restricted access 2. The Setting
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12 2 The Setting Richard D. Garvin and Jane Holden Kelley Chihuahua is the largest of the 31 Mexican states, with an area of 247,460 km2 (an area slightly larger than Great Britain and 12.6 percent of the land mass of Mexico) (Schmidt 1973:91, 1992). It ranks twenty-­ eighth of the 31 states in population , and most of Chihuahua’s inhabitants live in the five largest cities, so rural areas can be very sparsely occupied (INEGI 2015). Historically, the state’s mainstays were ranching, mining, and forestry , but farming was also important; and before the Mexican Revolution of 1910, the area between Casas Grandes and Vincente Guerrero was the “breadbasket of Chihuahua” (Wasserman 1984). Interestingly, that historical breadbasket includes much the same geographical range as the Casas Grandes culture (Brand 1943; Carey 1931; Kelley and Burd Larkin 2003; Kelley et al. 1999, 2012). This historical picture no longer holds. Today the principal economic drivers in Chihuahua are the commerce and services sector (59.3 percent), followed by the industrial and construction sector (34.4 percent), trailed by the once dominant agriculture/ranching/resources sector (at a mere 6.4 percent of Chihuahua’s total economy) (INEGI 2015). The drop in the relative importance of farming and resource extraction has occurred despite the cultivation of far more agricultural land than a century ago thanks to mechanized tillage and water extraction, fertilizers , and pesticides. As part of that transformation , some landowners  — ​including ethnic Mexicans, Mormons, and Mennonites  — ​have greatly intensified per-­hectare production (Bennion 2004; Bridgemon 2012) and have intro­ duced orchard crops. For archaeologists looking to understand prehistoric farming in the area, the dryland farmers who still exist offer the best modern ana­ logues. Many prehistoric sites have been damaged by modern farms; while we lament that fact, we know that both sets of farmers were responding to much the same geological, topographic, and hydrological factors. For that reason we observed modern dryland farming during the project ’s 20 years and combined those observations with archaeological and modern environmental data. This chapter examines the natural factors that affected prehistoric farming in four subareas within the Proyecto Arqueológico Chihuahua (PAC) study area, and also for the area around Paquimé, north of where we worked. Where the link between natural factors and site locations appears obvious, we also discuss the latter. Environmental History Paleoenvironmental research in northwest Chihuahua has not been as extensive or intensive as it has been in comparable regions of the U.S. Southwest, but some studies have been done in or near the Casas Grandes culture area (e.g., Castiglia and Fawcett 2006; Hard and Roney 2005; Metcalfe 1987, 2006; Metcalfe et al. 1997, 2000, 2002; Nordt 2003; Palacios-­ Fest et al. 2002; Van Devender 1986a, 1986b, 1990; Van Devender The Setting 13 and Bradley 1990; Van Devender et al. 1987) and in the PAC study area in particular (Ortega-­ Ramírez 1995; Ortega-­Ramírez et al. 1998, 2000, 2011; Urrutia-­Fucugauchi et al. 1997). The pattern that emerges for the Holocene period is one of oscillation between warmer, drier periods and moister conditions. Specifically, the period from 3000 to 1500 BP was warmer and drier than today, with a return to a more balanced moisture regime afterward (Hard et al. 2006:474–475). The paleoenvironmental data vary slightly on a local scale, but results from studies in the Babícora Basin (within the PAC study area) seem to follow this general pattern (Ortega-­ Ramírez 1995; Ortega-­ Ramírez et al. 1998, 2000). Today one prominent environmental factor in northwest Chihuahua is its highly seasonal precipitation. Only 5 to 10 percent of the total annual precipitation in the region falls in the winter months; most rainfall occurs from July through September (INEGI 2003:32–33), ­usually as short but intense summer thunderstorms. The intensity and frequency of rainfall is strongly influenced by the El Niño-­ Southern Oscillation (ENSO) (Cavazos and Hastenrath 1990; Douglas et al. 1993; García et al. 1973; Kim et al. 2002; Menking and Anderson 2003; Poore et al. 2005). Díaz et al. (2002) analyzed Douglas fir (Pseudo­ tsuga menziesii) tree-­ ring data from seven locations in western Chihuahua to determine the frequency of winter–spring drought from 1647 to 1992. During this time span, four droughts lasted more than 10 years: 1664–1677 (14 years), 1751–1765 (15 years), 1798–1810 (13 years), and 1948–1964 (17 years, with 1952–1957 the most severe part of the...