Mayan ruins at Palenque, with regrown forests.
Severe deforestation the Mayans inflicted on their own environment hastened the end of their civilization in the 8th and 9th centuries, according to new research.
The deforestation in Central America contributed to drought, and researchers have long suspected that drought contributed to the end of Mayan society, along with internal conflicts and overpopulation.
According to LiveScience.com and MSNBC:
Using new reconstructions of vegetation stretching back 2,000 years, NASA Goddard Institute for Space Studies climatologist Benjamin Cook and colleagues found that forest-clearing by Mayan farmers worsened drought conditions in the area.
When the Mayans cleared forests, they exposed land surface with a higher albedo, or reflectivity, than the dark-green forest canopy. This land surface reflected energy back into the atmosphere rather than absorbing it, lessening the amount of energy on the land surface available to do things like convect water vapor to form clouds and thus rain. The result was a decline in precipitation by 10 percent to 20 percent.
With less rain, the soil dried out, so any extra energy went to warming the surface rather than evaporating water. The result was a rise in surface temperature by 0.9 degrees Fahrenheit (0.5 degrees Celsius). The lack of rainfall and boost in heat would have been bad news for a society whose survival depended on their farmlands.
European invaders after 1492 destroyed the Mayan population by up to 90 percent in areas, and the result was a regrowth of forest as human pressures were reduced. Cave records confirm the pattern of drying during deforested periods and more precipitation when forests bounced back.