Assessment of environmental impacts of genetically modified plants

The objective of this study was to carry out a survey of the current international status of research on the environmental impacts of genetically modified plants and to combine it with a scientific assessment of gaps and limits of biosafety research. Methods of genetic engineering and the risks associated with them were considered, followed by aspects such as gene spread by hybridization, horizontal gene transfer and spread of genetically modified organisms (GMO). Genes and traits transferred to plants can lead to direct and indirect impacts on the environment and biological diversity. 
Gene transfer by Agrobacterium tumefaciens or microprojectile bombardment is not precise. Integration of multiple copies of transgenes and superfluous DNA at multiple sites has been observed. Each gene transfer is a singular event that has to be looked at with regard to its impacts on the activity of transgenes and endogenous genes. The integration of bacterial DNA-sequences (e.g. antibiotic resistance genes) could increase the probability of horizontal gene transfer to microorganisms. Outcrossing of transgenic plants to related crop plants and wild plants is likely, physical and biological barriers to gene flow will not eliminate it completely.
Environmental impacts of transgenic plants depend mainly on the traits they carry, be they desired or unexpected as a side effect of the transformation. Indirect impacts can result from the changes in the agronomic practice linked to cultivation of GMOs. As most commercially used genetically modified plants carry resistances to herbicides and/or to insects, effects on pesticide use are likely. In addition, weeds will develop resistance to herbicides that are used more broadly and insect pests will become resistant to the toxins produced. Environmental impacts of genetically modified plants with traits that alter the plant metabolism more profoundly are more difficult to assess than those of herbicide- and insect-resistant plants.