Angkor lesson for cities

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  • Published 1.04.10

New Delhi, March 31: Scientists have discovered the first hard evidence that erratic rainfall precipitated the demise of Angkor, the world’s largest pre-industrial settlement built by a medieval Hindu empire in Southeast Asia.

A series of extreme droughts punctuated by spells of intense rainfall during the 14th and 15th centuries tipped the overgrown settlement in present-day Cambodia towards failure as a viable city, an international team of scientists has said.

The vast city of the Khmer civilisation whose ruins are renowned for the Angkor Wat temple failed to cope with the changing rainfall patterns because it had become overdependent on an elaborate network of canals and reservoirs, the researchers said.

Angkor’s fate, the scientists said, may hold a lesson for the modern world — a sign that heavy reliance on extensive and interconnected infrastructure reduces the resilience of cities, making them vulnerable to change.

Archaeological evidence suggests that the Angkor empire emerged during the 9th century, developed a settlement that grew to 3,000 square kilometres, and collapsed in the early 1400s. Archaeologists believe the settlement supported an estimated 750,000 people at its peak during the 12th century. Despite theories involving invasions and natural disasters, the decline and fall of Angkor remains unresolved.

Now, scientists from Australia, Thailand, Vietnam and the US have analysed climate in Southeast Asia over a 979-year period using tree rings — patterns on trees that serve as proxy indicators of moisture levels in the past.

Their findings, published in the Proceedings of the National Academy of Sciences on Tuesday, show that Southeast Asia had experienced severe droughts in the mid-1300s.

“While there had been some speculation about (the impact of) environment and climate on Angkor, this is the first hard evidence,” Brendan Buckley, lead author of the study at Columbia University told The Telegraph.

Angkor’s vulnerability lay in its size and its web of canals, embankments and reservoirs. The researchers said the droughts affected the water supply while heavy rainfall damaged the infrastructure when agricultural productivity was suffering.

“Angkor’s infrastructure was so large — it was impossible to avoid, and difficult to re-engineer to the changing circumstances,” said Daniel Penny, a team member from the University of Sydney.

“The system was hyper-coherent — each component relied on other neighbouring components to operate. If one canal was choked by sediments, the smaller canals and reservoirs depending on it became useless,” Penny said.

India also experienced droughts at the time — the period coincides with the Durga Devi famine that lasted from 1396 to 1407.

“But Indian cities of the same period were compact — most were under 30 square kilometres in extent,” Roland Fletcher, an archaeologist at the University of Sydney, said.

But researchers feel that features of medieval Angkor even appear in the modern world with cities depending extensively on roads, sewer systems and public transport.

“We’re all familiar with large infrastructural networks that no longer operate properly, that can’t be altered or replaced, or that have deleterious consequences for the environment, the economy, or other aspects of social life,” Penny said. “The concern is that humans now live predominantly in low-density sprawling cities, dependent on massive infrastructure,” said Fletcher. “We too face climate instability. The issue is topical, regardless of the debates about what or who causes global warming.”