November 9, 2012
Climate Change Influenced Mayan Political Systems
April Flowers for redOrbit.com - Your Universe Online
There has been a controversy in the scientific community about the role of climate change in the development and subsequent demise of the Maya civilization, which thrived from AD 300 to 1000. The debate has raged because of a lack of well-dated climate and archaeological evidence.
An international team of archaeologists and earth scientists from Pennsylvania State, ETH Zurich and the University of Durham, among others, has compiled a precisely dated, high-resolution climate record dating back over 2,000 years. The findings of this study, published in the journal Science, show how Maya political systems developed and disintegrated in response to climate change.
The research team reconstructed rainfall records from stalagmite samples collected from Yok Balum Cave, located approximately three miles from the ancient city of Uxbenka, which is in the tropical Maya Lowlands of southern Belize. The scientists compared the rich political histories carved on stone monuments at Maya sites throughout the region to their rainfall findings. One type of history in particular that they looked at is called a "war index," which is a record of hostile events. The war index was compiled by looking at how often certain keywords occurred in Mayan inscriptions, allowing the team to chart how increases in war and unrest were associated with periods of drought.
Dr. Martha Macri of the University of California, Davis recorded the war index in the "Maya Hieroglyphic Database Project."
Dr James Baldini, Department of Earth Sciences, Durham University said, "The rise and fall of Mayan civilization is an example of a sophisticated civilization failing to adapt successfully to climate change. Periods of high rainfall increased the productivity of Maya agricultural systems and led to a population boom and resource overexploitation. The progressively drier climate then led to political destabilization and warfare as resources were depleted."
"After years of hardship, a nearly century-long drought from 1020 sealed the fate of the Classic Maya."
The team analyzed the stalagmite using oxygen isotope dating in 0.1 millimeter increments to uncover the rainfall record. This allowed the team to link precipitation to political situations described on the stone monuments. Between 300 and 660 AD high and increasing rainfall coincided with a rise in population and political centers. From 660 to 1000 AD, a drying trend triggered political competition, increased warfare, overall sociopolitical instability and collapse. An extended drought between 1020 and 1100 AD brought about crop failures, death, famine and migration.
"Unusually high amounts of rainfall favored an increase in food production and an explosion in the population between AD 450 and 660" said Dr. Douglas Kennett, professor of anthropology at Penn State. "This led to the proliferation of cities like Tikal, Copan and Caracol across the Maya lowlands. The new climate data show that this salubrious period was followed by a general drying trend lasting four centuries that was punctuated by a series of major droughts that triggered a decline in agricultural productivity and contributed to societal fragmentation and political collapse. The most severe drought (AD 1020 and 1100) in the record occurs after the widespread collapse of Maya state centers (referred to as the Maya collapse) and may be associated with widespread population decline in the region."
"Over the centuries, the cities suffered a decline in their populations and Maya kings lost their power and influence" Dr. Kennett said. "The linkage between an extended 16th century drought, crop failures, death, famine and migration in Mexico provides a historic analog, supported by the cave stalagmite samples, for the socio-political tragedy and human suffering experienced periodically by the Classic Period Maya."
Because the Maya left such a rich archaeological and historical record, the team had the opportunity to examine the long-term effects of climate change for both the development and the breakdown of complex sociopolitical systems like our own.
The climate changes were driven by El Nino events and the shifting position of the Intertropical Convergence Zone (ITCZ), which is a belt of rainfall encircling the Earth. The team hypothesizes that during the Maya Collapse, the ITCZ didn't reach far enough north, which resulted in a catastrophic drought.
"The effects of climate change are complex and play out over multiple time scales," Kennett added. "Abrupt climate change is only part of the story. In addition to climate drying and drought, the preceding conditions stimulating societal complexity and population expansion helped set the stage for later stress on their societies and the fragmentation of political institutions."
"It has long been suspected that weather events can cause a lot of political unrest and subject societies to disease and invasion," Macri said. "But now it's clear. There is physical evidence that correlates right along with it. We are dependent on climatological events that are beyond our control."
Bruce Winterhalder, professor of anthropology at UC Davis, said, "It's a cautionary tale about how fragile our political structure might be. Are we in danger the same way the Classic Maya were in danger? I don't know. But I suspect that just before their rapid descent and disappearance, Maya political elites were quite confident about their achievements."