The “two most famous cases of internal collapse” (82) of empires are Rome, circa fourth century AD, and the Mayans, circa ninth century AD. As empires, both these cultures behave like pyramid schemes: “they gather wealth to the centre from an expanding periphery, which may be the frontier of a political and trading empire or a colonization of nature” (83-4). This expansive use of human and natural resources has the effect of destabilizing these cultures exactly as they reach their peak.

Like the Sumerians, deforestation impacted the peoples of the Mediterranean, which they carried out by the sixth century BC to provide goats grazing room. Though the Greeks saw this happening and tried to work against it, the ecological damage they had done to the region’s water system contributed to the wane of their cultural power in the region by 400 BC. Power shifted to Rome, which itself had to become reliant on foreign grain to survive this resource drought.

By the fourth century AD Rome controlled around 50 million people, roughly 25 percent of the human race. Roman conquest had become a private industry, with soldiers able to reap the rewards of conquered regions. As the military class grew in wealth, public land in Rome, including farmsteads, passed into the power of large estates established by wealthy military personnel.