Rocky intertidal habitat at San Juan County Park, Washington, USA, received augmented trampling to assess impacts of human visitation on ecological communities. For six weeks in spring, six 3-to 5-m-long intertidal transects perpendicular to the shore were experimentally trampled (250 steps three times a week) in the zone dominated by the brown alga Fucus gardneri Silva. Six additional control transects received only background levels of trampling from park visitors during a season of low visitor traffic. Five algal and invertebrate taxa were followed throughout the treatment period and for three months post-treatment. Repeated observations of percent cover or density were made for each taxon at three relative tidal elevations (high, mid, and low) along each transect using fixed quadrats (20 cm × 20 cm). Augmented trampling reduced cover of Fucus to 30% of its original value within six weeks, and cover remained lower in trampled than in control areas throughout the 3-month posttreatment period. Trampling also resulted in a short-term decline in taxon richness, from an average of eight to seven taxa per quadrat. Cover of the turf-like alga Endocladia muricata (Posteis et Ruprecht) J.G. Agardh did not decline significantly where trampled, nor did the cover of barnacles or density of mobile gastropods (limpets and whelks). Bare rock area increased in trampled areas one month after trampling ceased, indicating a delayed decline in living cover in response to trampling. This study highlights a management challenge of protecting natural habitats in parks and reserves while still encouraging public access and appreciation.

Carolyn Jenkins, Melora E. Haas, Ashley Olson and Jennifer L. Ruesink. 2002. “Impacts of Trampling on a Rocky Shoreline of San Juan Island, Washington, USA.” Natural Areas Journal 22(4):260-269.