13th Pan-African Association Congress and 20th Society of Africanist Archaeologists Conference (Dakar, Senegal; November
Finding and Protecting Heritage Resources: Predictive Modeling in Sabodala, Senegal
Richard Ciolek-Torello, Jeffrey H. Altschul, Gerry Wait, and William Hayden
Like many other regions of the world, development threatens the cultural heritage of Senegal with few financial resources and weak laws to turn to for protection. One of the first steps in preserving heritage resources, however, is identifying and protecting the resources that are at greatest risk. GIS technology, used under the rubric of predictive modeling, provides an efficient and cost effective tool for this purpose. Predictive modeling uses existing information on heritage resources and the local landscape to predict the number and locations of settlements and resource loci and to infer cultural behaviors that may have produced these distributions. The models generated by this process are evaluated by on-the-ground sample surveys, test excavations, and ethnographic interviews. The new data derived from the evaluation are incorporated into the model to identify those areas that are most sensitive to development (have the highest density or most important sites) and those areas that are at greatest risk (where most development or most destructive development is taking place), as well as to assess survey adequacy. In this presentation, we discuss the methods and results of recent investigations in the Sabodala region of southeast Senegal where SRI, in association with Nexus and IFAN, developed and tested a predictive model of heritage resources threatened by a large mining project.
Agricultural Sustainability in the Soudo-Sahel: Climate Change and the Application of Traditional Knowledge to Enhance Agricultural Productivity
Diane L. Douglas, Jeffrey A. Homburg, and Mark Vendrig
Analysis of physical and chemical soil properties of agricultural fields in southeastern Senegal was completed to assess the soil quality and sustainability of traditional agricultural practices in this region, and to assess the vulnerability and resilience of these practices to climate change. Although the current climate of southeastern Senegal is tropical, it is located on the boundary of the Sahel and Soudan zones, has a short wet season and is prone to drought. Sediment cores extracted from the eastern Atlantic Ocean, lakes and other water bodies provide evidence of both long-term (1000’s of years) and short term (30 to 70 years) dry and wet cycles in the Sahel. The longer cycles are likely driven by variation in earth’s orbit and solar output and the shorter cycles by variations in the El Nino Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), Indian Ocean sea surface temperatures, and solar output. Our paper examines the timing and amplitude of past drought cycles in western and northeastern Africa since the last ice age to provide a context for understanding the range of climate change that may occur in the region in the future. Natural cycles of climate change can create drought conditions that trigger desertification—a process that may have been accentuated and prolonged, in some areas of western Africa, due to unsustainable land use practices such as excessive wood-cutting. Historically, these environmental stresses have caused people to migrate in pursuit of favorable agro-climatic conditions. Areas such as southern Senegal have been a key pivot point as the Sahara desert has expanded and contracted. We examine how future climate change may affect migration in the Soudo-Sahel zone and how this may stress the carrying capacity of agricultural lands of the region. We also examine how ancient and traditional farming methods may provide a rich source of technology for communities that will need to adapt to climatic variation in the future.
Geoarchaeological Investigations in the Upper Senegal River Watershed of Southeast Senegal
Jeffrey A. Homburg and Massal Diagne
A geoarchaeological study was recently completed as part of the Sabadala Gold Mine Project, the first systematic cultural resources management project conducted in Senegal. Research objectives of this study included: (1) modeling the potential for buried archaeological sites in proposed impact areas (e.g., proposed mining, tailing piles, reservoirs, and haul roads); and (2) evaluating the anthropogenic effects of traditional agricultural management practices on soil quality and agricultural sustainability. A map of buried site sensitivity was produced for different landforms, based on interpretations of soil development and geomorphic process associated with different landforms and landscape positions. Buried site probability was interpreted as highest for the floodplains, but the site types there are most likely dominated by agricultural fields that leave few archaeological traces.
An ethnopedology study was completed to document: (1) traditional agricultural management practices and conservation measures for different farming systems (e.g., rain-fed, runoff, and floodwater recession systems); (2) an indigenous classification of agricultural soils and landforms; and (3) strategies that farmers use for recognizing soil degradation. Anthropogenic effects on soil quality were quantified by measuring and comparing soil properties (e.g., pH, organic carbon, nitrogen, calcium, potassium, magnesium, available phosphorus, particle-size distributions, and unsaturated hydraulic conductivity) for 14 agricultural fields relative to eight control fields from nearby uncultivated areas in analogous soil and landform settings. Soil test data identified no evidence of soil degradation in the fields. Malinke farmers have developed a number of techniques for recognizing early stages of degradation that prompt their slash and burn fields to be shifted; these techniques rely on observations of: (1) a weed known as lanlango that is the first plant to grow and die in fields; (2) growth of a grass known as tenengene kotio that migrates into fields and quickly becomes dominant over the crops; (3) formation of a gray acidic soil known as dougou khoto khouno; and (4) poor crop growth. Floodplains have the highest nutrient status but because floodplain soils are poorly aerated during the growing season, the gravelly and loamy soils of the first terraces are the prime agricultural land for the main crops (e.g., sorghum, maize, and peanuts). Mitigating the loss of agricultural land to industrial mining activities will require careful consideration of indigenous crops and management practices. If agriculture is expanded and intensified on marginal farm land outside of alluvial valleys, where top soils are thinner, less resilient and more erodible, soil degradation risks will be increased.
Soil Science Society of America (Long Beach, California; November
Anthropogenic effects on soil quality in ancient terraced agricultural fields of Chihuahua, Mexico
Jeffrey A. Homburg, Jonathan Sandor, Paul Minnis, Javier Gonzalez, Christina Whitbread, and Victoria Sotelo
Agricultural soil quality was investigated in ancient field systems near Casas Grandes (also known as Paquimé), one of the largest and most complex prehistoric settlements in the North American Southwest. This research was completed as part of an interdisciplinary study of the anthropogenic ecology of the Casas Grandes area during the Medio period (~A.D. 1200-1450). Dramatic human population rise at Paquimé during the Medio period must have increased pressure on subsistence resources such as agricultural land for food production and wild animal and vegetation resources. Soil quality of agricultural terraces was evaluated by measuring chemical and physical soil properties (pH, organic C, N, total and available P, SAR, CEC, bulk density, particle-size distribution, and unsaturated hydraulic conductivity) for four agricultural fields compared to similar soils and landforms that were uncultivated. Comparisons were made between fields in high versus low population valleys and between two fields thought to have been owned by chiefs based on their proximity to special administrative sites. Although a number of statistical differences were identified, there is no indication that agriculture reduced soil quality. Consequently, soil degradation does not explain the ultimate decline of the Casas Grandes cultural system. Soil differences were greatest between fields, likely due to geologic differences in the parent material. The chief’s fields have a lower fertility than other fields, but their placement in better watered landscape positions accounts for their larger size.
Long-term Perspectives on Anthropogenic Soil Change from Studies of Ancient Agriculture
Jonathan A. Sandor and Jeffrey A. Homburg
Among agents of anthropogenic soil change, agriculture’s impact on soil is immense in magnitude, spatial extent, and duration. Agriculture has profoundly altered soil properties, processes, and formation pathways world-wide since its inception about 10 millennia ago. Much knowledge about recent agricultural soil change at scales of years to a century has been gained through monitoring long-term experiments and observational studies. However, far less is known about agricultural soil change at scales of centuries to millennia. Deep time perspectives on soil change can help predict long-term effects of agriculture on land resources and to test for sustainability. Information on soil change in longer time frames can be obtained by studying ancient agricultural soils, even though data are more limited than those from modern agricultural soils. Ancient agricultural sites in archaeological and contemporary traditional contexts in the Americas and other regions are presented to illustrate the wide range of soil change in relation to complex, interacting factors such as kind of agricultural system, time scale, and environmental setting and resilience. Inferring soil change is primarily based on a space-for-time substitution method in which ancient cultivated soils are compared with nearby uncultivated reference soils with similar geomorphic and pedogenic settings. Soil changes detected in ancient fields are interpreted as a gradient from degradation to enhancement in the context of agricultural productivity and land resource conservation. Main forms of soil degradation inferred from ancient agricultural sites are accelerated erosion, structural deterioration, compaction, declines in organic matter and macronutrients such as nitrogen and phosphorus, salinization, and acidification. Soil enhancement inferred at some sites is A horizon thickening, structural stabilization, increased available water capacity, and gains of organic matter and nutrients. Findings from these studies are relevant to current agricultural challenges involving climate change, water resources, soil quality and conservation, and sustainability.
ESRI International User Conference (San Diego, California; July
Reburial Planning Efforts at the Joint Courts Complex Archaeological Project
Data recovery at the Joint Courts Complex Archaeological Project involved the removal of over 1,300 burials from an historic cemetery in downtown Tucson, Arizona. The vast majority of the human remains and associated artifacts were reinterred at another cemetery in Tucson. This paper describes and explains a variety of geographic information system (GIS) methods for converting the spatial layout of the excavated grave pits to a much smaller plot for reburial. A real-world coordinate 40-by-35 grid of cells was created to serve as the index for systematically linking the grave features to their respective reburial boxes. Emphasis was placed on respecting the original spatial relationships among the grave features while minimizing the area required for the reburial plot. Other considerations included the need to transfer the 3-D excavation space into a flat 2-D reburial plot and accommodating the varying number of reburial boxes per grave feature.
Close-Range Photogrammetry Techniques at Joint Courts Complex Archaeological Project
The Joint Courts Complex Archaeological Project involved data recovery of over 1,300 burials from an historic cemetery in downtown Tucson, Arizona. Preliminary field testing indicated that the application of close-range photogrammetry and digitization would be a viable and time-saving technique to replace hand-drawn in situ plan view maps of human remains. By georeferencing and rectifying digital photographs, we were able to obtain high-quality imagery for the burial features. With a rectified photograph root mean squared error (RMSE) typically less than 1 cm, the subsequent digitization of human remains proved to be extremely accurate in real-world coordinates. During the heads-up digitizing of human remains in ArcGIS, the use of the annotated photographs from the osteologists served as an invaluable guide that enhanced the accuracy of shape, position, and material interpretation.
75th Annual Meeting of the Society for American Archaeology (St. Louis, Missouri; April
Data Recovery at Christiansen Border Village: Nonriverine Late Archaic/Early Agricultural Period Archaeology and Mid- to Late-Holocene Cienega Environments in the Borderlands of Southeastern Arizona
Robert M. Wegener, Karry L. Blake, William M. Graves, and Richard Ciolek-Torrello
Data recovery efforts by Statistical Research, Inc., at Christiansen Border Village documented 3,000 years of aboriginal land use and included a regional study of Mid-to Late-Holocene cienega environments throughout southeastern Arizona. This work expands our understanding of Late Archaic/Early Agricultural land use with evidence of maize cultivation at 980–800 cal B.C. and likely cultivation of cotton at 820–510 cal B.C. The Late Archaic/Early Agricultural remains at the site are interpreted as the result of a rich hunter-gatherer heritage that flourished during the rigors of the mid-Holocene and ultimately incorporated Mesoamerican domesticates in nonriverine upland locales.
Consuming Ethnicity, Producing Hybridity in Dietary Decisions of Native Americans in the Late Holocene Los Angeles Basin
Sarah Van Galder, Justin Lev-Tov, and Richard Ciolek-Torrello
In southern California, contact between European and Hispanic immigrants and aboriginal populations greatly altered indigenous subsistence strategies during the Late Prehistoric and Mission Periods. Faunal assemblages from archaeological sites in the Los Angeles basin include abundant animal remains from contexts spanning 8,000 years of occupation. Comparison of pre- and post-contact assemblages show that with the introduction of foreign food procurement and processing technologies and tactics, aboriginal fishing yields increased while large mammal yields decreased, despite the introduction of domesticated animals. In addition, post-contact assemblages suggest that mammal remains were not as intensively processed as in earlier times, in that bone preservation is better. Here, we briefly present an overview of this evidence and explore hypotheses accounting for the observed changes.