A tree trunk from Vietnam has given researchers new insight into the downfall of one of the most impressive and most puzzling cities in history—Angkor.
Research being submitted for publication this week to scientific journals explores the discovery via dendrochronology, or tree-ring dating, of two major droughts which would have coincided with the end of the dominance of the Angkorian empire.
Spanning nearly 3,000 square km and supporting a population of perhaps more than one million at its height, the medieval capital of Angkor started a rapid decline at the beginning for the 15th century, the reasons for which scholars have been trying to piece together for more than a century. These most recent findings give further credence to an increasingly promoted theory that an earlier incarnation of climate change may have contributed to the collapse of the Khmer citadel.
“The work is based on a 1,000-year hydroclimate reconstruction from tree rings from Vietnam,” said Brendan Buckley, a Columbia University scientist who, along with colleagues at his Tree-Ring Laboratory in New York, used data culled from an ancient tree to paint a not-particularly-pretty picture of Southeast Asia’s climate in the 14th and 15th centuries. By studying the tree rings of a 1,000-year-old cypress discovered in Vietnam’s highlands, the scientists were able to track overarching weather patterns, according to Dan Penny, director of the Great Angkor Project, at the University of Sydney.
“The thickness of the tree rings corresponds to early wet-season rainfall (that is, the tree lays down thicker rings when there is ample water in the early wet season, and thinner rings when it is under water stress),” explained Dr Penny via e-mail yesterday. “Therefore [they are] a useful proxy for monsoon behavior over the last millennium,” he said.
In this instance it was the lack of monsoons which proved telling.
Dr Buckley’s research revealed two “megadroughts” lasting about a decade each during the mid-1300s and early 1400s.
This information, notes Dr Penny, “helps us explain some of the features we observe in what remains of [Angkor’s water management] system today (such as modifications to central infrastructure like the great baray [reservoir], numerous cases of canals and dykes being partially destroyed or made redundant either deliberately or as a result of changed river flow).”
But Dr Penny and other Angkorian researchers are quick to caution against viewing these findings as evidence that climate change in any way caused the downfall.
“This is indeed a confirmation that something went wrong. It is a confirmation that environmental factors contributed,” said Christophe Pottier, director of the Ecole française d’Extrême-Orient in Siem Reap. “But there are many internal factors and external factors which played a larger role in the decline.”
Dr Pottier, who has been working on Angkor for 18 years, explained that by the time these droughts would have hit, Angkor was decidedly in decline. The increased power Vietnam and Thailand were exerting on the Khmer empire, a power struggle surrounding the kingship and a general shift throughout Southeast Asia from an agrarian economy to one centered on international ties, were already conspiring to destroy what was at the time the largest city in the world.
Adding an unstable climate into that heady mix would have doubtless been volatile. “It seems likely that the 14/15th century droughts we see in the paleoclimate records hit Angkor when it was least able to adapt quickly,” noted Dr Penny.
And given the city’s reliance on water-integral for Angkor beyond being simply a daily necessity-a drought would have been a double blow. “You see evidence of a very complex and elaborate water management system, but you also see failures of this system…. Having to manage it made them vulnerable,” said Damian Evans, an archaeologist at the University of Sydney who is currently based in Siem Reap.
Nevertheless, noted Dr Evans, “water was a core component of the Angkorian way of life. Managing and maintaining the systems became a royal tradition. It helped them to establish dominance.”
“There has always been some doubt about the role of climate and water management,” added Dr Evans. “The new research shows if it is not the most, it is among the most important factors contributing to the decline.”
