What Happened to Angkor?
Columbia tree-ring scientists journey to a remote forest in Cambodia to search for clues about the demise of a lost civilization.by David J. Craig Published Spring 2011
Archaeologists, meanwhile, say that Buckley’s work is helping them justify further research on Angkor’s water-management system. Fletcher is now studying the remains of a stone dam built across the Siem Reap River to fill the reservoir that was renovated near the city center. “It looks like the dam was obliterated suddenly at some point, which we can tell by the way its remains are distributed in the riverbed,” he says. “It looks like there was a deluge.”
In a forthcoming book about Angkor, Fletcher lays out this hypothesis: The city had grown so sprawling by the 14th century, and its infrastructure so large and unwieldy, that its citizens couldn’t alter dams, reservoirs, and irrigation ditches quickly enough when the monsoons went haywire.
“When the rains were light, these people had to figure out how to collect every drop of water,” Fletcher says. “And when the monsoons got really heavy again, any infrastructure that had been renovated to accommodate the dry periods could have been torn apart. If this kept happening, the people would have lost faith in their rulers.”
Water for tomorrow
Today, Buckley and other Columbia tree-ring scientists, including Edward Cook, his son Ben Cook, Kevin Anchukaitis, and Rosanne D’Arrigo ’89GSAS, continue to sample trees throughout Southeast Asia. Among their goals is to improve the integrity of the rainfall data that form the basis of the Angkor drought study. They also want to expand their geographic coverage — they’ve sampled trees from 300 locations in India, Nepal, Myanmar, China, Japan, as well as in Southeast Asia, so far — to determine where droughts have been most severe over the past millennium.
“Ultimately, we want to be able to tell how a drought affected one country versus another in the same region,” says Buckley. “This will give us a detailed understanding of monsoon activity.”
This information, the scientists say, could help governments in the region determine where they ought to construct new reservoirs to prepare for the possibility of severe and prolonged drought. The scientists worry that the summer rains could be disrupted again if global warming causes water temperatures in the Indian and Pacific Oceans to rise. The monsoons, they point out, provide drinking water for hundreds of millions of people year-round, as well as irrigation for their crops.
“One of the powerful things about paleoclimate research is that it shows us what nature is capable of,” says Anchukaitis, who integrates tree-ring information into the computer simulations used by climate modelers. “We may not have any written record of a 30-year drought ever occurring in this area, but it happened once. The trees show that.”