Photo: The stalagmites of Yok Balum cave provided opportunities for researchers to study rainfall records. (Photo courtesy of Douglas Kennett, Penn State)
The ancient Mayan civilization, which developed a sophisticated culture in the Central American rainforests, vanished mysteriously a thousand years ago. Now, an international team of anthropologists, archeologists, chemists and climatologists says it has identified the cause of the Mayan collapse: climate change.
To create a weather record for the past 2,000 years, the scientists analyzed a natural mineral formation called a stalagmite from a cave in Belize, using oxygen-isotope dating to determine how much rain fell on the region over the centuries. Stalagmites build up incrementally, like tree rings, as water drips through the cave ceiling, preserving an accurate climate record.
Mayan rulers commissioned stone monuments to record important events such as their rise to power, major battles, civic unrest and strategic alliances. Pennsylvania State University Anthropology professor Douglas Kennett, the study’s co-author, says the team was able to compare changes in the society documented on those monuments with their new climate timeline.
Stone monuments like this stucco frieze in Caracol, Belize, document Maya battles, births and burials.
On a podcast for the journal Science, he said the team saw a relationship between rainfall levels and political stability.
“The growth of Maya civilization and increases in population and levels of sophistication actually correlate with a very wet interval that spans several hundred years and the decline of the Maya actually appeared to correlate with a downturn generally in climate and climate drying,” he said.
Abundant rainfall led to bumper crops and a population boom, but a climate reversal and drought triggered famine, political competition, increased warfare and eventually, the society’s collapse.
Scientists have long suspected that climate change played a role in the fall of the Mayan civilization, but the precise timeline - published in Science - provides them with new confidence in that connection. Kennett suggests their methodology could be used to increase understanding of the influence of climate on other ancient cultures that also have nearby cave systems.