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The Aral Sea basin in Central Asia and its major rivers, the Amu Darya and Syr Darya, have been the center of advanced river civilizations and a major hub of the Silk Roads for a period of more than 2000 years. The decline of the region has traditionally been attributed to the Mongol invasion of the early 13th century CE. But a new study, published in the Proceedings of the National Academy of Science, challenges this long-held view.
Toonen et al. questioning the long-held view that the fall of Central Asian river civilizations was determined by war and the destruction of irrigation infrastructure during the Mongol invasion. Image credit: National Library, Berlin.
“While the great Old World river civilizations have been the subject of archaeological and scientific studies for over a century, the ancient irrigation-based urban cultures that developed along the great rivers of Asia powerhouses are virtually unknown, ”said co-authored authors Dr. Willem Toonen of the Vrije Universiteit Amsterdam, Dr. Mark Macklin of the University of Lincoln and their colleagues.
“In the years 1950-60, archaeologists demonstrated that the Amu Darya and Syr Darya rivers, which flow northwest of the Pamir and Tien Shan mountains and flow into the Aral Sea, were the centers of societies flourishing urban areas from prehistoric times to the end of the Middle Ages. “
“The 50,000 km2 The area of land irrigated by flood waters has been estimated to be twice that of Mesopotamia. “
“The stagnation of the region at the end of the medieval period is generally attributed to a combination of the destructive Mongol invasion of the beginning of the 13th century AD and the gradual decline of the Silk Roads trading network.
“However, the hydroclimatic and hydromorphic contexts of these changes are largely unknown with only a handful of sites having been radiometrically dated.
Geomorphology and archeology of the Arys River watershed and Otrar oasis in Kazakhstan: (A) the Arys River watershed and research areas; (B) Otrar oasis with main irrigation canals and archaeological sites; (C) the low-flow Arys river; (D) Badam River during peak flow; (E) aerial view of the bifurcations of the irrigation canal south-east of Altyn; (F) aerial view of Otrar; (G) bifurcation of the irrigation canal with a fortified colony; (H) old irrigation canal near the town of Aris; (I) abandoned canals (white arrows) and abandoned agricultural plot (black arrows) east of Kuik Mardan. Image Credit: Toonen et al., doi: 10.1073 / pnas.2009553117.
The researchers focused on the archaeological sites and irrigation canals of Otrar Oasis, a UNESCO World Heritage Site that was once a Silk Road trade hub located at the meeting point of the Syr Darya and Arys rivers in southern Kazakhstan.
They surveyed the area to determine when the irrigation canals were abandoned and studied the past dynamics of the Arys River, whose waters fed the canals.
They found that despite the documented destruction of settlements, many sites in the Otrar Oasis persisted until drought-related contraction in the 9th century CE.
The Mongol invasion and destruction of the oasis in 1219 CE, however, came after more than 200 years of reduced rainfall, with evidence of large-scale canal abandonment.
“Our research shows that it was climate change, and not Genghis Khan, that was the ultimate cause of the disappearance of the forgotten river civilizations of Central Asia,” said Dr Macklin.
“We found that Central Asia recovered quickly after the Arab invasions in the 7th and 8th centuries CE due to favorable humid conditions.”
“But the prolonged drought during and after the subsequent destruction of Mongolia reduced the resilience of the local population and prevented the re-establishment of large-scale irrigation-based agriculture.”
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Willem HJ Toonen et al. A hydromorphic reassessment of the forgotten river civilizations of Central Asia. PNAS, published online December 14, 2020; doi: 10.1073 / pnas.2009553117
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