Basin-scale riverine ecosystem services vary with network geometry

Riverine ecosystems provide a variety of services supporting biodiversity, human livelihoods, and the maintenance of river health. Multiple anthropogenic threats to riverine ecosystem services (RES) have been identified and considered in river management strategies. However, the way in which the river network is spatially arranged across the landscape – river network geometry – may also play a role in the delivery of RES. Here we studied the effect of river network geometry on the delivery of five RES in 14 catchments of the Great Barrier Reef region, Australia. Our investigation has three parts. First, we conducted a sensitivity analysis on modelled RES, holding all non-geometric catchment characteristics, other than catchment size and slope, constant to allow attribution of modelled differences directly to differences in geometry. Second, we analysed the relationships between observed RES and network structural indices. Third we compared observed RES with modelled results. Modelled results suggest that RES are sensitive to the differences in river network geometry. Furthermore, correlation analyses show good agreement between observed RES and network structural indices, and there is good correlation between the modelled and observed RES. These results suggest an important role of river network geometry in the delivery of multiple RES by mediating upstream inputs as they pass through the river network. A one size fits all approach to river management may thus be ineffective and specific management interventions will be needed in catchments of different network geometries.