The Nasca people, famed for the lines that depict animals or geometric shapes most clearly visible from the air, became unable to grow enough food in nearby valleys because the lack of trees made the climate too dry, scientists said.

The report, led by Cambridge University in England, said that the findings showed a need for more action now to protect the world's arid lands.

"An ancient South American civilisation which disappeared around 1,500 years ago helped to cause its own demise by damaging the fragile ecosystem that held it in place," the university said in a statement.

The Nasca people cleared valleys for farming by felling huarango trees -- a key species which can live more than 1,000 years and helps regulate soil fertility and moisture.

"Eventually, they cut down so many trees that they reached a tipping point at which the arid ecosystem was irreversibly damaged," it said of the findings published in the journal Latin American Antiquity.

Previously, the disappearance of the Nasca people has been blamed by some archaeologists on an extreme El Nino weather event that caused rains and catastrophic floods.

"These were very particular forests," said David Beresford-Jones, leader of the study. "The huarango is a remarkable nitrogen-fixing tree and it was an important source of food, forage, timber and fuel for the local people."

Its extremely deep roots helped create a moist microclimate and its leaves provided fertiliser. Remaining huarango forest in the region is now being destroyed by illegal charcoal-burning operations.

The statement said that most scholars believe the Nasca lines, on a desert plain, were sacred pathways used in rituals. It said "wild theories" included that they were etched by aliens.

"The mistakes of pre-history offer us important lessons for our management of fragile, arid areas in the present," said co-author Oliver Whaley of the Royal Botanic Gardens, Kew.

Climate negotiators from 175 nations will meet in Barcelona, Spain, from Nov. 2-6 for a final round of talks before governments are due to agree a new U.N. pact to combat global warming in Copenhagen in December.

In Barcelona, measures to protect tropical forests will be under consideration to curb greenhouse gas emissions. Trees soak up carbon dioxide as they grow and release it when they rot or are burnt.