These effects are of concern because they appear to weaken or destroy ecosystems’ capacity for resilience—that is, an ecosystem’s ability to return to its initial state despite disturbance. Potential ecological effects of transgenic crops, and other crops bearing novel traits, may be heightened in this destabilized ecological milieu. This argues for a cautious approach to the release of any crop that bears a novel trait. Equally, it is an argument for a cautious approach to any extensive change in agricultural practices.

The two plant pest statutes (Federal Plant Pest Act and the Federal Plant Quarantine Act), which are used by APHIS to regulate transgenic plants, were originally developed to regulate the introduction of nonindigenous plant species. Because the amount of novel genetic information added to an ecosystem by the introduction of a new species is much greater than that added by a single transgene, the use of these plant pest statutes to regulate transgenic plants has been criticized. On the other hand, the use of these statutes for regulating transgenic but not conventionally improved plants has been defended because the introduced genes in transgenic plants can have a much more distant taxonomic origin (for example, bacterial genes transferred to plants). These arguments are based on a general assumption that the risks associated with the introduction of genetic novelty are related to the number of genetic changes and the origin of the novel genes.

The committee compared empirical evidence of environmental impacts involving small to large amounts of genetic novelty from taxonomically related and unrelated sources and found no general support for this assumption. More specifically, it was found that (1) small and large genetic changes have had substantial environmental consequences; (2) the consequences of biological novelty depend strongly on the specific environment, including the genomic, physical, and biological environments into which they are introduced; (3) the significance of the consequences of biological novelty depend on societal values; (4) introduction of biological novelty can have unintended and unpredicted effects on the recipient community and ecosystem; (5) a priori there is no strict dichotomy between the possibility of environmental hazard associated with releases of cultivated plants with novel traits and the introduction of nonindigenous plant species. However, the highly domesticated characteristics of many cultivated plants decrease the potential of certain hazards.

The conventional development of semi-dwarf, short-season varieties of rice and wheat that propelled the Green Revolution of the twentieth century clearly exemplifies how a small number of genetic changes to a crop can impact the environment. In the case of rice, a single gene for short stature made rice much more responsive to fertilizer, while a few



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