Environmental effects of genetically engineered woody biomass crops

The use of genetically engineered crop plants has raised concerns about the risks these crops pose to natural and agricultural ecosystems. The potential environmental hazards of transgenic woody biomass crops is discussed, and based on the biology of these crops and their transgenes, recommend a scientific framework for assessing risk. The potential impacts of transgenes based on both characteristics of the transgenic crop and potential for spread of the transgene to other organisms is considered. It is argued that risk assessment should focus exclusively on the phenotype expected from the transgene within a given plant host and environment, weighing both the costs of foregoing the benefits a transgenic variety can provide and the possibility of adverse environmental effects. Basic principles of population genetics can be used to facilitate prediction of the potential for transgenes to spread and establish in natural ecosystems. For example, transgenes that are expected to have neutral or deleterious effects on tree fitness, including those for lignin modification, reproductive sterility and antibiotic resistance, should be of little environmental concern in most biomass crop systems. In contrast, transgenes that are likely to substantially affect host fitness pose a greater risk, as are plants with transgenes which produce a substance known to disrupt ecological processes. Field experiments to determine population replacement and transgene flow are desirable for testing such predictions; however, the long generation times of tree crops makes such studies prohibitive. It is argued that a combination of demographic data from existing non-transgenic populations, simulation modeling of transgene dispersal, and monitoring field releases can be used to guide current risk assessment and can be used to further scientific knowledge for future assessment.