Anthropogenic Soil Change in Ancient and Traditional Agricultural Fields in Arid to Semiarid Regions of the Americas

Abstract

Soils form the foundation for agriculture and are changed by farming through active management and unintentionally. Soil change from agriculture ranges from wholesale transformation to ephemeral and subtle modification. The archaeological record of early agricultural systems holds information about soil change on centurial to millennial scales, with important implications for long-term soil condition and land use sustainability. Knowledge of early agricultural management can also be inferred from soils, including farming strategies in dynamic, challenging environments. This paper discusses soil change processes and outcomes mainly using studies of ancient and traditional agriculture in arid regions of the Americas. The potential and limitations of soil change research methods in ancient agriculture are also considered. Soil anthropogenic change involves complex and interactive physical, chemical, and biological processes across a wide range of spatial and time scales. Soil change outcomes in early agriculture relating to soil health and productivity vary from improvement to degradation. Soil productivity improvement commonly resulting from management includes soil-landscape physical stabilization for crops, increased topsoil thickness and plant-available water capacity, and improved soil tilth and fertility. Degradation commonly results from unintentional soil-geomorphic-ecosystem changes that cause accelerated erosion, destabilization of soil structure and compaction, and decreases in plant nutrients and soil fertility. Soil change outcomes vary across space and time in response to complex environmental, agricultural, and social factors.

Late Holocene anthropic degradation records in semi-arid environments (NE Spain and NW Argentina)

“…An especially significant aspect of these impacts is the mobilisation of silt: both horizontally by erosion; and vertically by increased flooding in areas of agricultural clearings (Homburg and Sandor, 2011;Sandor and Homburg, 2017). The creation of rills and gullies on the slopes -where erosion dominates -causes the transfer of large masses of sediments to valley bottoms and where accumulation becomes the dominant process (Fig.…”

Reviews and syntheses: Agropedogenesis – humankind as the sixth soil-forming factor and attractors of agricultural soil degradation

“…Examples of soil degradation leading to civilization collapses are well known, starting at least with Mesopotamia (18th to 6th centuries BCE; Diamond, 2002;Weiss et al, 1993). Notwithstanding all the negative impacts humans have on soils, the intention was always to increase fertility to boost crop production (Richter et al, 2011;Sandor and Homburg, 2017), reduce negative environmental consequences and achieve more stable agroecosystems. To attain these aims, humans have (i) modified soil physical and hydrological properties (for example, by removing stones and loosening soil by tillage, run-off irrigation, draining and terracing); (ii) altered soil chemical conditions through fertilization, liming and desalinization; and (iii) controlled biodiversity by sowing domesticated plant species and applying biocides (Richter et al, 2015;Richter, 2007).…”

“…The processes of additions, losses, transfers and translocation, and transformations of matter and energy over centuries and millennia produce a medium -soil (Simonson, 1959), which supports plant roots and fulfils many other ecosystem functions (Lal, 2008;Nannipieri et al, 2003;Paul, 2014). These functions commonly decrease due to human activities, in particular through agricultural practices because of accelerated soil erosion, nutrient loss (despite intensive fertilization), aggregate destruction, compaction, acidification, alkalization and salinization (Homburg and Sandor, 2011;Sandor and Homburg, 2017). Accordingly, the factor humankind has nearly always been considered to be a soil-degrading entity that, by converting natural forests and grasslands to arable lands, changes the natural cycles of energy and matter.…”

Progress in soil geography I: Reinvigoration

“…Since the emergence of farming, human impacts on the soil system have become an important aspect of soil dynamics (Grieve, 2001;McLauchlan, 2006;Veenstra and Burras, 2015). The change from a nomadic to a sedentary lifestyle for early cultures changed the relationship between soil and people, beginning an era of increasing impacts that people have on soil functions (Beach et al, 2006;Sandor and Homburg, 2017;Goudie, 2018). The recent exponential growth of the human population has intensified demand for food and resources, resulting in anthropogenic impacts on soil to unprecedented levels (Ferreira et al, 2018).…”