What caused the Maya collapse? The answer was hidden in a cave

A cave stalagmite has captured a season-by-season record of rain shortfalls during the final centuries of the Classic Maya. The stone’s chemical layers show eight wet-season droughts between 871 and 1021 CE, including one that dragged on for 13 consecutive years.

The pattern aligns with the era’s political turmoil and the halt of monument building at key cities.

Led by the University of Cambridge, a new study examined a cave in Mexico’s Yucatán, and managed to isolate rainfall in individual wet and dry seasons across the Terminal Classic period.

This research adds a precise climate timeline to the historical and archaeological evidence for the Maya collapse.

Rainfall recorded in rock

Stalagmites grow as mineral-rich water drips from cave ceilings and hardens on the floor. Each layer traps a chemical snapshot of the conditions outside. In this case, oxygen isotope ratios record how much rain fell when a given layer formed.

Earlier work measured lake sediments to gauge drought severity. Those cores are powerful, but they blur events across longer spans.

This stalagmite is different. Its annual layers are relatively thick, about one millimeter, allowing the team to pull apart the rainy and dry seasons year by year.

“It hasn’t been possible to directly compare the history of individual Maya sites with what we previously knew about the climate record,” said lead author Daniel James, who conducted the research while a Ph.D. student in Cambridge’s Department of Earth Sciences.

“Lake sediment is great when you want to look at the big picture, but stalagmites allow us to access the fine-grained detail that we’ve been missing.”

Crops and cities under strain

For farmers, annual averages can be misleading. What matters is the rainy season. If those months fail, harvests fail. The new record therefore tracks wet-season drought directly, identifying differences between subsistence and scarcity.

“Knowing the annual average rainfall doesn’t tell you as much as knowing what each individual wet season was like,” James said.

“Being able to isolate the wet season allows us to accurately track the duration of wet season drought, which is what determines if crops succeed or fail.”

Between 871 and 1021 CE, the stalagmite registered eight wet-season droughts that lasted at least three years. The longest persisted for 13 years. Even with reservoirs, canals, and cisterns, a deficit that long would strain food stores, trade, and social order.

Climate’s mark on Maya politics

The Terminal Classic saw southern lowland cities emptied and dynasties ended. Power shifted north, and monument programs faltered. The new drought timeline overlaps those disruptions.

“This period in Maya history has been a cause of fascination for centuries,” James said. “There have been multiple theories as to what caused the collapse, such as changing trade routes, war, or severe drought, based on the archaeological evidence the Maya left behind.”

“But in the past few decades, we’ve started to learn quite a lot about what happened to the Maya and why by combining the archaeological data with quantifiable climate evidence.”

At major northern sites, including Chichén Itzá, the carving of dated inscriptions stopped during severe, prolonged droughts. While that does not prove abandonment, it certainly marks a pivot in priorities.

“This doesn’t necessarily mean that the Maya abandoned Chichén Itzá during these periods of severe drought, but it’s likely that they had more immediate things to worry about than constructing monuments, such as whether the crops they relied on would succeed or not,” James said.

Seasonal view of the Maya collapse

Starting in the 1990s, researchers linked a series of droughts to the Maya collapse by comparing regional climate proxies with the dates on monuments.

The new stalagmite record builds on that foundation. It delivers the fine-grained detail that bridges climate processes and human decisions at specific places and times.

Researchers noted that earlier studies based on lake sediments offered a broad regional view, but lacked the resolution to pinpoint changes within specific years or seasons. Stalagmites, by contrast, allow researchers to match climate shifts to historical events more precisely.

By aligning wet-season failures with changes in building, ritual, and rule, scholars can test how drought pressure unfolded, how cities adapted, and when systems failed.

Beyond drought in the record

The team, which includes collaborators in the UK, U.S., and Mexico, argues that stalagmites from this and other Yucatán caves can do more. They could capture the fingerprints of tropical storms as well as drought, widening the environmental context for Maya history.

“In addition to what stalagmites can tell us about this period in Maya history, they might also be able to tell us about the frequency and severity of tropical storms, for instance,” James said.

“As a case study for fine-grained comparisons between climate and historical data, it’s exciting being able to apply methods usually associated with the deeper past to relatively recent history.”

James, now a postdoctoral researcher at University College London, said the next step is to expand the cave network and tighten links to site-by-site archaeology. The goal is a shared chronology that can help bring into focus the full sequence of droughts, decisions, and decline.

The study is published in the journal Science Advances.

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