Doctor of Philosophy (PhD)


Geography and Anthropology

Document Type



The causes of central Mexico’s environmental degradation are poorly understood. Scholarly contention centers on the role of introduced livestock as agents of soil erosion. This dissertation explores New Spain’s sixteenth-century livestock ecology by drawing upon archival and field data to reconstruct the spatio-temporal characteristics of sheep ranches in a southeastern section of central Mexico’s Valle del Mezquital. The introductory chapter outlines a scholarly disagreement from the 1990s that underscored differences between historical and geographical approaches to studying historical landscape transformations. On one side of this debate, geographer Karl W. Butzer finds in the sixteenth-century Mexican Bajío little evidence for environmental degradation from introduced livestock. On the other, environmental historian Elinor G.K. Melville’s research in the adjacent Valle del Mezquital suggests that sheep devastated that region’s environment by the sixteenth century’s close. This section looks beyond the finer points of methodology in search of other reasons for their disagreement, namely researcher positionality. Chapter 2 addresses the methodological concerns that arise from using colonial-era Mexican archival sources to study landscape transformations. This chapter outlines how previous scholars have approached these concerns and how this dissertation handles each of them. The discussion then turns to perceptions of environmental cause-and-effect with an emphasis on agricultural terrace abandonment as a possible mechanism of environmental degradation. The second chapter also reviews basic concepts in rangeland ecology. The two subsequent chapters focus on the natural environment and the pre-Hispanic inhabited environment together attempt to establish an ecological baseline with which to evaluate colonial-era landscape transformations. Chapter 5 leverages the relatively small size of this dissertation’s study area to map many of the sheep ranches to a relatively precise degree. A time-series of maps reveals the spatio-temporal development of the study area’s sheep ranch complex. A Geographic Information System analyzes the various spatial characteristics of each ranch’s location. This analysis emphasizes the reality of a three-dimensional landscape by considering the aspect, slope, and elevation of the ranching complex. The significant findings are: agricultural terrace abandonment likely instigated some of the region’s soil erosion; there appears to have been fewer sheep in the study area than previously thought; deep drought conditions operated synergistically with herbivory and land abandonment in the late sixteenth century to transform the Valle del Mezquital into the degraded region it is today.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Andrew Sluyter