Between 750 and 900 AD, the Maya lowlands of Central America experienced a dramatic decline in population and political power. For years, researchers have linked this decline to repeated severe droughts.
That explanation has long dominated scientific thinking. But new discoveries based on a 3,300-year-old sediment record suggest the story may be more complex than a simple climate crisis.
Benjamin Gwyneth, a professor of geography at the University of Montreal who studies environmental change and its impact on the Maya, is researching the Itzan ruins in modern-day Guatemala.
Gwyneth and his team have compiled a long-term record of both environmental conditions and human activity in the area by analyzing sediment cores from nearby lake Laguna Itzan.
Remarkably, their results show no signs of drought in Itzan during the period when the Maya population declined. Still, the local population collapsed around the same time as communities in other parts of Guatemala and Mexico that experienced drought.
So what caused the decline?
Clues from sediments reveal human and environmental history
To answer this question, the researchers looked at three types of geochemical markers preserved in lake sediments. These contained polycyclic aromatic hydrocarbons, which indicate the severity of slash-and-burn fires. The wax on the leaves reflects the vegetation and rainfall patterns. Fecal stanols are useful for population estimation.
By combining these indicators, the research team was able to track changes in population, agricultural practices, and climate over thousands of years, from the first signs of human presence around Laguna Itzan around 4,000 years ago until the site was abandoned around 1,000 years ago.
“The data reveals that the first settlements appeared 3,200 years ago,” Gwyneth said. “There was slash-and-burn agriculture and population growth. During the Preclassic period, 3,500 to 2,000 years ago, the Maya used fire extensively. They practiced slash-and-burn agriculture, where they used fire to clear forests and use the fertile ash to grow crops.”
Changes in Mayan agriculture and urban growth
During the Classic period, 1,600 to 1,000 years ago, there are significant changes in the data. Population density increased significantly, but the use of fire decreased sharply.
“This probably means that a large portion of the land has been cleared, which may have led to a change in farming strategy,” Gwyneth said.
Evidence points to more intensive farming methods, such as plowing rows and furrows to limit erosion, and more intensive horticultural practices. “Fire was no longer an important part of their farming methods,” Gwyneth said. “This change reflects gradual urbanization and suggests that the Maya were changing their agricultural strategies to feed their growing population.”
These findings match what researchers already understand about the Maya at their peak. Their societies were highly organized and urbanized, supported by advanced agricultural techniques adapted to local conditions.
Itzan’s stable climate casts doubt on drought theory
Another important piece of evidence comes from hydrogen isotope analysis, which helps reconstruct past rainfall patterns. Unlike areas further north that have experienced drought, Itzan appears to maintain a stable climate.
“Itzan is located near a mountain range, and atmospheric currents from the Caribbean Sea regularly generate orographic (mountain-related) rainfall,” Gwyneth explained. “While other Maya regions suffered devastating droughts, Itzan’s climate appeared to be stable.”
This discovery is particularly important because some scholars argue that the collapse of the Maya began in the southwestern lowlands of Itzan. If the drought did not affect this region, it may not have been the initial trigger.
“Despite the absence of local drought conditions, the Itzan population declined sharply during the Endclassic period, between 1,140 and 1,000 years ago,” Gwyneth continued. “Population markers showed a dramatic decline, traces of agriculture disappeared, and the site was abandoned.”
This raises an important question. Why did communities with reliable water and good conditions decline at the same time as areas affected by drought?
Interconnected Maya Cities and Chain Collapse
“The answer lies in the interconnectedness of Mayan society,” Gwyneth says. “Cities did not exist in isolation, but rather formed complex networks of trade relationships, political alliances, and economic dependencies.
“When the central lowlands were hit by drought, this could have triggered a series of crises: wars between cities over resources, the collapse of dynasties, mass migrations, and disruption of trade routes.”
In this scenario, Itzan did not fall due to local environmental stress. Instead, as the larger system disintegrated, it was drawn into broader regional fragmentation.
Mayan cities were so closely connected that problems in one area could quickly spread. Droughts in key areas could have caused instability, which could have rippled outward and set off chain reactions throughout the civilization.
“The transformation or ‘collapse’ of the Maya civilization was not the mechanical result of uniform climate change, but rather a complex phenomenon that intertwined climate, social organization, economic networks and political dynamics,” Gwyneth concluded.
“Local sociopolitical and economic factors played a decisive role.”
Gwyneth believes these insights are important beyond ancient history and provide a window into how today’s interconnected societies can respond to environmental challenges.
