Assessing the Ecological Condition of Wetlands on a Watershed Basis using a Rapid Method - the Cuyahoga River Watershed as a Case Study
By Siobhan Fennessy
Biology Department, Kenyon College, Gambier, OH
Decisions about wetland conservation and restoration have traditionally been conducted at the site scale. Due to the broad spatial distribution of wetlands however, there is a long standing need to assess the ambient condition of wetlands over large spatial scales. We used an assessment approach combining the USEPA EMAP probabilistic sampling design with the Ohio rapid assessment method and a landscape analysis (the Landscape Development Index) to evaluate the condition of wetlands in the 1,300 km2 Cuyahoga River watershed. We visited 366 mapped wetland sites and evaluated 243 wetlands to determine condition and report on their response to land-use change. We evaluated the scale at which the effects of land-use are strongest over six buffer widths: 100, 250, 500, 1000, 2000, and 4000 m. ORAM scores were negatively correlated with increasing intensity of land use (high LDI scores) for depressional, riverine, and slope wetlands for each buffer width to a distance of 1000 m. The correlation between LDI and ecological condition as measured by ORAM was strongest for the 100 and 250 m buffer distances with r = 0.59 for depressional and 0.41 for riverine sites. Classification and regression tree analysis indicates that wetland size is also a strong predictor of wetland condition, a probably by-product of landscape fragmentation. We also saw a differential ecosystem response to similar land-uses based on hydrogeomorphic class. This may indicate that wetlands vary in their responsive to anthropogenic stressors as a function of HGM class.
Keywords: wetlands, hydrogeomorphic, land use, urbanization, ecosystem response