The controversial field trials now underway in the United Kingdom are intended to investigate the consequences of genetically modified herbicide tolerant crops for biodiversity. The field trials will be very valuable, but will not tell us what will happen to bird populations. They are carried out on too small a scale. Several decades of intensified agriculture in Europe have had a particularly serious effect on birds, whose populations in the United Kingdom have declined by up to 90 percent in the last 25 years, Watkinson said. The study showed that a key issue in predicting the impacts on bird numbers was the pattern of farmers' uptake of the new genetically modified technology.
Most fields have very low seed densities.
It is the fields with high seed densities that are particularly important for bird populations. The researchers predict that the severity of the bird declines will depend upon which farmers are most likely to adopt the genetically modified herbicide tolerant crops. If their use is restricted to intensive farms with low seed densities then the effect will be minor. Some data from the United States, where genetically modified herbicide tolerant crops are currently growing, suggest that weed control with genetically modified herbicide tolerant crops may not be as effective as some of the model results indicate. Such differences emphasize the need for field trials to complement theoretical studies like this one, Firbank and Forcella point out.