Climate Change May Have Caused Mayan Civilization's Collapse By Charles Choi

For unknown reasons, the ancient Mayan civilization then disintegrated more than a millennium ago. The number of people declined catastrophically to a fraction of the empire's former size, and the ruins of its great cities are now largely overgrown by jungle.

 The ancient Mayan empire once stretched across an area about the size of Texas, with cities and fields occupying what is now southern Mexico and northern Central America, including the countries of Guatemala, Belize, El Salvador and Honduras. The height of the Mayan empire, known as the Classic period, reached from approximately A.D. 250 to at least A.D. 900.

The ancient Maya had what was arguably the most advanced civilization in the Americas. 

For instance, they made dramatic breakthroughs in astronomy that helped them very accurately predict where the moon and other planets would be in the sky centuries in the future. They also left behind many books and stone inscriptions regarding the stories of their gods and the history of their divine kings and queens.

For unknown reasons, the ancient Mayan civilization then disintegrated more than a millennium ago. The number of people declined catastrophically to a fraction of the empire's former size, and the ruins of its great cities are now largely overgrown by jungle. [Photos: 

Scientists have long drawn connections between the slow decline of the ancient Maya, which took about two centuries, "to climate change, and especially to drought," said researcher Martín Medina-Elizalde at the Yucatan Center for Scientific Research in Mexico. 

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

To see how much rainfall the ancient Maya saw before the demise of their civilization, the researchers combined the four most detailed records of past climate changes known regarding the civilization's collapse — three from nearby lakes and one from a stalagmite, a mineral formation that grows upward from a cave floor. This helped develop a model of "the region's balance between evaporation and rainfall," Medina-Elizalde said.

The scientists found that rainfall in the region decreased episodically for periods as long as a decade at a time.

"Our results show rather modest rainfall reductions between times when the Classic Maya civilization flourished and its collapse between 800 to 950," said researcher Eelco Rohling, a paleoclimatologist at the University of Southampton in England. "These reductions amount to only 25 to 40 percent 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." Read more@csmonitor.com