(NaturalNews) The collapse of the ancient Nazca civilization, long attributed to the El Nino weather phenomenon, may have actually been caused by deforestation, according to research conducted by scientists from Cambridge University and the French Institute of Andean Studies, and published in the journal Latin American Antiquity.
"The landscape only became exposed to the catastrophic effects of that El Nino flood once people had inadvertently crossed an ecological threshold," researcher David Beresford-Jones said.
The Nazca, who inhabited coastal desert areas in what is today Peru, are best known for constructing massive patterns in the desert sand that can only be seen from the air. Their civilization entered an abrupt decline roughly 1,500 years ago.
Researchers have now discovered that much of the Nazca environment was originally covered by a leguminous hardwood tree known as the huarango.
"It is the ecological keystone species in the desert zone, enhancing soil fertility and moisture and underpinning the floodplain with one of the deepest root systems of any tree known," Beresford-Jones says. "This remarkable nitrogen-fixing tree was an important source of food, forage timber and fuel for the local people."
By examining plant and pollen remains 1.5 meters (4.9 feet) down into the soil, the researchers were able to uncover how huarango forests gave way first to agricultural land and then to desert.
"At the bottom of the profile there is a lot of huarango pollen and little evidence of human impact," researcher Alex Chepstow-Lusty said. "Then, at 80 cm deep, maize pollen becomes common [and huarango pollen declines]. Then suddenly corresponding with the El Nino event at AD500 or shortly afterwards ... this landscape is now the desert seen today."
The researchers believe that with the huarango forests in place, El Nino floods were actually beneficial, aquifer-replenishing events. Once the trees were gone, the floods washed away topsoil and destroyed agricultural land.
"Human induced gradual change is just as important to the full story of Nazca collapse as the major climatic impacts that eventually precipitated them," Beresford-Jones said.