FEATURE ARTICLE
Climate and the Collapse of Maya Civilization
A series of multi-year droughts helped to doom an ancient culture
Larry Peterson, Gerald Haug
All in the Timing
Scholars generally agree that the terminal Classic collapse occurred first in the southern and central Yucatán lowlands and that many areas of the northern lowlands underwent their own decline a century or more later. This pattern of abandonment is opposite to what one might expect based on the modern pattern of rainfall, which diminishes markedly from south to north. Some Mayanists have pointed to this incongruity as evidence against drought having played a significant role. However, an additional factor that must be considered is the availability and access to natural water sources, which could have sustained the population during extended periods of drought.
During the peak of Maya civilization, as now, an important source of fresh water for human activities was from the natural underground aquifer. This aquifer is generally more accessible in the northern end of the peninsula, where the Maya were able to reach the water table at various sinkholes (places where the roof of an underground cavern had collapsed) or by digging wells. However, as one moves to the south, the landscape rises in elevation, and the depth to the water table increases, making direct access to groundwater unfeasible, at least for the Classic Maya with the technology of their time. Thus the more southern settlements, which were totally dependent on rainfall and reservoirs for their water needs, were more likely to be susceptible to the effects of prolonged drought than were cities with direct access to subsurface sources. This critical difference helps explain why drought could have caused greater problems in the normally wetter south.
Although there is general agreement that the abandonment of major population centers began first in the south and then spread to the north, Gill proposed a more controversial tripartite pattern of collapse. Based on an analysis of the last recorded dates carved into stone monuments known as stelae at major Maya sites. Gill argued that there were, in fact, three phases of drought-related collapse between about 760 and 910 A.D., with a distinct regional progression.
The first phase, according to Gill, occurred between 760 and 810. The second phase was largely over by about 860. The third and final phase terminated around 910. Noting a similarity between the end dates of these three phases and the timing of especially severe cold spells in Europe (as evidenced in Swedish tree-ring records), Gill speculated that the abandonments occurred rather abruptly at the end of each phase, that they were primarily the result of droughts and that these droughts were linked to the cold conditions at higher latitudes.
Gill's model of three phases of collapse, and especially the archaeological basis for their proposed timing, has been the subject of much debate. There is considerable disagreement, for example, over the interpretation of the last dated inscriptions on stelae as accurate records of city abandonment. Furthermore, Gill considered only the largest Maya sites in his original analysis. So there is certainly some room for doubt. Nevertheless, the drought events we inferred from the Cariaco Basin record match Gill's three phases of abandonment remarkably well.
The onset of Gill's first phase at about 760 A.D. is clearly marked in the Cariaco record by an abrupt decrease in inferred rainfall. Over the subsequent 40 years or so, there appears to have been a slight long-term drying trend. This period then culminated in roughly a decade or more of severe drought, which, within the limits of our chronology, agrees well with the end of Gill's first phase. Societal collapse at this time was limited to the western lowlands, a region with little accessible groundwater and where the inhabitants depended almost entirely on rainfall to satisfy their needs.
The end of Gill's second phase of collapse is also marked in the Cariaco Basin record by a distinct interval of low titanium concentrations, suggesting an unusually severe drought that lasted for three or four years. City abandonment during this phase of collapse was largely restricted to the southeastern portion of the lowlands, a region where freshwater lagoons may have provided a source of water up to that point.
According to Gill, the third and final phase of collapse occurred at about 910 A.D., affecting population centers in the central and northern lowlands. And low titanium values in the Cariaco Basin sediments indicate yet another coincident period of drought, one that lasted for five or six years.
Although the match between Gill's drought model and our findings is quite good, we accept that no single cause is likely to explain a phenomenon as complex as the Maya decline. In his recent book Collapse: How Societies Choose to Fail or Succeed, Jared Diamond argues that a confluence of factors may have combined to doom the Maya. These include an expanding population that was operating at or near the limits of available resources, environmental degradation in the form of deforestation and hillside erosion, increased internal warfare and a leadership focused on short-term concerns. (Sound familiar?) Nevertheless, Diamond posits that climate change, in the form of droughts, may have helped bring things to a head, triggering a series of events that destabilized Maya society.
Some archaeologists have pointed out that the control of water reserves provided a centralized source of political authority for the ruling Maya elites. Periods of drought might then have undermined the institution of Maya rulership when existing technologies and rituals failed to provide sufficient water. Large population centers dependent on this control were abandoned and people moved sequentially eastward and then northward during the successive droughts to find more stable sources of water. However, unlike what transpired during previous intervals of too little rainfall, which the Maya must certainly have weathered before, the landscape during the final stages of collapse was at carrying capacity (because of the growth of Maya population during wetter times), and migration to areas less affected by drought was no longer possible. In short, they ran out of options.
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