Not a vanishing, but a transformation
The word “collapse” invites a picture of a civilization wiped out overnight. That is not what happened. Between roughly 800 and 1000 CE, many cities in the southern Maya lowlands, in what is now northern Guatemala, southern Mexico and Belize, stopped building monuments, lost their royal courts and saw their populations fall. Over the same centuries, cities in the northern Yucatan kept growing, and the Maya themselves never disappeared: several million Maya people live in Mexico, Guatemala and Belize today. The real question is why one particular political and economic system in one region unravelled, and why climate is part of the answer.
How scientists read ancient rainfall
No weather station records survive from the ninth century, so researchers use natural archives that respond to rainfall.
Cave stalagmites. Water dripping through limestone leaves mineral layers that build a stalagmite, and the chemistry of each layer shifts with the amount of rainfall above the cave. Layers can be dated with uranium-series methods, giving a year-by-year or decade-by-decade record. Stalagmites from caves in Belize have been used to reconstruct rainfall over more than a thousand years.
Lake sediments. Cores from lakes on the Yucatan Peninsula and in the Petén contain layers of mud and minerals. The ratios of certain elements and isotopes in those layers, for example in gypsum, indicate whether the lake was drying out. Organic material in the cores can be dated using radiocarbon dating.
Both kinds of record, along with some from ocean sediments off Venezuela, point in the same direction: the Terminal Classic period saw drier conditions overall, with several multi-year or multi-decade dry episodes. Many researchers see a sequence of droughts across the ninth and early tenth centuries, with another dry phase around the early eleventh century. The overlap between records from different places is why Maya drought evidence is taken seriously.
What the evidence does not show
The climate data carry limits. First, they are regional proxies, not direct measurements at each city. The south was not uniformly dry, and rainfall in the north differed. Second, dates in the records carry uncertainties, often of decades, so lining them up with specific events such as the last carved monument at a given site is imprecise. Third, drought does not automatically cause a political collapse. Droughts had occurred earlier, and Maya communities had weathered them. In the Terminal Classic, drought probably hit a society already under strain from heavy population, intense warfare and competition between kings.
Another issue is the vulnerability of the system. Rulers justified their power partly by their ability to mediate with gods and bring prosperity. A run of failed harvests could erode belief in kingship. Cities that relied on stored rainwater, such as those with large reservoirs, could be especially exposed when rains failed in consecutive years. Evidence for these effects exists at some sites but not others, which is why most scholars favour combined explanations rather than a single cause. Other civilizations, from the Ancestral Puebloan migration in the American Southwest to debates such as the Moche decline theories in Peru, have been examined with similar mixes of climate and society, though each case is different.
Why the north kept going
If drought was the main driver, one might expect the whole Maya world to fail. Instead the north fared differently. Chichen Itza, in the Yucatan, reached its height around the tenth and early eleventh centuries, with a very large ballcourt, an observatory-like structure called El Caracol, and the Castillo pyramid. Cities in the Puuc hills, such as Uxmal, also flourished in the Terminal Classic before declining. Chichen Itza later weakened, and Mayapan became a leading centre in the thirteenth to fifteenth centuries.
Reasons for the contrast include access to water through natural sinkholes (cenotes), which provided reliable supplies even when rainfall dropped, and trade links by sea and along the coast. Different political structures may also have mattered.
People moved and adapted
Many southern residents seem to have dispersed rather than died out. Some moved to the coasts, rivers, lakes and the highlands, where new communities arose. Archaeological surveys show that populations in certain parts of the southern lowlands, such as around lakes in the Petén, persisted for centuries after the royal cities faded. By the time the Spanish arrived, there were Maya kingdoms in the Petén lakes region, in northern Yucatan and in the Guatemalan highlands.
Why the story is still told as a mystery
The “mystery” label lingers partly because the abandoned cities are so impressive and partly because early writers assumed a sudden catastrophe. Modern research shows a long, uneven process that varied by place. The best summary is that the Classic Maya collapse reflects overlapping pressures, with drought as a significant but not exclusive factor. Questions remain about timing, about how severe the dry spells were at individual sites and about why some cities held out longer. These are active research topics, and published views continue to be revised.