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Machines Like Us

800-year-old farmers could teach us how to protect the Amazon

Tuesday, 10 April 2012

Research indicates that raised-field agriculture can become an alternative to burning down tropical forest for slash and burn agriculture. Credit: Stephen Rostain

In the face of mass deforestation of the Amazon, recent findings indicate that we could learn from its earliest inhabitants who managed their farmland sustainably. An international team of archaeologists and paleoecologists, including Dr. Mitchell Power, curator of the Garrett Herbarium at the Natural History Museum of Utah and assistant professor in the Department of Geography at the University of Utah, report for the first time that indigenous people, living in the savannas around the Amazonian forest, farmed without using fire. These findings are published today, April 9, 2012, in the journal Proceedings of the National Academy of Sciences.

The research could provide insights into the sustainable use and conservation of these globally-important ecosystems, which are being rapidly destroyed. Pressure on the Amazonian savannas today is intense, with the land being rapidly transformed for industrial agriculture and cattle ranching.

By analyzing records of pollen, charcoal and other plant remains like phytoliths spanning more than 2,000 years, the team has created the first detailed picture of land use in the Amazonian savannas in French Guiana. This gives a unique perspective on the land before and after the first Europeans arrived in 1492.

The research shows that the early inhabitants of these Amazonian savannas practiced 'raised-field' farming, which involved constructing small agricultural mounds with wooden tools. These raised fields provided better drainage, soil aeration and moisture retention: ideal for an environment that experiences both drought and flooding. The fields also benefited from increased fertility from the muck continually scraped from the flooded basin and deposited on the mounds. The raised-field farmers limited fires, and this helped them conserve soil nutrients and organic matter and preserve soil structure.

"We used radiocarbon dating to establish the age of the raised beds," said Dr. Mitchell Power. We came to the conclusion that corn pollen we found dated to 800 years ago by dating charcoal deposits from above and below the sediment where the pollen was found."

It has long been assumed that indigenous people used fire as a way of clearing the savannas and managing their land. However, this new research shows that this was not the case here. Instead, it reveals a sharp increase in fires with the arrival of the first Europeans, an event known as the 'Columbian Encounter'. The study shows that this labor-intensive approach to farming in the Amazonian savannas was lost when as much as 95 percent of the indigenous population was wiped out as a result of Old World diseases, brought by European settlers.

The results of this study are in sharp contrast with what is known about the Columbian Encounter's impact on tropical forest, where the collapse of indigenous populations after 1492 led to decreased forest clearance for agriculture, which in turn, caused a decline in burning. This study shows that high fire incidence in these Amazonian savannas is a post-1492, rather than pre-1492, phenomenon. "Our results force reconsideration of the long-held view that fires were a pervasive feature of Amazonian savannas, said Power"