The ancient Peruvian Nazca people, famous for creating giant, elaborate lined images on a desert plateau that are visible from space, may have brought about their own destruction by cutting down trees that protected the land they lived on.
That鈥檚 the verdict of new research into pollen remains in the Ica river valley in southern Peru, where the civilisation thrived for 500 years until the people started to disappear at the start of the 6th聽century聽AD.
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The prevailing explanation for the Nazca people鈥檚 demise is that a huge flood wiped out not only their settlements but also their delicate irrigation systems, leaving a desert where no one has lived since.
The new findings agree that the flood was what finished off the Nazca, but suggest the people would probably have survived it if they hadn鈥檛 already cleared native huarango trees to make way for maize, cotton and beans.
Keystone chopped
With roots reaching as deep as 60聽metres underground to seek out water, lifespans beyond 1000聽years and leaves that trap airborne moisture, were a 鈥渒eystone鈥� species that turned otherwise arid river banks in Peru into oases flanked by fertile flood plains. They also fertilised the otherwise poor soil by dropping leaves and fixing nitrogen.
Their extensive root systems physically anchored the oases in place, and protected them from periodic floods; their huge branches deflected the wind, which can be fiercer than 100聽kilometres per hour. Once this protection was gone, the huge flood in around 500聽AD destroyed the agricultural systems with which the Nazca people had replaced the huarango, turning the terrain into desert.
The civilisation is best known for the Nazca lines, a series of hundreds of enormous images including human figures, hummingbirds, fish, llamas, lizards, monkeys and spiders. They were created by scraping away red surface pebbles to reveal white rock beneath, and some are more than 200聽metres across.
of the University of Cambridge and Alex Chepstow-Lusty of the in Lima, Peru, analysed 1.5-metre-deep profiles of pollen distribution in soil from Nazca oasis sites.
In the oldest, deepest layers, about 70聽per cent of the pollen is from huarango trees. Around 1.2聽metres down, pollen from crops such as maize and cotton joins that of the huarango, showing the beginnings of agricultural expansion.
And around a depth of 80聽centimetres, corresponding to around 200聽AD to 400聽AD, the crop pollen starts to dominate, and huarango pollen rapidly diminishes, showing that most trees had been felled.
Suddenly, about 50聽centimetres down 鈥� corresponding to about 500聽AD 鈥� the only pollen is from plants of the Chenopodiaceae and Amaranthaceae families, which thrive in salty water, marking the flood that doomed the Nazca. Thereafter, the salty soil could no longer support crops.
Lessons of history
The researchers also found hundreds of huarango stumps, confirming the trees had been chopped down.
They warn that that thrive in arid regions might be crucial as a fifth of the world鈥檚 poorest people live on arid land, much of which has suffered degradation induced by humans. Planting trees, on the other hand, has helped reclaim desert in Niger.
What happened to the Nazca carries lessons for us, says , an authority on deforestation at James Cook University in Cairns, Queensland, Australia. 鈥淎s they say, those who don鈥檛 learn the lessons of history are doomed to repeat them.鈥�
Journal reference: Latin American Antiquity, vol聽20, p聽303
