woensdag 15 september 2010

Written on the land (geoglyphs & others)

Amazonian Geoglyphs number in the thousands and are truly spectacular, let's look at the sources and find a google.map here and the Portguese website of Denise Schaan here.

Ring ditch sites are reported in the Bolivian Amazon, Matto Grosso, Acre, and Upper Xingu River regions (Erickson 2002; Heckenberger 2005; Parssinen et al. 2003; Ranzi and Aguiar 2004). These sites consist of a closed or U-shaped ditched enclosure or multiple ditches. Heckenberger (2005) describes numerous sites with large open plazas and radial roads marked by earthen berms extending through residential sectors enclosed by deep semicircular moat-like ditches and embankments. Early explorers described villages that were protected by wooden palisades and moats. If palisaded, a typical ring ditch site would require of hundreds or thousands of tree trunks, a considerable environmental impact. Ring ditch sites in Acre and the Bolivian Amazon, described as geoglyphs because of their impressive patterns (circular, oval, octagon, square, rectangle, and D-shapes), appear to be more ceremonial than residential or defensive. Some ring ditch sites are associated with ADE [Amazonian dark earths]. Modern farmers in the Bolivian Amazon intensively farm these sites and those covered with forest are good locations for hunting game and gathering fruit.
Anthropologist William Balee stands in a ditch that marks the perimeter of a geoglyph in the forest. Paleontologist Alceu Ranzi stands at the top of the interior wall

The earthworks found in western Amazonia were named geoglyphs by Alceu Ranzi, the scholar who first saw them from an aircraft and realised they were built by pre-Columbian societies. Geoglyphs can be defined as marks on the surface of the earth, whose dimensions make them better seen from above. Indeed, regardless of the function that the excavated ditches and associated walls had in the past, their perfect geometry speaks of their symbolic significance.

The fact that the Amazonian geoglyphs have only been noticed and publicised in the last few years deserves an explanation. After their abandonment, which we believed happened at least 500 years ago, they were heavily covered by vegetation. In the last 30 years, however, areas once believed to be pristine forest began to be cleared for the cattle industry. In their new treeless, savanna-like landscape, the ancient earthen structures became visible, especially from the sky. If they were initially visible from aeroplanes, researchers can now search for them using satellite imagery freely available in Google Earth. Aerial remote sensing has in fact been more efficient than ground survey, since some structures are filled in by recent sedimentation, and thus hard to see at ground level. In fact, their enormous size makes it easier to distinguish their shape and configuration from an aerial perspective. Preliminary surveys in a number of sites have been done in several short field seasons. In general, the geometric figures are formed by a ditch approximately 11m wide, currently 1-3m deep, with adjacent 0.5-1m high earthen banks, formed by deposition of the excavated soil. Ring ditches have diameters that vary from 90 to 300m. The circular structures are more common in the south, while composite and rectangular structures become more frequent as one moves north. When there are two or more structures, they are usually connected by embanked roads. Some of the single rectangular structures may have short roads coming out of their mid-sides or corners. Composite figures include a rectangle inside a circle or vice versa.

The function, or functions, of the geoglyphs remain a mystery. A nineteenth-century historical account gives a dubious clue, since it is not clear whether the explorer is talking about these geoglyphs, although he mentions the existence of a ditch in an Indian village in the area where geoglyphs are found today. Chandless (1866: 3) describes how, descending the Aquiry (today Acre) River, he observed that the Indians fled, leaving their belongings behind in fear, before they could reach them:
‘All that was portable they had taken . . . This village [maloca] seems to be the main one, and, so to speak, the capital of the nation. It has 3 or 4 houses, or, better stated, huts with open sides; of good size and well made; another, quite apart, all closed, and with an entrance of only three open hands tall, which is the storage room for things for festivities, some very curious as we discovered when we returned. Between the storage room and the houses there is a trench [sketched], the extremities leaving only a small entrance, next to the forest. This we thought to be a defensive work; but the Indians later told us that was no more than an arrangement for parties’. entrance, next to the forest. This we thought to be a defensive work; but the Indians later told us that was no more than an arrangement for parties’.
As laconic as this passage may seen, it is a reference to a possible reason for the earthwork’s construction – e.g. related to feasts and possibly ceremonies – although it has to be considered that the region had already gone through profound demographic transformations when Chandless travelled up the river in the 1860s. The people who then occupied the land had not necessarily built the geoglyphs.

Listen Charles C. Mann (Ancient Earthmovers Of the Amazon):
Researchers are still puzzling over whether and how these earthworks fit together and what they reveal about the people who created them. But already the implications of these enormous endeavors are clear, says Clark Erickson, a University of Pennsylvania researcher who has been working in the area with Bolivian colleagues since 1995. Far from being trapped by the Amazon’s ecological obstacles, he says, these large populations systematically transformed the landscapes around them. One example: Because geoglyphs cannot readily be constructed or even seen in wooded areas, the researchers argue that people must have made them at a time when the region had little tree cover—meaning that in the not-too-distant past the great forests of the western Amazon may have been considerably smaller. Not only did the peoples of western Amazon  alter their environments, but they also transformed the biota in them. Emerging evidence suggests that this little-known region may have been a place where long ago farmers first bred some of the world’s most important crops. In Erickson’s view, western Amazonia serves as a model of how human beings create and maintain productive landscapes from even the most apparently limited environments. the new findings show that the region was “a cosmopolitan crossroads” between the societies of the eastern Amazon and the
Andes, of whom the most famous were the Inka, says Susanna Hecht, a geographer at the University of California, Los Angeles: “You have every language group in lowland South America represented there.” She adds, “It was a major cultural center—and it’s incredible that this is just coming out.”
Causeways between two forest islands.

The study region is unpopulated today; thus, the earthworks are remarkably well preserved in contrast to areas subject to heavy cattle grazing. All surveyed forest islands larger than 1 km2 have ring-ditch sites of diverse size and shape: octagons, hexagons, squares, rectangles, “D” shapes, circles, ovals, and irregular shapes (Erickson 2002, 2006a, 2008; Erickson, Winkler, and Candler 1997; Vranich 1996) (Figure 10.3). Large forest islands have multiple, evenly spaced, ring-ditch sites. Ditches are often several meters deep and steep sided and some extend 1–2 linear km and include multiple concentric rings. The Jesuits described these features as forts with deep moats and palisades (Anonymous 1743; Eder 1985) (Figure 10.4). Although few have been investigated archaeologically, ring-ditch sites may have been cemeteries, sacred spaces, elite residences, settlements, and/or defensive structures. These features also are documented for Riberalta, Bolivia (Arnold and Prettol 1989), and the Acre and Upper Xingu river regions of Brazil (Heckenberger 2005; Pärssinen and Korpisaari 2003).
Although similar in shape and scale to the large circular villages with central plazas of the Central and Eastern Amazon basin (Wust and Baretto 1999; Heckenberger 2005, 2008), the ring-ditch sites of the Baures Region, Riberalta, and the Acre region tend to lack evidence of domestic activity, which suggests non-residential use. The Jesuits were impressed by the larger settlements, but also describe dispersed, dense occupation throughout the forest islands. As an early strategy of control and indoctrination, the Jesuits resettled peoples in their new mission towns, a settlement system that continues today. Archaeologically, settlements are difficult to document due to thick vegetation and soil cover and the ephemeral nature of Amazonian residential structures. Today, individual households often maintain several houses in different locations for farming and resource collection. A vast network of raised earthen causeways and canals provided a landscape of movement to connect these important places. A causeway is defined as a formal, intentionally raised road, usually of locally obtained earth. A canal is an intentionally excavated linear feature intended to hold water seasonally or permanently or simply the result of building causeways. 
Causeways and canals are usually associated as combined landscape features in the BHC. Causeways and canals vary in length from tens of meters to many kilometers. Most causeways and canals are straight. Many form radial patterns from a common source, usually located on a forest island. Most causeways and canals are associated with low-lying, seasonally or permanently inundated savannas or wetlands, although some penetrate the higher ground of forest islands. 

Listen to Doyle McKey et al (Pre-Columbian agricultural landscapes, ecosystem engineers, and self-organized patchiness in Amazonia) for research on human-made earthen water-managing cushions that have been invaded by critters (image above):
Combining archeology, archeobotany, paleoecology, soil science, ecology, and aerial imagery, we show that pre-Columbian farmers of the Guianas coast constructed large raised-field complexes, growing on them crops including maize, manioc, and squash. Farmers created physical and biogeochemical heterogeneity in flat, marshy environments by constructing raised fields. When these fields were later abandoned, the mosaic of welldrained islands in the flooded matrix set in motion self-organizing processes driven by ecosystem engineers (ants, termites, earthworms, and woody plants) that occur preferentially on abandoned raised fields. Today, feedbacks generated by these ecosystem engineers maintain the human-initiated concentration of resources in these structures. Engineer organisms transport materials to abandoned raised fields and modify the structure and composition of their soils, reducing erodibility. The profound alteration of ecosystem functioning in these landscapes coconstructed by humans and nature has important implications for understanding Amazonian history and biodiversity. Furthermore, these landscapes show how sustainability of food-production systems can be enhanced by engineering into them fallows that maintain ecosystem services and biodiversity.

Image: Washington Post

90 settlements found, the above shows a water reservoir, waiting for a proper paper.

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