For a period of time, the trade dwindled down, but during the Mongol Rule, it rose back to its peak during the Post Classical Era. This era also saw the rise of many cities, such as Medina, which rose due to the rise of Islam. Delhi rose when Islamic invaders settled under the Sultan after defeating the Hindus. African cities such as Timbuktu, Carthage and Tripoli. In Timbuktu, Mansa Musa built a capital to expand the kingdom past Ghana. The Islamic traders ended up pushed the Africa traders towards Carthage and Tripoli as they ventured into the Sahara.
There were a wide variety of effects caused by migration. New resources were discovered in new locations. Old resources depleted as a single region would provide for everyone through trade. Migration increased trade, which increased the need for surplus food. This resulted in the development of different agricultural systems such as the three field system and the terrace system. The nutrients were taken from the land as more crops were produced to