Monday, August 3, 2009 - 4:20 PM

COS 16-9: Invasive plants in private neighborhoods: Does neighborhood governance make a difference?

Sarah J. Cech, College Of Charleston, Joel M. Gramling, The Citadel, Norman S. Levine, College Of Charleston, Patrick Hurley, Ursinus College, and Angela Halfacre, Furman University.


Ecologists have studied the mechanisms, communities, distribution, and characteristics of non-native invasive plants.  These studies have taken place in both natural and urban environments along a variety of gradients with the underlying theme that urban/suburban land uses are highly disturbed and therefore have higher rates of invasive species.  Both anthropogenic and ecologic factors were examined as contributors to the spread of invasive species, but very few studies investigate how and if written policy effects invasive species distribution.  Nearly all subdivisions built in the last 20 years have neighborhood covenants.  This study asks two questions.  1) Does the level of environmental regulation within subdivisions affect the non-native plant richness?  2) What other factors within the boundaries of the subdivision contribute to the non-native plant richness?  Nine private communities in South Carolina’s Lowcountry were assigned a governance level with regard to environmental policies of strict, moderate, or not strict.  Plant surveys were conducted in the commonly owned land of each subdivision and the land uses found within each subdivision were digitized in a GIS.  Multiple regression analysis was then conducted to determine the best model for predicting the presence of non-native plants in subdivisions.  


Examination of descriptive statistics revealed that subdivisions with less-strict environmental governance had higher percentages of non-native species and higher non-native richness.  The plots in the low governance level frequently fell under the category of highly managed land.  Multiple regression analysis run at different scales revealed that governance level does affect non-native richness and the percent of non-native species.  Land use and ground cover (both litter and vegetative) were also factored into the regression models.  Predictor variables were divided into social and environmental variables and models were run with these variables separate and together.  The strongest models produced by multiple regression occurred when all of the variables were included as predictors, showing that anthropogenic and ecological factors cannot be considered separately in studies of plant communities.  These results also indicate that human policy decisions can influence the species composition under their jurisdiction.  Subdivision planners, therefore, should consider writing regulations about invasive species into the neighborhood covenants.