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 Sediment from Himalayas may have made 2004 Indian Ocean earthquake more severe
26.05.2017 | Oregon State University

nachricht Devils Hole: Ancient Traces of Climate History
24.05.2017 | Universität Innsbruck

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>