Subsequently, I saw cotton pollen and other weeds, but still a lot of huarango pollen. It seems at this stage farming was in balance with the environment," Chepstow-Lusty said.
Then, about 400 A.D., the Nazca apparently stopped growing cotton, switching to large crops of maize.
The researchers found a major reduction of huarango pollen, indicating that people started clearing the forests to plant more crops.
But the agricultural gain from clearing forests was short-lived. When a mega El Nino event hit the south coast of Peru in about 500 A.D., there were no huarango roots to anchor the landscape.
The fields and canal systems were washed away, leaving a desert environment. Today, only pollen from plants adapted to salty and arid conditions can be found, Chepstow-Lusty said.
"The bottom line is that the Nazca could have survived the devastating El Nino floods had they kept their forests alive. Basically, the huarango trees would have cushioned that major event," Beresford-Jones said.
According to the researchers, some important lessons can be learned today from the Nazca's disastrous environmental strategies.