surveys. Those early surveys allowed the type of land resources that existed in Iowa before colonization to be seen. Iowa began to be colonized in a gradient that began in the southeastern extreme and then migrated along river channels to the northwestern part of the state. The surveys of that period indicate that roughly 20 percent of the area of the state was covered in forest or forest openings, and most of the remaining land was different types of grasslands and wetlands (USGS, NPWRC, 2005). Since the beginning of Iowa’s colonization, the ecological transformation has been dramatic. At one time a diverse mix of agricultural species was produced in the state, including about 10 different livestock species and about 30 different crops. The picture today is very different. Ecologically, the system went from that originally encountered by the Europeans—a grassy plain with a complex ecological system similar to that of the Serengeti Plains of Africa—to a simple ecological system but a very complex and highly specialized industrial system, said Ricardo Salvador of Iowa State University.

The system primarily produces two row crop products—corn and soybeans—which are essentially managed as a unit that makes up the row cropping system in Iowa. The soybean crop entered the state in the 1930s and has essentially replaced oats. No state in the country has anywhere near the ecological simplicity of the row crop mixture that Iowa does, said Salvador. With the introduction of modern technology, machinery, pesticides, and fertilizers, the state’s agricultural productivity increased from an average of 30 to 182 bushels of corn per acre. However, this gain has not been without trade-offs, noted Salvador. For example, the industrial system of production initially increased soil erosion rates dramatically. In addition, the production of nitrogen for use in fertilizers is energy intensive, as its synthesis requires high pressures and temperatures, but massive amounts of nutrients like nitrogen must be imported to support the row cropping system in this area. These nutrients go through the crop and livestock production systems and end up in the environment, including watersheds, which are susceptible to contamination by imported nutrients. Humans are accustomed to having a natural environment that has a large buffering capacity, and the cognitive behavior of humans suggests that this will continue because historically the environment has always absorbed human waste products. Now, however, the fluxes of these materials are so abundant that the environment is not diluting human waste products to safe levels quickly enough, and there is a lag in recognizing the impacts of this important feature of the system, concluded Salvador.

Wackernagel and Reese (1996) developed a technique to analyze the ecological footprint of urban areas, noted Salvador. The technique has been widely adapted and applied by urban planners. There are four items in ecological footprint: consumed land, built land, energy land (energy consumed within each of consumption categories), and service land (service consumption is translated into land area equivalents based on the resource consumption). The concept of an ecological footprint is based on the premises that (1) any population’s consumption of food, housing, transportation, infrastructure, consumer goods, and



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