To Bolivia again

Hi everybody,

I have the flight to Bolivia in few hours and I will spend there the next month. No scientific post for the next weeks, but I will try to post a lot of photos, you will feel like you are there too :-)

Stay tuned!

Roadmap for amazonists to INQUA 2011

Next week (21-27 July 2011) The XVIII INQUA-Congress will take place in Bern, Switzerland.
As expected, very few contributions will deal with the Amazon Basin during the Holocene. I went through the program and I spotted the following presentations and posters that could be of interest to those who follow this blog. If I have missed something let me know and I will update the list. By the way, the first oral presentation on this list is mine :-) If you come to INQUA it would be great to meet up and have a good Swiss beer together!! Hope to see you there!!

ORAL PRESENTATIONS:

• Human occupation and environmental change in south-western Amazonia during the Holocene.

• Palaeobotanical evidences of pre-Columbian agriculture in black soils (Terra Preta do indio) in western Amazonia

• Ecological response on environmental change in tropical South America during the late Quaternary

POSTERS:

• Human occupation and paleoenvironment during the Holocene of southern Brazil: Sangão and Garivaldino sites

• Source-bordering dunes in the eastern Bolivian lowlands – geomorphic variety and paleoenvironmental significance

• Tropical Wetland Formation in Belize: Ancient Maya and Natural Interactions in the Late Holocene

• Vegetation, climate, and fire history of the Páramo of Jimbura, southern Ecuador

• Pre-Columbian human land-use and impact in the Bolivian Amazon

• Early to Late Holocene climate, vegetation and fire history in the upland savannas of Guayana, SE Venezuela: fire regimes and community structure in a savanna-dominated area

• Landscape transformation and crop cultivation in two contrasting environments in Colombia: evidences of ancient agricultural raised fields

• Palaeohydrological variability of the Bolivian Amazon throughout the Holocene

• Paleoecological study of a Gran Sabana lake (SE Venezuela) during the last millennia: implications for Mauritia colonization and human settlement

• Late Holocene environmental changes based on diatom and pollen records from lake sediments of Laguna Encantada, in the Neotropical Gran Sabana (Venezuelan Guayana)

• Rapid paleohydrogical Holocene changes in the Amazon river and its implications on the carbon accumulation in floodplain lakes

• Paleoenvironmental trends in Venezuela during the last glacial cycle

Less than 1% of Amazonia is made of Terra Preta. Is that enough?

I’ve just read a review written by William Balée (2010) about the book ‘Amazonian Dark Earths: Origins, Properties, Management’. Balée considers that the discovery of Terra Preta is proof that people in pre-Columbian Amazonia, rather than adapting to environmental conditions, ‘created’ the environment they inhabited. This allowed the development of complex societies in the region regardless of environmental constraints (such as poor soils, floods, lack of protein...). People overcame all these problems by creating Terra Preta. This is an extract from Balée’s introduction: “This contribution refutes, in essence, the adaptationist view of Amazonian indigenous societies […]. It is intriguing that this refutation takes place in light of what constitutes less than 1% of the forested part of the region’s surface soils (Woods and Denevan 3.1:1). That small fraction, nevertheless, like the difference in DNA between humans and chimpanzees, takes on profound significance in terms of understanding […] agriculture, population, and settlement in the prehistory of the region.”

Can we really consider this 1% like the difference in the DNA between humans and chimpanzees?

An answer to this question is given by Bush and Silman (2007): “The hypothesis of widespread Amazonian landscape management is based on analyses of archaeological sites and the assumption that there was a large pre-contact Amazonian population (> 10 million people). A caveat must be applied to these data, and indeed all of the data that we have to date about human disturbance in the Amazon, which is that they are derived from just a few locations, and do not represent either a systematic or a randomized sampling design. There is no ecological component predicting which forest was most likely to be occupied. Was disturbance spread evenly across all of Amazonia or concentrated near human habitation? Is it safe to extrapolate results from sites where we know human habitation occurred to the rest of Amazonia? Ecologists are familiar with problems of scale. […] extrapolating observations from dot maps can be dangerous, especially when the dots represent discrete activities of limited spatial extent (eg terra preta formation).”

It is striking how scholars can have such differing views at such a basic methodological level! (-:

Another interesting point is where that 1% is found: terra preta sites (the “dots” Bush and Silman are talking about) are found along the courses of the major Amazon rivers (fig. 1).

Figure 1 Terra preta sites. From Glaser (2007)

The preference for settling along rivers would seem to indicate that environmental conditions (in this case closeness to fish protein and waterways) did in fact condition the development of pre-Columbian societies. If we consider terra preta as evidence of the existence of large permanent settlements established by complex societies, then its spatial distribution along major rivers would suggest precisely that social complexity developed where environmental conditions were good. And, as so many archaeologists and anthropologists have stressed before me, there is no basis to infer that large permanent settlements were also established in other areas further away from rivers, where environmental conditions would have been tougher. 

P.S.

I have just discovered a new post in the Blog of Neves about the same issue. have a look (in Portuguese): http://arqueologiadaflorestatropical.blogspot.com/

William Balée (2010). Amazonian Dark Earths Tipití: Journal of the Society for the Anthropology of Lowland South America


Bush, M., & Silman, M. (2007). Amazonian exploitation revisited: ecological asymmetry and the policy pendulum Frontiers in Ecology and the Environment, 5 (9), 457-465 DOI: 10.1890/070018


Glaser, B. (2007). Prehistorically modified soils of central Amazonia: a model for sustainable agriculture in the twenty-first century Philosophical Transactions of the Royal Society B: Biological Sciences, 362 (1478), 187-196 DOI: 10.1098/rstb.2006.1978

Soybean industrial production is bulldozing pre-Columbian archaeological sites in the Bolivian Amazon and nobody gives a damn

The journal Applied Geography and the journal Land Use Policy have recently published two papers, “Spatiotemporal modeling of the expansion of mechanized agriculture in the Bolivian lowland forests” and “Deforestation dynamics and policy changes in Bolivia’s post-neoliberal era” respectively, that depict a desolating panorama. The rate of deforestation under Evo Morales’ government is even higher than it was during the previous governments. Muller et al. say that “While overall dynamics remained relatively stable over time, the expansion of mechanized agriculture between 2001 and 2005 became more tolerant to excessive rainfall and less dependent on fertile soils. This mirrors the increasing penetration of mechanized agriculture into humid and less fertile Amazonian rainforests in the northern portion of the study area [Santa Cruz]. The map of deforestation probability substantiates these patterns and shows the highest propensities for future deforestation in the north”, while Redo et al. point out that: “Although neoliberal policies triggered an unprecedented level of forest clearing in Bolivia, rates have generally continued to increase and can be indirectly linked to the administration’s new agrarian reform and pro-environmental regulations”. The “pro-environmental” regulations of Morales’ government have actually increased deforestation rates!

The Northern Bolivian lowlands are not only an extremely important reservoir of biodiversity and home of many indigenous communities; they also hold an impressive amount of archaeological sites, most of which have never been studied or surveyed. As deforestation for industrial soybean production is moving northward, it now starts to affect the Llanos de Moxos, where most of these archaeological sites are found. Soy producers cut down the trees using bulldozers, and, in this way, they also destroy all the archaeological sites they encounter on the way. In the eastern Llanos de Moxos, in a stripe of forest called Monte San Pablo, between the River Cocharca and the River San Pablo (Fig. 1), Bolivian Mennonites are bulldozing pre-Columbian human-made earth mounds, which hold valuable remains and information about past Amazonian cultures. The destruction of pre-Columbian archaeological sites in the Bolivian Amazon is taking place while national and local governments look another way, and regrettably, with the complicity of some of the indigenous leaders who live in the area. 

Figure 1 Shaded areas are forests. Continuous line indicates the area of pre-Columbian monumental mounds. Monte San Pablo is east of the area (dashed lines) shown in Fig.2. (Lombardo and Prümers, 2010)

Figure 2. Modis Image taken a few days ago. The yellow stripes highlighted by the arrow are the portions of Monte San Pablo that have already been cleared for soybean production. The deforested area is already larger than 10.000 hectares

I have surveyed more than one hundred pre-Columbian monumental mounds and hundreds of Km of pre-Columbian canals and causeways in the area east of Trinidad, in the Beni (see map in fig.3). The monumental mounds are huge earthworks (the average mound covers 5 hectares and is 9 meters high) entirely human made, built from 400 AD to 1500 AD. They are full of pottery and burials and only very few of them have been excavated by archaeologists. The Monte San Pablo, just east of the area I surveyed, is full of monumental mounds. Those are the mounds that are being destroyed by the Mennonite bulldozers to make room for soybeans.

Figure 3. Triangles are pre-Columbian monumental mounds, lines are canals and causeways, shaded areas are forests. (Lombardo and Prümers, 2010)

Daniel Redo, Andrew C. Millington, & Derrick Hindery (2011). Deforestation dynamics and policy changes in Bolivia’s post-neoliberal era Land Use Policy : 10.1016/j.landusepol.2010.06.004

Robert Müller, Daniel Müller, Florian Schierhorn, & Gerhard Gerold (2011). Spatiotemporal modeling of the expansion of mechanized agriculture
in the Bolivian lowland forests Applied Geography : 10.1016/j.apgeog.2010.11.018

Umberto Lombardo, & Heiko Prümers (2010). Pre-Columbian human occupation patterns in the eastern plains of the Llanos de Moxos, Bolivian Amazonia Journal of Archaeological Science DOI: 10.1016/j.jas.2010.02.011

New data about Amazonian Dark Earth (ADE).

The Journal of Archaeological Science has just published a new study on ADE. The study, of Birk et al. is entitled: “Faeces deposition on Amazonian Anthrosols as assessed from 5b-stanols”. I have just read it and this is my very first impression:

The new data are extremely interesting. The authors look at the presence of coprostanol (a marker for faeces) in Amazonian Dark Earth (ADE). They have found a clear change in the index used to asses different sources of stanols, when comparing samples from the topmost 10 cm with samples coming from a depth of 30-40 cm. It seems that litter degradation is responsible for this change. Moreover, it also seems that the normal indexes used to assess the human origin of the stanols do not work very well in Amazonia. This paper is going to be a valuable reference to similar studies performed in Amazonia in the future.

Natural Oxisol on the left; Terra preta on the right

However, while Birk et al. correctly notice that one of the most debated topics about ADE is its origin, they do not do very much to assess why the faeces were there and what is their meaning from an archaeological point of view. ADE is found in two different forms, terra preta and terra mulata. Terra preta is darker, contains more organic matter, P and charcoal and also contains lots of fragments of ceramic. Terra mulata is like a light version of terra preta, it contains more nutrients and charcoal compared with “natural” soils from the surroundings, but less compared to terra preta. Moreover, in the terra mulata sites there is no pottery. Terra preta is found in small patches of about 1 hectare and terra mulata if found surrounding the terra preta sites. Terra mulata can cover as much as 200 hectares. An interpretation could be that terra preta resulted from settlements while terra mulata resulted from agriculture. If this thesis was correct, the high fertility of terra preta would be a side effect of human waste disposal and not the intentional result of land fertilization. In the case of terra mulata, if we assume it has been produced by agricultural use, fertilization must have been intentional. In this case, it would have been very important to see if there is any coprostanol in terra mulata! But the study did not look at terra mulata. Many scholars talk about ADE as synonymous of terra preta, without making a distinction with terra mulata, despite the fact that the differences between the two are key to understanding the past of Amazonia (estimating past population density, the region’s carrying capacity, the levels of social complexity achieved, pre-Columbian settlement patterns, the extent of the human impact on pre-Columbian forest etc.)

Birk et al. only compared samples from 4 terra preta sites with samples from natural soils. I think they missed a great occasion. If they had also looked at 4 samples from terra mulata sites they might have been able to shed new light on the matter. Perhaps they did look at terra mulata and just decided to publish the results in a second paper…keeping us waiting GRRRR J

Birk, J. J., Teixeira, W.G., Neves, E.G., & Glaser, B. (2011). Faeces deposition on Amazonian Anthrosols as assessed from 5β-stanols Journal of Archaeological Science, 38 (6), 1209-1220 : doi:10.1016/j.jas.2010.12.015

RE:RE: Pre-Columbian raised field agriculture: a review

Dear Delphine Renard and Doyle McKey,

Having read your comments on my post, I think I was wrong with my critiques. I focused on specific technical details and overlooked the key issue. I will try to address that now.

A key controversy surrounding raised field agriculture is whether they were built as an opportunity (to produce more per unit of land and unit of work) or as a necessity (to gain marginal lands, regardless of increased labor costs per unit of production). This is the key point that needs to be addressed before raised field agriculture can be put forward as an alternative for today.

We can imagine 3 different pre-Columbian scenarios.

1) Population increased (or climate changed) and people had to gain marginal land for agriculture. In this scenario, raised field agriculture required more work for unit of production compared with slash and burn agriculture but served to increase the amount of overall arable lands and feed more people (this is Boserup’s idea).

2) Building raised fields required less work than practicing slash and burn agriculture. Pre-Columbians chose to cultivate the savannah instead of the forest. In this case they just build raised fields because it was easier than clearing the forest with stone axes (this is Denevan’s idea).

3) Raised fields were more productive per unit of land AND required less work per unit of production than slash and burn agriculture. Raised field agriculture triggered population growth and permitted the development of large complex societies despite poor soils (this is Erickson’s idea).

The archaeological and geomorphologic evidence in the Bolivian Amazon suggests that the most plausible scenario is likely to be the first one; because a) raised fields are built in forested areas and b) the model proposed where fertility is increased thanks to water logged between the fields is not applicable in Moxos (as I explain in my last paper)

You say “We think it likely that the need for a fallow period [in raised fields] was variable among these systems, depending on soil fertility”. But this doesn’t change the argument because the underlying fertility was there also for the agriculture without the raised fields! The need for fallow periods is the same for raised fields than for other forms of agriculture. If you have good fertile soils, why would you build raised fields, transforming (and losing) half of the good land into canals? The existence of raised fields in places where there were fertile sediments is itself evidence that fields were built to improve the drainage (as fertility was already there). In other words, to transform marginal lands subject to floods into agricultural surface.

When considering the idea of re-introducing raised field agriculture today, we have to bear in mind that people now have metal tools and mechanical saws. Clearing the forest is far easier than it was in the past and, on the whole, population density in the Amazon is very low. There is no doubt that today clearing forest is far cheaper than building raised fields (10 people can clear 1 hectare of forest in a couple of days).

Those who propose raised field agriculture have to demonstrate that they can get more output per unit of work than with slash and burn agriculture. Till now I haven’t seen any figures, experiment or theoretical model backing this. On the other hand, after 40 years of proposing the re-introduction of raised field agriculture, this technology hasn’t been adopted by indigenous people or any other group of farmers.

Coming back to your paper, the question I wish you had addressed in your conclusions is: are raised fields a necessity arising from population pressure or an opportunity to produce more with less effort? I think we have plenty of evidence to support the former and very little to support the idea that the regions where we find raised fields experienced a pre-Columbian Green Revolution :-)

RE: Pre-Columbian raised field agriculture: a review

Umberto: Hello again, here goes Delphine Renard and Doyle McKey’s reply to my last post. I am hoping to make this blog an open space for discussion about the Amazon’s past – so I’ll be more than happy to post people’s comments and views on the subjects here reviewed or any other that you might want to put forward for discussion. If you have articles, reviews or announcements you would like to share with other ‘amazonists’ pass them on to me and I will include them in future entries. 

Delphine Renard and Doyle McKey:

Thank you for your interesting comments on our paper. We would like to address two points you made.

First, you consider that some of the hypotheses about functioning of raised-field agriculture are “contradictory” and regret that we don’t “take a position” in these cases.  We see this a bit differently. Some of these hypotheses apply more to some systems and others to other systems. We thus see these hypotheses as complementary rather than contradictory. An example of the difference in our viewpoints is seen, we think, in your criticism that we do not take a position on whether fallows were necessary or not. We do “take a position” on this point. Our “position” includes two points: (1) We think it likely that the need for a fallow period was variable among these systems, depending on soil fertility. The chinampas were built on quite fertile young soils, with volcanic influence and alluvial import. The underlying fertility of this starting material may explain how agriculture can be conducted continuously there. In areas with poorer soils, fallows may have been necessary. Also, pest buildup could well be more rapid in warm lowland sites; escaping pests might thus confer a greater advantage of incorporating fallows in such sites. (2) We think that experimental field studies so far have been of much too short duration to settle the question in any site. As you pointed out in one of your JAS papers, some of these experiments have also had methodological problems that call their results into question.

Secondly, you conclude that better drainage is the only thing all these systems have in common, and wonder why we didn’t conclude the same. We think this view is too narrow, and that different raised-field systems also have other things in common. One of these is the alternation in time and space of aerobic and waterlogged compartments of the ecosystem, which introduces more complexity in nutrient dynamics and could, as we point out in our review, increase nutrient availability to crops. Input of muck from flooded inter-mound areas onto mounds is one way raised-field agriculture could benefit from this, but there are other ways, for example, putting onto mounds mulch from waterlogging-tolerant vegetation that grew in the flooded spaces during a fallow period. We thus think that the mix of waterlogged and aerobic compartments could have been of functional importance in many different raised-field systems.

Finally, we would like to point out that raised fields, like terra preta, are not “magic bullets” for achieving sustainable agriculture, and it is wrong to consider them so. But they could be useful ingredients of solutions. Some of the criticisms leveled at raised-field rehabilitation projects merely reflect paradoxes that we will have to overcome in any attempt to make agriculture ecologically sustainable today—the loss of knowledge and social capital on which such agriculture depends. Transforming agriculture anywhere is going to be difficult. But this doesn’t make it any less necessary, and we don’t think it’s wise to conclude on the basis of studies so far that raised-field agriculture has nothing to offer.