Tree rings give clues to ancient droughts

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FAYETTEVILLE, Ark., Feb. 3 (UPI) -- A study of tree rings in Mexico may give clues to the role major droughts played in the fates of long-gone ancient civilizations, U.S. researchers say.

Scientists at the University of Arkansas say their 1,238-year-long tree-ring chronology -- the longest and most accurate of its kind for Mexico and Central America -- is the first to reconstruct the climate of pre-colonial Mexico on an annual basis for more than a millennium, pinning down four ancient megadroughts to their exact years, an American Geophysical Union release reported Thursday.

One large ancient drought previously confirmed in the U.S. Southwest between 1149 and 1167 is shown to have extended into central Mexico, where it may have devastated maize crops, potentially giving a fatal blow to the declining Toltec culture, David Stahle, a UA paleoclimatologist, says.

The rainfall chronology provides confirmation of the so-called Terminal Classic drought that some anthropologists tie to the collapse of the Mayan civilization.

"Certainly these cultural changes were very complicated -- probably not one single explanation can account for the collapse of the Mayan civilization," Stahle says. "[But] our study will allow other scientists to more thoroughly investigate and understand the impact of these droughts."