Rural sprawl and plant invasions in Wisconsin’s forests

Rural sprawl, i.e., housing development within or near forests, is widespread. Ecological impacts are assumed to occur but few have been empirically confirmed.  Concurrently, exotic plant invasion is a rampant problem.  We hypothesized that rural sprawl and exotic plant invasions may be linked because housing development can create sources of invasive exotic plant propagules and foster the dispersion of invasive plants into neighboring forests by creating disturbed habitats.  In the Baraboo Hills, Wisconsin, we sampled 80 plots distributed in forests along a gradient of housing densities and recorded richness and cover of 9 invasive exotic plants.  Richness of exotic invasive plants was inversely related to distance to the nearest house (R²= 0.2068, P<0.0001), number of houses in a 1 km buffer (R²= 0.1746, P<0.0001), distance to road (R²= 0.106, P<0.005) and distance to forest edge (R²= 0.253, P<0.0001) and a multiple regression model captured 30% of exotic invasives richness based on the distance to the nearest house and cover of native shrubs and herbs (R²=0.3, P<0.0001). However, cover of exotic invasive plants was not related to housing and landscape variables. Based on our results, planners and resource managers need to consider the role of housing development in the spread of exotic invasive plant species into adjacent forest ecosystems.