Fire is the oldest and most powerful technology of environmental creation, transformation, and management available to native people (Figure 11.1). Thousands of fires can be detected daily on satellite imagery of Amazonia. For most natural scientists and conservationists, fires caused by humans are considered to be the worst threat to Amazonian rainforests and biodiversity. Complex fire histories documented in lake sediment cores, soil stratigraphy, and archaeological sites suggest that humans regularly burned Amazonia in the past (Oliveira and Marquis 2002; Lehmann et al. 2003; Sanford et al. 1985). Anthropogenic fires are distinguished from natural fires by their regularity, context, timing, and patterns (Pyne 1998).
Hunters and gatherers burn landscapes to remove old vegetation for new to attract browsing game, clear the understory for easier movement and harvesting of wild plants, encourage economic species attracted to light gaps and disturbance, and hunt game through cooperative drives employing fire and smoke. Farmers employ burning to clear and prepare
Figure 11.1. Savanna management using fire in the Bolivian Amazon. Baures in 1999. (Clark Erickson)
Fields, gardens, orchards, and settlements, fertilize fields, incinerate garbage, and reduce bothersome insects (Pyne 1998). Regular burning prevents runaway fires stoked by accumulated fuel. Burning and the production of charcoal is a key element in the formation of Amazonian Dark Earth (discussed below).
Most scholars now agree that fire plays a key role in the creation and maintenance of Amazonian environments, in particular savannas and dry deciduous forests that cover much of Amazonia (Langstroth 1996; Oliveira and Marquis 2002).
Settlement and Associated Landscape
Human settlements may be one of the most persistent and permanent transformations of the Amazonian environment. Scholars have recorded a wide variety of settlement types and regional settlement patterns for past and present Amazonian people (Denevan 1996; Duran and Bracco 2000; Erickson 2003; Heckenberger 2005; Neves and Petersen 2006; Roosevelt 1991; Wust and Barreto 1998). While most settlements were small (less than 1 ha), the archaeological site under the present day city of Santarem in Brazil covers 4 km2 and the Faldas de Sangay site in Ecuador is possibly 12 km2 (Roosevelt 1999). Traditional communities had large, open, clean central plazas and streets along which houses were arranged in linear, grid, radial, or ring patterns.
The typical Amazonian house is a simple example of resource use and local landscape transformation (Figure 11.2). The foundation requires 4 to 6 upright wooden posts plus additional beams (each representing a tree). Earthen floors are often raised 10-20 cm for drainage during the wet season (1.5-3.0 m3 for a 3 x 5 m house). Thick layers of palm and grass thatch cover the roof. A typical Pume community would require 13,498 fronds of palm which is replaced every 2 to 3 years, and 750,000 fronds from 125,000 palms for a large communal house of the Bari (Gragson 1995). Vegetation around the house is cleared to bare ground for protection against snakes and for aesthetic reasons. A small but densely packed house garden is established for spices, colorants and dyes, medicinal
Figure 11.2. Amazonian house, clearing, work areas and house garden. Fatima in 2006. (Clark Erickson)
Plants, tobacco, cotton, hallucinogens, and fish poisons. The garden is also a compost pile for kitchen waste. In humid tropical regions, houses last 5 to 10 years. In summary, the environmental impact of a single house is profound: rearranging and altering soils, accumulation of organic matter through garbage and human wastes, deforestation and opening of forest canopy, cutting of construction and roofing materials, replacement of natural vegetation with economic garden, crop, and orchard species, and mixing of the soil horizons. Denevan (2001) estimates a pre-European conquest native population of 6.8 million for Amazonia. Assuming 5 people per household, some 1,360,000 houses were required in a single moment. The environmental impact described above for a single household is now multiplied by over one million houses across the landscape.
House gardens were associated with individual residences and there was a larger clearing for staple crops in the forest with raised fields in savannas and wetlands or on exposed river banks beyond the settlement. Stream channels and wetlands were criss-crossed with fish weirs (corrals for harvesting fish). Any standing forest within a 5-km radius was a managed forest. Pathways were hacked through the forest and roads within settlements were often raised or defined by earthen berms, and other infrastructure. In the savannas, large earthen causeways with adjacent canals served as roads and canoe paths. In addition, each settlement required firewood, game, fish, and other wild resources in quantity.
A community’s permanent transformation of the environment for these basic needs and infrastructure is staggering (Figure 11.3). As a result, the forested environments that are typical today were scarce in the past and of a much different character. Based on the archaeology, these communities were stable, long-lived, and sustainable despite this impact.
Figure 11.3. The Amazonian settlement and adjacent landscape of gardens, fields, agroforestry, roads, paths, orchards, garbage middens, and forest regrowth at various stages. The dark circular feature in the center is a precolumbian ring ditch site. Jasiaquiri, Baures in 2006. (Clark Erickson)
Mounds
Many Amazonian cultures were impressive mound builders (see chapters in Part IV of this volume) (Denevan 1966; Duran and Bracco 2000; Erickson and Balee 2006). Farmers built mounds in the Llanos de Mojos of Bolivia, Marajo Island and the lower and central Amazon basin and Pantanal of Brazil, the Llanos de Venezuela, Mompos basin of Colombia, Sangay in the Upano Valley and Guayas Basin of Ecuador, and the coastal plains of Guyana, Brazil, Uruguay, and Ecuador. Mounds were constructed of earth with the exception of the sambaquis of coastal Brazil which are primarily of shell. Excavations show that many mounds served multiple functions, often simultaneously. Mounds generally contain fill or layers of domestic debris (bones, shell, and other organic food remains, pottery, and stone tools) typical of settlements. Some mounds have such a high percentage of broken pottery that scholars apply the term “potsherd soils” (Langstroth 1996). Mounds were formed over considerable time through the collapse and leveling of wattle and daub buildings, accumulation of refuse and construction debris, and the intentional addition of fill from adjacent large borrow pits, often filled with water. Mounds in the Llanos de Mojos and on Marajo Island contain hundreds of human burials in which a large pottery urn with lid was used for a coffin (Nordenskiold 1913; Roosevelt 1991). Other mounds were used as chiefly residences or ceremonial centers (Rostain 1999; Lopez et al. 2002).
Although most are small, the Ibibate Mound Complex in the Bolivian Amazon covers 11 ha and is 18 m tall with over 250,000 m3 of fill (Erickson and Balee 2006). Mounds
Are often found in groups of up to 40 for Marajo Island (Roosevelt 1991), and more than 50 mounds for the Huapula site (Rostain 1999). Mounds, as highly visible monumental features on the landscape, were probably a source of civic pride, a place where ancestors were buried in urn coffins, and an elevated spot above annual floodwaters to establish residences, gardens, cemeteries, ceremonial centers, elite complexes, and public space.
Mound construction required mass movement of soils, transformation of local topography, soil enrichment, and change in vegetation composition. Our study of the Ibibate Mound Complex in the Bolivian Amazon demonstrates that the biodiversity on the mounds was much significantly richer than that of the surrounding landscape and consists primarily of economic species, some 400 years after abandonment as a settlement (Erickson and Balee 2006).
Anthropogenic Forest Islands
Forest islands are common throughout the savannas and wetlands of Amazonia (Figure 11.4).
Forest islands range in size from a few hectares to many square kilometers. Most are raised less than one meter and often surrounded by ponds or a moat-like ditch. Excavations in forest islands in the Llanos de Mojos and Pantanal document their anthropogenic origins and use for settlement, farming, and agroforestry (Erickson 2000a, 2006; Walker 2004; Langstroth 1996). In Bolivia, archaeologists estimate the existence of 10,000 forest islands (Lee 1995; CEAM 2004). The Kayapo of Central Brazil create forest islands (apete) of improved soils through additions of organic matter from household middens and recycling of crop debris for intensive cultivation of crops (Posey 2004; Hecht 2003). These anthropogenic features are known for their high biodiversity and agrodiversity.
Figure 11.4. Forest island in the savanna, Machupo River, in 2006. (Clark Erickson)
Ring Ditch Sites
Ring ditch sites are reported in the Bolivian Amazon (Figure 11.5), 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 (Figure 11.6). Some ring ditch sites are
Figure 11.5. Precolumbian ring ditch site. The main ditch is approximately 3 m deep. A smaller ditch can be seen to the left. Baures in 2006. (Clark Erickson)
Figure 11.6. An octagon-shaped ring ditch site in the Bolivian Amazon. The ditch measures 108 m in diameter and 2 m deep. Santiago, Baures in 2006. (Clark Erickson)
Associated with ADE. Modem farmers in the Bolivian Amazon intensively farm these sites and those covered with forest are good locations for hunting game and gathering fruit.
Amazonian Dark Earth (ADE)
As discussed earlier, soils have been central in debates about environmental potential and cultural development in Amazonia and play a major role in enhancing resource biodiversity and biomass. Rather than adapt to limited soils, we now recognize the ability of Amazonian farmers to improve and manage marginal tropical soils through creation of settlement mounds, forest islands, raised fields, and Amazonian Dark Earth (ADE).
ADE or Indian black earth (terra preta do indio) is an important subclass of anthrosols or anthropogenic soils and associated with archaeological sites (Smith 1980; Erickson 2003; Lehmann et al. 2003; Glaser and Woods 2004; Neves and Petersen 2006). A lighter color ADE, terra mulata, often surrounds terra preta. ADE is estimated to cover between 0.1 to 10% or 6000 to 600,000 km2 of the Amazon basin. ADE sites range from less than one hectare to as large as 200 ha in size. ADE was probably used for settlement, house gardens, and permanent fields rather than slash-and-burn agriculture, the common practice today. Scholars believe that these soils were created specifically for permanent farming. Today ADE is prized by farmers for cultivation and in some cases, mined as potting soil for markets in Brazilian cities.
ADE is a rich in typical domestic debris found in archaeological sites including potsherds, bone, fish scales, shell, and charcoal. The extremely dark color and fertility is due to large quantities of charcoal and other organic remains that sharply contrast to the surrounding poor reddish tropical soils. In contrast to slash-and-burn agriculture where complete combustion of felled forest is the goal, ADE farmers practiced “slash and char,” a technique to produce biochar or charcoal through low temperature, incomplete combustion in a reduced atmosphere. Biochar has been shown to be a high quality soil amendment for enhancing and maintaining soil fertility over hundreds of years. In addition, ADE is a rich habitat for beneficial microorganisms. Once established, ADE is a living entity that may sustain and reproduce itself (Woods and McCann 1999). The presence of intact ADE after 400 to 500 years is evidence its permanence, sustainability and resilience. Ethnobotanical studies document high biodiversity on ADE (Balee 1989; Smith 1980). The number of soil microorganisms in ADE alone may be quite large. Although understudied, potential contribution of microorganisms in ADE to overall biodiversity is substantial.
If ADE was formed as the simple unintentional byproduct of long-term residence in a locale, we would expect to find black earth sites at any location where past human occupation was dense and of long duration. Archaeological sites fitting these criteria are common throughout Amazonia but do not have ADE. This suggests that ADE formation, which involves careful production of biochar and management of soil microorganisms, is intentional soil engineering. ADE is an excellent example of landscape domestication below the ground.
Raised Fields
Raised fields are probably the most impressive example of landscape engineering at a regional scale in Amazonia (Denevan 1966, 2001; Erickson 1995, 2006; Walker 2004). Raised fields are large platforms of earth raised in seasonally flooded savannas and permanent wetlands for cultivating crops (Figure 11.7). Excavations and agricultural experiments suggest that raised fields served multiple functions, including drainage of waterlogged
Figure 11.7. Precolumbian raised fields, canals, and causeways in the Bolivian Amazon. The clearing is now a ranch and the causeways are used as paths. San Ignacio in 2006. (Clark Erickson)
Soils, improvement of crop conditions (soil aeration, mixing of horizons, and doubling of topsoil), water management (drainage and irrigation), and nutrient production, capture, and recycling in canals alongside each platform. Crop production in experimental raised fields is impressive and up to double that of non-raised fields (Erickson 1995, 2006; Stab and Arce 2000; Saavedra 2006). Based on high productivity and substantial labor costs to construct, raised fields were probably in continuous production. In addition to traditional crop cultivation on the platforms, aquatic resources such as edible fish, snails, reptiles, and amphibians could be raised in the adjacent canals. Canals also trap organic sediments and produce organic “green manure” and “muck” that can be periodically added to the platforms for sustained cropping.
Raised field agriculture represents a massive landscape transformation at a regional scale through rearranging soils, changing hydrology, and imposing a heterogeneous microtopography of alternating terrestrial and aquatic ecosystems on landscapes that originally were relatively flat and biologically homogeneous and of limited production. Landscape engineering of this magnitude substantially increased biodiversity and biomass in savannas and wetlands. The presence of raised fields in deep forests of the Bolivian Amazon suggests that the landscape was open savanna maintained by regular burning when the fields were used. After abandonment and cessation of burning, forests returned with trees arranged in orchard-like rows on the eroded raised fields.
Transportation and Communication Networks and Water Management
Transportation and communication networks in the present and past have significant environmental impacts at the local and regional scale. Paths, trails, and roads connect settlements
And people and, like modern roads, bring development and new settlements, expand farming, and cause environmental change. All Amazonian societies use elaborate networks of paths and trails and roads between settlements, gardens, fields, rivers, resource locations, and neighbors. The Kayapo maintain thousands of kilometers of paths (Posey 1983 in Denevan 1991). Posey (2004) documents subtle anthropogenic impact along Kayapo paths created by the discard of seeds from meals and snacks and transplanting of economic species along path clearings. These resources also attract game animals, making them easier to find and hunt. The long linear disturbance and light gap created by clearing and maintenance of paths produces distinct anthropogenic vegetation communities that penetrate deep into the forest.
Some advanced Amazonian societies built impressive formal roads, causeways, and canals of monumental scale (Figure 11.8). Large and small sites in the Tapajos and the Upper Xingu regions are connected by traces of networks of straight roads with earthen berms suggesting hierarchical socio-political organization at a regional scale (Nimuendaju 1952; Heckenberger 2005). The earliest explorers of the Amazon River reported similar wide straight roads connecting large riverine settlements to the distant hinterlands (Denevan 1990).
The late pre-Columbian inhabitants of the Llanos de Mojos and Baures regions in the Bolivian Amazon completely transformed the environment into a highly patterned landscape of complex networks of raised earthen causeways and canals (Denevan 1990;
Erickson 2001, in press). These earthworks had multiple functions including transportation and communication, water management and production of aquatic resources, boundary and territorial markers, and as monumental ritual and political statements. Their
Figure 11.8. Four precolumbian causeways and canals connecting forest islands in the Bolivian Amazon. The palm covered causeways are 3 to 4 m wide and 1 m tall with adjacent canals of 2 to 3 m wide and 1 m deep. Baures in 2006. (Clark Erickson)
Construction was often intended for water management and the creation of artificial wetlands at the local and regional scale. On near flat savanna, a causeway of 1 m tall and 2 km long between the high ground of two adjacent river levees could potentially impound 5 million m3 of water. Canals brought water for irrigation and provided drainage when necessary.
Amazonians are classic canoe people and transport and communication by water is a basic element of tropical forest culture (Lathrap 1970; Lowie 1948). Most Amazonian people would rather paddle a canoe than walk. Nordenskiold (1916) pointed out that most of the major headwaters of Amazonian river drainages connect to the headwaters of adjacent river drainages. Some of these aquatic connections such as the Casquiare Canal between the major Negro and Orinoco drainages and the Pantanal between the Guapore and the Paraguay drainages are partially anthropogenic. Artificial river meander short cuts are common in the Llanos de Mojos of the Bolivian Amazon, Amapa Region of the Central Amazon basin, and the Ucayali River of Peru (Abizaid 2005; Denevan 1966; Nordenskiold 1916; Raffles and Winkler-Prins 2003). The large meander loops of typical rivers of Amazonia are challenges to canoeists, often requiring hours or even days of paddling to move short lineal distances. The problem is solved by cutting short linear canals or repeatedly dragging a heavy dugout canoes in the same location between the neck of a large looping meander to save travel time. In a number of cases, these anthropogenic canals created a new river course, dramatically and permanently changing the regional hydrology.
Inter-river canals are common in the Llanos de Mojos of Bolivia. Pinto (1987) describes a complex network of natural channels combined with artificial canals to allow canoe traffic over 120 km perpendicular to natural river flow. In other cases, artificial canals tapping the headwaters of two adjacent rivers diverted the flow of one into the other permanently transforming the hydrology of two drainage basins (CEAM 2003).
Fisheries Management
Fishing is now recognized as the major traditional source of protein in the Amazon basin (Chernela 1993; Beckerman 1979; Erickson 2000b). In contrast to other civilizations that domesticated fish, Amazonian people artificially enhanced the natural habitats of wild fish to increase availability through creation of artificial wetlands and expanding the capacity of existing wetlands through construction of raised field canals, causeways and other water management techniques.
The Baures region of Bolivia is an excellent example of landscape domestication for the improvement of natural fisheries (Erickson 2000b). Low linear earthen ridges zigzag across the seasonally inundated savannas between forest islands with funnel like opening located where the earthworks changed direction (Figure 11.9). These features are identified as fish weirs based on descriptions in the ethnographic and historical literature. Fish weirs are fences made of wood, brush, basketry, or stones that extend across bodies of water. Baskets or nets are placed in openings to trap migrating fish. Most fish weirs are simple ephemeral structures on a river or shallow lake. In contrast, the fish weirs of Baures are permanent earthen features covering more than 550 km2. Small artificial ponds associated with the weirs are filled with fish and other aquatic foods when the floodwaters recede. These were probably used to store live fish. Through fisheries management, the native people of Baures transformed savannas and wetlands into a productive landscape capable of providing hundreds of tons of protein to sustain large populations.
Figure 11.9. A network of precolumbian fish weirs in the Bolivian Amazon. The brush covered fish weirs measure 1 m wide and 50 cm tall. Straight features at the top and bottom of the image are causeways and canals, and circular features are artificial fish ponds. Baures in 1999. (Clark Erickson)
Agroforestry
Countering the view of Amazonian forests as pristine and natural, historical ecologists show that these forests are, to a large degree, the cultural products of human activity (Balee 1989; Balee and Posey 1989; Denevan and Padoch 1988; Posey 2004). Amazonian people past and present practiced agroforestry: tree cultivation and forest management (Peters 2000).
Analysis of pollen, opal phytolith, and sediment from lakes document local and regional anthropogenic disturbances of Amazonia over thousands of years including burning, clearing, farming, and agroforestry (Piperno and Pearsall 1998; Mora 2002; Piperno et al. 2000). Much of what was originally misinterpreted as natural change due to climate fluctuations is now considered anthropogenic. Records show a steady increase of “weeds” and secondary forest species, many of which are economic species, and later domesticated crops that thrive in open conditions and heterogeneous mosaic of forest and savanna and intermediate states created by human disturbance. At the same time, the frequency of species characteristic of closed canopy forests decreases until the demographic collapse after 1491. Fire histories are also documented in association with the formation of the anthropogenic forest. Evidence of fruit and nut tree use and human disturbance is documented by 10,500 years ago in the Central Amazon (and see discussion of dates in the Colombian Amazon in Roosevelt 1996; Mora 2002; see discussion of evidence for domesticated crops at some sites in Amazonia in Piperno and Pearsall 1998; Piperno et al. 2000; see also Chapter 12 in this volume).
The long-term strategy of forest management was to cull non-economic species and replace them with economic species. Sometimes, this involves simple thinning, planting, transplanting, fertilizing, coppicing, and weeding of valued species to enhance their productivity and availability. Many wild plants are often found outside their natural range due
To transplanting, cultivation, and habitat improvements. In other cases, wild and domesticated trees are tended as orchards. Useful plants that in the distant past relied on natural forces now depend increasingly on humans for seed dispersal, survival, and reproduction.
Slash-and-burn agriculture is characterized by low labor inputs, limited productivity per land unit, and short period of cultivation followed by longer periods of fallow or rest. Historical ecologists point out that slash-and-burn fields are never truly abandoned and unproductive during fallow. In Amazonia, agriculture is combined with agroforestry. In the initial cutting and burning to clear a field or garden, certain economic species are left to thrive while unwanted species are removed. In addition to basic food crops, useful fruit and palms are often transplanted to the clearing. As fields fall out of cultivation because of weeds and forest regrowth, the plots continue to produce useful products, long after “abandonment”.
Anthropogenic forests are filled with fruit trees, an important component of agroforestry. Eighty native fruit trees were domesticated or semi-domesticated in Amazonia (Clement 2006). Fruit trees, originally requiring seed dispersing frugivores attracted to the juicy and starchy fruits, became increasingly dependent on humans through genetic domestication and landscape domestication for survival and reproduction. In addition, humans improved fruit tree availability, productivity, protein content, sweetness, and storability through genetic selection. Oligarchic forests, characterized by a single tree species, often a palm, provide mass quantities of protein and building materials, and food for the game animals. In the Bolivian Amazon, thousands of kilometers of the buriti palm, the Amazonian tree of life, contributes protein and materials for buildings, basketry, weapons, and roofing. Forest islands of chocolate trees are agro-forestry resource legacies of the past inhabitants of the region (Erickson 2006).
Agroforestry and farming also attract game animals that eat the abundant crops, fruits, and nuts. Farmers often grow more food than necessary to attract game. As a result, “garden hunting” is a particularly efficient (Linares 1976). Many game animals of Amazonia would have a difficult time surviving without a cultural and historical landscape of human gardens, fields, orchards, and agroforestry. The biodiversity of animals can also be enhanced by domestication of landscape. In coastal Ecuador, Stahl (2000, 2006) reconstructs biodiversity and the character of the anthropogenic environment through the remains of diverse animals in garbage middens of 4,000-year old settlements. The majority of identified animals thrive in a disturbed mosaic environment with light gaps, edges, old gardens and field clearings.
Even hunters and gatherers contribute to anthropogenic forests. The nomadic Nukak of the Colombian Amazon change campsites 70 to 80 times a year (Politis 1996). When establishing a new location, a small number of trees are felled and hundreds of palm fronds are collected for construction of a simple lean-to structure. Wild fruits and nuts are collected and some end up discarded. After the camp is abandoned, palm seeds take root in the clearing and thrive. Repeated over hundreds of years, the selective cutting of trees for nomadic camps, creation of small light gaps or openings, and distribution of seeds can substantially change the forest composition to one rich in economic species of plants and animals.
While agroforestry focuses on management of certain economic species, studies show that overall biodiversity may be enhanced in anthropogenic forests (Peters 2000; Balee 1994, 2006). The Ibibate Mound Complex in the Bolivian Amazon is a well studied case of a biologically diverse anthropogenic forest (Erickson and Balee 2006). Surveys of forest growing on pre-Columbian mounds abandoned 400 years earlier and
Non-mounds were compared showing a significantly higher biodiversity in forest on the mounds, in addition to non-local economic species. Economic studies show that anthropogenic forests are more valuable for sustainable collection of renewable resources than logging (Balick and Mendelsohn 1992).
World History
