The consequences of this violent catastrophe were many. A cessation of wars and a sudden slump in trade immediately followed but were only of short duration. A more lasting and serious consequence was the drastic reduction of the amount of land under cultivation, due to the deaths of so many labourers. This proved to be the ruin of many landowners. The shortage of labour compelled them to substitute wages or money rents in place of labour services in an effort to keep their tenants. There was also a general rise in wages for artisans and peasants. These changes brought a new fluidity to the hitherto rigid stratification of society.
Military conquests by the Arab Empire and traders of Islamic faith were the primary means for spreading Islam to Africa, Europe, and Asia. I think its this one
