What causes civilizations to collapse? Surely, it has to be something as monumental and awe inspiring as the civilization itself: the arrival of a strange alien invading force from beyond the ocean, mass outbreak of disease, the turning of the cosmic clock signaling the changing of the ages. Maybe sometimes. Sometimes, however, it’s a lot more mundane, banal, and terrifying in its own right. That seems to be the case with the collapse of the Mayan empire, the mysterious and often misunderstood empire that dominated the Yucatan peninsula for thousands of years. According to a paper published in the journal Science, scientists say they’ve finally been able to measure and quantify one of the main factors in the slow decline of the mysterious classical Mayan civilization: just not enough water.
The first Maya villages formed around 2,000 BCE, from there a massive and singular empire grew for the next 2,800 years. The Maya developed their own hieroglyphic system, calendars, and astronomical measurement systems. They built pyramids and developed a time-keeping system not just for their growing seasons but for the passing of whole ages. Remember that part about the Mayas being misunderstood? Exhibit A is a film you might remember called 2012 (starring John Cusack). The Maya reached the height of their power between 600 and 800 CE. Huge city-states filled with pyramids and temples sat flourishing in the middle of the jungle, with populations between 50,000 and 120,000 and a political climate akin to classical Greece or renaissance Italy. It was a true force of civilization. Then, around 800 CE, something happened. The next 150 to 200 years saw the Mayas disperse from their city-states and a quick crumbling of an Mesoamerican empire. To be perfectly clear, this did not end Mayan civilization, the same way that the collapse of the Roman empire didn’t end Roman civilization, but it did mark the end of an era and a point of no return for the opulence and power of the classical Mayan civilization.
Severe drought has long been held as a probable cause of the Mayan collapse, but it’s only now that scientists have been able to measure how severe that drought was. The paper, titled Quantification of drought during the collapse of the classic Maya civilization details how, by looking at the water isotopes in the gypsum—a mineral found in lake beds and other water sources—in Lake Chichancanab, Mexico, researchers were able to track the course of the long drought and plot it against the period of rapid decline in Maya power during what is known as the Terminal Classic period of the Mayan empire.
Gypsum forms in lake and river beds and water in incorporated directly into the structure of the mineral. In periods of drought, the lighter water isotopes evaporate faster, leaving the heavier water isotopes behind. By measuring which isotopes of water are left behind in a source of gypsum, it’s possible to calculate the rate of evaporation and annual rainfall from a given period. Looking at the gypsum from 800-950 CE, the Terminal Classic period, scientists say that Mayas experienced a 41-54% decrease in rainfall during those years, with periods of up to 70% reduced rainfall. This, they say, was a key factor in the collapse of the Mayan empire.
We take fresh water for granted. Half the average rainfall over the course of a century is all it can take to dramatically change a society. Sure, we have have water purification and reclamation technology now. We’re in a totally different technological era than they Mayas, it’s true. It’s just something to think about.