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Multiple Causes Cited for Mayan Demise Including Climate Change

Two recently published studies delve into what happened to cause the collapse of the Mayan empire, a question many archaeologists have tried answering.
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Two recently published studies delve into what caused the collapse of the Mayan empire, a question many archaeologists have tried answering.

One of the studies, published August 20 in the journal Geophysical Research Letters points to drought hastened by deforestation as the lead cause of the decline of the Mayan empire.

“We’re not saying deforestation explains the entire drought, but it does explain a substantial portion of the overall drying that is thought to have occurred,” said the study’s lead author Benjamin Cook, a climate modeler at Columbia University’s Lamont-Doherty Earth Observatory and the NASA Goddard Institute for Space Studies, in a statement.

Researchers conducted computer simulations to figure out how the climate would have been affected by lands dominated by crops. They discovered that rainfall in the Yucatan peninsula—a heavily logged area—would have declined by as much as 15 percent. In other Maya lands, it could have declined by 5 percent.

The main culprit was corn. As it replaced the dense forest, more sunlight bounced back into space, Cook said. The ground was absorbing less energy from the sun, so less water was evaporating from the surface and this caused less moisture to be released into the air to form rain-making clouds. “You basically slow things down—the ability to form clouds and precipitation,” Cook said.

The idea that deforestation hastened climate change and caused the Mayas’ demise isn’t completely new. In 2010 climate modeler Robert Oglesby published a study in the Journal of Geophysical Research showing that rainfall could have declined 15 to 30 percent if the Maya lands had been cleared of trees.

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But deforestation and drought aren’t the only reasons researchers have found for the demise of the Maya civilization. Another study published August 21 in the journal Proceedings of the National Academy of Sciences, takes a more complete approach to explaining what happened to the 19 million people of the Maya empire.

“The ninth century collapse and abandonment of the Central Maya Lowlands in the Yucatán peninsular region were the result of complex human–environment interactions,” writes the team, led by B.L. Turner, a social scientist at Arizona State University. Turner and colleagues agree that deforestation contributed to the drought, but sees that as just one in a number of contributing factors that led to the downfall of the Maya.

The team detailed how the sapodilla tree, once favored as construction beams, was no longer used at the Tikal and Calakmul sites beginning in A.D. 741. Other resources showed signs of decline as well, such as the white-tailed deer.

“This environmental stress was complemented by a shift in commercial trade from across the peninsula to around it, which reduced the economy of the ruling elite to keep up the livelihood infrastructure to prevent the tipping point,” Turner said in an Arizona State University press release. The decision was made to vacate the central lowlands rather than maintain the investment. This theory is not only consistent with the data on collapse but on the failure of the central lowlands to be reoccupied subsequently.”

It’s hard to imagine the millions of people who once thrived in the Mayan cities between A.D. 250 and A.D. 900, especially when the buildings they once occupied are seen today overgrown with jungle. Ogelsby said that areas occupied by the Maya are still vulnerable.

“There’s a tremendous amount of change going on in Guatemala,” he said in the statement. “They may be that much more vulnerable to a severe drought.”