7. Prof. Fred J. Gould, Professor of Entomology, NC, USA, presented an overview of the impacts of introduction of Bt-crops in the environment. He described how the environmental risks and benefits of Bt-crops depend on a) the specific Bt-gene-construct, and the crop in which it is introduced, b) the geographical location of the crops and c) the period or timescale of its cultivation. The importance of these parameters were illustrated with specific case studies. The gene constructs make a difference because there are hundreds of different Bt-genes that produce different toxins which affect a range of pests. There are a variety of promoters that are used for the preparation of the gene-constructs. In addition, as major corn pests vary in different geographic locations, the same Bt-gene cannot be effective everywhere. For instance, cotton bollworm is the main pest in the USA, while it is boll weevil in Central America. In China, cotton cultivation is an insecticide-intensive process, and the benefit of cultivation Bt-cotton is that it has reduced sprays from 21 to 7 per crop season and has helped in a better control of the aphids by predators in cotton agro-ecosystems. It has, however, been associated with pest problems due to mites and hoppers. Therefore, the unequal regional impacts due to differences in pest pressure levels need to be considered. He emphasised that pest resistance and changes in pest pressure levels have to be documented among the potential long term impacts of using Bt-crops. Theoretical studies on resistance dynamics, based on experiments carried out using high-dose refuge approach; show an exponential increase in susceptibility in the long term. With regards to yield, he noted that the current Bt-crops have increased yield and at the same time have a high level of variance. There was a need for developing varieties that have higher mean yield stability and showed decreased variance through time.
8. The expert summarised that environmental effects of Bt-crops should be assessed on a case-by-case basis, including their potential impact on local soil micro flora and biodiversity. He indicated that scientists were at an early stage in their ability to discriminate the direct and indirect changes in such detail, but initiatives such as 'The GMO Guidelines Project2' was providing useful information in this area. Despite the practical challenges both for scientists and national authorities, there was a real need to conduct research on the long-term ecological effects. He called on FAO to facilitate such activities through partnerships of all stakeholders.
9. The participants discussed at length the range of practical information required for analyzing the full environmental effects of the Bt-crops. They agreed that the benefits and potential environmental hazards of the cultivation of Bt-crops should be considered within broader agro-ecosystems taking into account conventional agricultural practices. While scientific data was still limited on many of the ecological aspects related to GM crops, they emphasised that a case-by-case analysis should be the most appropriate approach. The key point from the discussion were as follows:
2 GMO Guidelines Project: http://www.gmo-guidelines.info/
