Fall of Mayan cities blamed on severe droughts

Ruins, such as this one in Guatemala, add to the mystery surrounding the fate of the Maya. www.mayaruins.com

The collapse of the Mayan civilization has been blamed on severe spells of drought, according to research carried out in Switzerland.

Scientists have long been baffled by the demise of the Maya, who flourished in present-day Mexico, Guatemala and Honduras until about 1,200 years ago.

But analysis of sediment extracted off the northern Venezuelan coast suggests they may have been devastated by severe droughts lasting between three and nine years.

One of the study’s authors, Gerald Haug from the Swiss Federal Institute of Technology in Zurich, said between 750 and 950 AD the Maya experienced a “demographic disaster as profound as any other in human history”.

At its height in 750 AD, the Mayan civilization is believed to have supported a population of between three and 13 million people.

The Mayans began cultivating maize in Central America around 2000 BC, and eventually developed sophisticated irrigation techniques involving raised fields, canals, reservoirs and gravity-powered rainwater distribution systems.

High and dry

But their renowned mathematical and engineering brilliance appears not have been enough to save them. By the early 9th century most of the Mayan cities were abandoned.

Haug told swissinfo that the droughts were what may have pushed Mayan society over the edge.

He says the era during which the Mayan civilization went into decline coincided with one of the driest periods since the birth of Christ.

“They were clearly running into problems,” said Haug. “One consequence of this was probably social upheaval and ideological decline… there is documentation of migration and war around this time.”

The report – published in the journal Science on Friday – says the fate of the Maya remains difficult to determine.

Studying ocean floors

Using equipment at the institute in Zurich, researchers analysed the concentration of titanium in sediment cores drilled from ocean floor of what is known as the Cariaco Basin, north of Venezuela.

Titanium is a key indicator of rainfall, because higher precipitation washes more of the metal from the land into ocean floor sediments.

“We looked in detail at the period corresponding to the 9th and 10th centuries – taking 6,000 measurements per 30 centimetres of sediment – and found three extreme minima, as well as a low background level that lasted about 100 years,” said Haug.

Experts divided

Nonetheless the drought theory remains contentious. “Perhaps it was the straw that broke the camel’s back,” Jeremy Sabloff, from the University of Pennsylvania told New Scientist magazine.

But Sabloff argues that the Maya had coped well through earlier droughts.

“The Maya thrived for 1,500 years before these droughts, so it’s clearly not climate alone that brought down the southern cities of the Yucatàn peninsula,” he said.

Another expert, Boston University’s Norman Hammond, also questioned the findings, pointing out that the northern Yucatàn city of Chichén Itzà was not abandoned until the 13th century.

swissinfo, Jacob Greber and Isobel Johnson

Key facts

The Mayan civilization may have collapsed because of several severe droughts.
Research done at the Federal Institute of Technology in Zurich found evidence of droughts that lasted between three and nine years during the 9th and 10th centuries.
These periods coincided with times of decline for the Maya, characterised by population declines and slower building rates.
By analysing levels of titanium (which is washed into the ocean during heavy rainfall) researchers could identify wet and dry years.