Key factors in the collapse of the Mayan civilization may have been located deep within a Mexican cave, as University of Cambridge-led researchers analyzed the chemical makeup of stalagmites that help explain the decay of a once-powerful civilization.
The work provided new insights into the rainfall occurring between 871 and 1021 CE, producing evidence that a single 13-year drought, along with several others lasting more than three years each, placed strain on the advanced Mayan society, leading to its eventual downfall.
Those years correspond to the known Terminal Classic period of the Maya, when large limestone cities at the southern end of their territory were abandoned and dynasties cut short.
Inside the Yucatán Cave
This is the first time researchers have been able to isolate rainfall conditions from this mysterious period with such clarity, marking the decay of Mayan political and economic power as their culture shifted northward. Researchers working on the study focused on stalagmites standing in a northern Yucatán cave, revealing new data about the local climatic past. From analyzing the chemical makeup of the stalagmites, the team found a significant number of wet-season droughts, lasting for years on end.
Stalagmites form as water dripping from a cave ceiling deposits minerals on the cave floor, eventually producing the standing deposits. Oxygen isotopes residing within these deposits provide comprehensive data on the Terminal Classic climate. Researchers have previously attempted similar projects, including an oxygen isotope analysis of lake sediments, but the sediment provided much less detail than the stalagmites.
Daniel H. James installs a drip rate monitor upon a flowstone in Grutas Tzabnah (Yucatán, Mexico) as part of the wider cave monitoring campaign. Credit: Sebastian Breitenbach, 2022
Earlier Attempts to Understand Mayan Climate
“It hasn’t been possible to directly compare the history of individual Mayan sites with what we previously knew about the climate record, said lead author Dr Daniel H. James. “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.”
Previous attempts to study stalagmites to illuminate the Terminal Classic have been made, although those only provided a softer picture of annual rainfall, falling short of the precise details on specific wet and dry seasons recovered by the Cambridge-led group. This precision is due to the thick 1mm annual layers, which provide much more real estate for the team to work with.
“Knowing the annual average rainfall doesn’t tell you as much as knowing what each individual wet season was like,” said James. “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.”
Studying the Mayan Collapse
Mayan scholars first began to develop a comprehensive understanding of the Terminal Classic’s climate in the 1990s. A key indicator they found was the dates on monuments, with gaps in construction suspected to indicate a series of droughts during the period that may have induced sociopolitical unrest. In addition to the monuments, scholars identified decreased political activity during the period at multiple northern Mayan sites, such as Chichén Itzá. The detail and accuracy of this new climate data provide an essential tool for researchers seeking to understand how past humans interacted with their climate, including precise timing.
“This period in Mayan history has been a cause of fascination for centuries,” said James. “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 Mayan left behind. But in the past few decades, we’ve started to learn quite a lot about what happened to the Mayan and why, by combining the archaeological data with quantifiable climate evidence.”
The authors Daniel H. James, David Hodell, Ola Kwiecien, and Sebastian Breitenbach (L-R) at the Maya site of Labna in the Puuc region (Yucatán, Mexico), which was most likely abandoned during the Terminal Classic. Credit: Mark Brenner, 2022
Continuing to Pursue an Advanced Civilization
While academics know that the Mayan developed advanced water management techniques, a period of thirteen years without sufficient rainfall was beyond the scope of what their technology could mitigate. Correspondingly, monument building appears to have ceased during these droughts as their drought years match gaps in monument inscription dates.
“This doesn’t necessarily mean that the Mayan 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,” said James.
Continuing to investigate this and other caves in the area may lead to a richer understanding of the causes of the Mayan decline.
“In addition to what stalagmites can tell us about this period in Mayan history, they might also be able to tell us about the frequency and severity of tropical storms, for instance,” James concluded.
“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.”
The paper, “Classic Mayan Response to Multi-Year Seasonal Droughts in Northwest Yucatán, Mexico,” appeared in Science Advances on August 13, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.