New evidence links Mayan collapse to climate change

Voice of America: The ancient Mayan civilization, which developed a sophisticated culture in the Central American rainforests, vanished mysteriously a thousand years ago.  Now, an international team of anthropologists, archeologists, chemists and climatologists says it has identified the cause of the Mayan collapse: climate change.

To create a weather record for the past 2,000 years, the scientists analyzed a natural mineral formation called a stalagmite from a cave in Belize, using oxygen-isotope dating to determine how much rain fell on the region over the centuries. Stalagmites build up incrementally, like tree rings, as water drips through the cave ceiling, preserving an accurate climate record.

Mayan rulers commissioned stone monuments to record important events such as their rise to power, major battles, civic unrest and strategic alliances.  Pennsylvania State University Anthropology professor Douglas Kennett, the study's co-author, says the team was able to compare changes in the society documented on those monuments with their new climate timeline.

On a podcast for the journal Science, he said the team saw a relationship between rainfall levels and political stability. "The growth of Maya civilization and increases in population and levels of sophistication actually correlate with a very wet interval that spans several hundred years and the decline of the Maya actually appeared to correlate with a downturn generally in climate and climate drying," he said....

A Mayan zodiac circle, shot by theilr, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license

Mild climate change killed off ancient Mayans

ChannelNewsAsia via AFP: The collapse of the Mayan civilization was likely due to a relatively mild drought, much like the drier conditions expected in the coming years due to climate change, scientists said Thursday. Scholars have long believed that a major drought caused severe dry conditions that killed off the ancient culture known for its mastery of language, math and astronomy.

But researchers from the Yucatan Center for Scientific Research in Mexico and the University of Southampton in Britain said their analysis shows the drought only caused reductions of 25 to 40 percent less annual rain.

The smaller amounts of rain meant that open water sources in pools and lakes evaporated faster than could be replaced by more precipitation, said the study in the journal Science. "The data suggest that the main cause was a decrease in summer storm activity," said co-author Eelco Rohling of the University of Southampton.

The study is the first of its kind to attempt to assess exactly how much rainfall decreased between 800 and 950 AD when Mayan civilization went into decline, and bases its modeling data on records of past rainfall changes from stalagmites and shallow lakes.

The analysis showed that modest dry spells could have sparked major water shortages in an area with no rivers, and no source of water other than rain....

Mayan ruins in Belize, shot by Josh, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license