers will be ineffective against bovine TB.

Just a placeholder image
The bullet for Mr Badger? After E.H. Shephard's classic
illustrations for the Wind in the Willows
by Kenneth Grahame.

How do I know this? Because the best and most famous statistician in the UK, Sir David Cox, was charged by the government some years ago with the statistical design and analysis of a very large scientific survey to establish whether culling badgers will actually reduce TB in cattle. The study was conducted by the Independent Scientific Group on Cattle TB; its science was headed by Lord Krebs; it took nine years of exhaustive research, field trials comparing experimentally culled and unculled areas, with investigation and analysis of the results; and it found very clearly that culling badgers would be ineffective. 

See the article that Sir David and his colleague on the Independent Scientific group Cristl Donnelly wrote for Significance about it here.

Their report was delivered in June 2007. Its conclusion was this: “Given its high costs and low benefits, … badger culling is unlikely to contribute usefully to the control of cattle TB in Britain.” Indeed in some circumstances a cull might even be counterproductive, increasing the amount of cattle TB as infected badgers from neighbouring areas move in to replace the culled ones. 

That settled the science of the matter – or so one would have thought. Bizarrely, though, a mere two months later, the then Chief Scientific Adviser to the Government, Sir David King, came to an exactly opposite conclusion. His research had lasted not nine years but two days. A Parliamentary Select Committee was, understandably, rather amazed and summoned Sir David King to explain. ‘To be able to turn around a significant conclusion of the report in what would appear to be a cavalier and unsustainable fashion is something that you really ought to respond to’ was one MP’s comment to him. Sir David King was unable to give the grounds on which he had so summarily rejected the results of nine years of quality scientific and statistical work.

Culling badgers - ie killing them in large numbers - is an emotive issue and a political minefield for governments in Britain. Famers see a rising incidence of TB in their herds and say that it is transmitted by badgers. Some 25,000 cattle from TB-infected herds had to be slaughtered last year. Get rid of the badgers and you’ll get rid of the TB, say the farmers.

Conservation groups and animal lovers say that is rubbish. 80% of cattle TB is by cow-to-cow transmission, and badgers play a minority role at most. Those groups will be furious if the government allows a major badger cull; farmers groups will be furious if it does not. Successive governments have apparently done their best to avoid having to make a decision. But it seems that the crunch time has now come.

Badgers have been a protected species in England since 1973. It should be said that of course they are not remotely threatened with extinction, cull or no cull. It is estimated that the cull will kill about 30,000 of them out of a UK population of about 190,000; as it is, around 40,000 badgers are killed each year by motorcars on the roads. 

Animal-lovers feel emotional about their badgers. Farmers feel emotional about their cows (and their profits too, of course; the cost to the country of those 25,000 slaughtered cows has been given as about £90 million. That is not a small sum. Even non-farmers should sympathise.)

But whichever way the decision goes, animals will die. The question is whether they will die to some purpose. Lord Krebs, in charge of the ISG report, was quoted as saying that the data shows culling to be ineffective. Even proponents of the cull expect it to contribute no more than a 16% reduction in bovine TB.

The Minister’s decision is a political one, and politicians are entitled to make political decisions. Indeed it is their job. Nevertheless it is sad that the decision the Minster is ‘minded to’ make is the one that flies in the face of science and statistics. It is sadder still that she makes the claim that her decision is ‘based on scientific research.’ That claim at least is demonstrably false. 

As will emerge, we suppose, a few years from now, when badgers have been culled and TB in cattle herds is still at much the same level as it is now.

The Minister, of course, by then will have moved on.

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