October 18, 2005
The Virgin Forest? Amazon Myths and New Revelations
The Amazon has a long history of human settlement. Contrary to popular belief, sizeable and sedentary societies of great complexity existed in the rainforests of this region. These societies produced pottery, cleared sections of rainforest for agriculture and managed forests to optimize the distribution of useful species. The notion of a virgin Amazon is largely the result of the population crash following the arrival of the Europeans in the sixteenth century. Studies suggest that at least 10-12% of the Amazon's terra firme forests are "anthropogenic in nature" resulting from the careful management of biodiversity by indigenous people. However, unlike most current cultivation techniques, these Amazonians were attuned to the ecological realities of their environment from five millennia of experimentation and accumulation of knowledge, with a strong understanding of how to manage the rainforest to meet their requirements within a sustainable capacity. They saw the importance of maintaining biodiversity through a careful balance of natural forest, open fields and sections of forest managed so as to be dominated by species of special interest and greatest use to humans.
In her work, based on the collection of soil samples during the 1960s, Meggars concluded that the soil in Amazon region was so poor it could not possibly support the intensive agriculture necessary for the establishment and maintenance of large communities. She argued that the pre-Columbian Amazon was a pristine environment that had been little altered by humans.
Today Meggars' work is being increasingly undermined by evidence of extensive civilizations in the region, most notably the human-enhanced floodplains in Bolivia, remnants of ancient towns and road systems and the presence of rich, apparently man-made soils.
30,000 square miles of forested mounds
Near the Brazilian border of north-central Bolivia, there are some 30,000 square miles of raised forested islands in a grassy floodplain. Scientists speculate that the area may have been an extensive human-constructed landscape optimized for managing local fisheries and the distribution of vegetation. Building raised fields for agriculture and using fire to clear large areas of brush, native dwellers of the Beni region strongly influence if not controlled the distribution of plant species. Trees and crops that would otherwise drown in the waterlogged floodplain flourished in the raised gardens.
Deeper in the Amazon there is further evidence of widespread human settlement.
The discovery of a network of villages and towns connected by precisely engineered roads -- some up to 45 meters (150 feet) wide -- shocked many Amazon researchers when the study was published in 2003. The 10-year study, which covered 1000 square kilometers in the upper Rio Xingu region, found a cluster of nineteen villages that likely supported between 2,500 and 5,000 people.
Lead author of the research, Michael J. Heckenberger, says that the complex of communities could be just one of many complexes in the Amazon region. These societies were long overlooked by archeologists because they did not build the large cities and rock structures seen among the Mayans, Aztecs and Incas. Since stone is not widely available in the Amazon, settlements were constructed of wood, clay, bone and other materials that deteriorate rapidly in the warm, humid climate of the rainforest. Thus, once abandoned, buildings and roads constructed by Amazon dwellers quickly disappeared back into the jungle.
Amazonian societies supported large populations by the careful management of their surrounding environment. Instead of the European farm system where single crop monocultures were common, Amazon farmers may have cultivated and managed entire ecosystems. In his account of the pre-Columbian Indian societies, 1491, Charles Mann explains,
"Indians survived by cleverly exploiting their environment. Europeans tended to manage land by breaking it into fragments for farmers and herders. Indians often worked on such a grand scale that the scope of their ambition can be hard to grasp. They created small plots, as Europeans did (about 1.5 million acres of terraces still exist in the Peruvian Andes), but they also reshaped entire landscapes to suit their purposes... Unlike Europeans, who planted mainly annual crops, the Indians, he says, centered their agriculture on the Amazon's unbelievably diverse assortment of trees: fruits, nuts, and palms."
In an environment like the Amazon, without the benefits of iron tools or domesticated animals, clearing and sowing agricultural fields was a difficult and time-consuming process. Instead, Indians planted trees, yielding twenty years of productivity from their labor, as opposed to two or three years with a standard low-growing crop.
Creating orchards, instead of field, early inhabitants of Amazonian regions served themselves with great economy. Planting trees in the fertile river basin, Indians capitalized on the benefit of rich soil quality and the deep reaching roots of trees helped agriculture to survive during the dry season and in periods of drought. Experts now estimate that a significant portion of lowland forests, perhaps as much as 15 percent, were organized to benefit humans. The concept of a "built environment" contrasts sharply with the idealist and traditional version of an all-natural, virgin territory.
In 1990, Anna C. Roosevelt, an archaeologist from the Field Museum of Natural History in Chicago, along with a team of specialists, re-excavated the Amazonian site of Marajó. Their findings revealed compelling evidence that the mound-ridden archeological wonder likely supported more than 100,000 inhabitants and covered thousands of square miles. Marajó's presence, based on scientist's studies, enriched the environment, rather than causing the typical detriment or stress of a large, densely populated area. The only traces left behind of the settlement, a series of raised lumps of earth, still contain the most lush and diverse forth growth in the region.
The best explanation for this kind of botanical record is the past creation and use of terra preta do indio, meaning "Indian black earth" in Portuguese. This unique, mineral-rich soil was purposely created by pre-Columbian people through a process of adding charcoal and animal bones to regular soil to create a highly fertile hybrid, ideal for agriculture. Beyond the Amazon's notorious reputation for thin and poor-quality soil, terra preta provided unprecedented life and bounty for its inhabitants.
Charcoal is the essential ingredient of terra preta, which gives the soil a more substantial quality as organic matter latches on to the compounds within it through oxidation, retaining moisture and nutrients. Despite these benefits, charcoal lacks substantial nutrients on its own, so Indians enriched the soil with organic waste like the bones of turtles, fish and birds. Higher quantities of calcium, nitrogen, phosphorus and sulfur exist more in terra preta than is found in typical earth. If managed well, this matter can avoid exhaustion from agricultural stress far longer than regular soil. Soil ecologists believe they may be able to replicate terra preta to convert thin tropical soil into rich, substantial, sustaining and possibly self-replicating earth.
Scientists believe terra preta was created through a process one specialist calls the "slash-and-char" method. Essentially, instead of completely burning trees to ash, pre-Columbian farmers merely smoldered organic matter to form charcoal, and then stirred the charcoal into the soil. The added benefit of this method was that far less carbon was released into the air than now common slash-and-burn method. Carbon emissions, or rather an imbalance of carbon emissions, has a well-recognized negative effect on forests, so this ancient method was truly efficient and environmentally sensitive. Charcoal is capable of retaining its carbon in the soil for close to fifty thousand years.
Today, scientists and local inhabitants alike recognize the value and importance of terra preta. The earth is excavated and sold as potting soil known for its impressive productivity. Some individuals work it for years with only minimal fertilization. There is a wide range of estimates for the remaining quantity of terra preta. Estimates vary between 0.1 - 10 percent of the Amazon basin may harbor the soil. Ten percent encompasses an area the size of France. The largest collections of terra preta are located on low bluffs at the edges of floodplains, typically covering 5 to15 acres. The thickest layers of the material hover around six feet deep. Soil ecologists do not recognize a natural pattern for these bands of soil, suggesting that terra preta is indeed a man-made or directed substance. There are also typically broken ceramic pieces within the soil, further link it to a human design.
What all this information infers is that these inhabitants were essentially terra-forming the Amazon into a highly productive, sustainable agricultural region, managing a heady task that had evaded Europeans for centuries. Unfortunately, for the natives of the New World, the Old World arrived and both intentionally and unintentionally destroyed all they had worked toward.
What happened? Disease
Machu Picchu, Peru
Photo by R. Butler
Many of these populations flourished along rivers where means of transportation, excellent fishing, and fertile floodplain soils for agriculture were available in abundance. These locations were ideal for settlements, however, when the Europeans arrived, these were the first to be affected, and subsequently decimated, since the explorers used the major rivers as highways to the interior. Within the first one hundred years of European contact, the Amerindian population was reduced by at least 90 percent. The majority of the surviving peoples lived in the remote interiors of the Amazonian region, forced there by the encroaching Europeans, or those few already traditionally living there in smaller groups.
The premier cause of the massive reduction in population was disease. Smallpox was the first introduced malady to ravage the indigenous peoples. Subsequent epidemics of typhus, influenza and smallpox again in the 1500 and 1600s essentially erased all traces of living Incan culture. Dobyns, the first social scientist to trace the origins of the New World inhabitants' demise, estimated that prior to European contact, the Western Hemisphere supported between 90 and 112 million people. To put this already large figure into clearer perspective, Dobyns' estimate for the Americas' population in the late 1400s surpassed that of Europes for the same period.
The reason behind Indians' intense susceptibility to the diseases of the Old World lay in their isolation. Having never previously been exposed to certain biological agents, native inhabitants were utterly defenseless to the epidemics. Their ignorance about the diseases only aided the spread of these foreign ailments, as inhabitants remained with the sick for support instead of using the practiced European methods of quarantines and isolation.
Because the Amazon's most skilled agriculturalists were killed off by European diseases, much of what was known about cultivating the rainforest ecosystem has been lost. Undoubtedly, these forest farmers relied on a far different agricultural philosophy than that used today -- one, says Clark Erickson from the University of Pennsylvania, that sustained significant populations without destroying biodiversity. Their techniques, if uncovered, could prove useful and possibly essential in creating areas of high agricultural productivity without utter destruction. Instead of clearing large areas for crops with small yields and short life-spans and pastureland for low-density cattle grazing, perhaps the employment of ancient and apparently profoundly effective methods could revolutionize modern cultivation with minimal environmental impact.
It is probably unfair and unreasonable to expect Brazil and other Amazonian basin countries to leave the region's remaining forests completely untouched from development. However, if there is a way to minimize the damage to the forest and biodiversity losses while maximizing agricultural yields, then it should be examined, especially if past inhabitants proved the merits of such management. If specialists find success with these methods, the same principles could be applied to other at-risk areas. Already 15 percent of the Amazon rainforest is gone. We should not waste what remains.
To explore this topic further take a look at 1491 : New Revelations of the Americas Before Columbus by Charles C. Mann. Mann provides a fascinating examination of pre-Columbian societies and goes into much greater depth of the topics covered in this article.
This article used information and quotes from 1491 : New Revelations of the Americas Before Columbus by Charles C. Mann, Science, and Amazonia: Man and Culture in Counterfeit Paradise by Betty J. Meggers.