An ecological assessment of transgenic crops

Since the first commercial release of a transgenic crop in 1994, the land area planted to these crops has expanded to over 90 million ha worldwide, with approximately 8.5 million farmers in 21 countries cultivating transgenic crops. Public apprehension has mounted apace. Concerns include: (i) the potential for gene flow into wild plant populations or soil organisms; (ii) adverse effects on non-target organisms; (iii) gene products or crop residues persisting in the environment with deleterious effects and, for insecticidal crops; (iv) resistance developing in target pest populations. Numerous studies on the environmental risks of transgenic crops are published. Gene flow to a crop's wild relatives has been demonstrated in the field; hence, the use of these crops is restricted to regions where wild relatives are not endemic. Gene flow to soil organisms is yet to be demonstrated under field conditions and is unlikely given the safeguards employed, but not impossible. The weight of the evidence suggests that there is little risk to non-target soil organisms, but reduced numbers of non-target beneficial insects have been reported with the use of insecticidal crops in some systems. Population effects on non-target insects associated with the use of insecticidal crops are significantly less extensive than those experienced using chemical pesticides, and it has yet to be determined if observed population changes are ecologically significant in these cropping systems. Resistance of target pests to insecticidal crops is possible and eventually likely, but after nearly a decade of use has yet to be detected under field conditions. Several strategies to reduce potential ecological impacts are either under development or near release. Ecological risks posed by new technologies under development and the need for in-country risk assessment and post-release monitoring are discussed.