What is Terra preta?

Terra preta (literally "dark earth" or "black earth") is dark rich soil that appears to have been created by the addition of charcoal, made from wood and bones, and pottery shards over hundreds of years. The discovery of terra preta in the Amazon basin has sparked a commercial interest in biochar and might just provide a simple way of sequestering carbon from the earth's atmosphere, at least in modest amounts.

The default condition of the soil

Conventional wisdom might suggest that tropical rain forests in general and the Amazon basin in particular contain very rich soil. After all, they contain incredible vegetative growth, don't they? They do, and that is why the soil is, in general, very poor. Massive trees, lush vegetative growth and warm moist conditions for much of the year mean much of the organic matter is above the surface. Other than living roots, fungus and microbes, little is left below the ground but minerals. Such soil more closely resembles the subsoil found in more temperate regions than any sort of topsoil.

The creators of Terra preta

Little is known of the culture that created the terra preta soil, which stands in stark contrast with the generally very poor soil of the surrounding tropical rainforests. The people are conspicuous by their absence in recent history. Some believe that a large civilization existed in the Brazilian Amazon prior to the arrival of Spanish Conquistadors in the 16th and 17th century. This belief is supported by reports from Spanish explorer Francisco de Orellana who claimed (around 1542) to have seen large settlements along hundreds of kilometers of the lower Amazon river. Orellana was the first European known to have traversed the Amazon and subsequent explorers were startled to find the region very sparsely populated. One theory as to the cause of the rapid decline of this culture is all too familiar. They may well have perished due to infectious diseases brought to them by the first European expedition.

My own theory

The following is pure speculation on the part of the writer. I envisage a sophisticated civilization who had developed the skill to practice the methods of slash and burn agriculture, which is currently incredibly destructive. BUT... these people had learned to do it in a way that not only didn't destroy the soil, it actually improved it for future generations.

Now why didn't we think of that?

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