Anthropogenic Impacts on Riparian Forest Loss in East Tennessee: a GIS analysis

Streamside, or riparian, areas are vital components of a healthy watershed system. Natural riparian areas perform multiple ecosystem functions including filtering sediments and pollutants from upland areas, stabilizing banks and floodplains, regulating stream temperatures, and providing habitat for many native and migratory species. In eastern Tennessee, natural riparian forests have declined by 40 to 60 percent (SAMAB 1996b). I examined the spatial distribution of humans and their land-cover changing activities in an effort to contribute to a better understanding of the loss of riparian forests in the eastern Tennessee region.

This research is centered in the Central Ridge and Valley ecoregion area of Tennessee, a landscape diverse in its physical characteristics, land usage, and human population density. Using Geographic Information Systems (GIS), I derived the human population, the proportion of each land use type, and the proportion of non-natural riparian area for each eleven-digit watershed study unit within the study area. I first used this information to investigate human population density as an indicator of overall human presence within each watershed unit and its relationship to the loss of riparian forests. I then looked more closely at possible land use causes of the loss of riparian forests in the Central Ridge and Valley ecoregion.

Eleven watershed-level land use variables were derived from the Multi- Resolution Landscape Characteristics (MRLC) dataset for consideration as possible indicators of riparian forest loss. These land use classifications include natural, highiv density residential, low-density residential, commercial or industrial, croplands, pasture, mining, recreational grassy areas, and transitional. Watershed-level road density and riparian road density were also investigated in relation to riparian forest loss.

I tested the ability of population density to predict riparian forest loss, which resulted in a weak but highly significant positive relationship. Further research into specific land use classes showed over 85 percent of the variability in riparian forest loss was explained by four watershed-level land use proportion variables: pasture, low-density residential, croplands, and recreational grass. This study contributes to the understanding of anthropogenic effects on natural riparian systems and should prove useful in developing riparian protection and management strategies in the eastern United States.