The Rise and Fall of the Mayan Empire

Rising temperatures would have also disrupted rainfall patterns, says Oglesby. During the dry season in the Petén, water is scarce, and the groundwater is too deep (500+ feet) to tap with wells. Dying of thirst is a real threat. The Maya must have relied on rainwater saved in reservoirs to survive, so a disruption in rainfall could have had terrible consequences.

(Changes in cloud formation and rainfall are occurring over deforested parts of Central America today, studies show. Is history repeating itself?)

Using classic archeology techniques, researchers find that human bones from the last decades before the civilization's collapse show signs of severe malnutrition.

Photographed by Daniel Irwin Slash-and-burn agriculture in Petén, Guatemala

"Archeologists used to argue about whether the downfall of the Maya was due to drought or warfare or disease, or a number of other possibilities such as political instability," Sever says. "Now we think that all these things played a role, but that they were only symptoms. The root cause was a chronic food and water shortage, due to some combination of natural drought and deforestation by humans."

Today, the rain forest is again falling under the axe. About half of the original forest has been destroyed in the last 40 years, cut down by farmers practicing "slash and burn" agriculture: a section of forest is cut down and burned to expose soil for planting crops. It's the ash that gives the soil its fertility, so within 3-5 years the soil becomes exhausted, forcing the farmer to move on and cut down a new section. This cycle repeats endlessly ... or until the forest is gone. By 2020, only 2% to 16% of the original rain forest will remain if current rates of destruction continue.

It seems that modern people are repeating some of the Maya's mistakes. But Sever thinks disaster can be averted if researchers can figure out what the Mayans did right. How did they thrive for so many centuries? An important clue comes from space: