Tuesday, 3 September 2013

The rectangular and oriented lakes in the Bolivian Amazon are not tectonic, and now what?

Our latest paper has been published a few days ago in Geomorphology. The title is: "The origin of oriented lakes: Evidence from the Bolivian Amazon". Here goes a very short version of it.
The presence of hundreds of rectangular and oriented lakes is one of the most striking characteristics of the Llanos de Moxos landscape (Fig. 1). Many different mechanisms have been proposed for their formation, including subsidence resulting from the propagation of bedrock faults through the foreland sediments, scouring caused by large-scale flooding, paleo deflation combined with wind/wave action and human agency. Nevertheless, amid this diversity of hypothesis, the most commonly accepted cause of lake formation to date has been tectonics.
Figure 1. Landsat image of oriented and rectangular lakes in the Llanos de Moxos
Plafker’s tectonic model (Fig. 2) has never been tested. If faulting is involved, the displacement should be visible and measurable through sediment profiling. The only element needed is a stratigraphic marker that allows the measurement of the vertical displacement.
Figure 2. Tectonic model for lake formation (Plafker, 1967). According to Plafker, the lakes' rectangular shape results from the propagation of bedrock fractures through unconsolidated sediments.
Thanks to our recent discovery of a paleosol below mid-Holocene fluvial sediments in the south-eastern LM (Lombardo et al., 2012), where several lakes are found, it is now possible to test the tectonic hypothesis. If lakes were formed by local subsidence induced by bedrock faults, we should find the paleosol at a greater depth below the lake than in the area surrounding it. 

This is how we cored the lakes
Stratigraphic profiles from transects that cut across the borders of three lakes show otherwise (Fig. 3): the depth of the paleosol is the same. Hence, tectonics, as the mechanism behind the formation of the lakes, can be ruled out. The origin of the Moxos rectangular and oriented lakes is still very much unresolved. A more detailed discussion about the possible mechanisms behind the lakes' formation can be found in Lombardo & Veit (In Press)
Figure 3. Stratigraphic transects from the outside to the inside of the lakes. Dotted white lines define the lakes’ basins. The early to mid-Holocene paleosol acts as a stratigraphic marker (see Fig. 2). Cores 52, 63, 81, 170, 205 and 210 provide the reference depth of the paleosol outside the lakes; cores 77 and 204 have been performed in areas of the original lakes’ basins that have been infilled; cores 78, 169, 171 and 209_b come from inside the lakes. Continuous black lines reconstruct the original lake bottom (previous to lacustrine infilling); dashed black lines connect the paleosol. Source of digital images: Google earth.
Lombardo, U., May, J.-H., & Veit, H. (2012). Mid- to late-Holocene fluvial activity behind pre-Columbian social complexity in the southwestern Amazon basin The Holocene DOI: 10.1177/0959683612437872
Lombardo, U., & Veit, H. (2013). The origin of oriented lakes: Evidence from the Bolivian Amazon Geomorphology DOI: 10.1016/j.geomorph.2013.08.029
Plafker, G. (1964). Oriented Lakes and Lineaments of Northeastern Bolivia Geological Society of America Bulletin DOI: 10.1130/0016-7606(1964)75[503:OLALON]2.0.CO;2

Saturday, 31 August 2013

Amazing media response to our latest paper in PloS ONE

Our paper “Early and Middle Holocene Hunter-Gatherer Occupations in Western Amazonia: The Hidden Shell Middens” has been published less that 3 days ago in PLoS ONE. It was included in the press release of PLoS ONE and, once the embargo expired, we produced two other press releases (see previous post).
I am amazed by the interest that media from all around the world have shown! Till now I have counted more than 50 articles from USA, Spain, Germany, Brazil, Bolivia, Russia, Australia etc. Plus, several people posted about our research in their blogs.
Samples from the internet press of the last 2 days:

A blog post I liked:

Thursday, 29 August 2013

The Hidden Shell Middens - Press releases

Here two media releases, one in English written by Kat and the another in Spanish written by José, about our latest paper "Early and Middle Holocene Hunter-Gatherer Occupations in Western Amazonia: The Hidden Shell Middens" published in PLoS ONE the 28th of August 2013.

Traces of the earliest inhabitants of Bolivian Amazonia hidden in plain sight
The enigmatic ‘forest islands’ set amidst the grasslands of Bolivian Amazonia have yielded the earliest evidence of human habitation in the region.   Previously thought to be relict landforms cut away by shifting rivers, or long-term bird rookeries or termite mounds, these piles of freshwater snails, animal bones and charcoal are now known to have been built up over millennia, starting from at least 10,400 years ago, by ancient hunter-gatherers. 
Using novel approaches drawn from archaeology, geomorphology and geochemistry, an international team of researchers, led by Dr. Umberto Lombardo of the University of Bern, has conducted detailed excavations of a large mound known locally as Isla del Tesoro (Treasure Island).  Distinctive chemical signatures of human presence were recorded at high levels throughout the mound sediments, and studies of the animal bones and shells indicate they are the remains of ancient human meals.  Isla del Tesoro tells us that from over 10,000 years ago, hunter-gatherers were moving across the grasslands hunting a variety of mammals, catching fish and birds, and gathering large quantities of freshwater snails.
 Over time, the refuse of these hunting and gathering forays built up forming mounds which sat elevated above the floodplain.  These refuse or ‘midden’ mounds in turn provided a habitat for local plants and animals, transforming them into the forest islands so recognisable in the landscape today.  It is highly likely that many more midden mounds lie buried beneath the metres of silts under the current savannah.
Regularly flooded savannah landscapes such as those surrounding Isla del Tesoro have long been thought to be an inhospitable environment for early hunter gatherers.   The densities of animal prey are lower and less predictable than in coastal areas, near stable watercourses or in forested areas where early South American archaeological sites are typically found.  Lombardo and colleagues’ work at Isla de Tesoro tells us that early South Americans moved across a wider variety of landscapes than previously thought, and adapted their ways of life to cope in these challenging environments.
Paper details
Lombardo, Umberto1, Katherine Szabó2, Jose M. Capriles3, Jan-Hendrik May2, Wulf Amelung4, Rainer Hutterer5, Eva Lehndorff4, Anna Plotzki1, Heinz Veit1. 2013.  Early and middle Holocene hunter-gatherer occupations in Western Amazonia: the hidden shell middens. PLOS ONE.  Online from 28th August, 5.00pm (EDT)

1 University of Bern, Switzerland
2 University of Wollongong, Australia
3 University of Pittsburgh, USA
4 University of Bonn, Germany

5 Alexander Koenig Zoological Museum, Bonn, Germany

Conchales ocultos revelan milenaria presencia humana en la Amazonia boliviana

Un equipo internacional de investigadores, dirigido por el Dr. Umberto Lombardo, de la Universidad de Berna – Suiza y que incluye al arqueólogo boliviano, Dr. José M. Capriles, acaba de publicar en la revista científica de acceso abierto PLoS ONE, un estudio que documenta la existencia de asentamientos humanos en la Amazonía boliviana desde al menos 10.400 años atrás. En esta región se atribuía la ausencia de ocupaciones pre-agrícolas a condiciones ambientales desfavorables. Sin embargo, esta investigación multidisciplinaria combinó información de arqueología, geomorfología y geoquímica, para identificar restos de asentamientos de cazadores-recolectores en islas de bosque” o “islas de monte” en los Llanos de Moxos del Departamento del Beni. Los autores de la investigación informan que tres de estas islas son conchales o montículos formados por conchas (además de huesos, tierra quemada y carbón) desechados por grupos de cazadores-recolectores móviles. Análisis de radiocarbono indican que estos grupos se establecieron en la región a principios del Holoceno, es decir, hace aproximadamente 10.400 años y que mantuvieron su modo de subsistencia varios milenos. Las islas de bosque estudiadas parecen haber sido abandonadas hace aproximadamente 4000 años atrás para luego ser reocupadas poco antes de la conquista española por las sociedades agrícolas que construyeron las lomas y camellones del Beni. Esta investigación permite confirmar que la Amazonía boliviana estuvo poblada por seres humanos mucho más antes de lo imaginado y que sus pobladores fueron agentes activos en la formación del paisaje.


Umberto Lombardo, Katherine Szabo, José M. Capriles, Jan-Hendrik May, Wulf Amelung, Rainer Hutterer, Eva Lehndorff, Anna Plotzki & Heinz Veit. 2013. Early and Middle Holocene Hunter-Gatherer Occupations in Western Amazonia: The Hidden Shell Middens. PLoS ONE Vol. 8, No. 8, pp. 1-14. E72746.

Esta publicación es resultado del “Proyecto de Investigación Arqueológica: Ocupación Humana, Paisajes Antrópicos y Cambio Medioambiental durante el Holoceno en los Llanos de Moxos – Amazonía Boliviana” que cuenta con el apoyo del Viceministerio de Interculturalidad del Estado Plurinacional de Bolivia, la Gobernación del Departamento del Beni, la Fundación Nacional de Ciencias Suiza y otras institucionales internacionales y nacionales.

Monday, 7 January 2013

The diffusion of unsuccessful innovations: the myth of raised field agriculture

Pre-Columbian raised field agriculture is an extremely interesting topic that we have discussed in this blog before, here, here and here. We call raised fields “any prepared land involving the transfer and elevation of soil above the natural surface of the earth in order to improve cultivating conditions” (Denevan and Turner, 1974). Raised fields have received a lot of attention in studies related to pre-Columbian demography. They have been considered key in allowing dense populations of complex societies to inhabit seasonally flooded regions of South America in pre-Columbian times. Beyond their academic interest, raised field agriculture has also become popular among rural development workers and aid agencies working with small farmers in South America. For more than 30 years now, some archaeologists and NGOs have favoured the “re-introduction” of this pre-Columbian agricultural technique among modern day farmers. In their view, raised fields (which are considered analogous to the Chinampa system in Mexico) represent a promising pro-poor agricultural innovation which is more productive and sustainable than traditional agriculture (which, in the neo tropics is, basically, slash and burn).
A few days ago, Philippe C. Baveye published on-line a thorough debunk of such proposals  (Baveye in press) . It is a comment to a paper by Renard et al (Renard et al., 2012) where the authors advocate for the adoption of raised fields agriculture among modern farmers. The main points that Baveye puts forwards are: 1) There is no evidence that raised fields have supported dense populations in the past; 2) the pre-Columbian Chinampa system is unique. Therefore, it cannot be assumed that the productivity of the South-American raised fields, which are very different from the Mexican Chinampas, was comparable to that of the Chinampas; and 3) the purpose of raised fields was limited to water management:  soil drainage and/or irrigation. We reach very similar conclusions in (Lombardo et al., 2011). It is important to highlight that none of the projects designed to reintroduce raised field agriculture among small farmers in Bolivia and Peru have ever worked (actually, I am not aware of any successful rehabilitation anywhere in the Americas). Local farmers have no idea or knowledge about this ancient practice: this kind of indigenous knowledge was lost hundreds of years ago when the Spaniards got to America. Therefore, besides the technical problems described above, another reason behind this large scale failure is that raised field agriculture has been entirely “invented” by archaeologists and NGOs: the latest example I know of raised field rehabilitation project failures comes from an Oxfam project in the Beni - Bolivian Lowlands. The picture below shows the current state of the raised fields built by Oxfam in 2009, amid an important media coverage and support (for example, see this BBC article).

In 2011 raised fields were also built in the northern Beni.You see the state of the fields during the summer 2012 (photo below).

Hopefully, Baveye’s comment will contribute to make researchers more cautious before proposing the ‘reintroduction’ of raised field agriculture in rural communities.

Baveye, Philippe C. (2013). Comment on “Ecological engineers ahead of their time: The functioning of pre-Columbian raised-field agriculture and its potential contributions to sustainability today” by Dephine Renard et al Ecological Engineering

Denevan, W. M., and Turner, B. L., 1974, Forms, functions and associations of raised fields in the old world tropics: Journal of tropical geography, v. 39, p. 24-33.

Lombardo, U., Canal-Beeby, E., Fehr, S., & Veit, H. (2011). Raised fields in the Bolivian Amazonia: a prehistoric green revolution or a flood risk mitigation strategy? Journal of Archaeological Science, 38 (3), 502-512 DOI: 10.1016/j.jas.2010.09.022

Renard, D., Iriarte, J., Birk, J., Rostain, S., Glaser, B., & McKey, D. (2012). Ecological engineers ahead of their time: The functioning of pre-Columbian raised-field agriculture and its potential contributions to sustainability today Ecological Engineering, 45, 30-44 DOI: 10.1016/j.ecoleng.2011.03.007