From: "Lawrence F. London, Jr." <lflj@bellsouth.net>
To: permaculture <permaculture@lists.ibiblio.org>
Subject: [permaculture] Ancient farming method may help conserve savannahs
Date: Sat, 28 Apr 2012 22:11:56 -0400
Ancient farming method may help conserve savannahs
Aleida Rueda
26 April 2012 | EN | ES
The study found slash-and-burn may not be the most effective method for
managing savannahs
Flickr/Ben Sutherland
A fire-free farming method practiced by early inhabitants of the
Amazonian savannahs could help inform efforts to conserve and
rehabilitate these important ecosystems around the world, a study has found.
The research provides greater historic context forfindings presented at
a conference earlier this year (26 January), which suggested that
slash-and-burn — in which trees are felled, left to dry and then burned
to prepare land for farming — provides better growing conditions for
valuable trees such as mahogany.
This latest study, published in Proceedings of the National Academy of
Sciences (9 April), found that 800 years ago, prior to European
settlement of Latin America, indigenous farmers had developed a
technique known as 'raised-field' farming to manage land sustainably
without using fire.
The method involved constructing small agricultural 'mounds' which
promoted drainage, soil aeration and moisture retention. It conserved
soil nutrients and organic matter, and preserved soil structure.
The ancient technique was studied by researchers, who have created the
first detailed picture of land use by documenting the very low
frequencies of charcoal particles — an indicator of fire — in the
savannahs of French Guyana.
"Modern indigenous groups living in savannah environments regularly burn
the savannahs. From there paleoecologists extrapolated that all
savannahs have been burned regularly in the past. But this was not the
case," José Iriarte, researcher at the University of Exeter, United
Kingdom, and leader of the study, told SciDev.Net.
"Building small mounds was the only way that they could cultivate these
seasonally flooded savannahs. They were creating an elevated, dry,
fertile platform," Iriarte said.
The researchers say that the study gives a unique perspective on
land-use before as well as after the first Europeans arrived, and
reveals that the high fire incidence in Amazonian savannas was a
post-settlement phenomenon.
Iriarte says raised-field and slash-and-burn are techniques developed to
suit different environments, but commented that burning resulted in the
long-term depletion of soil nutrients. "In the long run, if [land] is
not left fallow for a long period [of up to 20 years, it] is
impoverished," he said.
The authors say their findings suggest that raised-field agriculture
could also provide better water infiltration and storage in soil and
crop roots, and promote crop growth. They also say their findings may
apply in flooded savannah settings elsewhere in the world.
"We think that raised-field agriculture, which would require careful
management of organic matter, could be applicable in all seasonally
flooded savannas," said Doyle McKey, professor at the Université de
Montpellier II, in France, who also participated in the study.
Link to full article in PNAS
[permaculture] Ancient farming method may help conserve savannahs,
Lawrence F. London, Jr., 04/28/2012