14. Dr. George Kowalchuk, IBED, Netherlands gave a comprehensive overview of soil ecosystems, and the below-ground effects of microbial-plant interactions, the current knowledge status in understanding the effects of GM plants of soil-borne communities, and identification of possible indicators. He highlighted the existing gaps in assessment of GM crop-induced effects on soil ecosystems and provided suggestions for assessment of current and future GM crop introductions based upon present knowledge and technology. Soil microbes are the greatest source of biodiversity on the planet and soil-borne microbial communities are the engines driving numerous key ecosystem functions. Important soil functions include decomposition, nutrient cycling, disease suppression and groundwater purification while plants provide the major input of energy and carbon to soil-borne microbial communities. He noted that in some cases, the impact of microbial groups and/or processes that were likely to be susceptible to the introduction of GM crop could be assessed or predicted. However, there was only a limited understanding and lack of base-line reference which limited the possibility of predicting tentative effects of GM crops on soil ecosystems. Therefore, all new challenges associated with risk assessment of GM crops needed to be documented. This was particularly important for those GM crops with entirely novel traits like pharma-crops and neutraceuticals. He noted that recent advances in molecular techniques provided a way for meaningful assessment of GM crop-induced effects on soil-borne micro-organisms and processes for the first time. These included broad-targeted and group-specific nucleic acid-based fingerprinting methods for the detection of shifts in the microbial community, measurements of general enzyme activities, community structure with phospholipid fatty acid analysis and measurement of general soil fungistasis. There is still an absence of a full understanding of GM crop-induced effects. However, to date all available evidence revealed only very minor effects of GM crops; effects that pale in comparison to other sources of variation in soil-borne ecosystems. However, the knowledge base for existing crops was growing, thereby providing a good frame of reference for future evaluations. However, such a knowledge base did not exist for the new crops under development in particular those engineered for the production of pharmaceuticals. Under the circumstances, he recommended a two-pronged approach for environmental assessment of GM crops; incorporation of information on what is known, and an indication of other relevant information that needed to be ascertained.
The discussion revolved around the environmental impacts of GM crops on soil microorganisms, and the nature of these interactions. Studies conducted on Bt and its impact on rhizosphere and the persistence of Bt in soil at a level higher that the natural background of Bt organisms were mentioned. Queries were raised on the need and means of detecting the interactions especially for regulatory purposes. It was argued that agriculture practices, not any single gene-construct, affects soil systems. In general, the experts agreed that so far, no real impact on soil ecosystems had been detected from the cultivation of GM crops. However, there was a need for better tools for assessing the changes in functions of the soil communities and a better documentation of the results. At present there was no reason to believe that GM crops present any undue risk to soil ecosystems, but as new crops and products are developed, it is important to have monitoring schemes, provided that they were practical and feasible.
