Did climatic conditions trigger Angkor's collapse?

via CAAI News Media

2010-03-30

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.