This chapter focuses on the third wave of globalization (land-based globalization), the Classical Age of the Roman Empire and the Han Empire in China, and the role of physical ecology in shaping geopolitics and imperial dynamics. Professor Sachs notes that the Roman Empire follows the Mediterranean climate zone east to west; their conquest was supported by wheat and olive crops, and limited north and south by climate zones. The Hellenic empire of Alexander and the Han Empire of China follow this same east-west orientation. Sachs talks about history, trade, and empire dynamics such as Roman, Han, Hun empire via an ecological lens.

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