An interesting article in New Scientist about how deforestation probably sealed the fate of Peru’s Nazca Indians (500 year civilisation ending approx 500 – 600 AD)….

According to the article, the Nazca foolishly cut down local deep-rooted, long-lived trees (called huarango).The article calls the species a “keystone” as it “…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…”

The ancient Nazca from Peru probably sealed their fate by the massive clearing of riverside trees.

Research on ancient pollen trapped in sediments showed this progression from deepest to shallowest:

1 Mainly huarango pollen

2 Mixed huarango and food crop pollens

3 Mainly food crops with little or no huarango pollen + lots of old tree stumps in this layer

4 No food crop or huarango pollen but lots from plants that flourish on exhausted soil.

There was also a flood involved at the end that probably washed away topsoil and inundated the area with salty water that rendered the ground infertile.

From the article:

In the oldest, deepest layers, about 70 per cent of the pollen is from huarango trees. Around 1.2 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 centimetres, corresponding to around 200 AD to 400 AD, the crop pollen starts to dominate, and huarango pollen rapidly diminishes, showing that most trees had been felled.

Suddenly, about 50 centimetres down – corresponding to about 500 AD – 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.

Unfortunately many countries (including mine) are repeating this exact same sequence (where I live, river red gums have been cleared to make way for wheat and lucerne). As the article says, “those who don’t learn the lessons of history are doomed to repeat them.”

River red gums do the same job in inland Australia - but have largely been cleared.

Related posts:

1. Can more reflective crops reduce global warming?
2. Ancient climate change drove reptile evolution
3. Is Climate Change Killing America’s Giant Trees?