After centuries of splendor, the Mayan civilization began to decline in the seventh century of this era, collapsing completely in the next two. They left their cities, with their pyramids, stadiums, ceremonial squares … and their fields, sustained with a hydraulic engineering as ingenious and technological as that of their contemporaries, the Arabs. This process of decline has been blamed for neighborhood wars, invasions from the north and south, diseases, climate change … or a combination of all or several of these factors. But among all of them, the impact of the climate stands out on the basis of such agrarian societies. Now, the study of a stalagmite of a cave near Mayan cities such as Chichén Itzá has allowed to specify its role: according to this analysis, published in the last 200 years of the classic period, in at least 44 of them there were extreme droughts.
Like those, based on the urban exploitation of the surplus of cereals in the countryside, the Mayan cities depended on the production of various crops, highlighting that of corn. And, drought could take them ahead. What has now discovered a group of researchers is that from 870 to 1100 of this era there were eight extreme drought events in the Yucatan Peninsula, one of the central areas of the Mayan civilization. And they limit what an extreme drought means: three or more consecutive years with the elongated dry season at least three months or, directly, in which there was no wet station.
The first of these droughts began in 894. It followed a year with a normal rainfall regime, to which another five years in a row with hardly any rains happened. The most durable event occurred in 929, where rainfall was anomally low for 13 years. It was the most durable drought since there are records, both pre -Columbers and in the later centuries.
Sediments in the background of lakes and the study of other stalagmites had already shown the leading role of drought during the so -called Mayan terminal classic period. The different speleothems (such as stalactites or stalagmites) grow drop by drop with the minerals present in the filtered water and do so year after year, sheet to sheet. This allows, such as trees rings, using them as environmental witnesses, particularly the falling rain. The great contribution of this work here is that they have been able to see the variation in rainfall not sheet to sheet or year by year, but almost month by month.
“Knowing the average annual rainfall does not say as much as knowing how each rainy season was,” recalls Daniel James, a researcher specialized in the reconstruction of the past climate at the University College in London (United Kingdom) and first author of the study. The corn grows along the wet station, being collected at the end. And the harvest performance depends on the falling water. “Being able to isolate the rainy season allows us to precisely track the duration of the drought of the rainy season, which is what determines the success or failure of the crops,” adds James.
The researchers verified that their dating on drought events corresponded relatively well with those obtained from other specimen and sediments in lakes. Together, they saw that the climatic data coincided with the archaeological ones: the inscriptions in commemorative stelae, the construction of monuments and the political activity in several important Mayan sites of the North were arrested at different times during this period of climate stress.
The thing could be well worse. The stalagmit segment that they have studied, from the Grutas Tzabnah, a few kilometers from Mayan cities such as Chichen Itzá and Uxmal, records the period between 870 and 1100. But there is a hiatus of about 50 years, between 1021 and 1070, in which the Espeleotema did not grow. James, who conducted this study when he investigated for the University of Cambridge, recalls in an email that “there are many possible reasons for this, one is that it could have rained so little that the drip stopped completely during a severe drought.” Or “quite the opposite,” says the Geologist of the University of Salamanca, David Domínguez. “If it rains a lot, there is a solution that does not grow,” says the Spanish scientist, an expert in speleothems that has not intervened in this research.
The stalagmites are formed when the water drips from the roof of a cave and the minerals, in particular the calcite, precipitate. It is trapped isotopes of elements such as oxygen or carbon that help know where that water comes from. In the case of the Mayan cave, they have estimated that the water dropped on the surface took a month to infiltrate. Through the dating and analysis of the oxygen isotope layers within the stalagmite, the researchers were able to detect droughts and their duration. The different sheets do not say how much it rained, but, “the years that rains little, the isotopes are heavier,” Domínguez explains.
Cities like Uxmal were abandoned at the end of this period. But others show ambivalent signs. Everything indicates that the old chichén declined, but what is now known as Chichen Itzá prospered for a while. “The differences between the sites reflect the different social responses to the drought,” says James, the first author of the research. “Chichen Itzá had a wide range of commercial networks and was highly centralized, which would have allowed the accumulation or import of resources in times of shortage,” completes.
In 2021, a study not related to this, showed how a short -term drought, of no more than a few months or a single wet season, would cause supply problems, but 89% of production would still move forward. However, in cases of extreme droughts, as they have defined here, it would cause. However, one of its authors, Scott Fedick, Professor Emeritus of the Department of Anthropology at the University of California, Riverside, believes that the authors overlook the resistance capacity of Mayan cities.
“In our article [el de 2021]there is a marked difference between the food plants available to a moderate drought and an extreme drought. Although most of the annual species will not produce what is necessary, a wide variety of nutritional perennial food plants would do it, ”writes Fedick. For him, the authors of the new study put too much emphasis on the impact of drought on annual species, such as corn, beans and pumpkin, without recognizing“ the possible contribution to food safety of numerous perennial species A moderate drought and would only gradually decrease after an extreme drought. ”
The historian Rafael Cobos, professor at the Autonomous University of Yucatán (Mexico) and expert in the Mayan civilization, recalls that the cities of the region had similar pressures. “My investigations suggest that both Uxmal and Chichen Itzá were contemporary and both pre -Columbian cities ended their development and apogee at the end of the eleventh century, just when the great drought that affected Yucatan and the rest of the world was at its maximum,” he says by mail. Although he acknowledges that there are those who, based on the archaeological registry, defend the survival of centers such as Chichen Itzá flourished even in this context of climatic adversity, finally, “the Mayan civilization, with its society that depended on the production of corn cultivation fields for its food, could not sustain its large population and the social-political-economic debacle, the collapse, was produced.
