Once in a while you run across something that challenges just about everything you thought you knew. “Terra preta” (Portuguese for “black earth”) are anomalous deposits of deep, rich soil found in large pockets of land throughout the Amazon. Once thought to be 100% comprised of thin, fragile soil that would immediately desertify if the trees were removed, it now turns out there are significant sections of Amazonia where this terra preta is abundant. But the biggest mystery is this: The Amazon’s best soil, terra preta, possibly was deliberately created by Native Americans.
|The Amazon basin’s best soil, agrichar, possibly
was deliberately created by Native Americans.
As put forth in 2002 in a lengthy article in the Atlantic Monthly entitled “1491″ by Charles C. Mann, there is a growing body of evidence that the indigenous population of the Americas in pre-colombian times was far greater than is typically estimated.
In Mann’s report several thought provoking bits of evidence are presented: The great mass of carrier pigeons that filled the skies and the great masses of bison that dominated the endless prairies in the 18th century were not always there – if they had always been there, in archeological sites we would see their bones in far greater abundance. Instead they were “outbreak species,” whose numbers mushroomed in the wake of human demographic collapse. Read the article for more arguments supporting this new theory – which basically says the impact of European disease on Native American populations was far, far greater than previously conjectured, and in fact abruptly destroyed a network of complex urban civilizations numbering well over 100 million people.
The presence of Amazonian terra preta is another piece of evidence allegedly supporting this theory, because the placement of these deposits of charcoal rich black earth are not explained without human intervention. The theory holds that this black earth was created by a process called “slash and char,” something very distinct from slash and burn. In this process the seasonal crop residue was not burned, but charred and turned into the earth. Doing this sequestered most of the carbon in the crop residue, and created an extremely hospitable amendment to the otherwise thin and fragile soil – something that in turn nurtured beneficial microorganisms that broke down the poor native soil and transformed it in to extraordinarily rich humus. Read this from “1491″:
“Landscape” in this case is meant exactly—Amazonian Indians literally created the ground beneath their feet. According to William I. Woods, a soil geographer at Southern Illinois University, ecologists’ claims about terrible Amazonian land were based on very little data. In the late 1990s Woods and others began careful measurements in the lower Amazon. They indeed found lots of inhospitable terrain. But they also discovered swaths of terra preta—rich, fertile “black earth” that anthropologists increasingly believe was created by human beings.
Terra preta, Woods guesses, covers at least 10 percent of Amazonia, an area the size of France. It has amazing properties, he says. Tropical rain doesn’t leach nutrients from terra preta fields; instead the soil, so to speak, fights back. Not far from Painted Rock Cave is a 300-acre area with a two-foot layer of terra preta quarried by locals for potting soil. The bottom third of the layer is never removed, workers there explain, because over time it will re-create the original soil layer in its initial thickness. The reason, scientists suspect, is that terra preta is generated by a special suite of microorganisms that resists depletion. Apparently at some threshold level … dark earth attains the capacity to perpetuate—even regenerate itself—thus behaving more like a living ‘super’-organism than an inert material.
In as yet unpublished research the archaeologists Eduardo Neves, of the University of São Paulo; Michael Heckenberger, of the University of Florida; and their colleagues examined terra preta in the upper Xingu, a huge southern tributary of the Amazon. Not all Xingu cultures left behind this living earth, they discovered. But the ones that did generated it rapidly—suggesting to Woods that terra preta was created deliberately. In a process reminiscent of dropping microorganism-rich starter into plain dough to create sourdough bread, Amazonian peoples, he believes, inoculated bad soil with a transforming bacterial charge. Not every group of Indians there did this, but quite a few did, and over an extended period of time.”
If rich topsoil was literally engineered by humans on this scale, this is an encouraging possibility to address the today’s challenges of depleted soils and desertification. Organizations have sprung up to study the potential of employing similar techniques today, creating what is now referred to as biochar (or agrichar), such as the International Biochar Initiative. And the notion that Native Americans manipulated and nurtured the ecosystems of the Amazon over 500 years ago also challenges today’s conventional definitions of what is pristine – indeed by taking away one of our most reliable archetypes of living without a footprint – perhaps shakes the whole idea of pristine wilderness to its roots. And needless to say, if carbon sequestration is truly an imperative for our species, creating biochar could hold more potential – and side benefits – than virtually any other scheme.