Examination of Witnesses (Questions 40
MONDAY 18 JUNE 2007
BOURNE CBE, PROFESSOR
OBE AND PROFESSOR
Q40 Mr Drew: We have had at least
a week of inspired leaks in the press which said that Ministers
were going to bite the bullet and were going for large-scale culls.
We have now had all the stuff this weekend where effectively Ministers
are now saying they do not need to bite the bullet because there
is no need for large-scale culls. We have obviously had various
organisations, like the Badger Trust, making its own threepenny-worth.
This has not been helpful in trying to get a scientific rationale
of your report. You make a comment about that in terms of some
of the critics that you have had to deal with over the years.
They all seem to have got their retaliation in first. Have any
of them helped you at all in trying to make your case?
Professor Bourne: Not at all.
Absolutely not. Absolutely and utterly not. I certainly made the
case to Ministers, both to Mr Bradshaw and to Mr Miliband, and
collectively, in the meetings we had in November last year and
February this year that it would really be helpful if Defra embraced
the science and stimulated discussions with the NFU in particular
based on science to develop science-based policies. I have seen
no sign of that. It may be happening in the background but I am
not aware that it is happening and, if it is, it has certainly
had no impact on the NFU response.
Chairman: Come back on Wednesday and
you can see the other side of the coin.
Q41 Mr Gray: I am new to the Committee
since you were here in 2006. I have just been reading the papers
and forgive me if I have missed something. It seems to me there
is a difference in tone between what you said particularly in
your letter in 2006 and what you said in your report. If I could
just quote a couple of bits that confused me rather, in your open
letter of January 2006 you said, "Intensive culling over
a large area and over an extended period of time could in principle
reduce cattle breakdown rates", which I interpreted to mean
that you thought that there could be a place for extensive culling
over a long period.
Professor Bourne: Read on.
Q42 Mr Gray: In the second half you
say there are logistical difficulties, yes, but let us leave aside
Professor Bourne: Read on, read
Q43 Mr Gray: Perhaps you would like
to answer the question in a moment and then you can tell me the
bits that I have not actually
Professor Bourne: The bits that
you have missed out said it can only be considered as a policy
option with a cost benefit analysis.
Q44 Mr Gray: Professor Bourne, perhaps
you would let me ask the question before you seek to answer it.
Professor Bourne: You were quoting
a letter and you were not properly quoting that letter.
Q45 Mr Gray: Perhaps I can ask the
question. Perhaps that is a better way to do it, ask the question
first and then let you answer it. My naïve interpretation
of your letter thenand you can correct me in a momentwas
that you said that under some circumstances, although there are
logistical difficulties attached and there are costs attached,
intensive culling, in your words, over a large area over an extended
period of time could in principle reduce cattle breakdown rates.
Am I wrong in thinking that means you think that under some circumstances
extensive culling could break down cattle breakdown rates? Is
that right or wrong?
Professor Bourne: Mathematical
modelling in extrapolation from trial data suggests that if you
cull over a large area, you would ultimately get positive gains
with respect to the area culled relative to the area that you
were not culling, where we know one had this perturbation effect.
Q46 Mr Gray: So the answer is yes.
Professor Bourne: I also stated
very clearly in that letter that there would be extreme logistical
difficulties in achieving this with respect to culling over a
large area repeated regularly over a large period of time, and
it could only be considered as a policy option if there was an
adequate cost benefit analysis.
Q47 Mr Gray: What sort of logistical
Professor Bourne: The logistical
difficulties are the ones that we had to face in doing full surveys
of these areas, getting a trapping force into the field to do
culling across the whole piece at the same time and continuing
it for this very long period. There is a real logistical difficulty.
Mr Gray: Hang on a minute. The logistical
difficulties of doing it
Q48 Chairman: Let Professor Bourne
Professor Bourne: We also stated
that if one required a cost benefit analysis and we have subsequently
been able to do that because we have been able to identify the
number of breakdowns that would be saved as a result of this sort
of practice and the costs that would be incurred, but the fact
the Government stated very clearly that they would not do this
themselves, they would not be responsible for this, but farmers
would in fact have to do this off their own bat, increases the
logistical problems of doing this.
Q49 Mr Gray: Let us leave the logistical
difficulties to one side because there is no logistical difficulty
in the world that it is not possible to overcome. What I want
to focus on is what you said in your January letter, which was
that in principle an extensive cull over an extensive period might
well be beneficial in terms of reducing TB. That is what you said
in your letter. Was that wrong or has the science developed since
Professor Bourne: As an extrapolation,
as a modelling exercise, that was correct but we are bound to
write caveats to that, which I would have thought would have been
a clear message to Ministers of the difficulty of doing that and
the likelihood that the whole thing just would not be achievable.
Subsequently, of course, we have been able to do a cost benefit
Q50 Mr Gray: We will come back to
the cost benefit analysis and cost, of course, is a separate matter
but the important principle which has not really come over in
the coverage today is that in that letter you accepted the principle,
leaving aside the difficulties, leaving aside the logistics, leaving
aside the costs, and those of course are big difficulties, according
to my naïve reading of it, that an extensive cull over a
wide area might have some benefits for reducing TB, leaving aside
the logistics, leaving aside the costs. If that is the case, can
I ask you a second question about areayou hinted at it
a moment ago but we did not actually develop it quite as much
as we perhaps could have done. Given that the tests were over
ten square kilometres, and quite good effects were seen inside
the ten kilometres squares, although there were bad effects around
the border, what would happen if that were very much wider? For
example, in the old days it used to be that the cull was across
the whole of the county. Imagine that all the badgers in the county
of Wiltshire were exterminated, what effect do you think that
would have? Do you not think that possibly your tests being in
small areasten kilometres is a very small area in terms
of the land mass of Great Britaingiven that you accept
the principle that it does actually work, and leaving aside the
logistics and leaving aside the costswe will come back
to that in a momentdo you think the small area over which
the test was done might have constrained the outcome?
Professor Bourne: If you look
at page 105 of report, we express there the confidence limits
that extrapolation suggests you might expect with trapping over
a very large area. They are very wide confidence intervals. You
ask if one culled out the whole of Wiltshire, what would the effect
be on the whole of Wiltshire. The data from the trial would suggest
that you would have a positive impact on cattle breakdown within
the Wiltshire area, and it would be difficult to tell you what
that was; one could extrapolate. One sees the very wide confidence
intervals. But you would certainly have an unwanted effect in
the neighbouring counties of Hampshire, Somerset, Dorset, what
counties there are surrounding Wiltshire. Pragmatically, I think,
attempting to cull badgers over such a large area would present
extreme difficulties, difficulties which we have mentioned, with
respect to how you would have to cull that area.
Professor Woodroffe: If I could
just continue on the theme that Professor Bourne has started,
this issue about logistics is not just a question of you would
have to do it and it is always achievable. The problem is what
happens if you do not achieve it. If you attempt to cull badgers
across the whole of Wiltshire, if you fail to achieve that, if
there are chunks that you cannot access, if you do not do it all
simultaneously, if you do not do it as we did it in this case,
where we had large numbers of people coming in simultaneously
over large areas to cull badgers, anything that you do which reduces
a simultaneous, very widespread effect risks making the situation
worse. So where culling is localised, you get the perturbation
effects, you increase TB risk to cattle.
Q51 Mr Cox: Subject to permeability
Professor Woodroffe: Wiltshire
being really quite permeable.
Mr Cox: I understand that.
Q52 Mr Gray: There is a lot of rain
Professor Woodroffe: So, for example,
we showed that, as I mentioned previously, every time you do a
proactive cull across the whole area, the prevalence of infection
in the badgers goes up on each cull. If you do not do that simultaneously
but instead you do that cull as several sectors that you do successively,
the increase is actually 1.7 times as much. So if you do not do
a simultaneous cull, it makes the situation not just a bit worse
but quite a lot worse in the badgers. So simultaneous culling
is very important, good land access is very important, targeted
culling around inaccessible areas is very important, and everything
that you do which, because of logistical constraints, because
of lack of land owner compliance, because you are just trying
to do something on a massive scale, takes you away from an absolutely
simultaneous cull, performed very extensively simultaneously,
is going to take you more towards piecemeal culling, which is
going to entail a high risk of making the situation worse rather
than better. There is a big difference between saying in principle
that you could reduce TB risk to cattle by culling badgers over
very extensive areas, although within the range of areas we have
projected the differences, the net effect is pretty small. The
overall effects are very modest but there is also an increasing
chance that you make it worse, especially if you are going to
do that as one of the culling approaches that was formerly included
in the consultation document was licensing farmers or farmers'
representatives to do the culling. Without the resources of being
a large government department, farmers trying to do it themselves
or having contractors trying to do it themselves and so forth
is going to take you more towards this piecemeal culling, which
will have a massive risk of making things worse rather than better.
Q53 Mr Gray: I see the logistical
difficulties but you get my point that if there were to be in
principle benefit from it and given that this is costing the nation
millions of pounds, it might well be we could devote huge resources
to it if indeed it was going to be the final solution. Is there
not some argument in favour of doing that? Is that something which
Professor Bourne: One could certainly
do that, just as the Irish plan to remove badgers from 30% of
their land mass.
Professor Woodroffe: I am actually
not sure that it is even achievable given the badger densities
we have in TB infected areas of Britain, the lack of geographical
boundaries. I think another difference between Britain and Ireland
is that we have substantially higher baseline background badger
density, so that immigration pressure is always going to be there.
I am not convinced that you actually could eliminate badgers from
Wiltshire, try as you might.
Professor Bourne: The feasibility
of it is extremely difficult but also, of course, it would not
be the end of the cattle TB problem. It would make cattle TB controls
very much easier but there would still be a very large cattle
TB problem that would have to be addressed through improved diagnosis.
Mr Gray: They have brought it to one
Mr Cox: You would have to bear down on
both sides of the disease.
Q54 David Taylor: My colleague Mr
Gray has been trying to tease out whether there really were differences
in time in the ISG's attitude between January 2006 and 18 months
later, as we are now. I would like to see if there are differences
within the ISG. I know it is not a seminar on semiology but nevertheless,
can I point to Professor Bourne's letter to the Secretary of State
where he refers to "badger culling can make no meaningful
contribution to cattle TB control in Britain", which is drawn
from paragraph 9 of the overview, where you mention a very similar
point, "cannot meaningfully contribute towards future control",
but yet, rather significantly, at paragraph 10.48 on page 172
we, the collective Committee, concluded that badger culling is
unlikely to contribute positively. "Unlikely" and "cannot"
are two distinctly different descriptions. I wonder what lies
within the two different boundaries that they represent, Professor
Professor Woodroffe: As the author
of several of these sentences, I am very happy to speak to them.
I will just add while Professor Bourne is looking it up that saying
badger culling is unlikely to contribute positively in a scientific
forum is pretty damning. That is about as strongly as you ever
say anything in a scientific paper.
Q55 David Taylor: It is not the Chairman
firming it up; it is just a scientifically alternative way of
expressing the same set of circumstances?
Professor Bourne: No, I think
there are two issues here. What we are saying is that badger culling,
in the way it can be conducted in the UK, we believe, cannot possibly
contribute to cattle TB control, and in using the word "meaningfully",
what we mean there is that if it is the only inducement that would
encourage farmers to co-operate fully and introduce effective
cattle control, it could have an effect.
Q56 David Taylor: There is a difference
to me between "cannot", which is a zero percentage probability
and "unlikely", which is less than a 50% possibility.
There is a big void there, is there not?
Professor Woodroffe: There certainly
is not any disagreement within the group about the conclusions.
Professor McInerney: It is important
to get a little perspective on this. In 2006 when the letter was
written, a certain amount of data came through and the analysis
was leading to some conclusions. By the time we get to our final
report, there is a lot more data. The trends inside and outside
the areas have become more firm. Whereas in 2006 the net effect
on breakdowns was that the outside effects were neutralising the
inside ones, as the trends have developed, we now find within
100 kilometres squared there is a net positive effect, but it
is 1.4 breakdowns out of 50. This is where we do not think it
is meaningful, if you believe it is worth throwing all this culling
effort in order to prevent one and a bit breakdowns. We do not
feel that is very meaningful in terms of policy. It is the raw
numbers of what you achieve rather than technically whether it
is zero or just a little bit above zero. In the end, our judgment
is that this is not a very effective policy if all it achieves,
after all this effort, is a minimal effect on breakdowns when
there would seem to be opportunity to have a much bigger effect
doing other things.
Q57 David Taylor: To me, as a statistician,
an equivalent phrase to "cannot meaningfully" would
be "is highly unlikely to contribute positively".
Professor Bourne: We are working
within scientific confidence limits.
Q58 David Taylor: 95%?
Professor Bourne: Yes indeed.
It is difficult to be utterly positive about everything.
Q59 David Taylor: "Cannot"
is utterly confident to me.
Professor Bourne: We are confident
that it will make no useful contribution.