Author: By Steve Connor, Science Editor
For more than eight centuries, the Nasca culture prospered in the coastal
valleys of Peru until its sudden downfall around 600 AD, which many experts
put down to the torrential rains and dramatic flooding brought on by one of
the worst El Nino events in a millennium.
But a team of archaeologists has now found convincing evidence that this was
only part of the story. The researchers believe the decline was
self-inflicted and began with the cutting down of a tree that could have
protected them from devastating climate change.
The Nasca, one of the most important of the pre-Inca civilisations of South
America, are most famous for the “Nasca Lines”, a series of
elaborate geoglyphs etched into the desert covering huge areas, depicting
animals, deities and geometric shapes.
After the Nasca Lines were discovered by the first passenger flights over the
region, some pseudoscience authors suggested that since they could only be
seen frome above, they must have been made with the help of space aliens. It
is now accepted that the geoglyphs were created mundanely with long ropes
tied to stakes in the ground, rather like present-day crop circles.
The Nasca survived in the semi-arid region by building irrigation canals to
grow crops such as maize, squash, sweet potato and manioc. This reliable
food supply enabled them to build a relatively sophisticated civilisation
based on art and ritual, which nevertheless included the unpleasant practice
of collecting severed heads as trophies.
All this came to an abrupt end, according to a new study, because the Nasca
made the mistake of cutting down the huarango tree which would have
protected them from the El Nino flooding and subsequent soil erosion and
drought that turned the lush agricultural land into desert.
“The huarango is a remarkable nitrogen-fixing tree and it was an
important source of food, forage, timber and fuel for the people,” said
David Beresford-Jones, an archaeologist and Nasca expert at the University
of Cambridge. “It is the ecological keystone species in the desert
zone, enhancing soil fertility and moisture, ameliorating desert extremes in
the microclimate beneath its canopy and underpinning the floodplain with one
of the deepest root systems of any tree known.”
The researchers have excavated the lower Ica Valley of the Nasca domain and
found clear evidence that vast swathes of huarango trees had been cut down
to make way for crops. Dr Beresford-Jones believes that the Nasca eventually
changed the landscape forever. “In time, gradual woodland clearance
crossed an ecological threshold, which is sharply defined in such desert
environments, exposing the landscape to the region’s extraordinary desert
winds and the effects of El Nino floods.”
The huarango tree plays a “profound role” in preserving the sort of
semi-arid environments where the Nasca lived, the scientists say in their
study. “Successful agriculture is just not possible here without the
protection afforded by trees. Indeed, these findings have undoubted
When the El Nino struck, the river cut into its floodplain, washed away the
soil and destroyed the Nasca irrigation systems, making the farmland
unworkable. The generations of Nasca that followed suffered higher infant
mortalities and lower adult life expectancy.
Eventually, the Nasca capital of Cahuachi was abandoned and all that was left
of the culture were archaeological artifacts.
Lost civilisations: Destroyed by nature
It is thought that the native people felled the majority of the island’s trees
between 1200 AD and 1500 AD. The loss of palm trees upset the eco-system,
driving away wildlife and drying up water supplies.
Mayan civilisation stretched across the Yucatan Peninsula until 900 AD when
cities were mysteriously abandoned. It is believed that the culture was
wiped out by a series of droughts.
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