Demographic Changes
It was during the Southern and Northern Dynasties period that southern China (below the Yangtze River) was greatly developed from its previous state of early Chinese colonization and settlement. Beforehand, the south was inhabited by small and isolated communities of Chinese in a vast uncolonized wilderness of non-Chinese tribes, starting as a near peripheral frontier and changing into a thriving, urbanized, sinicized region of China. In his book Buddhism in Chinese History, Arthur F. Wright points out this fact by stating:
"When we speak of the area of the Yangtze valley and below in the period of disunion, we must banish from our minds the picture of the densely populated, intensively cultivated South China of recent centuries. When the aristocrats of the remnants of the Chin ruling house fled to the Nanking area early in the 4th century, the south contained perhaps a tenth of the population of China. There were centers of Chinese culture and administration, but around most of these lay vast uncolonized areas into which Chinese settlers were slow to move".
Read more about this topic: Southern And Northern Dynasties