Using the past to plan the future : retrospective assessment of landscape and land-use change in the Clear Creek watershed, Iowa

Rayburn, Andrew
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The vast majority of native landscapes in the Midwestern United States have been transformed by anthropogenic land uses, especially agriculture and pasture, since settlement by Euro-Americans in the early to mid-1800s. This is especially true in Iowa, where between 80-90% of the pre-settlement landscape has been converted from a mosaic of prairies, forests, and wetlands to production landscapes associated with corn, soybeans, and livestock forage. This dramatic conversion has had, and continues to have, significant impacts on both terrestrial and aquatic resources. Opportunities to mitigate potentially negative impacts associated with this landscape conversion exist, but in theory should be addressed at the landscape scale and should take into account the influence of historical trajectories of landscape change on present and future ecosystem properties. Because landscape change in the anthropogenically modified Midwestern United States reflects the interconnected relationship between the people and the land, it is appropriate to examine the phenomena from both ecological and social perspectives. In order to evaluate landscape change within a study area in eastern Iowa, I integrated a variety of historic data sources in a GIS environment in order to compute changes in landscape composition and configuration, stream sinuosity, and housing density. I also sought to delineate remnant patches of native habitat that have persisted to the present, despite dramatic changes in the surrounding landscape. My results suggest that forest cover has been increasing within the study area since the beginning of the 20th century, while crop cover has been declining since at least 1940. Furthermore, urban cover (as well as housing density) has been steadily increasing since 1940, echoing broader, regional trends. In addition, I observed a dramatic decline in the sinuosity of the main stream channel in the study area in the mid-1900s. The changes I detail have important implications in both ecological and social realms, and the remnant habitat patches that I delineated may serve as important conservation targets. Overall, my research indicates the dynamic nature of the landscape within the study area over the last 150 years and suggests that the evolution of the landscape will continue into the future.