Landscape Effects of Insect-Resistant Genetically Modified Crops

Abstract

Putative effects of incorporating GM crops into agricultural landscapes have long been proposed. Here we examine the evidence for such effects within dynamic and heterogeneous agroecosystems, based on widespread commercial deployment insect-resistant Bt crops for over 10 years. While there is good evidence for changes in the population sizes of several target pest populations and for the increasing importance of some secondary pests, there is no evidence of landscapelevel effects on non-target species. These findings were anticipated by laboratory and field characterization of the high specificity of action of the Bacillus thuringiensis proteins currently deployed, and the equivalence of the GM crops to their non-transformed conventional counterparts. Indirect effects of the insect-resistant GM crops on the agricultural ecosystems due to multitrophic exposure, loss of prey, or reduction of prey quality, are generally negligible compared with the direct effects of other more dramatic environmental manipulations that are standard agricultural practices.