Survival Lessons From an Ancient Failed City

(Photo: Shutterstock)

Angkor Wat Water Suburbanization, photo by Roland Fletcher

http://archive.org/details/AngkorTake2

Edward J. Blakely
The Atlantic Cities

The city of Angkor Wat, Cambodia, was a vibrant, growing metropolis in the late 17th century. Angkor was the New York, Paris or Rome of its time. At its peak from the 9th to 17th centuries AD, no one could have imagined any threat to this Khmer city-state. Yet, Angkor collapsed almost totally in the 17th century, and the reasons behind its demise offer an important lesson for today’s cities.

Angkor was built on a vast transportation network: canals acted substantially like freeways. The metropolis grew by expanding its network of canals from the central city to form a vast complex of suburban satellites. As depicted below, this was a gigantic enterprise. Ankgor grew exponentially as internal wealth and power increased. The waterways allowed goods and people to move well beyond the central core of the city.

But as Angkor continued to grow, its waterways became more fragile and vulnerable. Rain and other small but severe weather changes occurred, and the system began to crumble. My colleague Roland Fletcher, a professor of architecture at the University of Sydney in Australia, describes this process as “low density metropolitan collapse.”

Vast ancient settlement found at Angkor Wat

Aerial photos of remnants of Angkor settlement. Occupation mounds and ponds (upper left). Canals and embankments (upper right). Roadway and canal (lower left). Village temple area (lower right) (Image: Proceedings of the National Academy of Sciences) - Click on the photo to zoom in

The new map of Angkor Wat combines data from ground-sensing radar with aerial photographs and extensive fieldwork (Image: Proceedings of the National Academy of Sciences) - Click on the photo to zoom in

13 August 2007
NewScientist.com news service
Emma Young, Sydney, Australia

A huge urban sprawl once surrounded Cambodia’s famous Angkor Wat temple, according to a newly created map. The scale of the settlement makes it more plausible that the inhabitants of Angkor brought on their own society's collapse through environmental degradation.

The new map uses data from high-resolution, ground-sensing radar and aerial photographs to augment extensive fieldwork. By detecting slight variations in vegetation and ground moisture due to underlying ruins, the radar reveals in unprecedented detail the location of temples - including 94 newly identified temple sites plus another 74 that have yet to be checked on the ground - ponds, roads and canals.

Researchers in the Greater Angkor Project at the University of Sydney in Australia, together with colleagues in Australia, Cambodia and France, used the techniques to survey the entire watershed of the Angkor region.

The area covers nearly 3000 square kilometres, most of which is now blanketed with dense vegetation. Earlier maps suffered from problems with the resolution of aerial photographs and radar data, and from difficulties with accessing remote regions.

Urban sprawl

The researchers found that about two thirds of this region was once occupied, making it by far the biggest pre-industrial settlement yet documented. The main urban district of about 1000 square kilometres was surrounded by suburbs that seem to spread far beyond the north-western and south-eastern borders of the study site.

In fact, says Damian Evans of the University of Sydney, “there is just no obvious boundary” for the settlement. The population of the area was probably around half a million, he adds, though earlier estimates of a million inhabitants - suggested in the 1970s - could still be correct.

Such extensive settlement may help explain why Angkor, which thrived between the 9th and 16th centuries, had been overwhelmed by vegetation by the time European explorers first encountered the site in the 1860s.

The main theory for Angkor’s abandonment is that the creation of an extensive water management system caused environmental damage that ultimately led to the failure of the system, leading to food shortages. That scenario now seems even more likely.

Canal system

“This new map lays out definitively what the system would have looked like - and shows that it was capable of significantly impacting on the local environment,” says Evans.

Local people cleared land, creating a complex system to move water from a region of high ground spanning about 500 square kilometres to storage reservoirs in the centre, and on, via canals, to irrigate about another 500 square kilometres of land to the south. This system would have allowed the society to produce surplus rice to feed workers engaged in building monuments such as Angkor Wat.

The new map also reveals apparent failures of the canal system, with multiple dykes at certain sites. “There is massive redundancy in the canal network - and that gives us an indication that things were going wrong,” says Evans.

Researchers have not yet dated these sites to confirm that they coincide with Angkor’s collapse, however. Nor is it clear what exactly might have gone wrong. “We have evidence of a huge water-management system that had the capacity to impact significantly on the environment," says Evans. "But at the moment, the actual evidence that it did so is pretty thin on the ground.”

Journal reference: Proceedings of the National Academy of Sciences
(DOI: 10.1073/pnas.0702525104)