A case reported by Watrud et al. (2004) found cross-pollination of non-GM bentgrass in complex terrain occurred at distances of more than 20 km from the nearest GM source. This is an order of magnitude or more greater than typical recommendations for isolation distances. As a test for our model, we simulated six days from the bentgrass case that coincided with the days suggested as most likely for long-range cross-pollination. We used simulated winds at 1-minute intervals to drive the dispersion model and predicted the movement of particles forward-in-time.
We simulated pollen dispersion to distances over twenty kilometers from its source. Deposition was predicted in the locations where outcross was reported by Watrud et al. (2004). Our model also predicted that terrain produces complex patterns of pollen deposition, so that simple methods often used to compute pollen dispersion will produce misleading results.
Watrud, L. S., E. H. Lee, A. Fairbrother, C. Burdick, J. R. Reichman, M. Bollman, M. Storm, G. King and P. K. Van de Water, 2004: Evidence for landscape-level, pollen-mediated gene flow from genetically modified creeping bentgrass with CP4 EPSPS as a marker. Proc. Nat. Acad. Sci., 101, 14533-14538.