PARENT SESSION
Oral Session # 15: Wetland Ecology I: The Everglades and Southern Wetlands.
Presiding: J Chick
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 101.
Assessing visitor impacts from long-term sampling of wetland communities in the Everglades National Park, Florida.
Wolski, Lawrence*,1, Trexler, Joel1, Nelson, Eric2, 3, Perrry, Sue3, 1 Florida International University, Miami, FL, USA2 South Florida Natural Resources Center, Homestead, FL, USA3 Fish & Wildlife Service, West Palm Beach, FL, USA
ABSTRACT- Long–term monitoring requires repeated visits to a study site, greatly increasing the potential for cumulative visitation effects. For ecological studies in general, and for monitoring in particular, data must be evaluated for confounding artifacts from researcher presence. Using data from a long–term study (9 sites, each with 3 plots, continuously studied from 6 to 22 years) of aquatic communities in the Everglades National Park, we compared long–term sampling plots with previously unsampled reference plots adjacent to them. We identified two criteria that are sensitive to local habitat heterogeneity for assessment of visitation impacts. First, the long–term plots must differ from adjacent reference plots by a magnitude that exceeded variation among plots separated by equal or greater distance (i.e., the difference is greater than expected by scaling of community change proportional with distance); and second, multiple reference plots must consistently differ in direction (e.g., greater abundance or less abundance) from adjacent long–term plots. We also tested for increased heterogeneity among samples from long–term plots compared to those not previously visited. We found no evidence of visitor effects on fish or macroinvertebrates, and only suggestive results for emergent plants and periphyton floating mats. Our failure to document visitor impacts may result from either low visitation rate or the dynamic nature of the wetlands studied; we suggest that stable environments (aquatic and terrestrial) may be more susceptible to visitor impacts than dynamic ones like wetlands.
Key words: impact assessment , long–term monitoring