Culture and Ecology of Chaco Canyon and the San Juan Basin

Chapter TwoThe Environment and Natural Resources of the Chaco AreaScrub cedars, very thinly scattered, were to be seen on the heights; and the artemisia characterizedthe flora. Some patches of good gramma [sic] grass could occasionally be seen along the RioChaco. The country, as usual, on account, doubtless, of constant drought presented one wideexpanse of barren waste. Frequently, since we left the Puerco, the soil has given indications ofcontaining all the earthy elements of fertility, but the refreshing shower has been wanting to makeit productive. The Rio Chaco, near our camp, has a width of eight feet, and a depth of one and ahalf. Its waters, which are of a rich clay color, can only be relied upon with certainty during thewet season. (Simpson 1850:37)Simpson was not alone in describing the Chacoarea as bleak in appearance. Visitors and scholarsalike often wonder how past populations coped withthis semiarid setting, let alone created the many sitesthat provide testimony to a flourishing lifestyle duringthe eleventh century (Brand 1937c:45; Hewett 1905;Kidder 1924:54; Gordon Vivian and Mathews1965: 1). Water remains the key variable. Thischapter underscores the role that water played in thecreation of the area, and describes the water resourcesthemselves, and where those resources are located.The amount of water available to plants affects speciesdiversity, the size of their range, and their density. Intum, these affect animal species that depend on plantsfor nourishment. Studies of the behavior of plants andanimals in the current environment provide clues towhat may have happened in the past if the climate wassimilar to that of today.Some changes have occurred since the end of thePleistocene, but for several thousand years the climatehas been similar to that of today. Yet the amount ofprecipitation did vary slightly through time. Thesevariations in amount or timing of precipitation eventswould have placed some restrictions on humanpopulations who lived in this setting. Humans alsowould have brought changes to the local environment,especially once they settled into an agriculturaladaptation or became pastoralists. This chapterprovides a backdrop for the cultural ecology andsystems theory approach taken by the Chaco Project inthe chapters that follow.The Historic SettingThe eight-mile-long Chaco Canyon (Figure 1.3)is a unique feature in the approximate center of thesemiarid San Juan Basin (Figure 1.1); surrounding itare mostly open spaces with only slight topographicvariation until the mountain ranges that encircle thebasin are reached (Gwinn Vivian 1990). UsingLANDSAT imagery, Schalk and Lyons (1976:Figure2) were able to delineate gross ecological zones in theSan Juan Basin and reported that its sandstone mesasand canyons are not identical in the northeast andsouthwest sections. This erosional feature is locatedat the contact zone between northern terrestrialdeposits and southern marine deposits; thus, soils andtheir water-retention properties differ in these twolarge areas. Sandy soils in the northeast should retainmoisture for longer periods of time than the clayeysoils of the southwest, which are characterized bymore rapid runoff and poorer water retention. It is inthe latter area, therefore, that Schalk and Lyonsproposed that water control features would have beenmore useful to agriculturalists and would affect socialorganization when adopted.