Aquatic Condition Response to Riparian Buffer Establishment

Abstract

Although riparian buffers established along streams in agricultural landscapes are expected to provide water-quality functions similar to natural ecosystems, few studies have documented specific changes in the condition of aquatic resources resulting from buffer establishment. In 2000 the Commonwealth of Virginia, USA, began an extensive cooperative venture under the Chesapeake Bay Initiative to establish riparian buffers on agricultural lands, primarily through United States Department of Agriculture's Conservation Reserve Enhancement Program (CREP). Prior to CREP implementation, the Natural Resources Conservation Service (NRCS) developed a regionally tailored fish Index of Biotic Integrity (IBI) for use as a watershed assessment technique in Northern Virginia. Using this regional IBI framework, we evaluated the effects of recently established riparian buffers on aquatic condition. Within the geographic scope of the regional IBI, we evaluated all buffer segments planned between 2000 and 2003. Cumulatively during this period, we assessed stream physical condition on 36 buffer sites and 12 reference sites using the NRCS Stream Visual Assessment Protocol (SVAP); we also assessed the aquatic community at these sites using the IBI. Improvements in stream condition were clearly demonstrated at certain sites within one year of buffer establishment. Although not all buffer projects responded with positive trends, mean SVAP and IBI scores for buffered sites increased over the course of the study, whereas the trend on reference sites was level or slightly downward. We observed positive IBI response at sites with highly disturbed local conditions prior to buffer establishment combined with small, relatively undisturbed watersheds above. Simple solutions such as buffer establishment alone cannot be expected to protect streams from adverse human impacts that occur at a broader scale. Therefore, riparian restoration should be planned and carried out in concert with other conservation practices at a watershed scale in a way that maximizes buffer effectiveness.