Less predictable rainfall important for Maya decline

“A key ingredient for Maya agriculture was the timely arrival of sufficient rainfall. Farming in subtropical Central America is tough because freshwater is only available during the summer rainy season. Changes of onset and intensity of the rainy season can have serious repercussions for Central American societies”, explains Tobias Braun from PIK, lead-author of the study published in Communications Earth & Environment. While most scientists agree that repeated intense droughts were one of the key factors that led to the fragmentation of urban centers and redistribution of lowland Maya societies, evidence at seasonal time scale was so far missing. And this is exactly what the study takes into focus. “With a versatile method called ‘Recurrence Analysis’, we found that reduced seasonal predictability, in combination with severe droughts might have acted as a catalyzer for institutional destabilization and fragmentation of Maya societies,” Braun adds.

In the study region, the arrival of summer rains depends to a great extent on the so-called Intertropical Convergence Zone (ITCZ), a band of convergence between the northeast and southeast trade winds, which occasionally changes its position but also its width and regional strength. The observed changes in seasonal rainfall could have been caused by a less consistent ITCZ, which made it difficult for the Maya to predict seasonal rain from one year to the next.

“Being unable to secure sufficient crop yields, might have sparked social unrest in urban centers and, in turn, resulted in complex processes of sociopolitical disintegration that ultimately led Maya societies to return to more decentralized, less dense populated agrarian villages,” says Norbert Marwan from PIK, also author of the study. “Despotic Maya leaders were heavily invested in accumulating wealth and costly ceremonies, and likely far less interested in resilient responses to environmental change.”

Some Maya societies were able to adapt, others were not. Maya populations in the northern lowlands persisted and built the Postclassic center of Mayapan. Southern lowland societies, however, failed to organize in new urban settlements.