The collapse of the Han dynasty around 220 C.E. ushered in more than three centuries of political fragmentation in China and signaled the rise of powerful and locally entrenched aristocratic families. It also meant the incursion of northern nomads, many of whom learned Chinese, dressed like Chinese, married into Chinese families, and governed northern regions of the country in a Chinese fashion. Such conditions of disunity, unnatural in the eyes of many thoughtful Chinese, discredited Confucianism and opened the door to a greater acceptance of Buddhism and Daoism among the elite. (See Zooming In: Ge Hong in Chapter 5.)

Those centuries also witnessed substantial Chinese migration southward toward the Yangzi River valley, a movement of people that gave southern China some 60 percent of the country’s population by 1000. That movement of Chinese people, accompanied by their intensive agriculture, set in motion a vast environmental transformation, marked by the destruction of the old-growth forests that once covered much of the country and the retreat of the elephants that had inhabited those lands. Around 800 C.E., the Chinese official and writer Liu Zongyuan lamented what was happening:

A tumbled confusion of lumber as flames on the hillside crackle

Not even the last remaining shrubs are safeguarded from destruction

Where once mountain torrents leapt—nothing but rutted gullies.2