By Deborah Zabarenko
9 November 2012
WASHINGTON (Reuters) – For a clue to the possible impact of climate change on modern society, a study suggests a look back at the end of classic Mayan civilization, which disintegrated into famine, war and collapse as a long-term wet weather pattern shifted to drought.
An international team of researchers compiled a detailed climate record that tracks 2,000 years of wet and dry weather in present-day Belize, where Mayan cities developed from the year 300 to 1000. Using data locked in stalagmites - mineral deposits left by dripping water in caves - and the rich archeological evidence created by the Maya, the team reported its findings in the journal Science on Thursday.
Unlike the current global warming trend, which is spurred by human activities including the emission of atmosphere-heating greenhouse gases, the change in the Central American climate during the collapse of the Mayan civilization was due to a massive, undulating, natural weather pattern.
This weather pattern alternately brought extreme moisture, which fostered the growth of the Mayan civilization, and periods of dry weather and drought on a centuries-long scale, said the study's lead author, Douglas Kennett, an anthropologist at Penn State University.
The wet periods meant expanded agriculture and growing population as Mayan centers of civilization grew, Kennett said in a telephone interview. It also reinforced the power of the kings of these centers, who claimed credit for the rains that brought prosperity and performed public blood sacrifices meant to keep the weather favorable to farming.
When the rainy period gradually changed to dry weather around the year 660, Kennett said, the kings' power and influence collapsed, and correlated closely with an increase in wars over scarce resources.
"You can imagine the Maya getting lured into this trap," he said. "The idea is that they keep the rains coming, they keep everything together, and that's great when you're in a really good period … but when things start going badly, and (the kings are) doing the ceremonies and nothing's happening, then people are going to start questioning whether or not they should really be in charge."
The political collapse of the Mayan kings came around the year 900, when prolonged drought undermined their authority. But Mayan populations remained for another century or so, when a severe drought lasting from the years 1000 to 1100 forced the Maya to leave what used to be their biggest centers of population.
Even during the Mayan heyday, humans had an impact on their environment, Kennett said, mostly by farming more land, which in turn caused greater erosion. During the dry periods, the Maya responded with intensified agriculture. […]