More than a millennium ago, in present-day southern Mexico and Central America, the ancient Mayan empire stretched across an area the size of Texas. Then, in approximately A.D. 1000, the Maya inexplicably disappeared. For centuries, the collapse of the Maya civilization has puzzled researchers, but a recent study by Martin Medina, associate professor in Auburn University’s Department of Geosciences, determined that drought due to low tropical storm activity could be to blame.
“Paleoclimate records discovered in the last two decades show that the Mayans experienced severe drought,” said Medina. “We found that during the collapse, the Yucatán Peninsula in particular experienced eight events of drought. Knowing about the agricultural systems in the region and how they had to capture water in order to sustain their populations, a drop in precipitation by half would have had important implications for the Maya civilization.”
Medina developed a series of paleoclimate records by looking at stalagmites and stalactites in caves that are formed from drips of rainfall containing specific minerals. “Inside the stalagmite it has growth bands like tree rings, each corresponding to a certain time. We take samples and measure the proportions of two forms of oxygen in the carbonate, and these tell us how much it rained in the past. The more it rained, the more of one of those forms of oxygen there will be.”
Once Medina determined the droughts existed, he and his team then looked at the reason these droughts occurred. “There is a strong relationship between tropical cyclone frequency and precipitation variability in the region,” said Medina. “When cyclones were more frequent in the region, it rained more, and when the frequency of tropical cyclones was lower, there was a drought.”
The study forced Medina to look at tropical storms in a different way. “We never thought of tropical storms as being a positive force until we did this research. Typically, you think of tropical cyclones only as destructive forces. If we overcome the negative impacts, that will allow the natural systems to replenish themselves through tropical cyclones, which they’ve been doing for thousands of years.”
Medina’s study was the cover story for the September edition of the scientific journal, Quaternary Research. For more information on Medina and his research, visit his website at http://www.medinaelizalde.net/Martin/Welcome.