work that addresses many of the concerns of the public and the scientific community regarding biological risks associated with commercializing genetically engineered plants. Chapters 3 and 4 provide in-depth reviews of how the USDA-APHIS regulates genetically engineered plants, and Chapter 5 assesses how well the USDA-APHIS approach functions and how well it matches the framework described in Chapter 2. Chapter 5 ends with recommendations for specific improvements in the APHIS precommercialization process. One general conclusion from Chapters 1 to 5, and from other published studies is that it will be impossible to assess some types of environmental effects of genetically modified plants based on the small-scale field testing that can be conducted prior to commercialization. Therefore, Chapter 6 examines the prospects and problems associated with developing post-commercialization monitoring programs to detect and measure such effects. The potential environmental impacts of future products of genetic engineering may differ from those of the engineered crops that have recently been commercialized. Therefore, the final chapter of this report (Chapter 7) is devoted to examining potential future products of genetic engineering and to how sets of novel traits in crops could alter the use of land, chemicals, and other resources. This concluding chapter also discusses how the public’s view of agriculture and its regulation may evolve in the future.

ENVIRONMENTAL EFFECTS OF AGROECOSYSTEMS ON SURROUNDING ECOSYSTEMS

In recent decades agriculture has been intensified by increases in the use of mechanization, irrigation, high-yielding crops, synthetic fertilizers, and pesticides. This has led to major changes in the structure, function, management, and purposes of agroecosystems (Swift and Anderson 1993, Swift et al. 1995, Matson et al. 1997). Typical structural changes include large reductions in plant, animal, and microbial biodiversity (Swift and Anderson 1993, Lacher et al. 1999) and simplified patterns of abiotic resource stocks and flows (Swift et al. 1995, Matson et al. 1997, Vitousek et al. 1997). Intensified agroecosystems are now predominant in developed countries and in highly capitalized export and commodity production of developing countries. In these latter countries there has also been expansion of less capitalized, smallholder agriculture onto marginal and ecologically sensitive lands, again typically accompanied by reductions in biodiversity and simplification of resource stocks and flows (Holloway 1991, Swift et al. 1995, Perfecto et al. 1996).

These changes have increased the environmental effects of agroecosystems on neighboring ecosystems, relative to those exerted by preintensified agroecosystems. These environmental effects are primarily



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