Climate change and the political, human impacts among ancient Maya

In an article published Nov. 9 in the journal Science, the researchers outlined how they reconstructed rainfall records from stalagmite samples collected from Yok Balum Cave, located nearly three miles from ancient city of Uxbenka, in the tropical Maya Lowlands in southern Belize. They compared their findings to the rich political histories carved on stone monuments at Maya cities throughout the region.

"Unusually high amounts of rainfall favored an increase in food production and an explosion in the population between AD 450 and 660," said Douglas Kennett, lead author and 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, according to Kennett, the cities suffered a decline in their populations and Maya kings lost their power and influence.

"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," he said.

The rich archaeological and historical records of the Maya provide an opportunity to examine the long-term effects of climate change for both the development and disintegration of complex sociopolitical systems like our own, noted Kennett, an internationally known expert on the human effects of global climate change and the environmental impacts of expanding populations.

"The effects of climate change are complex and play out over multiple time scales," he said. "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."

The other co-authors are: Sebastian F.M. Breitenbach, Eidgenössische Technische Hochschule Zürich, Zurich, Switzerland; Valorie Aquino and Yemane Asmerom, University of New Mexico; Jaime Awe, National Institute of Culture and History, Belize; James Baldini, University of Durham, UK; Patrick Bartlein, University of Oregon; Brendan Culleton, Claire Ebert and Christopher Jazwa, Penn State; Martha Macri, University of California, Davis; Norbert Marwan, Potsdam Institute for Climate Impact Research, Germany; Victor Polyak and Keith Prufer, University of New Mexico; Harriet Ridley, University of Durham; Harald Sodemann, Eidgenössische Technische Hochschule Zürich; Bruce Winterhalder, University of California, Davis; and Gerald Haug, Eidgenössische Technische Hochschule Zürich.

The study was funded by the National Science Foundation, European Research Council, Swiss National Science Foundation, German Science Foundation, and the Alphawood Foundation.