Ryan C. answered 02/13/20
Certified High School Teacher- 6 Years' Experience (4 HS , 2 college)
The Black Plague (which reached epidemic levels in Europe in 1348) had devastating population loss- about one-third of medieval Europe's population- and, indeed, was the only time in world history where the net global population went DOWN, not up.
However, you're right to suspect that it did have some positive results in the long term. Chiefly, the Black Death led to scarcity of labor throughout medieval Europe. Simply put, as the Plague ravaged the manors and killed off peasants, there was a sudden labor shortage among the peasants/serfs. This led European peoples to migrate, either in search of labor or to flee the Plague or both, which in turn led to an overall decline of feudalism (the dominant medieval economic system in which service was exchanged for protection for peasants.)
The end result was a net decline of feudalism and a mass migration from the manors to the cities, a phenomenon called urbanization (ex.- Rome, Bologna, Cologne, Toledo, Oslo, London, etc.). Urbanization and the flow of early forms of credit were especially dominant in the Italian States and the Low Countries (modern-day Belgium and the Netherlands). It is no coincidence, then, that these two regions emerged as cultural centers of the Commercial Revolution and the Renaissance, two key cultural and intellectual turning points in early modern Europe.
Thanks for your question!