The silent cities
Around 750 CE, the Maya civilization was near its peak population, which may have been as high as 13 million people. In the southern lowlands of the Yucatán Peninsula, city-states like Tikal, Calakmul, and Caracol were sprawling urban centers. Tikal's population exceeded 50,000, and Caracol's was over 100,000. Then, over the next 150 years, a deep change occurred. This period, from roughly 800 to 925 CE, is known as the Terminal Classic. During this time, construction of stone monuments stopped, royal dynasties vanished, and the great cities were gradually abandoned. By 900 CE, the southern lowlands were almost completely depopulated, with population numbers falling by as much as 90%. The mystery is not that the Maya people disappeared, but that they abandoned a landscape they had occupied for centuries, leaving their stone architecture to the jungle.
A cascade of failures
There was no single cause for the collapse, but rather a fatal combination of pressures. The main problem was severe, prolonged drought. Analysis of sediment cores from Lake Chichancanab and other locations reveals that the period between 800 and 1000 CE was the driest the region had seen in 7,000 years. Scientists studying water isotopes trapped in gypsum layers found that annual rainfall decreased by an average of 41% to 54%, with peak drought periods seeing up to a 70% reduction. This climate event was worsened by extensive deforestation. The Maya cleared vast forests for agriculture and to fuel the fires needed to create lime plaster for their buildings; it took an estimated 20 trees to produce just one square meter of plaster. This large-scale clearing reduced humidity and worsened the drought.
This environmental stress fueled social and political turmoil. Evidence for endemic warfare increased in the Terminal Classic period. At sites like Dos Pilas in Guatemala, newly discovered hieroglyphic stairways detail a brutal, decades-long war between the superpowers of Tikal and Calakmul and their proxies. The inscriptions graphically describe battles where "blood was pooled and the skulls... were piled up". Cities began building defensive walls, signs of instability. The combination of crop failure, resource scarcity, and constant warfare made the large lowland cities unsustainable, leading to their eventual abandonment.