* Note: Following are some sections I’ve extracted from a research paper I wrote some years ago. This article should be read in conjunction with one I posted previously on the Chinampa raised-bed hydrological agriculture. Also relevant are some photos and notes on the Chinampa sites near Xochimilco in Mexico City, from a recent visit. I’ll upload photos to this article. I just need to find out if I can do that without infringing on someone’s copyright. If I can’t upload them I’ll provide links to sites where they can be viewed.
Most of the lowland savannas in South America are seasonally inundated by overflowing rivers or standing rainwater. In the sense that there is a consistent source of water, these regions share some similarities with the lake basins and floodplains on which Mexico’s chinampas were constructed. One major difference is that whereas the chinampas in Valley of Mexico were endowed with perpetual spring-fed water, the raised-bed systems in lowland regions of Amazonia receive water once annually over the period of a long wet season.
The Beni savannas of Bolivia, Los Llanos de Moxos, provide another example of raised-bed wetland agriculture. This is a flat geographic region located at the southwestern headwaters of the Amazonian drainage basin and composed of very poor clay-pan soils low in organic matter, due to infertility there is little attempt to cultivate the region today. Nevertheless, aboriginal people in the Llanos de Moxos did cultivate the savanna, as is evident from the remnants of tens of thousands of ridges, drainage ditches, and raised platforms which provide ground above water and navigational canals for when the savannas were annually inundated (Denevan, 1966b: 84-96). Not only is there ample evidence that these large, flat expanses were cultivated, but such practices were implemented on an intensive, year-round basis for thousands of years. A growing number of researchers believe the Beni once housed “some of the densest populations and the most elaborate cultures in the Amazon” (Mann 2000; Denevan 2001; Erickson 2001, 2006).
Up until recently the artificial earthworks and drainage features of the Llanos de Moxos had only been mentioned briefly. Oil explorations between 1958 and 1961 made available the first aerial photographs of the Moxo savanna, revealing the great extent and complexity of abandoned raised bed hydrological agriculture systems. These initial photos provided sufficient interest to spur on further investigation leading to more accurate estimations regarding the size, number and diversity of raised beds, causeways, irrigation canals and other landscape features (Plafker 1963; Denevan 1963).
Denevan (1966) was the first to provide detailed archaeological evidence that Palaeo-Indians made large-scale changes to the topography of much of the region, which allowed human habitation and food cultivation above the floodwaters. Denevan (1966) concluded that the basic vegetation patterns in the Llanos de Moxos savannahs have been determined by the degree of flooding, which is determined by local relief, but, perhaps most importantly he demonstrated that much of this relief was created by earthmoving activities of the pre-Hispanic peoples of the region. These populations permanently transformed regional ecosystems, creating what Clark Erickson ( 2005) has referred to as a “richly patterned and humanized landscape… one of the most remarkable human achievements on the continent”.
Some of the major elements that can be found in the artificial landscapes of the Beni include causeways, mounds of varying dimensions, a range of types and sizes of raised fields, canals, fish weirs, and circular ditches or moats. Abandoned remains are numerous and can be found throughout the Mojo savanna (Denevan 2001: 23-24; Erickson 2001: 23-25). The chronology for these various earthworks is limited, what evidence has been found indicates that that these societies have worked at modifying and maintaining their landscapes for at least the past three thousand years. All of these various forms of landscape engineering are indications that Moxos savannahs supported intensive fishing and farming industries, supplying, and maintained by, a much larger human population then that which exists in this part of Bolivia today (Maylle et al. 2006).
Clark Erickson has written that, beginning 3000 to 5000 years ago, cultures of the Beni savanna “erected thousands of linear kilometers of artificial earthen causeways and canals, large urban settlements, and intensive farming systems.” Originally Denevan estimated from aerial photographs that the raised field, canals and other earthworks of the region are estimated to cover an area of 77,000 square kilometers of land (Denevan 1966). However, based on more recent findings from ground surveys and enhanced satellite imagery, Erickson suggests that anthropogenic landforms cover a much larger area, demonstrating many raise fields are either under dense tree canopy or apparent only in faint traces often undetectable with the naked eye (Erickson, unpublished article).
Recent research from a variety of disciplines has steadily accumulated revealing more details and an altogether greater understanding of the Moxo savanna earthworks. The agricultural fields, or platforms, can vary greatly in terms of dimensionality but for the most part they were elongate and rectangular in shape, spaced anywhere from ten to a hundred feet apart and ranging from one to twenty five meters in width. Some of the larger fields extend to over three hundred meters in length. Smaller raised platforms typically occur in groups between several hundred and several thousand individual, sometimes interconnected, bodies. Interestingly while some fields are in parallel alignments, others angle off obliquely. These varying features have been interpreted as relating to the direction of natural flow of the water, or to unknown customs regarding sacred alignments. All in all there are tens of thousands of raise fields extending across the vast, flat landscape, highly indicative of large, well-organized populations (Denevan 1966: 85).
Circular mounds (lomas) are also common through the area, especially within peripheral gallery forests. The mounds have been variously interpreted as garbage piles, house mounds, ceremonial mounds or burial mounds. Linear ridges serving as causeways often radiate from mound sites, often connect mounds and forest islands. Based on the centrality of the mounds it is likely that they served as settlements, inhabited by up to a few thousand people. Judging by the overarching logic and intelligence behind the greater system it is unlikely that the populations produced and accumulated waste, as is typical of western cultures. Instead it appears as if waste was synonymous with building materials, fertilizers and other structural components. The composition of raised beds, causeways and fish weirs suggest that primarily “trash” served as a vital construction material (Erickson 2005: 235-267).
The causeways, which have been said to be one of the most spectacular features of Moxo landscapes, are thought to have performed multiple functions, for transportation, hydraulic control and as boundary markers. Major canals flanking either side of the causeways were most likely built both for transportation purposes and to regulate water levels within the system, diverting water to and from streams and rivers. Other highly impressive earthworks discoveries are the many complex networks of linear zigzag structures that have been interpreted by Clark Erickson (2000) to have functioned both as levees and fish weirs, used seasonally to capture and contain both water and edible water fauna. Erickson has conducted the most extensive archeological studies in the area and conclusively interprets all major features of the landscape as anthropogenic due to their “unnatural” shapes and because they have been found to be constructed from an assortment of materials not typically found in the area, including rock, ceramic, sticks and basketry (Maylle et al. 2006).
When were these landscapes constructed? How long were they were used? When were they abandoned? As of yet, none of these questions have been adequately answered, or empirically proven. Although, in regards to the latter question, as with the chinampas of Mexico, it is widely believed that the Conquest played a staring role in the demise and desertion of Moxo settlements. The Beni region of Bolivia was one of the last to be invaded and conquered. Local Indian populations were successful in building a reputation of ferocity thus deterring the European enemy for a time. There are a number of theories: one is that the extensive systems were preemptively abandoned in expectation of the imminent onslaught of ravenous Europeans. Under these circumstances it is thought that the many interconnected villages and societies would have necessarily fragmented, migrating to surrounding areas. Another possibility is that illnesses was brought to the continent by the Europeans, such as smallpox, which may have arrived to the Beni region before the Europeans did, effectively eliminating sufficient numbers of people to force abandonment. Interesting is the detail that the Beni savanna was pegged for a longtime as being a potential location of the fabled city of El Dorado. It is said that when the Spanish finally arrived to the region, upon seeing no golden paradise they promptly left, not to return for another few hundred years when in search of oil deposits (Mann 2000).