The ancient Nazca people of Peru are famous for the lines they drew in the desert depicting strange animal forms.
A further mystery is what happened to this once great civilisation, which suddenly vanished 1,500 years ago.
Now a team of archaeologists have found the demise of the Nazca society was linked in part to the fate of a tree.
Analysing plant remains they reveal how the destruction of forests containing the huarango tree crossed a tipping point, causing ecological collapse.
The team have published their findings in the journal of Latin American Antiquity.
“These were very special forests,” says Dr David Beresford-Jones from the McDonald Institute for Archaeological Research, University of Cambridge, UK who led the team.
The huarango tree (Prosopis pallida) is a unique tree with many qualities and played a vital role in the habitat, protecting the fragile desert ecosystem, the scientists say.
“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,” Dr Beresford-Jones says.
The tree was also a useful resource.
“This remarkable nitrogen-fixing tree was an important source of food, forage timber and fuel for the local people.”
Researchers have previously found evidence that suggests the disappearance of the Nazca society was a due to catastrophic flooding event as a result of El Nino around 500 AD. …
“Our research contradicts the popular view that Native American peoples always lived in harmony with their environment until the Spanish Conquest,” Dr Beresford-Jones says.
Dr Beresford-Jones explains that with sufficient huarango cover, El Ninos were in fact not great disasters and actually created years of abundance replenishing water aquifers.
Once too much clearance had occurred the landscape was exposed to the effects of the El Nino floods.
“The river down cut into its floodplain and that floodplain narrowed hugely, irrigation systems were left high and dry,” he says.
“Human induced gradual change is just as important to the full story of Nazca collapse as the major climatic impacts that eventually precipitated them.”