A SERIES of intense droughts coincided with the near-collapse of the great Mayan civilisation of Central America, an in-depth study of the region鈥檚 climatic history has revealed.
The ancient Maya established large cities on the Yucat谩n peninsula in what is now Mexico, and by the 8th century their population had peaked at 15 million. The civilisation largely collapsed in the 9th century, but one is sure why.
Now, Gerald Haug at the Swiss Federal Institute of Technology in Zurich thinks he has the answer. In the most detailed study to date, Haug and his team measured titanium levels at different depths in sediment cores drilled from the Cariaco Basin off the coast of Venezuela.
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The basin is 200 kilometres from the Mayan cities, but has an identical climate. The sediment shows alternate light and dark bands marking the wet and dry seasons of preceding years. Rain washes titanium from the land into the ocean floor sediment, making the metal a useful indicator of the amount of rainfall in each year, says Haug.
鈥淲e looked in detail at the period corresponding to the 9th and 10th centuries,鈥� says Haug. The team found that there were three periods with extremely low titanium levels, indicating droughts in AD 810, 860 and 910 (Science, vol 299, p 1731). These dates correspond to the three years of the Mayan collapse, the scientists say. Furthermore, they found that the entire 9th century suffered below-average rainfall. 鈥淚t was a dry period with three intense droughts,鈥� says Haug. 鈥淭he climate change must have been what pushed the Mayan society over the edge.鈥�
Experts on the Maya have greeted Haug鈥檚 data with caution. The civilisation had survived many droughts before and the Maya had expertise in hydraulics, equipping their cities with canals, viaducts and reservoirs. 鈥淥verpopulation, environmental problems and economic factors all made them vulnerable,鈥� says Jeremy Sabloff, director of the Museum of Archaeology and Anthropology at the University of Pennsylvania. 鈥淏ut perhaps climate was the straw that broke the camel鈥檚 back.鈥�