Climate change undid the centre of the ancient Khmer empire six centuries ago
Every year, a few million pairs of feet (in cheap flip-flops or trendy sandals, most in branded sports shoes, only a few bare) file across the ancient stone causeway of some 200 metres that connects the central citadel of Angkor Wat with the banks across its enormous encircling water body.
Intent on the magnificent galleries (there are eight, dense with marching or warring figures) or on reaching the massive platform in the centre that represents Mount Meru, many would give little thought to the reasons why Angkor (the city, not Angkor the monument) declined and fell into ruins for hundreds of years. Although almost every one of those visitors would carry a water bottle (usually plastic, purchased there, and which contributes to the dreadful mountain of plastic which the authorities of the famous World Heritage site must deal with) few consider the climatic aspect that may have triggered off, or hastened, the decline of Angkor Thom, the great urban heart of the ancient Khmer empire.
The last hundred years of archaeological investigation have shown that Angkor had an extensive and elaborate water management network for dispersing water and for distributing it to the rice fields which surrounded the capital region. Huge masonry structures were built to collect water and distribute it through a canal system whose sophistication — making no allowance for antiquity — would surpass any modern irrigation programme of the last century. Through the control of water and the zoning of the built and agricultural landscape, Angkor Thom was a re-engineering of the commons on a gigantic scale — there were thousands of square kilometres of rice fields. The natural forest was steadily replaced by economically valuable trees and shrubs around the numerous timber houses, along embankments and within enclosures.
The engineering of Angkor has been documented in detail by archaeologists of the erstwhile Indochine: G. Coedes wrote his Inscriptions du Cambodge that unveiled the world beyond the great Wat, George Groslier examined the vibrant urbanism of the Khmer in Angkor: Les Villes d’Art Celebres, R.C. Majumdar described in detail the implications environmental and social in his pathbreaking Inscriptions of Kambuja, and Henri Parmentier examined the Khmer and their densely rich world in L’Art Architectural Hindou dans L’Inde et en Extreme.
And yet our understanding of the gradual but irreversible decline of the heart of the once powerful Khmer empire continues to deepen. New methods have used high-altitude remote sensing to read again the landscape of inner Cambodia — the Kambuja and Cambodge of old — and these inform us that the Angkorians were affected by climatic instability between the 14th and the 16th centuries, for there is evidence of very heavy monsoons (which would have flooded the flat, low central Cambodian river basin) and also of crippling drought (which would have exhausted the stock of annual water, given the demands of the huge urban population). Those famous temples were surrounded by densely populated suburbs — greater Angkor covered about 1,000 square kilometres and was home to about 750,000 people at its 12th century peak.
We have now learnt that large deposits of sand filled the southern canals in the 14th century, that the Siem Reap river (which wanders through the town of the same name before debouching into the Tonle Sap, the vast freshwater lake which is Cambodia’s dominant geographical feature) today runs several metres below its course in the heyday of empire. The cumulative tale is one of a Greater Angkor that dazzled ancient Southeast Asia with its extensive, low-density capital city, one that controlled to a minute degree the natural and human flows around a fully re-engineered landscape, was dependent on an infrastructure so massive that its creation was the basis of the non-agricultural economy for several generations, but which nonetheless was affected by climatic instability to a degree that is an eerie historical echo of our own troubled times of severe climatic events having become the norm rather than the rarity.
The tale that has been unlayered by archaeological techniques classical and modern ought to be heeded in a region that still bases its idea of economic growth on accumulating people and capital in urban centres. Angkor Thom as the urban engine — which both sustained and placed demands upon a complex and thriving agrarian system (a highly productive one, for three harvests a year were not unknown) — cut out of a tropical forest environment.
Technically sophisticated and economically powerful, it still perished, for the same reasons which in our time we call climate change.
Rahul Goswami is an expert on intangible cultural heritage with Unesco