Ancient Amazon Agriculture
The Terra Preta Story
by Gary Kline

Five hundred years ago, perhaps stretching back a couple thousand years before that, a large area of the Amazon basin, now predominantly jungle, was agricultural land. It is said that this area, which includes the drier region of Bolivia, was the size of California and Oregon combined. This is mind-boggling news, but nonetheless true and proven.

Here there was a sophisticated agrarian civilization with diked fields, extensive canals and well-built roads tying together a multitude of villages and towns. Then it all but vanished in a few, short years. The demise of this civilization was caused by alien diseases brought in from Europe; by the Spanish, specifically.

This story is well told in The Biochar Debate (2009) by James Bruges, and presented here in condensed version. More so than the story of these ancient people, this story is about the rich agricultural lands they built and left behind. The astonishing part is that those nutrient-rich lands remain just as fertile centuries later as they were when created, whereas soils outside those farmed lands, like rainforest soils generally, are nutrient and mineral poor, despite the lush jungle growth which retains and rapidly recycles what nutrients there are.

This Amazonian agrarian civilization apparently is unnamed, but their uniquely created soil is known as Terra Preta, which is Spanish for dark soil. The enabling component of this highly productive, long-sustained soil is a form of charcoal known as biochar. A number of other ingredients (chiefly plant and animal wastes) are involved to create the richness, but biochar holds it together and retains it against leaching and decline. Indeed, Terra Preta, and its biochar, harbors high populations of helpful microorganisms and has the capability of regenerating itself as it is farmed.

The biochar of this region was created by burning wood in a fashion that excluded oxygen from parts of it, possibly in earthen chambers within the fields or surrounding dikes. Probably, the air was often smoke-filled. Charcoal making differs from slash and burn particles, which result in loss of the carbon, leaving a residue of ash. Broken pieces of pottery are found throughout the black soil, and might have played a role in creating or retaining its fertility. The pottery made from clay conceivably was used in manufacturing the charcoal. It is now known that other civilizations in other times experimented with charcoal as a soil amendment and noted its fertility-enhancing effects. Charcoal acts as a moisture and nutrient sponge.

But it is the Terra Preta’s discovery as the basis of a previous large agricultural civilization by archeologists, beginning the 1950’s, that brought biochar into prominence. There has only recently developed strong interest in reviving its use for substantial soil improvement. Furthermore, the making and burying of biochar represents one of the most promising avenues for large scale sequestering of carbon to offset global warming (or climate change), while at the same time revolutionizing prospects for a future sustainable agriculture that may well rescue civilization as petroleum runs out and depletion and ruination of farmable soils reaches its end point. We need to get going on this ASAP.

Why was the significance of biochar and the existence of Terra Preta unknown or lost for centuries? Why were we totally unaware that so much of the Amazon had been farmland, supporting a civilization that had numbered in the millions? That aspect is equally as fascinating as biochar and as Terra Preta itself. Parts of this story I am filling in by surmising what took place.

In the Fifteenth Century, Spanish conquistadors conquered Peru on the Pacific side of northern South America. They were led by Pizzaro in a ravenous search for gold, and had heard rumors of an Indian civilization on the other side of the Andes that was rich in gold. Pizzaro appointed a loyal follower named Francisco de Orellana to conduct an expedition across the mountains and down a river into the jungle in search of the rumored gold. The expedition was a success in that Orellana was able to reach the Atlantic and return upstream to Peru, but without the gold.

Orellana did not find gold, but he did encounter Indians living in villages and towns, which he marveled at, at many locations along the rivers. He kept a detailed journal of the towns and their locations, and wrote descriptions of them and of the farmlands. At one point he encountered a tribe of women warriors, whom he dubbed Amazons, after a Greek story about women warriors given that name.

Out of Orellana’s journey and journal grew the regional name and the story of El Dorado, a hidden location of gold. A few decades later other explorers and treasure hunters went looking for gold along the same route, but found no villages and few Indians at the locations described by Orellana; nor did they find El Dorado (though the search still goes on).

Obviously, they concluded, Orellana had made up the accounts of large populations inhabiting villages and towns along the rivers and stretching into the interior. It was some kind of elaborate hoax. Probably, however, the returning jungle had taken over the village structures following the decimation of their inhabitants by the diseases left from their encounter with Orellana’s expeditionary force (there is actually an incredible parallel with the Lewis and Clark expedition to the Pacific and back, and the disease die-offs among the Indians they saw in 1804). But what all of them had missed was the gold that is Terra Preta, and it’s still there. GLK

© 2012 Gary L. Kline
All Rights Reserved