Consequences of isolation distances on the allocation of GM maize fields in agricultural landscapes of Germany

摘要

Background Coexistence measures such as isolation distances aim at minimizing conflicts between genetically modified (GM) and non-GM agricultural systems. Depending on landscape structure such as field sizes, field distribution and cropping patterns, these measures may spatially restrict GM cropping. Additional restrictions on GM cropping may be caused by environmental concerns, for instance protected sites or habitats of selected species may require isolation distances. To explore possible GM cropping restrictions in German agricultural landscapes, we conducted scenario simulations with 10% and 70% GM maize cropping shares, 1,000-m isolation distances to protected sites, and 150- and 300-m isolation distances to neighboring conventional and organic maize fields, respectively. While previous simulation studies applied smaller isolation distances (40 to 50 m), our research question was whether the conservative nature of isolation distances in Germany constitutes limitations to GM maize cropping. We investigated a variety of landscapes on two spatial scales: 4 federal states and 42 rural counties. Results On the state scale, we found that the maximum percentage of fields planted with GM maize compared to all potentially available fields was approximately 30%, indicating no limitation to GM cropping. On the scale of counties, the relevance and variability of landscape metrics was much greater. This resulted in potential limitations to GM cropping, especially for counties with more than 40% maize share. One thousand-meter isolation distances to protected sites had only marginal effects on the area available for GM cropping. Conclusions Isolation distances usually disregard landscape specifics. Our results suggest that the average shares of arable areas and 1,000-m distances to protected areas do not limit the allocation of GM maize. Limitations may occur in counties with more than 40% maize.