LIKE most people, Roland Fletcher鈥檚 overriding impression was 鈥渨ow . . .
BIG鈥�. It was a humid night in 1999 and the Sydney University archaeologist was
being driven around the ruined Cambodian city of Angkor by his colleague
Christophe Pottier. As they neared one of the famous temples, the moonlight
transformed the moat into a gleaming sheet of silver, two kilometres long. 鈥淚t
was blinding,鈥� Fletcher recalls. 鈥淚 was struck by the magnitude, the sheer
magnitude of the place.鈥�
Since that night-time encounter, Fletcher has got to know Angkor even better.
And if he thought the city was vast then, one can only wonder what he makes of
it now. He and Pottier, an archaeologist at the French School of Far Eastern
Studies in Siem Reap, Cambodia, belong to a new breed of researcher that is
looking beyond Angkor鈥檚 breathtaking temples and exquisite stone carvings to
learn more about the city that surrounded them. The evidence they鈥檙e digging up
suggests that Angkor wasn鈥檛 just a ceremonial centre, it was something much
bigger鈥攁 vast metropolis that sprawled across more than 1000 square
kilometres. That conclusion is helping them to bury some old ideas about why the
city collapsed. And it may even carry warnings about the future of the Mekong
basin鈥攁nd other parts of the world as well.
Today Angkor is a magnet for tourists and archaeologists. They鈥檙e drawn by
the site鈥檚 religious monuments, notably the temple complexes of Angkor Thom and
Angkor Wat and the royal monastery Ta Prohm, which were built between the 9th
and 15th centuries when Angkor was the capital of the mighty Khmer empire. In
its heyday, its domain stretched from the South China Sea to Thailand, and from
the uplands of Laos in the north to the Malay Peninsula in the south.
Advertisement
But in the 15th century the empire collapsed and Angkor disappeared under
jungle. The conventional explanation is that the empire鈥檚 rulers lost their grip
on power after generations of political instability, provincial revolts, and
attacks by neighbouring kingdoms. Angkor itself was abandoned after being sacked
by Thai invaders in 1431.
In recent years, though, new findings have challenged that view. After
decades of civil war in Cambodia, researchers are starting to return to Angkor.
Many, like Fletcher and Pottier, are driven by a belief that the most basic
information about the city is still missing. How big was it? How many people
lived there? And above all, what caused its demise? To find out, they鈥檝e roped
in a high-tech blend of aerial photography, remote sensing and computer
analysis, as well as the traditional tools of ecology and archaeology.
Massive disruption
The emerging view doesn鈥檛 dispute the fact that Angkor was abandoned in a
hurry. 鈥淐learly, something dire happened,鈥� says Fletcher, an expert in the rise
and fall of cities. But he has a different notion of what the trigger was. He
believes it wasn鈥檛 political unrest. Instead, the new findings suggest Angkor
was brought down by ecological collapse, driven by voracious deforestation and
massive disturbance of the waterways round the city. What鈥檚 more, Fletcher fears
it may be happening again. 鈥淭he Khmers engaged in a cycle of ecological and
environmental degradation which we may be beginning again,鈥� he says, pointing to
the escalating demand from the countries of the Mekong basin for hydroelectric
power and land for crops.
The first hints that Angkor collapsed under ecological
stress came in 1992. That鈥檚 when Pottier and two local assistants began
exploring the land south of the main temples. So far, they have pinpointed the
remains of roughly 600 buildings, which Pottier says were part of a network of
鈥渟uburbs鈥� occupied by ordinary people. 鈥淭hese are temples of the common people
or private temples of village chiefs and landlords,鈥� he says. 鈥淭hey didn鈥檛 have
the means to build large monuments, so they used a smaller number of stone
blocks, and most of the sculpture is made in wood. There is nothing to see,
really鈥攎ounds, a few blocks, some broken pieces of pottery. No huge
迟别尘辫濒别蝉.鈥�
The buildings are nothing special but they do suggest that Angkor鈥檚
population wasn鈥檛 confined to the city centre, as historians have long believed.
Pottier and Fletcher now argue that most of the city鈥檚 inhabitants lived well
away from the grand, walled edifices, in a dispersed settlement of timber houses
clustered on low mounds and along a vast network of roads, canals, reservoirs
and embankments.
More support for that idea came, independently, in 1994. John Stubbs of the
World Monuments Fund, which has worked at Angkor since 1989, read a newspaper
article about the archaeological applications of Earth-imaging radar. He asked
NASA to add Angkor to an upcoming mission and in September 1994 the space
shuttle Endeavour and its radar mapping equipment passed over the ruined
city.
The data collected during the shuttle flight was processed at NASA鈥檚 Jet
Propulsion Laboratory in Pasadena, California. When JPL released the resulting
image in 1995, Angkor experts worldwide were amazed at the detail it revealed.
The image showed a huge network of fields, paths, mounds and irrigation canals
stretching northwards from the city centre
(see Diagram). Back in Sydney,
Fletcher and colleagues enhanced the image even further, hoping to see where and
how far the canals and roads ran. Their results showed that the urban complex of
Angkor was truly enormous. The entire area from the Kulen Hills in the north to
the giant lake, Tonle Sap, in the south鈥攎ore than 1000 square
kilometres鈥攚as criss-crossed by a network of roads, canals and
reservoirs.
To Fletcher and Pottier, this suggested that the area was under extreme
environmental pressure which eventually led to its collapse. Their hypothesis
goes something like this: as the city prospered, demand for agricultural land
grew. Farmers cleared more land along the rivers flowing south from the hills,
releasing extra sediment into the waterways. Increasing sedimentation clogged up
the city鈥檚 irrigation channels and the surrounding waterways. 鈥淭he canal system
was degrading, channel erosion was developing, and the people were farming
poorer and poorer land,鈥� Fletcher says. Eventually, Angkor became too big for
its breeches and began to fall apart.
Fletcher, Pottier and colleagues are now waiting for images from another
Earth-observing mission, PacRim 2000, which flew over Angkor late last year.
The data is likely to be the best yet鈥攊t was gathered by instruments on
NASA鈥檚 DC-8 Flying Laboratory from an altitude of 12,800 metres. In contrast,
the shuttle orbited at 224 kilometres, so its images were lower resolution. JPL
has already processed one image and Fletcher says it鈥檚 stunning. 鈥淭he image
allows us to see Angkor in its ecological and regional context, to identify its
limits more clearly, to see the relationship between contemporary land clearance
and the former field networks of the city, and to look at the flow of
飞补迟别谤.鈥�
Still, an important question remains unanswered: were those outlying features
inhabited suburbs, as Fletcher and Pottier suggest, or just the traces of a
transport and irrigation system used by the people who lived in and around the
temples of Angkor? The answer to the question is important because, Fletcher
says, low-density cities appear to have few limits on their capacity to
expand鈥攁nd they initiate regional collapse when they fail.
To find out more, Fletcher and Pottier have begun a coring project. In 1999
they drilled numerous test cores from channels located at four sites in central
and southern Angkor. The idea was that if people lived along the canals, they
would have dumped large amounts of household rubbish into the water, much as
many rural Cambodians do today.
The pair literally hit pay dirt. 鈥淥ur initial explorations revealed a deep
sequence of natural and cultural deposits containing charcoal and even small
fragments of pottery,鈥� Fletcher says. While this was expected, given that the
cores were taken in areas likely to be residential, the trial suggested that
cores of other sites could show whether or not people lived there. The
scientists are now planning to repeat the process in outlying channels, and they
predict that these cores will turn up evidence of permanent occupation.
The cores also promise to reveal whether the environment around Angkor was
under stress, says Dan Penny, a palaeoecologist at Edinburgh University. He鈥檚
looking for funds to analyse pollen, small organisms and charcoal found in the
cores, which he believes will tell him about variations in forest cover, changes
in water flow, and the presence or absence of crops, especially rice These
should all build up a picture of the prevailing ecological conditions. Penny may
also be able to determine if charcoal in the cores came from household braziers
or natural sources, which would help test the theory that people lived along the
canals.
Right now, Penny is analysing five cores from the bed of Tonle Sap, which
could reveal how sedimentation rates in the lake have changed. Such information
is important in testing the archaeologists鈥� claim that deforestation caused the
Khmer irrigation system to clog up. Any sediment released into the waterways by
land clearance would eventually have found its way into the lake.
Fletcher believes that if Tonle Sap silted up, it would have had a disastrous
effect on the inhabitants of Angkor. The lake was a major source of food for the
Khmer people, he says, from fish and crocodiles to plants and invertebrates.
Increased sedimentation would have cut productivity sharply. 鈥淭hey severely
damaged their protein return from the lake,鈥� he says.
But archaeologists aren鈥檛 the only ones interested in what the cores from
Tonle Sap reveal. The Mekong River Commission, a research and management body
set up in 1995 by the governments of Cambodia, Laos, Thailand and Vietnam, is
also waiting on the outcome. They need good environmental information if they
are to keep the basin healthy鈥攁nd prevent the people of the Mekong from
repeating the mistakes that caused Angkor鈥檚 collapse.
Even today, Tonle Sap is an important seasonal source of food, water and
fertiliser for the people who live around Angkor. During the early months of the
year, little rain falls over much of the Mekong watershed. But once the monsoons
begin in May, rainwater floods down the river and swells the delta in Vietnam.
Along some stretches of the river the water level can rise as much as 20 metres.
The deluge is more than the Mekong and its tributaries can carry. Much of the
excess water backs up into Tonle Sap.
As it enters Tonle Sap, the water deposits nutrients on farmland. In
Cambodia, some land receives around 10 millimetres of rich silt during normal
years and up to 30 millimetres during peak floods. From Tonle Sap the water
flows into the surrounding wetlands, increasing the lake in size from about 3000
square kilometres to as much as 10,000. The flowing water also brings fish from
the upper regions of the river basin to the lake. Local people catch these fish
in vast quantities, perhaps hundreds of thousands of tonnes every year.
Asking for trouble
The problem is that the nations of the Mekong basin are dramatically altering
the flow of the river and its tributaries by building hydroelectric dams. China
has already built one on the river鈥檚 main stream and has an ambitious plan for
14 more. In addition, there are 15 dams on tributaries in Thailand, Laos,
Vietnam and Cambodia鈥攁nd plans for nine more.
No wonder, then, there is growing concern that the nations of the Mekong
basin are setting themselves up for an ecological disaster. River ecologist Jean
Lacoursiere, former chief of the Mekong River Commission environment unit,
shares Fletcher鈥檚 fear that history is poised to repeat itself. 鈥淭oday we have
the technology to repeat, on a larger scale, what happened at Angkor,鈥� says
Lacoursiere, who is now at the University of Lund in Sweden. 鈥淭he principles are
the same: reduction of habitat, and changes in the overall ecology of Tonle
厂补辫.鈥�
So will it happen again? Will food supplies dwindle across the region as the
population soars? Will ever more national wealth be soaked up to maintain
intensive agricultural schemes? Will the people of the Mekong River basin find
themselves trapped in a ruinous cycle, as, perhaps, the Khmer people did 600
years ago?
If research ultimately proves that the Khmer people were the agents of their
own demise, then Fletcher says that more than the fate of South-East Asia is at
stake. 鈥淭here鈥檚 a warning to us,鈥� he cautions. 鈥淭he fate of Angkor indicates
that when settlements adopt a very low-density occupation pattern鈥攍ike the
US East Coast megalopolis and parts of Europe and Australia鈥攖hey appear to
have no limit on their capacity to spread out across the landscape. If we don鈥檛
bring the spread under control, we will get to the point where we can鈥檛 stop
it.鈥� It may sound unlikely, but look at Angkor. Would its people have believed
their fabulous city would one day be swallowed by the jungle?