Monthly Archives: May 2010

Terra Preta

One of the most fascinating topics that’s come up in my permaculture class is terra preta soil, one of the most fascinating examples of humanity prospering by enriching life instead of stripping it.

Here’s the usual story of the Amazon:  like most tropical forests, very little of its nutrient reserve is actually in the soil; rather it is in the actual living organisms.  There’s no cold winter causing the leaves to drop and nutrients to go into reserve as in temperate climates, which can build deep soil that stands up to European-style sedentary plowing.  Instead, if anything dies, its nutrients are released and quickly consumed by fungi and put right back into the cycle.  Our interaction with it has been largely to slash and burn it for agriculture, and when the ash disperses, nearly all of the nutrients that were there are gone forever, leaving a desert.  This is happening more and more, especially for growing more soy and biofuel: the biological equivalent of burning the house down to stay warm.

Prior to Columbus the natives at various sites of the Amazon were creating, via pyrolytic processes still mysterious to us, a black and highly bioactive soil; this is terra preta, and it is still highly sought after.  Its nutrient value is high, its CO2 sequestration is high, and it purportedly regenerates itself at up to 1cm a year under the right conditions.  It’s likely that the way the Amazon rain forest spread across savannahs was by the natives spreading this soil – the exact opposite of what we’re doing now.

Scientists are still researching how this soil was made, how to recreate it, and together with other research into pyrolysis techniques as a tool of both supplying carbon-neutral heat energy and regenerating soil, this is one of our biggest opportunities to reverse the destructive paradigm we’re in.  Links!

http://en.wikipedia.org/wiki/Terra_preta
http://www.springerlink.com/content/ch88m96jtrfrj4gk/

There is a strong case to be made now that the extent of the pre-European Amazon rain forest was a product of human activity, quite possibly intentionally.  Isn’t it fascinating that on one side of the Atlantic, humanity turned a fertile grassland into the Sahara and the deserts of the Middle East, and on the other side, a large population lived by helping the rain forest grow?  Totally opposite legacies.

Quoth wikipedia:  “One focus of these researchers is the prospect that if biochar becomes widely used for soil improvement, it will involve globally significant amounts of carbon sequestration, remediating global warming.”

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