Environmental and agronomic monitoring of adverse effects due to cultivation of genetically modified herbicide tolerant crops

Herbicide tolerance allows a specific crop variety to survive a herbicide treatment without injury despite the fact that the herbicide cannot be used selectively in a common variety of the same crop. Widely adopted and used worldwide are genetically modified herbicide tolerant (GMHT) crops with tolerance to the non-selective herbicide active ingredients glyphosate and glufosinate. Development of GMHT crops has substantially changed weed control systems and sometimes crop rotations and soil tillage systems. Attention must be given to the environmental and agro-environmental aspects and sustainability of agro-ecosystems based on HT crops because some adverse effects with this technology can appear, especially if used without knowledge of the risks involved and their prevention. This paper identifies main areas that should be monitored and discusses such potential adverse effects as hybridization with related taxa, occurrence of feral crops, and evolved herbicide resistance within weed communities. If there is no principal difference between conventional and GM crop cultivation, we propose monitoring approaches shall be based mainly on existing methods and monitoring networks. Scientific approaches as basis, decentralization with site-specific focus, as well as reasonable extent of data collection and their effective utilization should be the main features of the monitoring.