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.”

Angkor Wat: city that lived and died by the environment

ANIMATIONS: TOM CHANDLER, MONASH UNIVERSITY

KATE CHAILLAT
Down To Earth (India)

The famous temple site of Angkor Wat was once much more than that. A new map shows that the magnificent temples were part of a huge urban sprawl, with an extensive rural hinterland. People here created an elaborate system of reservoirs and canals—for irrigation, trade and travel—that began to silt up as the population grew, and perhaps saw failures that resulted in flooding and water shortages. But at its peak, the agglomeration was the largest of its kind in the pre-industrial world, according to a team of archaeologists working at this ancient Cambodian site.

The Greater Angkor Project (GAP), led by a team of Australian, Cambodian and French archaeologists, has used remote sensing satellite imagery by nasa to uncover what lay hidden under vegetation at Angkor Wat. By detecting slight variations in vegetation and ground moisture due to underlying ruins, the satellite images reveal Angkor’s urban sprawl in unprecedented detail. The archaeologist say the map “displays the ancient Cambodian site as an inhabited space: not a scattered collection of discrete temples, but an integrated, interdependent rural and urban residential network, larger than anything discovered in the ancient world so far.” The findings were published in the August 14th issue of the Proceedings of the National Academy of Sciences.

After Mouhot

Angkor was the capital of the Khmer Empire, which held sway over modern Cambodia between the 9th and 14th centuries. In 1866, French explorer Henri Mouhot alerted the Western world to the ruins of a temple complex in Angkor. The place had been visited by Europeans before but Mouhot’s posthumously published Travels in Siam, Cambodia and Laos is believed to have been influential in arousing European interest in the site. Scholars following in the Frenchman’s footsteps were so overwhelmed by the artworks and architecture, that they ignored the archaeology. Angkor was believed to be around 40 sq km.

But GAP archaeologists say the city state was actually “stretched for at least 1,000 sq km”. They say that the closest pre-modern equivalent to the Cambodian city state was the Mayan city of Tikal in Guatemala, at its peak around 150 sq km.

“There is not a single square kilometre in Angkor that wasn’t intensively modified and engineered,” says Damian Evans, a gap archaeologist. Besides reservoirs and residential clusters, the map reveals 74 new temples and an elaborate grid of walled field systems.

Evans says there has been an ongoing debate about whether the water network of Angkor could have supported intensive rice cultivation. “The elaborate inlets and outlets on all the major reservoirs coupled with distributor canals connected to every single water source in the region suggest water was intensively exploited at Angkor and could well have been used for rice agriculture. The canals were either made of stone or compacted earth and there was a series of very sophisticated water control devices such as spillways—sometimes massive structures built in stone—which have the capacity to provide irrigation for rice,” he writes.

Old theory

GAP findings confirm a theory, first put forward in 1955 by Bernard-Philippe Groslier. The French archaeologist had argued that the ancient irrigation network, which had been ignored by researchers who followed in Mouhot’s footsteps, “was both built and used for irrigation, specifically, to ameliorate variations in agricultural output caused by an unpredictable annual monsoon and to support a huge population of greater than a million people in a constellation of suburbs”.

Evans, however, is not so sure of Angkor’s population. “The GAP study doesn’t provide any direct evidence of an extremely large urban population. Our study is more revealing about the spatial extent of the settlement than about its population,” he says.

Environmental demise?

Population figures aside, the expansion of Angkor is impressive and bears witness to the extent the Khmers were able to alter their environment, ultimately engineering Angkor Wat’s demise. It was earlier believed that the city state was deserted after Thai armies ransacked it.

But the GAP research has a given a different perspective to the city’s fall. Evans explains that the “massive infrastructural network of roads and canals was built to give coherence to the extended settlement area and to provide a means of communication and of transporting vast amounts of people, stone, and other goods across the landscape”. However the system might have been difficult to maintain especially with potential competing interests for water control (temples, domestic an agricultural use).

Groslier had already suggested that over-intensive irrigation and land-use led to the city’s decline. “Excavations conducted during the mapping did reveal a series of ad hoc adaptations, breaches, modifications to the irrigation system suggesting systemic problems in the network could indeed have caused the downfall of the Angkorian state,” Evans notes.

Furthermore, water-intensive rice agriculture required forest clearing and walled fields, which increased risks of runoffs, sedimentation and caused erratic water flows. In fact remote sensing and ground observations have revealed that “the Siem Reap river is now incised 5-8 metres into the Angkorian floodplain, and a major canal in the south of Angkor that postdates the 14th century ad (when the city was abandoned) is entirely filled with cross-bedded sands, indicating rapid movement of large quantities of sediment-laden water.”

But what led to Angkor’s collapse in the 14th century? Evans admits, “We don’t know that at this stage. There is too little data on both population and on climatic variation in this area”.

What the GAP archaeologists do know though is that expansion of the settlement created increasing difficulties for the movement of people, information and goods around the landscape.

GAP’s current goal is to ascertain if Angkorians were able to deal with the environmental consequences of their settlement if their failure to factor in ecological changes lead to their downfall. Evans says that the increased sedimentation in canals due to deforestation caused by rice cultivation cannot be ruled out.

The archaeologist notes that Angkor’s demise is a lot similar to the collapse of many pre-industrial civilisations. “It’s something to bear in mind, considering that many of our contemporary cities are expansive, low-density urban sprawls as Angkor appears to have been,” he says. Controlling the environment helped Angkor become the great political centre it was but also led to it losing that place.

Archaeologists to dig for more clues about demise of ancient Angkor

Wednesday, August 15, 2007
The Associated Press

PHNOM PENH, Cambodia: Excavations are planned at Angkor to scour for more clues about ecological problems which led to the demise of Cambodia's great ancient city, an Australian archaeologist said Thursday.

"We have clear evidence now that Angkor was big enough to have caused environmental problems," Damian Evans said.

"But we need finer-grained detail to determine for sure how severe those problems were, and whether or not the local population was able to deal with them or not," said Evans, deputy director of the Greater Angkor Project at the University of Sydney.

His group published its findings in this week's online edition of Proceedings of the National Academy of Sciences.

They reveal that Angkor, during its zenith between the 9th and 14th centuries, was "the world's most extensive preindustrial low-density complex" and far larger than previously thought. It included an elaborate water management network encompassing nearly 1,000 square kilometers (390 square miles).

Research found that the complex was too vast to manage. Extending rice fields to support a population of more than 1 million resulted in serious ecological problems, including deforestation, topsoil degradation and erosion.

The study's conclusions supported a theory in the early 1950s by Bernard-Philippe Groslier, a prominent French archaeologist, that the collapse of Angkor stemmed from over-exploitation of the environment.

The study produced a comprehensive digital mapping database detailing tens of thousands of individual features across nearly 3,000 square kilometers (1,160 square miles).

Previously, there were around 800 known temple sites in the mapped area, Evans said in an e-mail, adding that the number will likely be between 950 and 1,000 once results from the excavations have been verified on the ground.

In a separate statement posted on his group's Web site, he said some of those sites and other delicate traces of great archaeological significance are under serious threat from uncontrolled development in Siem Reap province to meet rising tourist demand.

He said the development is good for Cambodia, but that proper heritage management systems must be in place so that "small local temples sites and so on can be properly excavated and studied by archaeologists before they are destroyed for modern development."

He said he also hoped that the study will give a "stimulus for greater recognition of the need to stop the illicit international trade" in Cambodian antiquities.

The Angkor temples have suffered extensive destruction by nature and pillaging by looters during three decades of warfare and revolution in Cambodia.

The impoverished country is now at peace and the monuments, including the famed Angkor Wat, are the country's main tourist attractions, earning much-needed hard currency.

But in recent years, conservationists have expressed concerns about stress to the monuments from the tourist invasion.

Evans' study is a wake-up call for more vigilance in Cambodia's efforts to conserve its centuries-old heritage, an official of the Apsara Authority, the government agency managing the site, said Wednesday.

The official, Soeung Kong, said what happened to ancient Angkor in the past "appears to be repeating itself now" and thus highlights current challenges in managing and conserving the temples.

"Since we are aware of this, we have to take measures to prevent it from worsening or to minimize the impact as much as possible," he said.

___

On the Net:

Greater Angkor Project:
http://acl.arts.usyd.edu.au/angkor/gap/index.php

Proceedings of the National Academy of Sciences:
http://www.pnas.org/current.shtml

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?

15 August 2007
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.

Lack of water doomed Angkor

Overpopulation and deforestation filled the Cambodian city's canals with sediment, researchers say.

August 14, 2007
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 Cañada 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.

thomas.maugh@latimes.com

Urban Sprawl Might Have Doomed Angkor Wat

Artist's impression of settled areas in and around Angkor Wat complex. Credit: Tom Chandler, Monash University

13 August 2007
By Ker Than,
LiveScience Staff Writer

A new map made from satellite data reveals Cambodia's Angkor Wat temple was the center of one of the largest cities of the pre-industrialized world.

The research also sheds light on the extent of the city's sprawl and on its mysterious downfall, factors that could be linked in a way that bears on today's extensive and suburbanized metropolises.

Using ground-sensing radar provided by NASA, researchers found evidence that the ancient Cambodian capital took up an area of nearly 400 square miles (1,000 square kilometers). For comparison, Philadelphia covers 135 square miles, while Phoenix sprawls across more than 500 square miles, not including the huge suburbs. Each has about 1.5 million residents in the city limits.

"In terms of population, however, Angkor would only have had a few hundred thousand people," said study team member Damian Evans, an archaeologist at the University of Sydney in Australia. "There were cities with much larger populations—for example, in China—before, during and after the Angkor period."

The new radar technique, which senses differences in plant growth and soil moisture content created by topographical differences, also identified more than 1,000 new manmade ponds and more than 70 long-lost temples.

The work, detailed in the Aug. 14 issue of the journal for the Proceedings of the National Academy of Sciences, provides fresh evidence for an idea put forward more than 50 years ago— that Angkor relied on a complex irrigation system consisting of linked ponds and that the city's downfall might have been the result of land overexploitation.

The Khmer capital

Angkor was the capital city of the Khmer empire from the 9th to the 16th centuries. The now-crumbling and decadent temple, Angkor Wat , was constructed in the 12th century at the bidding of one of its kings.

The new maps show that Angkor's water system consisted of canals in the North that funneled water into massive reservoirs in the city's center where the temple resided. "From there, a series of distributor canals dispersed the water through the southern parts of Angkor and down towards the lake," Evans explained.

In the 1950s, the late archaeologist Bernard-Philippe Groslier speculated that traces of a hydraulic network were part of an ancient irrigation network that ferried water to farmers in the city's suburbs. Groslier also argued that the breakdown of the network, triggered perhaps by overexploitation of the landscape, was implicated in Angkor's downfall.

Supporting Groslier's hypothesis, the new maps and excavations reveal breaches in dykes and attempts to patch up the system. Whether such phenomena were the cause, a symptom or a result of Angkor's decline remains to be determined, Evans said.

Modern lessons

"Our research shows that Angkor was certainly extensive enough, and that land-use was certainly intensive enough, to have impacted profoundly on the regional ecology," Evans told LiveScience.

Angkor was surrounded by a vast expanse of rice fields that would have required extensive forest clearance. Over time, the intense farming could have led to serious ecological problems, including those associated with deforestation, overpopulation, topsoil degradation and erosion.

The consequence of overexploiting the environment isn't the only lesson Angkor's fate has for modern society, Evans said. Angkor required a massive infrastructural network of canals and roads to keep it running.

"This increasingly complex elaborate system would have been very difficult and expensive to maintain," Evans said. "This is obviously something to bear in mind, considering that many cities in our contemporary world are expansive, low-density urban sprawls as Angkor appears to have been."

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)

Radar discovers temples in ancient city

Tuesday, 14 August 2007
University of Sydney (Australia)

Australian researchers using NASA technology to map the medieval city of Angkor have discovered at least 74 new temples.

"We've mapped a huge settlement beyond the main temples at Angkor using radar imaging and other satellite data," said Damian Evans, a deputy director of the University of Sydney-based Greater Angkor Project.

"This is the first time a complete, detailed and comprehensive map of Angkor has been presented," he said.

The research and images will be published this week by the PNAS, the world's most-cited general science journal, published by the National Academy of Sciences of the USA.

Carpeted with vegetation and obscured by low-lying cloud, the ruins spill over 1,000 square kilometres outside the World Heritage site, located in present-day Cambodia, and are linked by a complex water management system.

Mr Evans and colleagues from Australia, Cambodia, and France have worked for years to integrate information from hand-drawn maps, ground surveys, airborne photography, and ground-sensing radar provided by NASA.

"The radar can sense differences in plant growth and moisture content that result from topographical variations of less than a meter," Mr Evans said.

"We have identified over a thousand new man made ponds and at least 74 long-lost temples, by correlating the radar data with on-the-ground sampling."

One single hydraulic system links the entire network, which appeared to provide Angkor's citizens with a stable water supply despite the unpredictable monsoon season.

The system, thought to be purely decorative and ceremonial by many scholars for the past 30 years, may actually have been used for irrigation and the intensification of rice agriculture.

Mr Evans said there "are also signs that the large-scale city engineered its own downfall by disrupting its local environment by expanding continuously into the surrounding forests and exposing the water management system to increased sedimentation and erratic water flows."

This caused a radical re-engineering of the landscape, and increased reliance on a massive and delicately balanced infrastructural network.

Ancient urban sprawl surrounded Cambodia's Angkor

August 13, 2007
By Tan Ee Lyn
REUTERS

HONG KONG – Archaeologists have published a new map showing an extensive ancient settlement surrounding Cambodia's Angkor Wat that supported large numbers of inhabitants before and after the famous temple was built.

Now obscured by vegetation and low-lying clouds, the ruins spread over 1,000 sq km and were made up of thousands of houses, roads, manmade ponds and canals, researchers from Australia, Cambodia and France said in the latest issue of the Proceedings of the National Academy of Sciences.

'We now know that instead of being just (a collection of) temples, Angkor was actually a continuous and interconnected network of temples and small scale residential features like small village ponds, small village temples as well,' Damien Evans of the Archaeological Computing Laboratory at the University of Sydney told Reuters in a telephone interview.

'Very little remains now, they are just piles of brick ... a thousand years ago (it) would have been a huge and popular city, full of life, rather than this image of temples in a jungle.'

Angkor Wat was built in the early 12th century, while the settlement existed between 500 AD and 1500 AD, Evans said.

'What we can see, even on a preliminary basis, is that several hundred thousand people must have lived in the Angkor area ... which is defined by the infrastructure, the roads, the canals, huge embankments,' he added.

Using hand-drawn maps, ground surveys, satellite imagery, aerial photography and ground-sensing radar provided by NASA, the researchers identified what they believed to be more than a thousand former manmade ponds, temples and moats – all of which were now replaced by vegetation.

Ranging from 20 metres to 8 km long, the ponds were used for drinking, irrigation, livestock and other domestic purposes and were especially crucial for the dry season.

'The slightly lower elevations of the rice fields in the former moats and reservoirs ... result in different stages of rice maturity and in differential levels of soil moisture content, which strongly affect the returned radar signal,' Evans said. 'You get more mature rice in these wetter areas.'

The researchers believe the settlement was abandoned around 1500 AD because of overexploitation and deforestation.

'What our work proved for the first time was that Angkor certainly was large enough and its water management system was complex and extensive enough to have created very serious environmental problems,' Evans said.

'In such situations, infrastructure becomes very important and increasingly complex and difficult to maintain.'

Future studies will look at how serious these problems were and if the inhabitants were able to deal with them.

Sprawling Angkor engineered its own end

August 14, 2007
Leigh Dayton, Science Writer
The Australian

A NEW archaeological map confirms that Angkor in Cambodia was the biggest pre-industrial city ever founded and provides tantalising clues about its mysterious demise 500 years ago.

Sprawling about 1000 sq km out from its central religious heart with its legendary temples and reservoirs, known as Angkor Wat and Angkor Thom, the vast city was roughly the size of Singapore, or greater Sydney from the coast to Parramatta.

Angkor itself was the capital of a sparsely settled agricultural empire that stretched from Thailand in the north, across the flood plains, and southwards towards the Cambodia-Vietnam border.

"Like the modern world there was a vast expansion of the urban environment out into the rural world," said Sydney University archeologist Roland Fletcher, founder and co-director of the Australian, French and Cambodian Greater Angkor Project.

A goal of the project was to nail down the geographical extent of the city. According to GAP deputy director Damian Evans, a Sydney University doctoral student, the new map does just that.

"This is the culmination of about 15 years of mapping work," said Mr Evans, who led the effort to integrate the data into the map, revealed overnight in the US journal Proceedings of the National Academy of Sciences.

Sources included hand-drawn maps, ground surveys and airborne photography provided by GAP members and ground-sensing radar images provided by the US space agency NASA.

Not only does the map reveal the extent of Angkor -- a Khmer kingdom from the 9th to the 15th centuries -- it pinpoints over 1000 new water storage ponds and more than 74 long-lost temples. In its heyday, as many as 500,000 people may have lived in the sprawling low-density city. The map will allow scientists to tighten population estimates.

According to Mr Evans, the map also provides hard evidence backing the controversial hydraulic hypothesis.

This states that Angkor was linked by a vast network of irrigation channels, storage ponds and reservoirs. As the city grew, land was cleared, causing soil to clog the channels. Eventually, it became too expensive and complicated to keep the system free-flowing and it collapsed, taking Angkor with it.

The city, in essence, engineered its own demise by disrupting the environment.

"We can certainly see there were problems in the hydraulic networks," said Mr Evans.

"There's evidence of water courses punching through dykes and inadequate attention (to maintenance)."

Said Professor Fletcher: "It's a cautionary tale for the modern world."