Forest Razing by Ancient Maya Worsened Droughts
Xunantunich El Castillo : Wiki Commons
For six centuries, the ancient Maya flourished, with more than a hundred city-states scattered across what is now southern Mexico and northern Central America.
“We’re not saying deforestation explains the entire drought, but it does explain a substantial portion of the overall drying that is thought to have occurred,” said the study’s lead author Benjamin Cook, a climate modeler at Columbia University’s Lamont-Doherty Earth Observatory and the NASA Goddard Institute for Space Studies.
As crops like corn replace a forest’s dark canopy, more sunlight bounces back into space, said Cook. With the ground absorbing less energy from the sun, less water evaporates from the surface, releasing less moisture into the air to form rain-making clouds. “You basically slow things down—the ability to form clouds and precipitation,” he said.
Archeologists attribute a variety of factors to the collapse of the Classic Maya, whose ancestors are still living today in parts of Mexico, Guatemala, Belize, El Salvador and Honduras. In addition to a drying climate in several regions, the city-states struggled with overpopulation, changing trade routes, war and peasant revolts.
The Maya cleared the forests to grow corn and other crops, but they also needed the trees for cooking large amounts of lime plaster used in constructing their elaborate cities. Thomas Sever, an archeologist at the University of Alabama, Huntsville, and a co-author of the 2010 deforestation study, said that it would have taken 20 trees to produce a single square meter of cityscape. “When you look at these cities and see all the lime and lime plaster, you understand why they needed to cut down the trees to keep their society going,” he said.
The Maya also lacked the technology to tap the groundwater several hundred feet beneath them. Their reservoirs and canals were able to store and distribute water when rain plentiful, but when the rain failed, they had nowhere to turn. “By the time of the collapse, every square mile of soil had been turned over,” said Sever.
Today, many of the Maya’s abandoned cities are overgrown with jungle, especially on the Yucatan peninsula. Satellite images, however, show that deforestation is happening rapidly elsewhere, including in other regions the Maya once occupied. The study may offer a warning about the consequences: “There’s a tremendous amount of change going on in Guatemala,” said Oglesby. “They may be that much more vulnerable to a severe drought.”