Clearing oasis trees felled ancient Peru civilisation

• 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’s 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 century AD.
• The prevailing explanation for the Nazca people’s 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’t already cleared native huarango trees to make way for maize, cotton and beans.
• With roots reaching as deep as 60 metres underground to seek out water, lifespans beyond 1000 years and leaves that trap airborne moisture, huarango trees (Prosopis pallida) were a “keystone” 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 kilometres per hour. Once this protection was gone, the huge flood in around 500 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 metres across.