There are many instances of human appropriation of natural resources having a profound impact on natural environment. I would submit that one such example would be the American settlement of the frontier in the hopes of finding gold and other natural resources. In the last nineteenth century, American prospectors, seeking to enhance their own personal riches, started expanding Westward in attempts to discover gold, iron ore, silver, as well as other natural resources. This had a profound impact on the natural setting in a couple of ways. The first is that it created a situation where human appropriation of the natural setting disrupted ecological niches and forever changed the balance of the region. Prospecting out West led to settlement of the West and continued harvesting of the land. Another way it changed the natural environmental setting was its accompanying industrial growth, including the building of centers of commerce where environmental concerns were put behind economic interests. This is the same level of appropriation that the Eastern part of the United States experienced earlier in that century when Industrialization and the building of factories led to air and water pollution, as well as urbanization and increased human consumption of natural resources. In a more side effectual manner, human appropriation of the ecological homeostatic balance can be seen in Carlson's book, Silent Spring. Set in the late 1950's the book explores the use of pesticides to kill insects that were harming crops and impeding commercial advances. Carson analyzes the ecological harm of such uses, in terms of disruption of the natural balance of life in the particular settings. This might be one of the best studies of how human appropriation of the most natural of resources, ecological niches and balances, can profoundly alter the environmental setting.