Relative importance of Conservation Reserve Programs to aquatic insect biodiversity in an agricultural watershed in the Midwest, USA

The Conservation Reserve Program (CRP) and the Conservation Reserve Enhancement Program (CREP) in the USA offer farmers government financial incentives to take erosive agricultural lands out of production. Many conservation practices are used along streams to improve habitat for stream biota. However, the ecological benefits of these programs to streams are yet to be demonstrated. This study investigates the responses of communities of three sensitive aquatic insect orders (Ephemeroptera, Plecoptera, and Trichoptera or EPT) to CRP and CREP practices in the Kaskaskia River basin, a predominantly agricultural watershed in Illinois, USA. A total of 10,373 EPT specimens were examined from 84 sites across the basin during 2013–2015. Nine environmental variables were used to account for variance in EPT taxonomic diversity, and sets of best regression models were selected based on Akaike information criterion (AICc). AICc importance values and hierarchical variance partitioning revealed three important variables associated with EPT taxa richness: link (number of first order tributaries), soil permeability, and urban land. Two important variables were associated with Shannon and Simpson diversity measures: link and dissolved oxygen. The percentage of CRP/CREP land in the watershed was less important, suggesting that this mosaic of conservation practices as currently implemented in the basin may not affect EPT taxonomic diversity.