ISIS Report 12/03/04
Bogus Comparison in GM Maize Trial
The research paper claiming that GM maize is better for the
environment than non-GM even if atrazine is not used is highly misleading.
Prof. Peter Saunders and
Dr. Mae-Wan Ho report
Caught between fierce opposition from the public and heavy pressure from
the biotech industry, the UK government agreed in 2000 to fund the Farm
Scale Evaluations (FSEs) at a cost of £3 million to the taxpayer.
Three genetically modified herbicide tolerant (GMHT) crops maize,
oilseed rape and sugar beet - would be grown side by side with conventionally
managed counterparts, so they could be compared.
The FSEs were severely criticised for being rigged in favour of the
industry right from the start. First of all, organically managed crops were not
included in the evaluations, nor were the crops grown under other low-input,
integrated management regimes.
The FSEs were not intended to address safety issues, as these were
assumed to have been satisfactorily resolved. There would be no evaluations on
the risks of gene-flow, nor threats to a whole range of wildlife, livestock or
human beings, nor effects on the soil ecosystem. There would be no data
collected on yields or other important agronomic indicators.
The FSEs would estimate the effects on biodiversity using only a few
indicator species of weeds and insects; and if these proved to be the same, or
"substantially equivalent", then the GM crops would be given the go-ahead.
It is rather like giving a MOT certificate to a car just by checking
that the tyres are OK.
But to everyones surprise, when the results were published, it
turned out that GM oilseed rape and sugar beet had a more deleterious effect on
biodiversity than conventionally managed crops. GM maize, however, appeared to
do better than the conventional maize crop. The Government therefore announced
that it would permit GM maize to be grown commercially but not the other
This was a very convenient result. It allowed the Government to portray
itself as being very cautious and responsive to scientific evidence and, at the
same time, let the GM lobby go ahead with commercial growing of GM crops. What
is at stake is the principle that GM crops can be grown commercially in
the UK, and it matters little whether it is maize, oilseed rape or sugar beet.
Once one GM variety has been agreed, then more will follow, if for no other
reason than that pollen from GM variety will pollute the non-GM varieties, as
is already happening in North America and elsewhere.
Unfortunately, there was a snag. Almost all the conventional GM maize
had been treated with atrazine or other triazine herbicides, and just as the
results were announced, the EU banned these herbicides on environmental
grounds. This meant that the maize trial results were no longer valid.
Then, just before the environment secretary Margaret Beckett was due to
give the official go-ahead for the GM maize, a paper that claimed to rescue the
Governments case was rushed online in the high prestige journal
Nature. It bore the confident title: "Ban on triazine herbicides likely
to reduce but not negate relative benefits of GMHT maize cropping." The eleven
authors of this paper come from a whole collection of Government-funded
Institutes: Rothamsted Research in Harpenden, Hertfordshire, NERC Centre for
Ecology and Hydrology, Lancaster, Cumbria, Brooms Barn Research Station
in Bury St. Edmunds, Suffolk, NERC Centre for Ecology and Hydrology in
Huntingdon, Cambridgeshire and Scottish Crop Research Institute in Dundee,
The claim is that, according to further statistical analysis, the ban on
triazine herbicides, although it might reduce the benefits of GM maize, is
unlikely to cancel them out altogether. This would be a very significant
result, if only it were true.
From the data presented in the paper, there were indeed a few fields
four of them to be exact - where non-triazine herbicides were used. Did
the researchers compare those to the GM maize fields in order to arrive at
their conclusion? No. Possibly because there was no significant difference
between the two groups, and in any case, the number of plots was too few to
support the claim that the GM maize would be better from the standpoint of
So what did they do instead? The authors noted that on 16 occasions,
triazine herbicides had been applied before the maize emerged. On 24 occasions,
it had been applied post-emergence only, as had the non-triazine herbicides.
They decided to leave out the data from the plots on which triazine was applied
pre-emergence, which clearly showed a greater deleterious effect on
biodiversity than any other treatment.
The GM maize was thus compared with data from the 24 plots on which the
now banned triazine herbicides had been used post-emergence plus the 4 on which
non-triazine herbicides were used. There was now a significant difference,
which allowed the lead researcher, Perry, to say on the BBC Radio 4 Today
Programme that about one-third of the benefits of GM maize would remain after
triazines are no longer used.
But this is a highly misleading claim, because 24 out of the 28 plots
compared with the GM maize had in fact been sprayed with the banned triazines.
They write in the paper, "If this pooled category of herbicide regimes
is indeed representative of weed control in post-triazine conventional crops,
and if the weed management in GMHT maize remains the same as observed with the
FSE, then final weed numbers would still be larger in GMHT than in conventional
maize." There is nothing that would justify the first half of this statement
(in fact the authors themselves point out that the non-triazine herbicides had
a consistently smaller effect on biodiversity than triazines) and so the claim
in the title of the paper is simply bogus.
In reply to criticisms from the House of Commons Environment Audit
Committee reported in the Times newspaper, Les Firbank, one of the
authors of the Nature paper and also the coordinator of the FSEs,
"I find it astonishing that the chairman of the committee should
announce that the work is "neither robust nor particularly credible science"
within a few hours of its publication in Nature, the most highly
acclaimed scientific journal in the world."
We find it astonishing that the paper got past the referees of any
respectable journal, let alone "Nature, the most highly acclaimed
scientific journal in the world".
But thats not the whole the story. The reason yield is not
measured is because, if it were, it would very likely reveal a highly
significant difference between the GM maize and non-GM maize fields.
Jean Saunders, a citizen opposing the planting of GM crops, has taken
the trouble of photographing her local GM maize trial (see the
here), documenting the severe stunting of the GM maize crop, delayed flowering,
and much smaller and fewer cobs compared with the conventional non-GM maize.
This finding is surely a lot more relevant to the farmer than data that the
scientists have collected and the spin that they have put on the data to allow
commercial approval to go ahead.
Perry JN, Firbank LG, Champion GT, et al. Ban on triazine herbicides
likely to reduce but not negate relative benefits of GMHT maize cropping.
Nature 2004 |doi:10.1038/nature02374|www.nature.com/nature
Letter to the Editor from Les Firbank, Times on line