Mayan misteries

Centuries before Europeans arrived, an advanced civilization flourished in Mesoamerica, a region extending from southern Mexico through Central America. The Maya mastered astronomy, developed an elaborate written language, built towering monuments, and left behind exquisite artifacts.
According to NASA archaeologist Tom Sever, the Mayan civilization in Mesoamerica was one of the densestpopulations in human history. Around 800 A.D., after two millennia of steady growth, the Mayan population reached an all-time high. Population density ranged from 500 to 700 people per square mile in the rural areas, and from 1,800 to 2,600 people per square mile near the center of the Mayan Empire (in what is now northern Guatemala). In comparison, Los Angeles County averaged 2,345 people per square milein 2000. Yet by studying remains of Mayan settlements, Sever found that by 950 A.D., the population had crashed. “Perhaps as many as 90 to 95 percent of the Maya died,” he said. August 24, 2004
Title graphic image: The Rain God Chac appeared in one of the few Mayan texts to escape burning by the Spanish. (Image adapted from the Madrid Codex appearing on the NOAA Paleoclimatology Mirror Site,photo by David A. Hodell.)




For Sever, figuring out how the Maya flourished—but ultimately failed—in Mesoamerica is about more than simply solving a 1,200-year-old mystery. Since the 1980s, he has tried to understand the history of the Maya and their natural environment, a story that may hold important lessons for people living there today. Using satellite data and climate models,Sever and his colleagues hope to help governments and citizens throughout Mesoamerica ensure that the region can continue to support the people who live there. By learning from the Maya, modern humans may avoid sharing their fate.
Mayan Deforestation
Before its collapse, the Mayan empire stretched out from its center in northern Guatemala’s Petén region across the lowlands of the YucatánPeninsula. Pollen samples collected from columns of soil that archeologists have excavated across the region provide evidence of widespread deforestation approximately 1,200 years ago, when weed pollen almost completely replaced tree pollen. The clearing of rainforest led to heightened erosion and evaporation; the evidence of the erosion appears in thick layers of sediment washed into lakes.
“Anotherpiece of evidence,” explained Sever, “is the thickness of the floor stones in the Mayan ruins. They would have needed about 20 trees [to build a fire large and hot enough] to make a plaster floor stone that is about one square meter. In the earliest ruins, these stones were a foot or more thick, but they progressively got thinner. The most recently built ones were only a few inches thick.” Sever’scolleague, atmospheric scientist Bob Oglesby of Marshall Space Flight Center, calls the Mayan deforestation episode “the granddaddy of all deforestation events.” Studies of settlement remains show that this deforestation coincided with a dramatic drop in the Mayan population.
“After the Mayan collapse, this area was abandoned and the forest recovered. But as people have returned over the last threedecades, the deforestation has returned,” Sever explained. Today, the regenerated forests of the Petén are the largest remaining tropical forests in Central America. While present-day deforestation in the Petén region hasn’t yet occurred on a Mayan scale, today’s technology could easily enable modern residents to surpass the Maya in cutting trees. According to the Food and AgricultureOrganization of the United Nations, deforestation in Guatemala averaged 1.7 percent annually between 1990 and 2000.
Besides a cautionary tale about what can happen to civilizations when they clear-cut surrounding forests, the long-gone Mayan civilization also offers clues to a more sustainable use of the landscape. Before their catastrophic decline, the Maya thrived in Central America for two millennia....