GMOs crop up again!

Research into genetic modification harvests mixed results

 

The way a crop is managed can significantly affect biodiversity. This was the clear message from the results of a four-year programme of experiments carried out on Genetically Modified Herbicide Tolerant (GMHT crops).

 
The Farm Scale Evaluations (FSEs) were the first ever large-scale comparison of the impacts on biodiversity of two cropping systems. They compared weeds and invertebrates in GMHT and conventionally managed maize, spring oilseed rape, and sugar and fodder beet. Results showed that GMHT beet and oilseed rape had significantly lower biomass of weeds following herbicide applications, and this resulted in fewer weed seeds. There were also lower numbers of pollinators (bees and butterflies) in these two GMHT crops.
 
These results were in line with the expectations of English Nature, which acts as Lead Agency on GMOs on behalf of JNCC. The conservation agencies called for the experiments to be set up in 1997, when several GMHT crops were in the pipeline for commercial release despite concerns about their indirect impacts on biodiversity. The Head of English Nature's Biotechnology Advisory Unit, Dr Brian Johnson, was instrumental in setting up the experiments.
 
"Faced with continuing declines in farmland biodiversity, the last thing the UK needed was a set of new crop varieties that would further intensify farming", says Dr Johnson. "We had data from small plot trials showing the highly effective and reliable weed control achieved with GMHT crops, and growing evidence that linked weed and seed abundance to numbers of invertebrates and birds on farmland. This was our starting point, but these early experiments were not designed to assess biodiversity and did not adequately reflect real commercial management."
 
Despite the clear pointers from the early experiments, the results came as quite a surprise to ecologists, perhaps for two main reasons. The first was simply the magnitude of the impacts on biodiversity. Following application of the herbicide glyphosate, weed biomass in GMHT beet was 85% lower than that in conventional beet, and seed rain was 80% lower. Similar effects were seen in oilseed rape.
 
The second surprise was that GMHT maize held substantially more biodiversity than conventional maize. Although it was already recognised that the residual herbicides used on maize give good weed control and are toxic to many invertebrates, the beneficial effect of switching to a contact herbicide like glufosinate ammonium had not been fully appreciated.
 
The evaluations are a clear example of the precautionary principle put into practice. They are also a flag-bearer to the statutory conservation agencies' rigorous scientific approach to the protection of biodiversity. Most importantly, they have dramatically improved our understanding of agro-ecosystem ecology, giving us a workable protocol that can be used to compare other agricultural systems in the future.

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