Paleoenvironmental history of the West Baray, Angkor (Cambodia)

1. Mary Beth Day^a,¹,
2. David A. Hodell^b,
3. Mark Brenner^c,
4. Hazel J. Chapman^a,
5. Jason H. Curtis^d,
6. William F. Kenney^c,
7. Alan L. Kolata^e, and
8. Larry C. Peterson^f

Author Affiliations

1. ^aDepartment of Earth Sciences, Downing Street, University of Cambridge, Cambridge, UK, CB2 3EQ;
2. ^bDepartment of Earth Sciences and Godwin Laboratory for Palaeoclimate Research, Downing Street, University of Cambridge, Cambridge, UK, CB2 3EQ;
3. ^cDepartment of Geological Sciences and Land Use and Environmental Change Institute, P.O. Box 112120, University of Florida, Gainesville, FL, 32611;
4. ^dDepartment of Geological Sciences, P.O. Box 112120, University of Florida, Gainesville, FL, 32611;
5. ^eDepartment of Anthropology, 1126 East 59th Street, University of Chicago, Chicago, IL, 60637; and
6. ^fRosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, University of Miami, Miami, FL, 33149

1. Edited by Mark H Thiemens, University of California San Diego, La Jolla, CA, and approved November 22, 2011 (received for review July 15, 2011)

Abstract

Angkor (Cambodia) was the seat of the Khmer Empire from the 9th to 15th century AD. The site is noted for its monumental architecture and complex hydro-engineering systems, comprised of canals, moats, embankments, and large reservoirs, known as barays. We infer a 1,000-y, ¹⁴C-dated paleoenvironmental record from study of an approximately 2-m sediment core taken in the largest Khmer reservoir, the West Baray. The baray was utilized and managed from the time of construction in the early 11th century, through the 13th century. During that time, the West Baray received relatively high rates of detrital input. In the 14th century, linear sedimentation rates diminished by an order of magnitude, yielding a condensed section that correlates temporally with episodes of regional monsoon failure during the late 14th and early 15th century, recorded in tree ring records from Vietnam. Our results demonstrate that changes in the water management system were associated with the decline of the Angkorian kingdom during that period. By the 17th century, the West Baray again functioned as a limnetic system. Ecologic and sedimentologic changes over the last millennium, detected in the baray deposits, are attributed to shifts in regional-scale Khmer water management, evolving land use practices in the catchment, and regional climate change.

http://www.box.com/s/417223af487284459b76

Learning from Cambodia's bloody experience

November 9, 2010
By Geoff Gallop
(Geoff Gallop is the former premier of Western Australia)
WAtoday.com.au (Australia)

Through their own expansion, and their own self-destruction, we can learn a lot from our Asian neighbours.

Finding out about human nature by exploring its manifestations in different places and at different times was one of the features of the great Enlightenment project that saw science and reason take the scalpel to religion and tradition in the eighteenth century. Learning from history mattered as it should today. Indeed no matter how small a country is there will always be aspects of its history and experience that provide lessons for us all.

Take Cambodia for example. A small nation of just over 15 million people, it occupies 181,000 square kilometres of land and water (WA, by comparison has an area of 2,252,500 square kilometres). Since retiring from politics in 2006, my work as an academic has taken me there on four occasions. Last week I was there lecturing to public servants at the Royal School of Administration in Phnom Penh. Like many Australians I have also taken the opportunity to visit Angkor Wat and other temples located around Siam Reap.

What then can we learn from the experience of the Khmer people?

Lesson One – great cities can decay and collapse.

From the ninth to the 14th centuries the Angkor Empire stretched across much of South-East Asia. At its centre was a great city covering an area similar to the size of greater London today. It possessed a sophisticated network of roads, canals and irrigation ponds. Intensive agriculture supported a city of one million people, arguably the largest in the pre-industrial world.

Visit Angkor today and all that is left of this city is a handful of the estimated 1000 temples constructed in the era of Empire.

What happened? We know that the Empire was already in decline in the 13th and 14th centuries and that the city was sacked by Thai invaders in 1431, causing its population to move south.

Certainly the strains associated with war and conflict played their role but recent research, including that by scholars from the University of Sydney, has been focused on the impacts of climate change, population pressure and the over-use of natural resources. Damien Evans from the Greater Angkor Project put it this way: "You can see the city pushing into forested areas, stripping vegetation and re-engineering the landscape into something that was completely artificial." In a sense the city built itself out of existence.

Add to this evidence of decades of drought interspersed with intense monsoon rains which destroyed much of the infrastructure. Overstretched, over-engineered and vulnerable to external shocks like climate change – does it sound familiar?

Lesson Two – fanaticism and the evil associated with it is never far below the surface of human society.

In more recent times, we know about Cambodia because of the Pol Pot era (1975-79) and his government's campaign of systematic genocide, known as the Killing Fields. Caught up in the Cold War in South-East Asia and preceded by five years of foreign meddling, bombardment and civil war, Cambodia was ripe for revolution in 1975 a situation the disciplined and well-organised Khmer Rouge exploited.

Little did many know, however, about what was to follow. Writing in A HISTORY OF DEMOCRATIC KAMPUCHEA (2007) Khamboly Dy summarised the four years of Khmer Rouge government in this way:

"They wanted to transform Cambodia into a rural, classless society in which there were no rich people, no poor people and no exploitation. To accomplish this, they abolished money, free markets, normal schooling, private property, foreign clothing styles, religious practices, and traditional Khmer culture. Public schools, pagodas, mosques, churches, universities, shops and government buildings were shut or turned into prisons, stables, re-education camps and granaries. There was no public or private transportation, no private property, and no non-revolutionary entertainment. Leisure activities were severely restricted. People throughout the country, including the leaders of the CPK (Communist Party of Kampuchea), had to wear black costumes, which were their traditional revolutionary clothes."

Just as the great city of Angkor was deserted in 1431, so too was Phnom Penh in 1975. In this case it was forced removal of the residents to the countryside in order to fulfil the dream of starting history again in the year zero, free of foreign influence and capitalist temptation.

It is estimated that nearly two million Cambodians died either from disease, starvation, exhaustion from overwork or execution. Torture was commonplace as the country was transformed into what Dy described as "a huge detention centre". It is very difficult to fully comprehend or describe the level and intensity of the suffering that was involved.

Cambodia wasn't the first and probably won't be the last to experience a politically driven attempt to remake human nature at the point of a gun. It reminds us of the dangers of fanaticism and nationalism, just as Angkor reminds us of the dangers of human arrogance in the face of a fragile and interconnected environment.

Angkor's Ancient Drought

By Art Chimes, VOA
Original report from Washington
06 April 2010

For hundreds of years the Khmer empire ruled in what is now Cambodia.

But in the 13th century, the capital city, Angkor, fell into ruin. A new scientific study indicates that climate, specifically decades of drought interspersed with intense monsoons, helped bring down the Khmer capital.

Brendan Buckley, the Columbia University scientist who led the study, says that in the ancient world, Angkor was known for its sophisticated water system.

"Well, Angkor was really the dominant civilization in that part of the world without any question. It was the center of their universe. And it was called the 'hydraulic city' because it had really remarkably massive arrays of barays, which are these giant water tanks and a series of canals and interconnected waterways that was really unparalleled in the ancient world in that part of the world."

Buckley isn't an archaeologist. He studies tree rings, which record the growth history of trees that can be hundreds of years old, or even older. A new ring is added every year, and thicker rings represent a kind of savings account, when the tree collects more nutrients than it can use. Thin rings show the tree is barely getting along, like during a drought year.

Using samples from around Southeast Asia, Buckley and his colleagues saw this pattern in tree rings from recent years, when he could corroborate the rings with other historical climate information. His newest tree ring samples, from [a rare cypress, Fokienia hodginsii, in] southern Vietnam, enabled him to take the climate record back much further.

"We realized we have trees that are more than 1,000 years old. And we started seeing these big, giant periods of drought that took place around that time. And as I started to get more interested in the history of Southeast Asia I realized that that was the time of the collapse of Angkor."

The research team used what are called core samples from hundreds of trees throughout Southeast Asia. Using a hollow tube, they drill into the tree and extract a 5-mm wide cylinder that shows each ring starting with the most recent, just under the bark.

By comparing rings from different trees and with other historical data, you can often identify particular rings with the exact calendar year that they grew.

"We were able to match up the narrow and wide rings exactly so that we can assign the exact calendar dates to the exact rings of every tree. In the tropics, a lot of tree species don't even form rings that we can see. So to be able to get a tree that, first of all, has very clear rings that we're able to visually match to each other and then go through and produce these long records was remarkable."

The rings tell a story of decades of drought, which dried up Angkor's extensive water works, followed by monsoons that overwhelmed the 'hydraulic city.'

But the climate shifts weren't the only factor at work in the decline of the Khmer capital, which was a long time coming. Buckley quotes his co-author, Daniel Penny, as saying the climate was the "final nail in a coffin that took about 200 years to build," as Angkor and the Khmer empire were being buffeted by political, social, and economic stress.

"The times were changing, [shifting] toward an economic system that was taking them more to the coastline so they could trade with Chinamore readily. I believe that drought was one of the things that piled onto the pile of things that were affecting the Angkorians at that time. And it may very well have provided that final impetus to really kind of kill off this inland agricultural system."

The idea of a civilization being pushed over the edge by climate change resonates in the modern world, of course, and Brendan Buckley says his research on 13th century Southeast Asia has some lessons for us today.

"We probably have more abilities to adapt than they did at the time. But one of our biggest problems is a very large agrarian based population in places like India or Southeast Asia. And it's very hard to adapt to that giant population being in an area that is likely to be hit by these kinds of problems. The other thing is that rising sea level, which we're already seeing the evidence of in places like Ho Chi Minh City is a great example. So this is becoming an actual problem that we can see in real time on the ground. I guess that remains to be seen how we're going to cope with it."

Prof. Brendan Buckley's paper on climate's contribution to the demise of Angkor in present-day Cambodia was published online this week in the Proceedings of the National Academy of Sciences.

Did climatic conditions trigger Angkor's collapse?

2010-03-30
IANS

Decades of drought, alternating with intense monsoon rains, may have sounded the death knell for Cambodia's ancient Khmer civilization at Angkor nearly 600 years ago.

Columbia University researchers say this based on an analysis of tree rings, archaeological remains and other evidence.

Their findings may also shed light on what drives - and disrupts - the rainy season across much of Asia, which waters crops for nearly half the world's population.

'Angkor at that time faced a number of problems - social, political and cultural. Environmental change pushed the ancient Khmers to the limit and they weren't able to adapt,' said the study's lead author, Brendan Buckley.

Buckley is a climate scientist and tree-ring specialist at Columbia Univewrsity Lamont-Doherty Earth Observatory. 'I wouldn't say climate caused the collapse, but a 30-year drought had to have had an impact.'

Some scientists suspect that warming of the global climate may intensify these cycles in the future, raising the possibility of alternating Angkor-like droughts and destructive floods that could affect billions.

Historians have offered various explanations for the fall of an empire that stretched across much of Southeast Asia between the 9th and 14th centuries, from deforestation to conflict with rival kingdoms.

But the new study offers the strongest evidence yet that two severe droughts, punctuated by bouts of heavy monsoon rain, may have weakened the empire by shrinking water supplies for drinking and agriculture, and damaging Angkor's vast irrigation system that was central to its economy.

The kingdom is thought to have collapsed in 1431 after a raid by the Siamese from present-day Thailand.

Scientists led by Buckley were able to reconstruct 759 years of past climate in the region surrounding Angkor by studying the annual growth rings of a cypress tree, Fokienia hodginsii, growing in the highlands of Vietnam's Bidoup Nui Ba National Park, about 700 km away.

By hiking high into the mountain cloud forests, the researchers were able to find rare specimens over 1,000 years old that had not been touched by loggers.

After extracting tiny cores of wood showing the trees' annual growth rings, researchers reconstructed year-to-year moisture levels in this part of Southeast Asia from 1250 to 2008.

The tree rings revealed evidence of a mega-drought lasting three decades-from the 1330s to 1360s-- followed by a more severe but shorter drought from the 1400s to 1420s. Written records corroborate the latter drought, which may have been felt as far away as Sri Lanka and central China.

The study also finds that the droughts were punctuated by several extraordinarily intense rainy seasons that may have damaged Angkor's hydraulic system, said a Columbia University statement.

These findings were published this week in the Proceedings of the National Academy of Sciences.

Climate Helped Bring Angkor to Its Knees

Studying tree rings has revealed a record of wet and dry times that helps make sense of the mysterious and gradual demise of Angkor, the capitol of the Khmer Empire in Cambodia from the 9th to 14th centuries. A very wet period with rich monsoons and plentiful crops from 1258 to 1300 was followed by many years of drought from 1350 to 1370. (Credit: Zina Deretsky, National Science Foundation)

Press Release 10-048
Source: National Science Foundation (USA)

Tree ring record reveals abrupt end to empire

March 29, 2010

Throughout written history there have been many abrupt ends to empires and civilizations that have little explanation. Political climates deteriorate, passions rise, revolts happen and the next thing you know--the culture is a thing of the past relegated to a short chapter in a textbook.

The natural world leaves a record in the form of tree rings, which can be read like a very detailed book, covering a long period of human history. Now a team of researchers has correlated the demise of Angkor, the capitol of the Khmer Empire in Cambodia, with a decades-long drought interspersed with intense monsoons in the 14th and 15th centuries.

Brendan Buckley of Lamont-Doherty Earth Observatory of Columbia University and his colleagues have put together a high-resolution record of periods of drought and moisture in Southeast Asia that is over three quarters of a millennium long from 1250 to 2008 AD.

Just as satellite photos do--large sets of information like this tree ring data bring into focus patterns and phenomena that are larger than one lifetime. In fact they are on the scale of civilizations.

A look at tree ring data, and an analysis of rain, drought and temperature can show a remarkable link from climate in the environment to climate in the king's court. And this has been shown to be true for the enigmatic demise of Angkor, an empire that stood strong from the 9th to 13th centuries.

Angkor was a city that relied heavily on water. The National Science Foundation-funded work of Buckley and his colleagues reveals that the mid- to late 1300's experienced persistently dry conditions that spanned decades, followed by several years of severe wetness that may have caused damage to the city's infrastructure. Afterwards, a shorter but more severe drought in the early 1400's may have been more than this urban complex could handle.

Bringing insights such as these into focus in the 21st century, there is a sense of urgency in interpreting what the natural world is telling us. The very cypress trees (Fokienia hodginsii) that allow the long-range glimpse backwards are becoming more and more rare as their wood is harvested for the illicit timber trade. The highlands of Vietnam and Laos are home to some of the region's most diverse biota, and are under threat of over-exploitation.

-NSF-
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Media Contacts
Cheryl L. Dybas, NSF (703) 292-7734 cdybas@nsf.gov
Kevin Krajick, The Earth Institute, Columbia University (212) 854-9729 kkrajick@ei.columbia.edu
Kim Martineau, The Earth Institute, Columbia University (845) 365-8708 kmartineau@ei.columbia.edu

Principal Investigators
Brendan M. Buckley, Lamont-Doherty Earth Observatory of Columbia University (845) 365 8782 bmb@ldeo.columbia.edu

Related Websites
Tree Ring Video, The Earth Institute, Columbia University: http://www.earth.columbia.edu/videos/watch/108

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2010, its budget is about $6.9 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions. Each year, NSF receives over 45,000 competitive requests for funding, and makes over 11,500 new funding awards. NSF also awards over $400 million in professional and service contracts yearly.

Archaelogists have breakthrough regarding the decline of Angkor

25 June 2009
The University of Sydney (Australia)

One of archaelogy's greatest mysteries has been solved. According to soon-to-be published paper by a team headed by Professor Roland Fletcher, the great medieval city of Angkor was destroyed by the combined effects of a mini ice age, and over-development of its complicated water system.

The findings were based on new pollen and tree-ring-dating evidence that uses long-lived species in the region such as the 900-year-old po mu tree. Evidence that extreme weather conditions had occurred from 1362 to 1392 and from 1415 to 1440 was found in the annual growth rings of the tree.

At its height from the 9th to 15th centuries, the elaborate city of Angkor had about 750,000 citizens and was the most comprehensive urban development of the preindustrial world. By the 16th century, the city was in ruin.

The archaelogical team investigating the phenomena of Angkor includes the University of Sydney's Professor Fletcher, and paleoclimatologist Dr Dan Penny; and paleoclimatologist Brendan Buckley of New York's Columbia University. It is part of the Greater Angkor Project, an international, multidisciplinary research programme studying the decline of urbanism at Angkor, in Cambodia.

The Greater Angkor team will hypothesise in its paper that the decline of the city was due to extensive problems with its vast and complicated water system and the compound effect of a series of droughts and monsoonal floods in the mid-14th to late 15th centuries.

In an article in The National Geographic Professor Fletcher said, "Angkor really had no fat to burn. The city was more exposed to the threat of drought than at any other time in its history. Prolonged and severe droughts, punctuated by torrential downpours, would have ruined the water system."

The findings have important lessons for contemporary readings of climate change. As experts debate the effects of human-made climate change, the tree rings of the po mu tree around Angkor reveal that even natural variations in weather can bring about catastrophe.

Contact: Sarah Stock
Phone: 02 9351 4312 or 0419 278 715
Email: sarah.stock@usyd.edu.au