Scaling and Demographic Issues in Global Change Research

This paper is about the scales at which demographic data are available, and demographic research is conducted, and their implications for understanding the relationship between population and environment. It describes a multi-disciplinary project designed to study the long-term relationship between population, land use, and environment in the U.S. Great Plains. The paper begins with a discussion of the scales at which data are readily available for demographic, agricultural land use, and environmental data for the United States. Some of these data can be obtained at relatively high resolutions, but the lowest common denominator for many of the long term data is the county, a fairly large unit. I then discuss the advantages and disadvantages of the different scales available. The third section of the paper uses county net migration as an example of research that can be done, and the scale at which it is effective. The example shows that the county is an effective unit for the study of migration, and that the research results are significant. The conclusion suggests that the study of population processes in an environmental and economic context is appropriate at the county level for some questions, but that scaling the results to larger units may be difficult because of the need to be certain about the contexts in which those processes take place. We probably should not study net migration at the national or continental scale, but aggregating county-level or regional studies to a larger scale may be successful.