Sometimes a city disappears first in the tiny traces it leaves at the bottom of a lake. A little ash, molecules arriving from human and animal excrement, waxes from leaves that ended up in the mud, dark layers deposited year after year. Looking at them from the outside they just look like sediment. Inside, though, they can keep a kind of record without writing: how many people lived around the water, how they farmed, how much they burned the forest, how much rain actually fell.
It is from here that the collapse of the Mayan civilization it becomes harder to tell with just one cause. For decades the most convenient explanation, and partly supported by various studies, revolved around drought. Between 750 and 900 AD the lower Maya lands, that is, that tropical area of Mesoamerica which includes areas of present-day Guatemala, southern Mexico and nearby regions, went through a strong demographic and political decline. Many cities lost inhabitants, dynasties and power. The climate crisis of that period seemed the most obvious thread to follow. Then Laguna Itzan, in northern Guatemala, returned an uncomfortable clue: in one of the key areas, Itzan, the climate appears stable just as the population was collapsing.
The study published on Biogeosciences worked on sediment cores taken from Laguna Itzan, near the archaeological site of the same name. The researchers reconstructed approx 3,300 years of environmental and human historyusing chemical indicators capable of describing human presence, agricultural practices and rainfall patterns together. The area is of great interest to archaeologists because it belongs to the low southwestern Maya lands, a region that some scholars have indicated as a possible starting point of the crisis of the Terminal Classic period.
The most shocking fact concerns the drought. Analyzes of hydrogen isotopes in leaf waxes, used to reconstruct past humidity and rainfall, indicate a more limited climatic variability for Itzan compared to other Maya sites further north-east. Laguna Itzan is located near the Cordillera, where the currents coming from the Caribbean favor orographic rains, that is, precipitations generated when humid air meets the mountains and rises, cooling. In very concrete terms: while other Mayan areas faced harsh dry periods, Itzan still received water with some regularity.
Yet the city emptied. During the Classic terminalbetween approximately 1,140 and 1,000 years ago, population indicators dropped sharply, traces of agriculture faded, and signs of the use of fire almost completely disappeared. The site is abandoned, or in any case loses the density it had achieved in previous centuries. This makes the Mayan collapse less like a local famine and much closer to a systemic failure. Itzan had water, favorable conditions, a long agricultural history behind it. He gave in anyway.
The transition changes the perspective quite a bit. If a community with relatively stable rainfall enters into crisis in the same period of time as regions affected by drought, the problem runs along the relationships between cities, trade, alliances, wars and economic dependencies. Maya cities lived within complex networks. They traded, made political pacts, depended on interconnected routes, elites, dynasties, countryside and urban centers. A drought in the central lowlands could therefore produce effects much wider than the directly affected perimeter: conflicts over resources, population movements, disruption of trade routes, fall of ruling houses, loss of stability in regional hierarchies.
From fire in the fields to chemical writing in mud
The most interesting part of the sediments of Laguna Itzan lies in their concreteness. The researchers observed three families of geochemical markers. The polycyclic aromatic hydrocarbons indicate the intensity of fires and slash-and-burn practices; the leaf waxes they help read vegetation and rainfall; The fecal stanolsmolecules linked to fecal matter, offer an indirect estimate of human presence. Put together, these signals allow us to follow the life of the territory for millennia: inhabitants, fields, fires, agricultural changes, moments of growth and phases of retreat.
The first traces of human activity around Laguna Itzan date back to ca 4,000 years ago. The first permanent settlements emerge around 3,200 years agowhen signs of population increase and fires appear compatible with the transformation of the landscape. In the Preclassic period, between about 3,500 and 2,000 years ago, fire was a central tool: it was burned to open the forest, clear land and cultivate on the ashes made fertile by combustion. It was physical, immediate agriculture, made up of cuts, smoke and newly conquered soil.
During the Classic period, between about 1,600 and 1,000 years ago, the picture changed. The population becomes denser, while the use of fire drops markedly. One plausible explanation is that much of the land had already been cleared of forest and that communities needed more intensive methods to feed a growing population. The data suggests more specialized agricultural practices, such as ridge-and-furrow fields to limit erosion, better-kept vegetable gardens and strategies that make better use of available space. The reduction of fires is therefore linked to a more urbanized, organized society and less dependent on the simple opening of new land.
This transformation fits well into what we already know about the Mayan civilization at its peak: complex cities, stratified societies, agricultural techniques adapted to local landscapes, a remarkable ability to modify the environment without always relying on the same method. Corn remains an important element of Mesoamerican agricultural history, however in Itzan the relationship between crops, population and fire appears variable, never linear. In some phases the human presence increases while certain agricultural signals change direction. The life of a territory, seen from a lake, bears little resemblance to a straight arrow.
Then comes the fracture. In the Terminal Classic, when many Maya areas were in deep crisis, Itzan also showed a sharp decline in fecal stanols, a decrease in fire-related hydrocarbons, and signs consistent with site abandonment and the end of local agricultural practices. Vegetation takes back space. The forest returns to close off portions of the landscape. The lake records fewer people, fewer camps, less burning. All this happens in the absence of a strong local trace of drought.
The cascading collapse of Mayan cities also speaks to today’s societies
The word “collapse” always risks making everything too neat. It makes you think of a building falling because a pillar gives way. In the case of collapse of the Mayan civilizationItzan sediments push towards a more irregular image: a system of closely connected cities, where climate pressure acts in some areas and produces consequences elsewhere through politics, economics, human displacement and war. Drought remains a part of the story. In Itzan, however, the crisis arrives without the most expected local sign.
The climate, therefore, enters the story as a powerful and unequal factor. It hits some regions harder, leaves others seemingly more protected, then travels through networks built by humans. A city can have water and still lose stability if trade fails, if conflicts increase, if sudden migrations arrive, if the dynasties that govern alliances and redistribution of resources collapse. Itzan, in this reading, becomes a community dragged into a regional earthquake despite having less harsh local environmental conditions.
The conclusion of the study remains cautious. We need other high-resolution data, other natural archives, other sites studied with the same attention to understand how uneven the crisis in the Maya lowlands really was. The researchers themselves point out the limitation: the lack of dense paleoclimate records in space and time still makes it difficult to fully test the hypothesis of a drought-related collapse in the southwestern lowlands. But the signal from Laguna Itzan weighs heavily. Where many expected the dry imprint of a lack of water, a dirtier, more human, more intertwined story emerges.
