Thursday, February 23, 2012

Collapse of Maya Civilization May Have Been Result of "Modest" Decline in Rainfall

Archaeologists studying the ancient civilisation centred on present day Mexico and Guatemala claim rainfall reductions of just 25 per cent were enough to cause 'the disintegration of a well-established civilisation'.
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'These reductions amount to only 25 to 40 per cent in annual rainfall. But they were large enough for evaporation to become dominant over rainfall, and open water availability was rapidly reduced.

The data suggest that the main cause was a decrease in summer storm activity.'

The study combined records of past climate changes from stalagmites and shallow lakes to model 40 per cent reductions in summer rainfall and reduced tropical storm activity over the region.

Professor Medina-Elizalde added: 'For more than a century, researchers have related the demise of the Classic Maya civilisation to climate change, and especially to drought.

No sound estimates had been made about the severity of this drought, but some have suggested extreme scenarios.

'New data made it possible to finally get detailed estimates. To do this, we developed a model that coherently explains changes in critical datasets of change in the region's balance between evaporation and rainfall.'

Professor Rohling explained such modest rainfall reductions would have caused the disintegration of a well-established civilisation.

'Summer was the main season for cultivation and replenishment of Mayan freshwater storage systems and there are no rivers in the Yucatan lowlands.

Societal disruptions and abandonment of cities are likely consequences of critical water shortages, especially because there seems to have been a rapid repetition of multi-year droughts,' he said.

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