I decided to publish my write-ups from my comprehensive exam reading fields. I am publishing them *as is.* Thus they represent my thoughts as a new PhD student. They were written between September 2011 and July 2012.  The full collection is accessible here

A Plague of Sheep: Environmental Consequences of the Conquest of Mexico

Elinor G.K. Melville

A Plague of Sheep: Environmental Consequences of the Conquest of Mexico is a case study of the effects of pastoralism in the Valle del Mezquital, or, as more broadly, as Elinor G.K. Melville puts it, the book is a study that “focuses on the changes associated with the introduction of Old World grazing animals into New World ecosystems.” (xi) Melville is openly building on Alfred Crosby’s ideas about the significant role of biological conquests in the European take-over of the New World. Europeans did not come to the Americas alone, but brought with them animals, plants, and bacteria. This biological revolution particularly that which pertains to the pastoral process enabled the European conquest of the native population, according to Melville.

Unlike Crosby, Melville does not seem to prescribe to the idea that humans are part of nature. She emphatically states that what she discusses in A Plague of Sheep is not a case of environmental determinism. Rather, in Melville’s tale, humans are outside agents that act on knowledge (or the lack there of), necessity, and often times greed. It was a series of personal choices that led to the transformation of the Valle del Mezquital; these choices were made primarily in regards to political, cultural, and other man-made social structures, not in regards to environmental forces outside of their control. However, I think that any claim by an environmental historian that their story is not about environmental determinism is at least a little bit bogus. The choices that the Spanish made in regards to pastoralism, while politically and culturally influenced, were ultimately determined by their natural surroundings.

Two processes dominated the biological conquest of the New World: virgin soil epidemics and ungulate irruptions. The first, relates to Crosby’s portrayal of the role of diseases in the Americas. Virgin soil epidemics, Melville writes, are episodes where isolated population are exposed to microbes that they have not come in contact with before, often having fatal, catastrophic results. Although, she admits that this played a large role in the demographic take-over of the indigenous people, Melville seems to be satisfied with the content of prior works. Melville’s main focus is on elaborating on the process of ungulate irruptions, which deals with the way in which grazing animals move into a new environment.

By looking at the process of ungulate irruption, Melville further illustrates the idea, which Crosby initiates in Ecological Imperialism, that the populations of indigenous peoples and domestic, grazing animals are inversely related. The progression of ungulate irruption starts with an excess of food suitable for grazing animals. People try to take advantage of this excess by using it pastorally, which eventually leads to animal overpopulation. This overpopulation leads to the dying off of these animals. With a smaller population of animals to support the grasses are able to grow back, but are often of a very different strain than the grasses that originally grew in the location.

Like Charles Elton, Melville is mainly concerned with the loss of biodiversity in the Valle del Mezquital. The introduction of sheep to the area set off an ecological revolution, in which the land was changed from a lush landscape to an arid desert. The native horticultural subsistence has been replaced by a monoculture that benefits urban centers, not the individuals that actually live in the area. It is clear that Melville also draws a great deal of her language from the Ecology of Invasions. She frequently uses the term invasion and describes how the species that Europeans brought to the New World did not peaceably move into open ecological niches, but rather exploded into the environment. The use of this kind of language is quite effective, not just because it emphasizes the significance of these occurrences, but also because, by imbuing these plants, animals, and environments with descriptors that normally bring images of synthetic, human inventions and warfare to mind, Melville and Elton further accentuates the level of involvement mankind has in these ecological changes and, additionally, paints these changes in a violent and negative light.

Feature Photo

  • Title: Sheep at the Ladder Livestock Ranch, which is based literally across the highway from Colorado in Carbon County, Wyoming. The ranch runs sheep in Wyoming and brands and tends to newborns at this facility near the tiny town of Dixon. The cattle operation is centered mainly across the state line in Colorado
  • Creator(s): Highsmith, Carol M., 1946-, photographer

Published by Jessica M. DeWitt

Dr. Jessica M. DeWitt is an environmental historian of Canada and the United States. She is passionate about the use of digital technologies to bridge the gap between the public and researchers. In addition to her community and professional work, she offers various editing and social media consultancy services.

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