National Geographic : 2009 Jul
• ANGKOR, IT APPEARS, WAS DOOMED BY THE VERY INGENUITY THAT TRANSFORMED A COLLECTION OF MINOR FIEFDOMS INTO AN EMPIRE. have failed completely. In other years, mega- monsoons lashed the region. To a tottering kingdom, extreme weather could have been the coup de grâce. Decades earlier, Angkor s waterworks were already ail- ing, to judge from the idled West Baray. "We don t know why the water system was operating below capacity---it s a conundrum," says Penny. "But what it means is that Angkor really had no fat to burn. e city was more exposed to the threat of drought than at any other time in its history." Prolonged and severe droughts, punc- tuated by torrential downpours, "would have ruined the water system," says Fletcher. Still, Penny says, "we re not talking about the place becoming a desert." People on the Tonle Sap oodplain south of the main temples would have been buffered from the worst effects. The Tonle Sap is fed by the Mekong River, whose headwaters in Tibetan glacier fields would have been largely immune to the e ects of an altered monsoon. But Khmer engineers, skilled as they were, could not alleviate parched conditions in the north by moving Tonle Sap water against the lay of the land. Gravity was their only pump. If inhabitants of northern Angkor were starv- ing while other parts of the city were hoarding rice, the stage would have been set for severe unrest. "When populations in tropical countries exceed the carrying capacity of the land, real trouble begins," says Yale University anthro- pologist Michael Coe. " is inevitably leads to cultural collapse." A malnourished army, preoc- cupied with internal strife, would have exposed the city to attack. Indeed, Ayutthaya s invasion and the Khmer king s ouster happened near the end of the second megadrought. Add to the climate chaos the shi ing political and religious winds already bu eting the king- dom, and Angkor s fate was sealed, says Fletch- er. " e world around Angkor was changing. Society was moving on. It would have been a surprise if Angkor persisted." e Khmer Empire was not the rst civili- zation felled by climate catastrophe. Centuries earlier, as Angkor was rising, halfway around the world a similar loss of environmental equi- librium was hammering the Maya city-states in Mexico and Central America. Many scholars now believe that the Maya succumbed to over- population and environmental degradation fol- lowing a series of three punishing droughts in the ninth century. "Essentially, the same thing happened to Angkor, " says Coe, who in the 1950s was the rst to discern similarities be- tween the Khmer and Maya civilizations. Modern societies may need to brace for simi- lar climatic challenges. According to Buckley, the most likely trigger of the Angkor mega- droughts was intense and persistent El Niño warming of the surface waters of the central and eastern tropical Paci c Ocean. Scientists debate whether human-caused climate change will lead to more pronounced El Niños, but the Vietnam- ese tree rings show that even natural oscillations in the Paci c can spark catastrophe. Angkor s end is a sobering lesson in the limits of human ingenuity. The Khmer had transformed their world---a monumental in- vestment that would have been excruciating for the kingdom s rulers to forsake. "Angkor s hydraulic system was an amazing machine, a wonderful mechanism for regulating the world," Fletcher says. Its engineers managed to keep the civilization s signal achievement running for six centuries---until, in the end, a greater force overwhelmed them. j A woman named Pronh Kin receives a water blessing poured by a monk to bring luck and health. Such benedic- tions served kings and commoners alike in the glory days of Angkor. Learn how long-ago canals and reservoirs might have kept water flowing. See Secrets of Angkor on the National Geographic Channel, July14at9p.m.ETintheU.S. Fly over Angkor Wat---and dive down for a closer look---at ngm.com.