Angkor's temples and climate change doom

Wednesday, July 01, 2009
By Sen Lam
Radio Australia

The ancient civilisation based at Angkor in Cambodia collapsed in the late 16th century because of problems with a very modern ring to them, research by an international team indicates.

The Greater Angkor Project, based in Sydney, is preparing a paper arguing that extreme climate change and the failure of Angkor's complicated water systems were to blame.

The temple complex was the heart of the mighty Khmer empire and its ruins are one of the most popular attractions in South-East Asia.

The Angkor Wat temple, the centrepiece, was built in the ninth century and surrounded by huge reservoirs and canals - believed to be partly Hindu symbols and partly for irrigation.

Sydney archaeologist Professor Roland Fletcher, co-director of the team of scientists from France, Cambodia and Australia on the project, told Radio Australia's Connect Asia program: "It was actually the largest low density pre-industrial city on earth."

"It covers nearly 1,000 square kilometres, but that's all spread out, something like modern Los Angeles.

"So it was really enormous and it had somewhere in the order of, at the top end, 750,000 people in it."

Among the challenges for the authorities of Angkor were to manage the South East Asian monsoon and then a long dry season - that is, flood control and water delivery.

Professor Fletcher says this involved a massive water system, with canals as long as 40 kilometres, which "appears to have been the mechanism for holding water and using it as reserve in case monsoons were bad".

But from 1350 to 1500 AD, the region was hit by a very unstable climate, with droughts and severe monsoons mixed up.

Are there lessons from that period for modern cities?

"I would suspect there are, in the sense that what you see in Angkor is a landscape that has been completely cleared of forests in order to grow a dominant crop, so basically . . . simplification of the landscape and removing the tree cover," he said.

"On the other hand, [there is] the dependency on very big infrastructure for managing daily life - so, for instance, if you have really heavy monsoons that these canals and systems weren't designed to deal with."

"With severe monsoons, you would get severe damage to the structures, and we actually find that there is a dam up in the north that's been torn away and the big southern canals of Angkor are full of sand, which suggest very severe flooding."

For modern observers, "the situation is not absolutely equivalent - one reason being that we know a great deal more in the modern world, and we have a great deal more capacity available to us to deal with situations".

"But when you consider that Angkor was a giant low-density city, that had cleared its regional landscape of its natural vegetation cover, was dependent upon massive infrastructure and hit by climate change, it does sound a little topical.

"It does sound a little like the modern world."

Climate change helped Angkor's decline: scientist

July 1, 2009
ABC Radio Australia

Cambodia's Angkor temple complex was the heart of the mighty Khmer empire and the ruins are one of the most popular attractions in Southeast Asia.

Angkor Wat, the centerpiece of the Angkor complex, was built in the 9th Century and was surrounded by huge reservoirs and canals - believed to be partly Hindu symbols and partly an irrigation system. So why did the pre-industrial city apparently collapse in the late 16th Century? That's a question that's fascinated historians and archeaologists for decades.

Presenter: Sen Lam
Speakers: Professor Roland Fletcher, archaeologist at the University of Sydney and co-director of the Greater Angkor Project

Click here to listen to the audio program in English (Windows Media)

FLETCHER: Well, it was actually the largest low density pre-industrial city on earth. It covers nearly 1,000 square kilometres, but that's all spread out, something like modern Los Angeles. So it was really enormous and it had somewhere in the order of at the top end 750,000 people in it, so it was pretty spectacular.

LAM: Indeed, water as you've heard was a key factor to Angkor's success, but how did it shape Angkor's downfall?

FLETCHER: Well, the key things to bear in mind is that as you would well know, people in South East Asia have to manage a massive monsoon and then a long dry season and the great water system some of whom canals are about 40 kilometres long appears to have been the mechanism for holding water and using it as reserve in case monsoons were bad.

LAM: Right, and so this is matter of managing the rainfall and the vast amounts, the copious amounts of water that's falling down.

FLETCHER: That's right, to control flooding and to deliver water.

LAM: Mmm, so it wasn't the case of the city growing too fast and outgrowing its infrastructure?

FLETCHER: Well, it's probably more that it built too massive an infrastructure, rather as we're tending to do today, it built an infrastructure that you could not move. The West Baray for instance, has 20 million cubic metres of dirt in its banks. This is massive engineering and between [the years] 1350 and about 1500, the whole region is hit by a very unstable climate period, where there are droughts and severe monsoons all mixed up with each other, in other words, the degree of difference between the years greatly increased.

LAM: So, even all those centuries ago, climate change played a role as well?

FLETCHER: Oh climate change has been occurring all the time. The planetary temperature goes up and down on a very long cycle, quite normally. The period of Angkor, for instance, coincides with what's called the Medieval Warm phase, from about the 9th Century through to about the 15th, 16th Century. And then we got into what's called the Little Ice Age, which is a cold period that ran up to about the 18th Century.

LAM: Professor Fletcher, are there lessons there in Angkor for modern cities?

FLETCHER: Well, I would suspect there are in the sense that what you see in Angkor is a landscape that has been completely cleared of forests in order to grow a dominant crop, so basically a focus on a simplification of the landscape and removing the tree cover and on the other hand, the dependency on very big infrastructure for managing daily life. So, for instance, if you have really heavy monsoons that these canals and systems weren't designed to deal with, you would get severe damage to the structures and we actually find that there is a dam up in the north that's been torn away and the big southern canals of Angkor are full of sand, which suggest very severe flooding.

LAM: You mentioned the forest cover. I understand that some of the trees were studied. What did they show?

FLETCHER: Well, it's the trees in Vietnam, not in Angkor, but in northern Vietnam that actually provide the climate sequence. Trees as you know grow annually and some trees enable you to see how much water was available in a given year. So in a very dry year, you'd get a very thin tree ring growth and in a very wet year, you'd get a big ring and that's what we've used in the work of Brendan Buckley from Colombia to identify the change in the climate and then my colleague, Dan Penny, who is a paleo-environmentalist, has been looking at the changing conditions inside Angkor, looking at the pollen particularly and algae.

LAM: And just briefly Professor, how useful is it for us in modern times to get to the heart of what happened in Angkor?

FLETCHER: Well, I think the thing to bear in mind is the situation is not absolutely equivalent and one reason being that we know a great deal more in the modern world and we have a great deal more capacity available to us to deal with situations. But when you consider that Angkor was a giant low density city, that had cleared its regional landscape of its natural vegetation cover, was dependent upon massive infrastructure and hit by climate change. It does sound a little topical, it does sound a little like the modern world.