National Park Service managers are faced with the increasing challenge of accommodating intensive visitation in areas that contain rare plant communities and species. In the Potomac Gorge area near Washington, D.C., visitors venturing off formal park trails to sightsee, explore, climb, and fish have created extensive networks of informal trails in the biologically significant natural area. Past efforts to restrict off-trail activities have been largely unsuccessful in reducing impacts to the riparian rocky areas that support the highest densities of rare plants.

Responding to these concerns, a team led by Jeff Marion, a U.S. Geological Survey scientist and adjunct professor in the Department of Forest Resources and Environmental Conservation, developed a research program to make park visitation more sustainable by documenting the nature and severity of visitor impacts and developing management recommendations to avoid or minimize those impacts.

In one study, GPS units were used to locate and map a surprising 27.7 miles of informal trails, which were evaluated for various attributes. Another study assessed the efficacy of several experimentally applied treatments designed to reduce off-trail activity, including educational signs and site management actions. A visitor survey and observation of off-trail hiking behaviors along a popular park trail were used to evaluate success. Based on this research, off-trail hiking was reduced from 70 percent to 43 percent of visitors for the best treatment. The final study examined visitor impacts to cliffs and rocky areas at Potomac Gorge. “Visitor trampling has created 122 informal recreation sites with approximately two acres of intensive vegetation and soil disturbance,” noted Marion.

Research results will document visitor impacts, describe the principal factors that influence them, and present a comprehensive array of recreation and site management options for increasing the sustainability of park visitation, including actions to promote low impact outdoor practices, close and restore duplicative or unnecessary recreation sites and informal trails, and reduce rates of off-trail hiking.