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Farm Scale
Evaluations of spring-sown genetically modified crops
A
themed issue from Philosophical Transactions: Biological
Sciences,
The Royal Society
Series
B Volume 358 Issue 1439 29 November 2003
October 16, 2003
The publication today of the
results of the Farm Scale Evaluations (FSEs) in Philosophical
Transactions: Biological Sciences, a journal of
the Royal Society,
reveals significant differences in the effect on biodiversity
when managing genetically modified herbicide-tolerant (GMHT)
crops as compared to conventional varieties. The study
emphasises the importance of the weeds within crops in
sustaining natural communities within and adjacent to farmers'
fields.
About 60 fields each were sown
with beet, maize and spring oilseed rape. Each field was split,
one half being sown with a conventional variety managed
according to the farmer’s normal practice, the other half being
sown with a GMHT variety, with weeds controlled by a
broad-spectrum herbicide (glufosinate-ammonium in maize and
spring oilseed rape, and glyphosate in beet). Comparisons in
biodiversity were made by looking at the levels of weeds and
invertebrates, such as beetles, butterflies and bees, in both
the fields and the field margins immediately surrounding them.
A total of eight papers are
published – two looking at the effects on weeds in the fields,
two looking at the effects on invertebrates in the fields, one
looking at weeds and invertebrates in the field margins and one
looking at the effect of the contrasting herbicide regimes on
both weeds and invertebrates as a whole. Another looks at the
background to the study and the rationale for its design and
interpretation and a final paper compares the management of the
crops in the study with current conventional commercial practice
to provide readers with contextual information against which the
results should be considered.
Effects on weeds in fields
(1,2)
The study showed significant and variable impacts of GMHT
cropping in beet, maize and spring oilseed rape on the arable
weeds when compared to current commercial practices. In GMHT
beet and oilseed rape crops more effective weed control lead to
the decline of the number of weed seeds left in the soil at the
end of each growing season (known as the seedbank). Although
this has been going on in cropped fields in Britain for many
decades it could be accelerated by the management associated
with these particular crops. In contrast, GMHT maize showed the
opposite effect. Typically conventional maize has lower weed
burdens because of the widespread use of persistent herbicides –
the herbicide regimes used on the GMHT maize were not as
effective at controlling the weeds.
In beet and oilseed rape, the
densities of weeds shortly after sowing were higher in the GMHT
treatment. This effect was reversed after the first application
of broad-spectrum herbicide in the GMHT treatments. By the end
of the season, the weight of weeds collected from a fixed area
(biomass) and number of weed seeds falling to the soil (seed
rain) in these GMHT crops were between one-third and one-sixth
those of conventional treatments. The changes in seed rain
affected the seedbank, resulting in seed densities about 20%
lower in the GMHT treatments.
In maize the effect was
different. Weed density was higher throughout the season in the
GMHT treatment. Biomass was 82% higher and seed rain was 87%
higher than in conventional treatment. However, this had no
detectable effect on the seedbank as total seed return was low
after both treatments.
Twelve of the most common weed
species in the UK were examined. The biomass of six species in
beet, eight in maize and five in oilseed rape was significantly
affected. Generally, biomass was lower in GMHT beet and oilseed
rape and higher in GMHT maize. Significant effects on seedbank
change were found for four species of weed. However, for many
species in beet and oilseed rape (19 out of 24 cases), seed
densities were lower in the seedbank after GMHT cropping. These
differences, if compounded over time, could result in large
decreases in population densities of arable weeds. In maize,
populations may increase.
Effects on invertebrates in
fields (3,4)
Differences in GMHT and conventional crop herbicide regimes had
a significant effect on the capture of most surface-active
invertebrate species and larger groupings (higher taxa) in at
least one crop, with most increases occurring in GMHT maize and
most decreases occurring in GMHT beet and oilseed rape. One
species of carabid beetle that feeds on weed seeds was less
frequent in GMHT beet and oilseed rape, but more frequent in
GMHT maize, showing how the numbers in some invertebrates
tracked the amounts of food available to them.
Most higher taxa of
invertebrates active on weeds and in the litter layer were
little affected by the treatment. However, smaller numbers of
butterflies were recorded in GMHT oilseed rape and smaller
numbers of bees, butterflies and Heteroptera (‘true bugs’) were
found in GMHT beet.
However, in all crops under
GMHT management there were significantly more Collembola, a type
of detritivore known as a ‘springtail’, which feeds on dead and
decaying weeds. This is because the herbicides were applied
later in the GMHT crops, and so weeds tended to be larger when
killed, providing more food for these insects.
Effects on weeds and
invertebrates in field margins (5)
Three components of field margins were sampled: the uncropped
tilled area, the field verge (the grassy strip between the
tilled land and the fence or hedgerow that forms the actual
field boundary) and the boundary itself. In oilseed rape, the
cover, flowering and seeding of plants were 25%, 44% and 39%
lower, respectively, in the GMHT tilled margin. For beet,
flowering and seeding were 34% and 39% lower in the GMHT
margins. For maize, the effects were reversed, with plant cover
and flowering 28% and 67% greater in the GMHT half. These
results corresponded to the effects on weeds within the crops,
because these plants had also been affected by the herbicide.
Fewer, smaller effects were found in the verges and boundaries,
and levels of herbicide damage were low.
24% fewer butterflies were
counted in margins of GMHT oilseed rape, reflecting differences
in the amount of flowers available. Few differences were found
for bees, slugs and snails, or other invertebrates sampled in
the field margins.
Effects on plants and
invertebrate trophic groups (6)
The effect of GMHT cropping on the interaction between
invertebrates with different feeding habits was studied by
examining the relations between plants and the abundance of
insects grouped according to their feeding preferences (trophic
groups). The negative effect of GMHT cropping on weeds in beet
and spring oilseed rape, and the positive effect in maize,
resulted in similar changes higher up the food chain.
Where the weed flora was less
abundant, there were fewer herbivores, pollinators and natural
enemies (the insects which prey on the herbivores). Detritivores
increased under GMHT management across all crops due to the
greater input, later in the season, of dead weeds on which they
feed. Compared to large differences through the season and
between crop species, GMHT management imposed relatively small
(less than twofold), but consistent, differences in the
abundance of most trophic groups. The direction of change
depended on how effective the herbicide was compared to
conventional management.
Rationale and interpretation
(7)
This paper provides the background information that was analysed
to guide and interpret the FSEs. Previous surveys of soil,
vegetation and field management were used to ensure that the
chosen fields were typical and representative of commercial
practice. Knowledge of the plants and invertebrates, and their
sensitivity to the GMHT crop and herbicide, was used to guide
the sampling plans applied to each field-half. Historical and
recent changes in the buried, living weed seeds – the seedbank –
were used to assess the initial diversity of sites and the
longer term trends that might result from growing GMHT crops.
Re-interpreting field experiments from the 1990s indicated that
changes in management practice may cause large differences in
biodiversity (e.g. a 50% difference). The experiment was
designed to ensure that such differences between conventional
and GMHT management would be detectable.
Crop management and wider UK
context (8)
It was important that the crop management systems on the studied
sites reflected the activities of farmers in the UK countryside.
The locations of field sites and intensities of cropping had to
represent the range found in the UK and this was found to be the
case.
The amounts of herbicide used,
and when it was applied, were recorded and compared well with
current commercial practice for conventional crops, and the
industry-recommended guidelines for application to GMHT crops.
Comparison of the amounts of
herbicide applied with the density of weeds showed that farmers
applied more herbicide when the density increased in beet and
maize. Generally GMHT crops were found to receive less
herbicide, later in the season, than the conventional crops.
Commenting on the results,
Dr Les Firbank, Centre for Hyrdrology and Ecology, Merlewood,
and co-ordinator of the project that submitted the papers, said:
“The results of these Farm
Scale Evaluations reveal significant differences in the effect
on biodiversity when managing genetically herbicide-tolerant
(GMHT) crops as compared to conventional varieties. The study
emphasises the importance of the weeds growing among crop plants
in sustaining natural communities within, and adjacent to,
farmer’s fields.”
“One of the key points to
remember is that the results are only applicable to the three
crops studied, and only under the regimes of herbicide usage
which were employed. Each new application of GM crop technology
must be looked at on a case-by-case basis, using a rational
evidence-based approach.”
References:
- Weeds in fields with contrasting conventional and
genetically modified herbicide-tolerant crops. I. Effects on
abundance and diversity
- Weeds in fields with contrasting conventional and
genetically modified herbicide-tolerant crops. II. The effects
on individual species
- Invertebrate responses to the management of genetically
modified herbicide-tolerant and conventional spring crops. I.
Soil-surface-active invertebrates
- Invertebrate responses to the management of genetically
modified herbicide-tolerant and conventional spring crops. II.
Within-field epigeal and aerial arthropods
- Invertebrates and vegetation of field margins adjacent to
crops subject to contrasting herbicide regimes in the Farm
Scale Evaluations of genetically modified herbicide-tolerant
crops
- Responses of plants and invertebrate trophic groups to
contrasting herbicide regimes in the Farm Scale Evaluations of
genetically modified herbicide-tolerant crops
- On the rationale and interpretation of the Farm Scale
Evaluations of genetically modified herbicide-tolerant crops
- Crop management and agronomic context of the Farm Scale
Evaluations of genetically modified herbicide-tolerant crops
Notes
- Philosophical Transactions B is published by the
Royal Society and publishes peer-reviewed research in all
aspects of biology, including clinical science.
Transactions publishes theme issues devoted to an area of
advancing research and discussion meeting issues publishing
proceedings of two-day scientific symposia led by the world’s
leading researchers.
- The research was undertaken by a consortium made up of The
Centre for Ecology and Hydrology, Rothamsted Research and the
Scottish Crop Research Institute. The work was overseen by a
scientific steering committee made up of experts in the field.
For more information go to:
www.defra.gov.uk/environment/gm/fse
- An Advisory Board of internationally distinguished
scientists and experts in the field was appointed to assist
the Editor, Professor Semir Zeki. The Advisory Board also
included eminent broadcaster Sir David Attenborough in order
to maintain a broader perspective on the desirability of
publishing the papers. The composition of the board was as
follows:
Professor Dr Muhammad Akhtar FRS
Emeritus Professor of Biochemistry at the University of
Southampton; Director General of the School of Biological
Sciences, University of the Punjab, Lahore, Pakistan; and
Member of the Third World Academy of Sciences.
Sir David Attenborough CH FRS
Broadcaster.
Professor Roland Douce
Director of the Institute of Structural Biology, Grenoble,
France; and Member of the French Academy of Sciences and the
National Academy of Sciences, USA.
Dr Gurdev Singh Khush FRS
Visiting Professor at the Department of Vegetable Crops,
University of California, Davis, CA, USA; former Director of
the International Rice Research Institute; and Member of the
American National Academy of Sciences, USA and recipient of
the World Food Prize 1996.
Professor Daniel Simberloff
Director, Institute for Biological Invasions, Department of
Ecology and Evolutionary Biology, University of Tennessee, TN,
USA; and Member of the National Science Board (USA).
- The Royal Society is an independent academy promoting the
natural and applied sciences. Founded in 1660, the Society has
three roles, as the UK academy of science, as a learned
Society, and as a funding agency. It responds to individual
demand with selection by merit, not by field. The Society’s
objectives are to:
· strengthen UK science by providing support to excellent
individuals
· fund excellent research to push back the frontiers of
knowledge
· attract and retain the best scientists
· ensure the UK engages with the best science around the world
· support science communication and education; and communicate
and encourage dialogue with the public
· provide the best independent advice nationally and
internationally promote scholarship and encourage research
into the history of science
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Banning GM crops not enough
to save wildlife
Article from
Andy Coghlan
The New Scientist via
Checkbiotech.org
Genetically modified crops are now grown in more than 16
countries. In 2002, farmers around the world planted 60 million
hectares of land with dozens of varieties of GM crops. Yet in
the UK, the decision to approve or reject the technology could
hinge on the results, out on Thursday, of four-year trials
involving 280 fields of three GM crops.
Although these farm-scale evaluations are being portrayed as a
test of the environmental credentials of GM crops, it is really
the weedkillers to which they are resistant that are on trial.
The studies looked only at the effect that these herbicides had
on "wildlife" in fields, in the form of weeds and insects. But
if the aim of the exercise really is to save farmland wildlife,
banning any of the GM crops tested is unlikely to make much
difference.
That is because herbicide use in the UK is soaring even before
any GM crops are introduced. And in the long term, farmers
denied GM crops may instead turn to non-GM crops bred to be
resistant to herbicides. That might seem like a good thing to
those who oppose GM technology, but like GM crops, the
conventionally bred strains allow farmers to splash on the
herbicide.
Their impact on farmland wildlife in Europe could be worse than
that of the weedkiller-resistant GM crops, because many allow
the use of more noxious herbicides than GM strains. And as with
GM crops, the herbicide-resistance could spread to other crops
and wild relatives.
Desired trait
Despite this, these crops do not have to undergo the same
scrutiny as GM crops because they are not genetically
engineered. The only hurdle they face in the UK is tests
designed to confirm that they are indeed new varieties. And
while GM crops can be banned under world trade rules on the
grounds that they pose a threat to human health or the
environment, the same is not true of conventional
herbicide-resistant crops.
"We're as concerned about them as GM crops," says Brian Johnson,
an adviser on GM technology to the conservation group English
Nature. "The same principles should be applied to all crops,
irrespective of their origin." The sequencing of plant genomes
is making it much easier for breeders to create non-GM plants
with a desired trait, he points out.
None of these crops is yet grown in the UK, unless one counts
maize, which is naturally resistant to the herbicide atrazine.
But one company has already tried to market them. An application
to sell imidazolinone-resistant rapeseed in the UK was turned
down in 1998 only because the strain proved low-yielding when
trialled (New Scientist print edition, 27 February 1999).
This strain and others like it are already grown in several
countries. More are being developed. And companies are likely to
redouble their efforts if GM herbicide-resistant crops are
banned in Europe. "We're continually looking at GM and non-GM
solutions. If the market is there, we'd explore all avenues," a
Syngenta spokesman told New Scientist.
"We would be foolish to turn our backs on the possibility that
other methods of plant breeding could generate the same results
without the transgenic approach," says a Monsanto spokesman.
"The regulatory systems effectively ignore all these other
methods, and are driven by politics, not science. As things
stand, a non-GM plant would bypass the arguments against GM."
Rapid breakdown
But so far Monsanto has been unable to create conventional crops
resistant to glyphosate, the herbicide it sells as Roundup.
Glyphosate is regarded as one of the most benign herbicides
because it breaks down relatively rapidly. That is not true of
many of the herbicides to which companies have been able to
breed resistant crops.
For instance, almost all Australia's oilseed rape now consists
of strains bred to be resistant to broad-spectrum herbicides.
The most popular, accounting for 72 per cent of the total grown,
is "TT canola", which tolerates the triazine herbicides,
including atrazine, an older herbicide suspected of poisoning
frogs and polluting rivers.
The original strains were created by researchers at the
University of Guelph in Ontario, Canada, who cross-bred
commercial canolas with a weedy relative, Brassica rapa,
which had evolved resistance to triazines.
Another variety, "Clearfield" rapeseed, is resistant to the
imidazolinone family of weedkillers. Scientists made it by
chemically mutating rapeseed strains until they produced some
strains resistant to the herbicide.
Both strains were approved without the fuss surrounding GM
crops, despite arguments that imidazolinones and atrazine are
worse for the environment than the herbicides such as
glyphosate. "The two canolas that were classically bred have
greater problems with persistence of herbicides and resistance
than the GM ones do," says Rick Roush, now of the University of
California at Davis, who served for five years with Australia's
GM regulation body, the Office of the Gene Technology Regulator.
"Atrazine is probably the most problematic of these two
herbicides, as it is mobile in water and frequently appears in
groundwater and waterways," says Chris Preston of the University
of Adelaide. "Atrazine is persistent and in dry years may cause
minor damage to subsequent wheat crops."
Rising use
Imidazolinones, meanwhile, can last so long in soil that it is
impossible to grow a crop the following season. "Australians
opposed to GM crops have totally ignored the fact that most of
our canola is already herbicide tolerant, and have also ignored
problems with currently used herbicides," says Preston.
In the UK the use of atrazine has increased from 34,000
kilograms a year in 1992 to over 130,000 kg in 2002, mostly
because more naturally resistant maize and sweetcorn is being
grown. Atrazine was one of the "conventional" treatments against
which GM glyphosate-resistant maize was evaluated in the UK's
farm-scale trials.
Critics say that glyphosate-resistant GM maize is bound to look
good compared with atrazine, and that the comparison is
irrelevant because of an impending European ban. But the UK has
applied for an exemption from the ban for sweetcorn.
The EU ban does mean that TT Canola is unlikely to be grown in
Europe. But Clearfield products are edging closer, with launch
this year of imidazolinone-resistant sunflowers in Turkey, and
the development of similar varieties for southern and eastern
Europe. BASF, the company that makes Clearfield strains, has
just launched imidazolinone-resistant wheat in Australia and may
develop variants for the European market.
Even without herbicide-resistant crops, GM or otherwise,
herbicide use has soared in the UK, with glyphosate use more
than quadrupling in a decade (see graph). The biggest rise has
been on farms, where farmers receive subsidies to reduce
overproduction by temporarily leaving fields fallow, but keep
these "set aside" fields free of weeds with glyphosate.
Glyphosate use has also soared on cereals such as wheat and
barley, to compensate for a side effect of a popular fungicide.
"There's no strategic control over technologies used in the
countryside," says Johnson. "We have many well-meaning
technologies, but not a means to regulate them." |
