Tuesday, August 14, 2007

Angkor's ancient urban sprawl

The newswires in the last two days have been awash with stories of Angkor's past following the release yesterday by the Greater Angkor Project, of their research into the area surrounding Angkor and the news that they've identified another 74 long-lost temples amongst their findings. Wow, that'll keep me occupied for a few more visits. Here's one of the stories from the Los Angeles Times.

Lack of water doomed Angkor
Overpopulation and deforestation filled the Cambodian city's canals with sediment, researchers say. By Thomas H. Maugh II, Los Angeles Times Staff Writer.

The medieval Khmer city of Angkor in Cambodia was the largest preindustrial metropolis in the world, with a population near 1 million and an urban sprawl that stretched over an area similar to modern-day Los Angeles, researchers reported Monday. The city's spread over an area of more than 115 square miles was made possible by a sophisticated technology for managing and harvesting water for use during the dry season - including diverting a major river through the heart of the city. But that reliance on water led to the city's collapse in the 1500s as overpopulation and deforestation filled the canals with sediment, overwhelming the city's ability to maintain the system, according to the report in the Proceedings of the National Academy of Sciences. The hydraulic system became "not manageable, no matter how many resources were thrown at it," said archeologist Damian Evans of the University of Sydney in Australia, the lead author of the paper. But during the six centuries that the city thrived, it was unparalleled, particularly because it was one of the very few civilizations that sprang up in a tropical setting, said archeologist Vernon L. Scarborough of the University of Cincinnati, who was not involved in the research. Just one section of the city, called West Baray, "was 900 times larger than the entire 9-square-kilometer hillock on which sat Tikal, the largest city in Central America," he said. "The scale is truly unparalleled," added archeologist William A. Saturno of Boston University, who also was not involved. "Forest environments are not good ones for civilizations . . . because they require intensively manipulating the environment. Angkor is the epitome of this, and it is going to be the model for how tropical civilizations are interpreted."

Old and new technologies
The new data come from an unusual agglomeration of both old and new technologies. The core data came from a synthetic aperture radar unit flown on the space shuttle in 2000 and managed by NASA's Jet Propulsion Laboratory in La CaƱada Flintridge. The radar pierced low-lying clouds and vegetation to give an accurate picture of soil density, local structures and moisture in soil, which reflects growing conditions. The images revealed, for example, the characteristic moat-enclosed local temples and artificial ponds used for water storage and irrigation.This information was supplemented with photographs taken from ultralight aircraft flown over the city at low speeds and altitudes. Finally, the researchers used motor scooters to traverse the city and closely examine sites revealed on the radar images. But so many sites have been revealed, Evans said, that the researchers are only partway through this process.The group, collectively called the Greater Angkor Project, released a partial map three years ago. The new one released Monday contains, among other things, an additional 386 square miles of urban area, at least 74 long-lost temples and more than 1,000 newly recognized artificial ponds. Angkor was the capital of the Khmer Empire, which got its start in AD 802 when the god-king Jayavarman II declared the region's independence from Java. At its height, the empire covered not only Cambodia but also parts of modern-day Laos, Thailand and Vietnam. It is perhaps best known for Angkor Wat, the magnificent temple built by King Suryavarman II in the early 12th century. Angkor has been studied for more than a century, but early scholars were so overwhelmed by the artworks and architecture, as well as the political successions, that they ignored the archeology, said coauthor Roland Fletcher of the University of Sydney. In the late 1960s, French archeologist Bernard-Philippe Groslier began a more formal study of the ruins, but that work was halted for more than 20 years by the war that broke out in 1970. After the war, archeologist Christophe Pottier of the Ecole Francaise d'Extreme-Orient in Siem Reap, another coauthor, renewed the work, beginning what eventually grew into the current project.

Disputes over history
In the process, the researchers have begun solving many of the disputes that have arisen over the city's history, Evans said. "The debate has always been . . . was it large enough, was the manipulation of the landscape intensive enough to cause environmental problems?" Evans said. "The answer is definitively yes." Other arguments have been based on the assumption that Khmer hydraulic engineering technology was rather rudimentary, he said. "What our research has shown is that it was extremely sophisticated and highly complex," he said. Many of the reservoirs and walls of canals were constructed of compacted earth, he said, but junctions and other crucial points in the system were "quite sophisticated stone structures." The Khmer built, for example, a massive stone structure to divert the Siem Reap River from its old bed through the center of the city. Other sites have stone structures built into the walls to manage the inflow and outflow of water, he said. The system was complex enough that the Khmer could have grown rice throughout the year and not just during the rainy season, Evans said. It is not yet clear if they did so, however. "The intentional movement of earth to create the whole water system is just really mind-boggling," Saturno said. "It was an enormous undertaking" that required not just administrative skills, but also engineering know-how and massive amounts of physical labor. But in the end, maintenance became too labor-intensive, Evans said. As trees were removed from the landscape, sediment began accumulating in the canals at a rate more rapid than it could be removed. Many dike walls collapsed, although it is not yet known when that occurred. "We're going now and excavating [the sites] on the ground, and trying to get a grip on when they happened -- whether they were a precursor of the decline, a symptom or the system gradually falling into ruin after they left," he said.
Link: GAP.


Andy said...

Vast ancient settlement found at Angkor Wat...NewScientist.com news service by 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)

Andy said...

Metropolis: Angkor, the world's first mega-city.

The discovery that the famous Cambodian temple complex sits in the midst of a vast settlement the size of London, which flourished until the 15th century, has astounded archaeologists - but also baffled them: why did it disappear?

By Kathy Marks, The Independent (UK)

The huge sandstone temples of Angkor, built nearly 1,000 years ago and unearthed from the Cambodian jungle in the last century, are considered one of man's most outstanding architectural achievements. Last year more than a million tourists wandered through the ruins and watched the sun rise over the main temple's distinctive towering spires.

But, magnificent though the temple complex may be, it tells only part of the story of Angkor: a thriving metropolis, the world's first mega-city so mysteriously abandoned in the 15th century, and the former capital of the vast Khmer empire.

An international team of archaeologists has ascertained that the temple environs were just the core of a sprawling urban settlement that covered 700 square miles - a similar size to Greater London. They have spent 15 years mapping the area and putting together a picture of life in what is now established to have been the world's largest medieval city.

The "lost city of Angkor" was painstakingly uncovered by French archaeologists who spent much of the last century rescuing it from the forest and restoring it. Not surprisingly, they concentrated their efforts on the massive temples, which were built between the ninth and 13th centuries as monuments to the power and wealth of the Khmer kings. The rest of the region remained carpeted with vegetation, with few remnants of the ancient civilisation visible to the human eye at ground level.

A French, Cambodian and Australian team used aerial photographs, satellite imagery and high-resolution ground-sensing radar, provided by Nasa, to investigate what lay beneath the green cloak. What they found was the remains of 74 temples, as well as the sites of thousands of houses, roads, embankments, canals and ponds - all believed to have been part of an extensive, interconnected residential complex that included a large system of waterways. The team has just published its findings, together with a detailed map, in Proceedings of the National Academy of Sciences, a US journal.

Damian Evans, an Australian archaeologist who is deputy director of the Greater Angkor Project, said yesterday: "People never really considered Angkor as being much more than a scattering of temples in the landscape. In fact, it would have been a huge and popular city, full of life."

He and his colleagues report in their paper that, "even on a conservative estimate, greater Angkor at its peak was the world's most extensive pre-industrial low-density urban complex" - far larger than the ancient Mayan cities of central America, for instance, which covered 100 square miles at most. Mr Evans, who is based at the University of Sydney's archaeological computing library, said the Khmers of 1,000 years ago appear to have lived very similar lives to modern-day Cambodians. "They lived in clusters of houses on raised mounds to keep above the floodwaters in the wet season," he added.

"The mounds were in clusters, and scattered through them were these small village ponds. Between the houses were rice fields. And the core of this system was the village temple, in much the same way that Buddhist temples are the core of contemporary Cambodian communities."

The Khmer people subsisted on rice agriculture, just as many Cambodians still do, and the water management system - designed to trap water coming down the hills in the north - was partly used for irrigation, it is believed. The village ponds, from 25 to 60ft long, were used for drinking and domestic purposes during the dry season, as well as for watering livestock.

Mr Evans said the newly discovered temples, were not grand, like those at the heart of Angkor. Most now consist only of a pile of brick rubble, plus the occasional sandstone doorframe or pedestal, which once bore a statue. But while they hold little interest for tourists, they are valuable archaeological finds - and there are nearly 100 others out there, the team believes.

Mr Evans said the temples not only had a religious function, but were centres of taxation, education and water control. "So they can tell us about the everyday life at Angkor," he said.

A succession of Khmer kings ruled the Angkor area from about 800 AD, producing the architectural masterpieces and sculpture now preserved as a World Heritage site. By the 13th century the civilisation was in decline, and most of Angkor was abandoned by the early 15th century, apart from Angkor Wat, the main temple, which remained a Buddhist shrine. When the lost city - swallowed by the jungle for centuries - was rediscovered, archaeologists were, understandably, absorbed by the need to rescue and conserve the dozen or so main temples and their bas-relief carvings. Few excavations were carried out outside the temple precinct.

"No one really thought to look beyond them and into the broader landscape, to see how people actually lived," Mr Evans said.

By the 1960s it was clear that rich archaeological pickings lay beyond the walled city. A programme was put in place to investigate the wider area, but never got off the ground because of civil war, followed by the advent of the Khmer Rouge and Pol Pot's murderous regime. It was not until the 1990s that the security situation improved, enabling work to resume. But when the international mapping team started their project, they still needed an armed escort for protection in certain areas. And even now, Mr Evans said he never steps off marked paths, because of the risk posed by unexploded landmines.

Until now, Angkor was never looked at as an extended urban area. The city was thought to consist of the central walled precinct, covering about one square mile, where tens of thousands of people lived. "No one really considered the fact that there might be an urban fabric that stretched between and beyond the temples of Angkor," Mr Evans said.

The settlement mapped by the team existed from AD500 to AD1500, and could have supported a population of up to one million people. But some of the terrain may have been sparsely populated, particularly in outlying areas. "Now we have the map, we can quantify this residential space," Mr Evans said.

"We can start to do proper demographic studies and work out how many people were living on these mounds. But we can say now, from a preliminary point of view, that it would have had a population of several hundred thousand, at least."

The city was criss-crossed by roadways and canals, and was similar to modern cities that suffer from urban sprawl. Mr Evans said: "It had the same sort of dense core and pattern of spreading out into rural areas."

The team may also have found the key to Angkor's collapse - or, at least, confirmed an existing theory: that the city "built itself out of existence". Mr Evans said: "The water management system, in particular, had the potential to create some very serious environmental problems and radically remodel the landscape. You can see the city pushing into forested areas, stripping vegetation and re-engineering the landscape into something that was completely artificial.

"The city was certainly big enough, and the agricultural exploitation was intensive enough, to have impacted on the environment. Angkor would have suffered from the same problems as contemporary low-density cities, in terms of pressure on the infrastructure, and poor management of natural resources like water. But they had limited technology to deal with these problems and failed to, ultimately, perhaps."

The team also found evidence of embankments that had been breached, and of ad hoc repairs to bridges and dams, suggesting that the water system had become unmanageable over time. Mr Evans said over-population, deforestation, topsoil erosion and degradation, with subsequent sedimenation or flooding, could have been disastrous for medieval residents.

Excavations in the next few years will examine the theory in more detail, and try to gather more data, for instance, on sedimentation in the canals.

The radar images provided by Nasa distinguished the contours of the landscape under the surface of the earth, identifying the location of roads and canals. The radar also showed up different levels of soil moisture in the rice fields. When excavations were carried out, they proved to have been the site of a canal or temple moat. The new archaeological evidence will pose a challenge for conservationists, as the current World Heritage site covers 150 square miles, which are intensively managed and protected.

Cambodian authorities, meanwhile, are grappling with the problem of how to preserve the precious ruins within the temple precinct from increasing numbers of visitors. Just 7,600 people ventured to Angkor in 1993, when it was added to Unesco's World Heritage list. Since then, with Cambodia becoming accepted as a "safe" destination, tourism has boomed. The government is expecting three million visitors in 2010, and many of those will head to the temples. Angkor Wat is now one of south-east Asia's leading attractions.

Tourism, which brought impoverished Cambodia $1.5bn (£750m) in revenue last year, is helping the country to rebuild after its long dark period. But Soeung Kong, deputy director-general of the Aspara Authority, which oversees Angkor's upkeep, told Agence France Press recently: "The harm to the temples is unavoidable when many people walk in and out of them. We are trying to keep that harm at a minimal level."

Teruo Jinnai, Unesco's senior official in Cambodia, said: "When you have such a huge mass of tourists visiting, then we are concerned about damage to the heritage site and the temples and the monuments. Many temples are very fragile."

The main problem lies in Siem Reap, the nearby town that has mushroomed in recent years to accommodate the growing numbers of tourists. There are more than 250 guesthouses and hotels, and they have been sucking up groundwater and destabilising the earth beneath Angkor. At least one monument, the Bayon temple, famous for the serene faces carved on its 54 towers, is collapsing into the sandy ground - a development confirmed by its sinking foundations, and widening cracks between its carefully carved stones.