The presence of weed seeds in crop fields at harvest affects crop quality, yield, and suitability of agricultural exports. The emergence of herbicide-resistant weeds can fundamentally alter farming practices, forcing less profitable and often less reliable crop rotations, and potentially necessitating the use of tillage practicies known to adversely impact soil health and increase erosion. Furthermore, the inadvertent blending of grain with weed seeds can contaminate other grain from the region along the export pipeline. Overseas importers use weed seed contamination limits as leverage to block the import of Pacific Northwest wheat.