Upheaval in Ukraine could cause shipping delays and disrupt grain supplies across the globe, according to an Iowa State University economist.

Ukrainian farmers have ramped up their production of corn and soybeans in recent years, most of which is exported. But recent tensions with Russia, focused in the Crimea region and the Black Sea, could create a bottleneck that shuts down Ukrainian exports to the rest of the world.

The Black Sea is the main avenue by which Ukrainian crops reach international markets. If shipping traffic on the Black Sea is shut down for an extended period, Ukrainian grain will have nowhere to go, said Chad Hart, an Iowa State University ...