Thursday, 3 November 2011

The extent of human disturbance in pre-Columbian Amazonia

Understanding the extent to which pre-Columbian peoples altered and deforested the Amazon basin is key in order to assess i) the impact that pre-Columbians had on global climate during the Holocene [Dull et al., 2010] and ii) the resilience of the Amazon rainforest to human disturbance [Bush and Silman, 2007]. The first point is essential to our understanding of the major drivers behind climate fluctuations during the Holocene, and hence to help predict future fluctuations. The second point is important to inform conservation and development policies in Amazonia. Unfortunately, the scarcity of archaeological and paleoecological data from the Amazon Basin has favoured the proliferation of “reconstructions of the past” that are hard to test.  Some of these theories have reached broad audiences thanks to the echo provided by popular media and books [Mann, 2005]. New archaeological findings that suggest the existence of complex societies in pre-Columbian Amazonia have led some researchers to define the Amazon Basin as a “manufactured landscape” or an “anthropogenic cornucopia” [Balée and Erickson, 2006; Erickson, 2008].  There are 3 different lines of research that can help assess whether or not these reconstructions are accurate. One is to focus on those regions that host important archaeological remains and study the evidence of complex societies. This work is already being carried out by some archaeologists such as Heiko Prümers. The second area of research is to examine if and how the development of complex societies in the region were influenced by local environmental constraints and opportunities. This is the kind of work that I am carrying out in the Llanos de Moxos and  hope to discuss in another post quite soon J (briefly introduced here…). Another area of research that can help us understand the Amazon’s past is to test if the level of human disturbance associated with the sites where evidence of complex societies has been discovered can be extrapolated to the rest of the Amazon basin.  A milestone paper that looks at the latter, and that has been often cited in this blog, is Bush and Silman (2007).
A few weeks ago, The Holocene published on-line a new paper that delves deep into this question, providing interesting new data [McMichael et al., 2011].  McMichael et al. test the hypothesis that human disturbance was widespread in the Amazon Basin during pre-Columbian times (as some authors have suggested). If this hypothesis is true and the disturbance was widespread then, the authors argue, the sites where permanent settlements were likely to have established should show sedimentary evidence of that disturbance. Hence, they cored lakes (considered by the authors as preferred settlement sites) and sampled soils in the vicinity of the lakes and looked at charcoal and phytoliths. They found that charcoal record was discontinuous and localized. They then concluded, based on the sedimentary evidence: “Our data suggest that while all of the settings examined were occupied or used, the halo of influence around each was limited. It should not be assumed that intensive landscape transformations by prehistoric human populations occurred throughout Amazonia or that Amazonian forests were resilient in the face of heavy historical disturbance”. The paper suggests that pre-Columbians developed into complex societies and substantially altered their environment in those areas where environmental conditions were favourable. They predict that these sites can be found along the main rivers and in those parts of the Amazon Basin that are characterized by a strong seasonality (like the Llanos de Moxos).
In my opinion this paper is a beautiful piece of Science and I invite you to read it!


Balée, W., and C. L. Erickson (2006), Time, complexity and historical ecology, in Time and complexity in historical ecology: studies in the neotropical lowlands, edited by W. Balée and C. L. Erickson, pp. 1-17, Columbia University Press, New York.

Bush, M. B., and M. R. Silman (2007), Amazonian exploitation revisited: ecological asymmetry and the policy pendulum, Frontiers in Ecology and the Environment, 5(9), 457-465.

Dull, R. A., R. J. Nevle, W. I. Woods, D. K. Bird, S. Avnery, and W. M. Denevan (2010), The Columbian Encounter and the Little Ice Age: Abrupt Land Use Change, Fire, and Greenhouse Forcing, Annals of the Association of American Geographers, 100(4), 755-771.

Erickson, C. L. (2008), Amazonia: the historical ecology of a domesticated landscape, in Handbook of South American archaeology, edited by H. Silverman and W. H. Isbell, pp. 157-183, Springer, Berlin.

Mann, C. C. (2005), 1491 New revelations of the Americans before Columbus, Vintage books, New York.

C. H. McMichael, M. B. Bush, D. R. Piperno, M. R. Silman, A. R. Zimmerman, & C. Anderson (2011). Spatial and temporal scales of pre-Columbian disturbance associated with western Amazonian lakes The Holocene : 10.1177/0959683611414932

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