By Fred Pearce
Illustration by ©James Marsh
Surely in the Amazon, the greatest rainforest on the planet, virginity can be discovered—nature red in tooth and claw? That’s what everyone thought until an American oil prospector named Kenneth Lee first climbed aboard a beach buggy and bounced across the grassy lowlands of Baures in the Bolivian Amazon in the early 1980s. After a while, Lee began to wonder why he was bouncing so much in the grass.
On closer inspection, the landscape appeared to be corrugated. It was composed of a remarkably symmetrical series of ridges and trenches stretching as far as the eye could see. From time to time, he came across higher ridges that looked like roads, and wider depressions that seemed as if they might once have been canals. He began to think that this must be a manmade landscape and would take occasional visitors to see his “lost civilization of Baures,” which he believed must extend into the rainforest proper to the north and east.
And so it has proved. Subsequent research by Clark Erickson of the University of Pennsylvania has found tens of thousands of kilometers of raised banks across the Bolivian Amazon that he believes were dug by humans. By corrugating the flooded fields, farmers created ridges on which they could plant their crops, clear of the floodwaters and also of highland frosts, while also collecting water for irrigation in the dry season. It was a flatland equivalent of the ancient practice of terracing hillsides. The digging and earth-moving involved in creating these structures, he says, is “comparable to building the pyramids. They completely altered the landscape.”
Erickson also stumbled on something else: a vast system—estimated to cover 500 square kilometers—of fish ponds and weirs. When the grassland flooded in the rainy season, the people captured the fish, put them in ponds, and kept them for eating during the dry season. They were fish-farming on the edge of the rainforest.
Erickson believes that the fish ponds and raised fields stretching across the plains for thousands of square kilometers could have sustained maybe a million people. Buried charcoal in the roads and mounds suggests that they were created up to 2,000 years ago. Could it be true? Surprisingly, there is evidence from early Spanish accounts that seem to describe just such settlements. An expedition to Baures in 1617 described entering towns along causeways that could take four riders abreast. Jesuit records confirm this and suggest that some islands and causeways remained in use into the eighteenth century, before being left to regrowing forest and populations of tapirs, peccaries, and deer. “Some people want to preserve their forests,” says Erickson. “That is fine by me, but there is no way they are pristine. Every feature of this land is man-made.”
After Lee and Erickson upset the Amazon myths in Bolivia, along came Anna Roosevelt, an archaeologist at the Field Museum of Natural History in Chicago. She was digging on Marajó, a flat, forested island twice the size of Wales in the mouth of the river Amazon, which was recently the setting for the Brazilian version of the reality-TV show “Survivor.” Roosevelt expected to find evidence of a few village communities on this strategic but inhospitable island. Instead she found hundreds of large earthworks on the forest floor, each some 20 meters high and covering up to a square kilometer. Remains inside the mounds showed that they had been the focal points for numerous urban centers. She concluded that, a thousand years ago, the entire island was crossed by roads and irrigation and drainage networks and dotted with large towns in which maybe 100,000 people lived and worked. Roosevelt called it “one of the outstanding indigenous cultural achievements of the New World.”
Today, Marajó is just on the fringes of the rainforest region, so since Roosevelt’s discoveries, other researchers have looked for evidence of similar civilizations further west in the heart of the rainforest. Michael Heckenberger of the University of Florida at Gainesville went to one of the deepest, darkest areas of continuous tropical rainforest, in the upper Xingu region of the state of Mato Grosso. It is an area that has been inhabited by the Xinguano people for at least a thousand years—something we know because of the bits of ceramics they have left behind on the forest floor. But what he found was that the ground has not always been forest floor. In fact, most of this primeval forest had been cleared at least once, and perhaps several times, by the Xinguano for farming.
This was not an ostentatious urban society with pyramids and so on, as in the Mayan civilization. Instead, it seems that what is today one of the largest tracts of rainforest in the world was, until relatively recently, a chunk of tropical suburbia. “This really blew us away,” says Heckenberger. “It’s fantastic stuff. Everyone loves the ‘lost civilization in the Amazon story.’ But what the upper Xingu shows us is that Amazon people organized in an alternative way to urbanization. We shouldn’t be expecting to find lost cities. But that doesn’t mean they were primitive tribes, either.”
Heckenberger focused on one of these suburban areas called Kuikuro. Here he found the remains of 19 settlements. They were about four kilometers apart, each on a raised area a couple of kilometers long—rather like Roosevelt’s mounds on Marajó—and linked to the others by a system of wide boulevards up to 50 meters across. At the heart of each settlement was a big plaza with roads radiating from it toward a surrounding moat, like a huge castle in the forest. In the surrounding and sometimes swampy land between the settlements, there were bridges and dams, dykes and causeways, canals and ponds, manioc gardens and surviving forest patches housing orchards and places where medicinal plants and other “fruits of the forest” grew.
It was, Heckenberger says, “a highly elaborate built environment, rivaling that of many contemporary complex societies.” The settlements were permanent, and all seem to have been thriving communities until the Europeans turned up at the end of the fifteenth century. After that, the settlements were abandoned and the high forest returned to reclaim the suburbs. Some areas, says Heckenberger, are still regrowing; others are almost back to what they must once have been. The strange truth is that, by inadvertently wiping out the Indian populations, it was the Europeans who created the modern Amazon rainforest. Across the Amazon, local civilizations seem to have crashed shortly after the first substantial contacts with western Europeans.
Why did we not know about these societies before? Did the conquistadors not notice them as they passed through the Amazon? The strange thing is that some did notice. Take this from Francisco de Orellana’s famous first expedition down the Amazon in 1542, in search of El Dorado. As he entered the Rio Negro, one of the Amazon’s biggest tributaries, he wrote in his journal: “There was one town that stretched for 15 miles without any space from house to house, which was a marvelous thing to behold. There were many roads here that entered into the interior of the land, very fine highways. Inland from the river to a distance of six miles more or less, there could be seen some very large cities that glistened in white and besides this, the land is as fertile and as normal in appearance as our Spain.”
But knowledge of these civilizations largely died out as the people who made them retreated back into the bush to escape from the Europeans or were destroyed by Old World diseases that hitched a ride with the human invaders. Probably millions died in the decades after the Spaniards came and, as disease literally decimated their societies, the survivors fled into the jungle. It seems likely that, while the farmers and ranchers and metal-makers and priests and scholars who must have made up these societies gave it all up to become hunters and gatherers, the European invaders and despoilers were barely aware of what was going on in front of their eyes.
For American Indians, the arrival of the Europeans had a similar impact to what Europeans imagine might happen in the event of a nuclear holocaust. The primitive nature of some tribes still being “discovered” from time to time in the Amazon rainforests is due in large part to the arrival of Europeans. Likewise much of the “virgin” forest of the basin may be regrowth following the exterminations of the conquerors. If anyone made the jungle and their “stone-age inhabitants,” it was the Europeans.
For Erickson, this debunks some potent myths. The greatest of these is “the myth of the pristine environment,” in which the landscapes of the Americas were largely undisturbed by nature until the arrival of Europeans. Biologists have assumed, almost as an article of faith, that the areas with the greatest variety of species must be the most natural. Far from it, he says. “In fact, we find that high biodiversity is clearly related to past human activities, such as creating clearings, burning, and gardening.”
The wonderfully productive forest that biologists have lauded as an example of wild fecundity—filled with Brazil nuts, lianas, palms, bamboo, and other economically valuable forest species—may be the deliberate invention of man rather than the accidental beneficence of nature. “We now know,” says Erickson, “that much of what has traditionally been recognized as wilderness in the Amazon is the indirect result of massive depopulation after Europeans brought diseases, slavery and war.”
How did scientists get things so wrong for so long? In large part, archaeologists have not found remains in rainforests because they haven’t gone looking: the plains of Kenya, after all, are rather more easily investigated than the jungles of the Congo. And they have rather assumed that because they found the jungle environment hostile, others before them would have avoided it, too. Equally, many of the detailed observations about rainforest regions in the interiors of the continents—the ones that established our ways of looking at them—took place during a period when, especially in the Americas, native populations had been decimated by disease and conquest. As Stephen Pyne from Arizona State University puts it: “Virgin forest was not encountered in the sixteenth and seventeenth centuries; it was invented in the late eighteenth and early nineteenth centuries.”
The forests then looked to many as if they had always been empty, even though many had only recently been emptied. And yet, even at that time, the most acute observers were aware of something different, that the forest inhabitants were not so much noble savages as the traumatized survivors of past societies.
One of the most persuasive pieces of evidence about the extent of human occupation and transformation of the Amazon rainforest is the widespread presence in inhabited areas of the forest of what archaeologists have dubbed “black soil.” This is superficially very like the regular “yellow soil.” But mixed with it is a mulch of organic waste and partly burnt plant material, rather like charcoal. Both fertilize the soil. This mulch has permeated the black soils with microorganisms that ensure that it regenerates itself even as it is used for cultivation. It is also often full of pottery shards and other detritus of civilization, much of it now dated to 2,000 or more years ago. This has convinced many researchers that the “black soil” is not just a convenient natural soil: it is in all probability manmade.
Bruno Glaser of the University of Bayreuth in Germany says, “the really important point here is that the soils contain charred residues. That is different from the residues of [natural] burning. Both of them improve soil fertility, but burning residues don’t last for long, while charring residues have a long-term effect on soil fertility, acting over centuries. It’s at least as good as manure. In some places we know that Indians successfully farmed land containing black soil for 2,500 years or more.” Indeed, scientists are becoming so convinced that this stuff is man-made that they have begun mapping the black soil as a surrogate for the extent
of human occupation and transformation of the jungle.
If all this is true, then the ancients had a far better idea of how to farm in the jungle than their modern counterparts. Burning is what modern slash-and-burn farmers do. It leaves behind fine ash that washes away in the rain. Most of it is gone within four years. But charring, which leaves organic material permanently in the soil, seems to be a skill that has been lost. To this day, the black soils are more fertile and provide good crops of manioc, maize, and bananas. Local farmers still prize it because yields are so much greater than when they plant on “yellow soil.” In places, locals dig up the black soil in the forest and transplant it to improve their garden soils, like Americans buying bags of peat at the local garden center.
Black soils pervade the banks of the Amazon and its key tributaries, like the Rio Negro and the Tapajos. The story away from the rivers is less clear, but some researchers believe it will turn out to extend deep into the heart of the Amazon and to occupy perhaps a tenth of all the rainforest soils, an area the size of France. But whatever the extent of black soil turns out to be, it is clear that the Amazon is, in places, capable of sustaining large populations and that, across the Amazon, farmers have—probably for millennia—improved soils using fire; planted crops like manioc, palm and Brazil nuts; and cleared forests to let in the sun and grow corn. And that in all probability, the Amazon was dotted with urban centers and crisscrossed by networks of causeways and irrigation canals at the same time as the Greek empire flourished in Europe.
And what goes for the Amazon appears to be true for most other tropical rainforests. The primeval, virgin rainforest is a potent modern myth. But it may be just that. The truth is that, far from being virgin natural ecosystems, many rainforests, perhaps all, are complex artefacts. They are partly natural but partly also created by human activity, much of it constructive and beneficial to the wider forest. Rather than wilderness, they are abandoned gardens.
1. Scientific Bases for the Preservation of the Hawaiian Crow. National Academy Press, Washington, D.C.1992. Committee on the Scientific Bases for the Preservation of the Hawaiian Crow, National Research Council.
About the Author
Fred Pearce is a freelance writer based in London, U.K. He is environment consultant for New Scientist magazine as well as a regular contributor to the Boston Globe and The London Independent.