Pre-Hispanic Anthropogenic Landscape Change in the Nochixtlán Valley of Oaxaca, Mexico as Seen through Extensive Buried Paleosols

The Nochixtlán Valley of Oaxaca, Mexico is the location of several important archaeological sites (Yucuita, Etlatongo, and Cerro Jazmin). These sites span the time during which development of agriculture, early villages, and the rise of urban centers occurred. Extensive and severe landscape degradation seen in the Nochixtlán Valley is often attributed to post-Conquest European agricultural practices.

Our research indicates that environmental degradation and subsequent erosion was related to economic and demographic changes occurring much earlier, during the Formative and Classic Periods. Initial sedentism and agricultural expansion during the Early Formative Period led to land clearance. Later population increases led to an increase in agricultural land and additional land clearance. Subsequent erosion resulted in valley alluviation and burial of existing landscapes. The buried paleosols represent stable land surfaces separated by sediments eroded from adjacent hillslopes.

Well-developed paleosols occur in vertically multiple sequences are laterally extensive and can be used to reconstruct the archaeological landscape at different time periods. Radiocarbon dating of 36 samples indicates that most hillslope erosion and valley alluviation occurred prior to Spanish Conquest. We argue that the collapse of complex urban polities at the end of the Classic Period resulted in a reduction in labor investments leading to terrace failure and increased erosion. Recent stream incision revealed these landscapes in the form of paleosols which were radiocarbon dated and showed most of the erosion occurred prior to Spanish occupation.