How did an agricultural surplus relate to expanded trade during the High Middle Ages?.

The trading surplus of food led to urbanization.

The demand for goods increased and so did the number of craftworkers in town. Older tows began to grow and new ones were built as rural peasants migrated to the cities searching for a better life. There was a boom in the medieval economy as industries changed and farming tecniques advanced. Since food became plentiful, surplus crops from one region were traded for surplus crops from another, which was the first form of capitalism to develop.