3.3 THE EFFECTS OF GLUFOSINATE HERBICIDE

The views produced in response to the PGS application indicate that many, and perhaps the majority, of concerns about growing glufosinate-tolerant oilseed rape actually relate to the environmental impact of the use of glufosinate (3.2.3) rather than the GMO itself. As discussed earlier, and in Chapter 4, this aspect largely falls outside ACRE's remit. For this reason, it does not form part of our review of the original risk assessment made by ACRE. However, it may be helpful to refer briefly to some of the issues which have been raised, and which might form part of a wider assessment of the environmental impact of the commercial release of glufosinate-tolerant oilseed rape.

Although the safety and efficacy of glufosinate (indeed, of all herbicides) has been fully evaluated (by PSD and MAFF advisory committees), the chief concern is that the increased use of a broad-spectrum herbicide (which kills most plants) will have a deleterious impact on farmland biodiversity. Not only may populations of weeds and other non-weedy farmland plants be significantly reduced but also the invertebrate populations which depend directly as herbivores, or indirectly as predators, on those plants, and, in turn, farmland mammals and birds may be seriously affected. In particular, a decline in farmland birds such as grey partridge and the corn bunting has been at least partly attributed to the use of herbicides and broad-spectrum insecticides. On the other hand, glufosinate herbicides have lower mammalian toxicity and environmental persistence than most selective herbicides and, in conjunction with the genetically modified crop, may not need to be applied as frequently to achieve weed control. This may generally enhance biodiversity.

Whatever the impact on farmland biodiversity, the pattern of herbicide use is likely to change in a way which is not easily predicted but which may increase the dependence on herbicides in agriculture. This point, made strongly by Finland, Sweden and Denmark in their objections to the PGS application (3.2.3), is also made by several environmental groups who wish to see a reduction in the use of agrochemicals and, in some cases, an expansion of organic farming.

Finally, it has to be admitted that many of these wider issues are difficult to resolve in advance of actually growing the glufosinate-tolerant oilseed rape on a commercial scale. The many variables, not only in the management of the crop but also in the way in which it may be integrated with non-tolerant crops or crops tolerant to other herbicides, make accurate prediction impossible. Some of the major uncertainties in making predictions have been detailed recently in a thoughtful paper by Marshall (1998).