The Aral Sea in Central Asia and its major rivers, the Amu Darya and Syr Darya, were the center of advanced river civilizations and an important hub of the Silk Roads for over 2,000 years. The region’s decline is traditionally attributed to the Mongol invasion in the early 13th century CE. But a new study, published in the Proceedings of the National Academy of Science, challenges this long-held vision.
Toonen et al. disputes the long-held view that the fall of the river civilizations in Central Asia was shaped by warfare and the destruction of irrigation infrastructure during the Mongol invasion. Image credit: National Library, Berlin.
“Although the great river civilizations of the Old World have been the subject of archaeological and scientific study for over a century, the ancient irrigation-based urban cultures that developed along the major rivers of Central Asia are virtually unknown,” said co-lead. authors Dr. Willem Toonen of the VU University Amsterdam, Dr. Mark Macklin of Lincoln College and their colleagues.
“In the 1950-60s, archaeologists showed that the rivers Amu Darya and Syr Darya, which flow northwest from the Pamir and Tien Shan mountains and drain into the Aral Sea, were the centers of thriving urban societies from prehistoric times to the late Middle Ages. “
‘The 50,000 km2 The area of flood-irrigated land was estimated to be twice that of Mesopotamia. “
“The region’s stagnation at the end of the Middle Ages is generally attributed to a combination of the devastating Mongol invasion in the early 13th century and the gradual decline of the Silk Road trade network.”
“However, the hydroclimatic and hydromorphic context of these changes is largely unknown, with only a handful of sites having been radiometrically dated.”
Geomorphology and archeology of the Arys catchment area and the Otrar oasis in Kazakhstan: (A) The catchment area and areas of research of the Arys; (B) Otrar oasis with the main irrigation channels and archaeological sites; (C) the Arys River at low flow; (D) the Badam River during peak discharge; (E) aerial photograph of bifurcations of irrigation channels southeast of Altyn; (F) Aerial view of Otrar; (G) bifurcation of irrigation channels with a fortified settlement; (H) old irrigation canal near the town of Arys; (I) abandoned canals (white arrows) and abandoned agricultural parcel (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 channels of the Otrar Oasis, a UNESCO World Heritage Site that was once a Silk Road trading hub at the meeting point of the Syr Darya and Arys rivers in southern Kazakhstan.
They surveyed the region to determine when the irrigation channels had been abandoned and studied the past dynamics of the Arys River, whose water fed the channels.
They found that despite documented settlement destruction, many sites in the Otrar Oasis persisted until the drought-related contraction in the 9th century AD.
However, the Mongol invasion and destruction of the oasis in 1219 CE came after more than 200 years of diminishing rainfall, with evidence of extensive canal abandonment.
“Our research shows that it was climate change, and not Genghis Khan, that ultimately caused the demise of Central Asia’s forgotten river civilizations,” said Dr. Macklin.
“We found that Central Asia recovered rapidly after Arab invasions in the 7th and 8th centuries CE due to favorable wet conditions.”
“But continued drought during and after the later Mongol destruction reduced the resilience of the local population and prevented the recovery of large-scale irrigation-based agriculture.”
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Willem HJ Toonen et al. A hydromorphic re-evaluation of the forgotten river civilizations of Central Asia. PNAS, published online December 14, 2020; doi: 10.1073 / pnas.2009553117