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UA Center Studies Climate-Civilization Link

Posted June 12, 2015

How did long-gone peoples respond to changing environments in their homelands? How did catastrophic events impact human populations? What conditions allowed empires to rise and triggered their collapse, and what can today’s societies learn about the future?

A new interdisciplinary research center bringing together faculty from the University of Arizona’s School of Anthropology, Laboratory for Tree-Ring Research, Accelerator Mass Spectrometry Laboratory and Department of Geosciences is poised to shed light on how people in the Mediterranean — often referred to as the cradle of civilization — dealt with shifting weather patterns, deluges and droughts, and dearth and abundance.

The establishment of the Center for Mediterranean Archaeology and the Environment, or CMATE, builds on a legacy of more than 75 years of cross-disciplinary collaboration between the world’s founding laboratory for dendrochronology and colleagues in the School of Anthropology (currently celebrating its centennial year), geosciences and other units at the UA. Dendrochronology is the science of dating wood based on its growth rings­.

Ballast stones and broken ceramic vessels lie scattered among harbor pilings at this Byzantine harbor site excavated near the Turkish capital, Istanbul. Image credit: Charlotte Pearson

Ballast stones and broken ceramic vessels lie scattered among harbor pilings at this Byzantine harbor site excavated near the Turkish capital, Istanbul. Image credit: Charlotte Pearson

The creation of CMATE was celebrated in a special joint issue of the journals Radiocarbon and Tree-Ring Research, both housed at the UA.

By combining different perspectives and methodologies for reconstructing the past, the goal is to assemble a continuous, high-resolution chronology of the Mediterranean region spanning multiple millennia. Such a chronology will help researchers gain a greater and more highly resolved picture of past human and environmental interactions in the cradle of Old World civilizations.

“In addition to improving our understanding of the development of Mediterranean civilizations, CMATE aims at improving and transforming the region into the world’s premier ‘observatory’ for the study of human-environment interactions in deep time,” said CMATE director Steven Kuhn.

“Just as the present may provide a key to understanding the past, understanding the past may provide the key to future predictions,” said Charlotte Pearson of the Laboratory for Tree-Ring Research, the associate director of CMATE, who also is affiliated with the School of Anthropology. “Why did some civilizations decline and some endure? How were past societies impacted by natural events such as droughts, forest fires, volcanic eruptions, tsunamis or earthquakes, and over what time frame? Those are the kinds of questions we want to answer.”

Parallels between the Mediterranean and the American Southwest allow the CMATE scientists to apply decades of expertise in connecting tree-ring research to archaeology and climate research, according to Pearson. For example, both regions share the occasional appearance of droughts at critical moments in history, which needs investigation. Other aspects are very different.

“In the Mediterranean, we don’t have trees like ‘Prometheus,’ bristlecone pines that are up to 5,000 years old, growing undisturbed in remote locations,” Pearson said. “There, people have cultivated and populated the land, practiced agriculture, cut down trees, built structures, gone to war with each other and so forth. Therefore, the wood they left behind is disturbed. It’s a cultural record of wood, so we have shorter sequences of tree rings with gaps for some critical periods that we are constantly working to fill.”

Accordingly, scientists visualize the Mediterranean as a complex puzzle, and solving it requires the collaboration of several disciplines.

“We can get one part of the picture with tree-ring science, another with archaeology or geology, and another with radiocarbon dating,” Pearson said. “CMATE brings together just that combination of expertise, knowledge and skills to form a bigger, better, composite image.”

Dendrochronology, the science of analyzing the growth rings of trees to reconstruct the past, was invented at the UA. Image credit: LTRR

Dendrochronology, the science of analyzing the growth rings of trees to reconstruct the past, was invented at the UA. Image credit: LTRR

The UA experts contributing to the CMATE Special Issue are pioneering fresh chronometric approaches such as analyzing signatures of Earth’s magnetic field recorded like timestamps in ancient fired ceramic structures (Eleni Hasaki in the School of Anthropology with collaborators from the University of Thessaloniki, Greece).

“In recent decades, our European colleagues have constructed extensive archaeomagnetic databases that facilitate the dating of fired ceramic artifacts, from metal furnaces to pottery kilns and bread ovens,” Hasaki said. “They join forces with archaeologists to refine dates of artifacts and sites over wide chronological horizons. Closely-dated activities enrich our understanding of a variety of topics, from craft technologies to human interaction within social and commercial networks.”

Others are applying radiocarbon dating to figure out that hackberries found in Neolithic trash heaps in Turkey were left behind there about 12,000 years ago (Jay Quade of the Department of Geosciences and Mary Stiner of the School of Anthropology).

By unlocking the stories hidden in the tree rings of wood that once was part of cargo ships and harbor pilings excavated in what today is the Turkish capital of Istanbul, associate research professor Tomasz Wazny of the Laboratory of Tree-Ring Research discovered that the wood was hauled in over large distances around the Black Sea.

Other tree-ring research professors, Ramzi Touchan and David Meko, are starting in the present and working back in time, reconstructing the first detailed histories of drought across the Mediterranean and North Africa over the last 2,000 years. Meanwhile, Valerie Trouet is investigating the regional and global forcing on Mediterranean climate. Just as in the Southwest today, drought is becoming a pressing issue in the Mediterranean. It also was a big issue in the past.

One such time was the so-called 4.2 kiloyear event — a period of unusual drought so named because it started about 4,200 years ago. It is the subject of the lead article in the special issue authored by Malcolm H. Wiener, an internationally acclaimed prehistorian and member of the CMATE steering committee who recently received the Gold Cross of the Order of Honor by the Hellenic Republic for his contribution to the study of Aegean prehistory.

“Around that time, the pyramid-building in Egypt ceased, and carvings show emaciated figures, hinting at a famine,” Pearson said.

But the changes described by Wiener were not limited to the Mediterranean and Near East.

“China appears to have undergone major fluctuations in this broad general time period, although the dates are still somewhat uncertain,” Wiener said. “Human history has been marked by major episodes of climate change, pandemics — perhaps climate-related — and human response including migrations, sometimes accompanied by independent innovations such as the widespread appearance of bronze weapons and of sailing vessels.”

Wiener currently is working on a publication on the collapse and revival of Mediterranean and Near Eastern societies at the end of the Bronze Age.

Said Pearson: “Much debate surrounds questions like whether climate really did cause the collapse of ancient empires. The further you go back in time, the fuzzier things become, and the only way we can get answers is to pull together lines of evidence from multiple disciplines and arrange them in a chronologic framework that is as precise and accurate as possible.”

Source: University of Arizona

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