Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New drought record from long-lived Mexican trees may illuminate fates of past civilizations

04.02.2011
A new, detailed record of rainfall fluctuations in ancient Mexico that spans more than twelve centuries promises to improve our understanding of the role drought played in the rise and fall of pre-Hispanic civilizations.

Prior evidence has indicated that droughts could have been key factors in the fates of major cultures in ancient Mexico and Central America (Mesoamerica). But there have been many gaps in the paleoclimate record, such as the exact timing and geographic extension of some seemingly influential dry spells.

The new, 1,238-year-long tree-ring chronology, the longest and most accurate of its kind for Mesoamerica, 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.

One large ancient drought previously confirmed for the Southwest of the United States is shown to have extended into central Mexico (1149-1167 AD) by the new dendrochronology, or tree- ring reconstruction. There it may have devastated the local maize crops, potentially giving a fatal blow to the declining Toltec culture, says David Stahle, a paleoclimatologist at the University of Arkansas at Fayetteville and lead author of the new study. Stahle and his colleagues present their new findings in a paper that has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

The new record also pins down more precisely than ever before the time periods of two other extended and severe dry periods, possibly leading to new insights into the Aztecs's rise to power, and into the spread of exotic diseases that Spanish Conquistadores brought to America.

This far-reaching rainfall chronology also provides the first independent confirmation of the so- called Terminal Classic drought, a megadrought some anthropologists relate to the collapse of the Mayan civilization. This decades-long dry period had been previously determined by analysis of lake and basin sediments in other areas of Mexico and the Caribbean. But Stahle's team has narrowed the event's timing to 897-922 AD and confirmed that it had a wider geographical impact than previously thought, extending into the highlands of Central Mexico, where other classic period cultures were located.

"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."

Stahle and his team used data from 74 core samples extracted from 30 specimens of millennium- old Montezuma baldcypress trees (Taxodium mucronatum) growing in the canyon of Amealco, Queretaro -- only 90 kilometers (56 miles) away from Tenochtitlan, capital of the Aztec empire, and 60 km (37 mi) northeast from Tula, the Toltec state's main city. Stahle says this tree species, related to North American sequoias, is the only plant in Central America that frequently lives up to one thousand years or more.

"This is the national tree of Mexico, and it tells such an interesting story of the decline of the Mexican empires", says Stahle, adding that previous tree chronologies for Mexico were only three to four centuries long. "This is the first one that goes back into pre-Hispanic times,"

The researchers determined the year of formation for each tree ring and analyzed what the rings' growth patterns had to say about how soil moisture varied from growth season to growth season over the years, a parameter directly associated with rainfall. "The beauty of tree rings is that they're annual: you get an estimate for wetness for every single year -- you don't get it from other archives, not as precisely," Stahle says.

"This research ... highlights the role fine-grained climate data can play in helping us understand the trajectories of past human societies," says David Anderson, an archaeologist at the University of Tennessee, Knoxville who was not involved in the new study. "This study will prompt a great deal of follow-up research by archaeologists and paleoclimatologists alike, and offers lessons for our own civilization -- specifically how vulnerable complex societies may be to drought- induced crop failures."

This research received funding from the National Science Foundation's Paleoclimatology Program and the Inter-American Institute for Global Change Research.
Title:
"Major Mesoamerican Droughts of the Past Millennium"
Authors:
D.W. Stahle, D.K. Stahle, D.J. Burnette, F.K. Fye, M.K. Cleaveland: Department of Geosciences, University of Arkansas, Fayetteville, Arkansas, USA;
J. Villanueva Diaz, J. Cerano Paredes: Laboratorio de Dendrocronologia, Instituto Nacional de Investigaciones Forestales, Agricolas, y Pecuarias, Durango, Mexico;

R.R. Heim, Jr.: Climate Services and Monitoring Division, NOAA's National Climatic Data Center, Asheville, North Carolina, USA;

R. Acuna Soto: Departamento Microbiologia y Parasitologia, UNAM, Mexico, D.F., Mexico;

M.D. Therrell: Department of Geography, Southern Illinois University, Carbondale, Illinois, USA.

Contact information for the author:
David Stahle, Telephone: +1 (479) 575-3703 or +1 (479) 443-0346, Email: dstahle@uark.edu

Maria-Jose Vinas | American Geophysical Union
Further information:
http://www.agu.org

More articles from Earth Sciences:

nachricht 'Quartz' crystals at the Earth's core power its magnetic field
23.02.2017 | Tokyo Institute of Technology

nachricht NASA spies Tropical Cyclone 08P's formation
23.02.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>