Badger culling has a longer history than I realised. The link between badgers and TB was first posited in 1971 following the discovery of a dead TB-infected badger on farmland where TB was common in cattle. MAFF concluded in 1973 that badgers should be culled through gassing to reduce the spread of TB and by 1982 badgers were virtually eliminated in the South West (where TB was most prevalent) and there were no outbreaks for a decade. However, the Dunnet report (1986) found that while TB rates had declined in the South West as gassing was occurring, TB rates also decreased in other parts of the country where culling had not taken place. At the same time there were greater restrictions on cattle imports from Ireland and a better test that reduced false positives.
TB rates in cattle began to rise again during the 1980s and in 1996 the Krebs review was begun which published its findings in 1997. It concluded that there was "compelling" evidence that badgers were implicated in the spread of TB to cattle and so the Independent Scientific Group on Cattle TB (ISG) was formed in 1998. The ISG then established the Randomised Badger Culling Trial (RBCT) to test the impact of culling. The final report of the ISG (PDF) was published in 2007 and concluded that,
The report is really interesting and I recommend that anyone interested read it as it well written.1. On the basis of our careful review of all currently available evidence, we conclude that badger culling is unlikely to contribute positively, or cost effectively, to the control of cattle TB in Britain (10.48 and 10.92).
2. We conclude that there is substantial scope for improvement of control of the disease through the application of heightened control measures directly targeting cattle. Therefore, we recommend that priority should be given to developing policies based on more rigorous application of control measures to cattle, in the absence of badger culling (10.57 and 10.93). [p23]
It points out that,
It's a lovely example of correlation not equalling causation....the evidence of an association between M. bovis infection in badgers and in cattle, which is undisputed, is not the same as evidence of transmission from badgers to cattle. This therefore injects considerable uncertainty into how effective badger culling will be in reducing the risk of TB breakdowns...
...the magnitude of risk reduction resulting from badger removal may not be simply proportional to the quantitative importance of badger infection as a risk factor. The dynamics of the disease may involve two-way interactions between infection in badgers and in cattle. The badger culling policies of the past have been based on the implicit assumption that, in those areas where the incidence of TB breakdowns is high, it is infected badgers that have been the main source of continuing cattle infection, discounting the possibility that it could be transmitted in multiple directions and, in particular, from cattle to badgers.(p30)
The ISG report notes that in undisturbed populations, badger groups generally occupied exclusive territories whereas in culled areas home-ranges expanded and overlapped, reducing territoriality (p70). This matches with an anecdote a local farmer told me which was that the best thing you could want was an uninfected badger group on your land because they'll keep any infected badgers away.
Incredibly, culling actually increased TB rates in badgers,
Despite all the data collected,Overall, by the fourth cull the prevalence of infection was approximately double that recorded on the initial cull... Because of this rise in prevalence, the reduction in the density of badgers achieved by proactive culling was not associated with an equivalent reduction in the density of infected badgers (p78)
The foot-and-mouth outbreak in 2001 provided a natural experiment to test the impact of cattle-to-cattle and cattle-to-badger transmission (see p84 for the details). They found that rates of TB increased in badgers and cubs, and this was taken as potential evidence to suggest that,...[it] cannot conclusively demonstrate the direction of transmission. Hence, these patterns could be generated by badger-to-cattle transmission, cattle-to-badger transmission, or some combination of the two. (p83)
Analysis of the culling data found that,cattle-to-badger transmission may be an important factor in TB dynamics [and] that cattle controls may have the capacity to influence not only cattle-to-cattle transmission but also, indirectly, the chances of reinfection from badgers through their effect on cattle-to-badger transmission. (p84)
A year later the government announced they would not pursue culling, instead favouring vaccination options....proactive badger culling reduced the incidence of cattle TB inside trial areas, but elevated incidence on unculled land up to 2km outside. (p103)
And the authors concluded that,
So in 2007 we knew that culling did not work. And the government listened. In 2008, Hilary Benn announced that the government would not support culling to control TB outbreaks based on the evidence of the ISG report....that there is convincing evidence that reactive culling of badgers, in the form and time span implemented in the RBCT, does not offer a beneficial effect large enough to make it useful as a practical policy option and that indeed there is substantial evidence of an adverse effect of that reactive culling strategy. (p113)
Despite all this the coalition government decided (PDF) that,Having listened carefully to a wide range of views from scientists, farming, veterinary and wildlife organisations, and many others, and having considered all the evidence, I have decided that although such a cull might work, it might also not work. It could end up making the disease worse if the cull was not sustained over time or delivered effectively, and public opposition, including the unwillingness of some landowners to take part, would render that more difficult. It would not be right to take that risk. Therefore, in line with the advice that I have received from the Independent Scientific Group, our policy will be not to issue any licences to farmers to cull badgers for TB control, although we remain open to the possibility of revisiting that policy under exceptional circumstances, or if new scientific evidence were to become available.
And so the latest round of ineffectual culling began. This time with far less scientific scrutiny than previous culls and while more evidence was being released that pointed out the ineffectiveness of culling and the need to focus on biosecurity in farms.Having carefully considered all the evidence and the responses to the public consultation we held last autumn, we are of the view that badger culling could make an important contribution to our fight against TB as part of a comprehensive package of measures.
I don't know how many badgers have been culled since 2013, I don't even know if the government really knows, but it's clear that it's been a huge waste of time, money, and badger lives. It's good that the government is finally (if probably only temporarily) listening to the evidence but I can't help but feel this isn't really about evidence as much as it is political winds blowing against farmers for some reason.
Especially given the 
