Drought, Not War, Felled Some Ancient Asian Civilizations

https://eos.org/articles/drought-not-war-felled-some-ancient-asian-civilizations

Source:  By Richard J. Sima, Eos/AGU. 

Excerpt: Radiocarbon dating, luminescent sand grains, and climate records point to drought as the reason for the civilizations’ demise. When we read about the fall of ancient civilizations in history books, we may think of warfare and other struggles on the human stage as leading causes for a culture’s decline. But climate change also accounts for many a society’s ruin. Such seems to be the case for the central Asian civilizations of the Otrār oasis located at the junction of the Syr Darya and Arys Rivers in what is now southern Kazakhstan. In a new study published in the Proceedings of the National Academy of Sciences of the United States of America, an interdisciplinary team of researchers report that the Otrār oasis had already been in a prolonged period of decline long before the Mongols invaded. ...The clues lie in irrigation canals that the ancient civilizations of Transoxania relied on for agriculture. ...Transoxania’s canals were previously thought to have been destroyed by the Mongols during their invasion, helping to precipitate decline in Transoxania. But Macklin and his colleagues were able to determine that much to their surprise, the canals fell into disrepair before Mongols ever set foot in the region. They used a combination of radiocarbon dating and a technique called optically stimulated luminescence (OSL), which dates the last time that sand was exposed to sunlight. ...The researchers also reconstructed climate records in the region over the past 2,000 years, which revealed that the canals were abandoned during periods of prolonged drought that both weakened the civilizations before the Mongols arrived and stunted their recovery afterward. Archaeological records further corroborated the coincident timing of the region’s cultural decline....