Representing the sediment retention ecosystem service within an ecosystem account of the Mitchell catchment
If soil resources and the benefits derived from water quality are to be maintained, the on- and off-site effects of soil erosion must be adequately represented so that appropriate management responses can be identified and communicated to decision makers. The System of Environmental-Economic Accounting - Ecosystem Accounting (SEEA-EA), is one approach to quantify both the contributions that ecosystems make to the economy, and the impacts of economic activity on ecosystems. However, due to the
... fficulty of obtaining empirical data on ecosystem service flows, in many cases such quantification is informed by ecosystem service models. Previous research in the Mitchell catchment, Queensland Australia allowed us to explore the implications of using different modelling approaches to estimate the sediment retention ecosystem service. We compared predictions from a model of hillslope erosion and sediment delivery in isolation (as in the frequently used ecosystem service model - InVEST), to predictions produced by a more comprehensive representation of locally important erosion and deposition processes through a sediment budget calibrated against multiple lines of empirical data. Estimates of the magnitude of hillslope erosion modelled using an approach similar to that in InVEST differed by an order of magnitude from those derived from a calibrated sediment budget. If an uncalibrated InVEST model was used to inform the relative distribution of erosion magnitude and significance, results indicate the approach would not correctly identify the dominant erosion process contributing to suspended sediment loads in the catchment. However, the sediment budget model could only be calibrated using data on sediment sources and sinks that had been collected in the catchment through a sustained and concerted research effort. A comparable level of research investment may not be available to inform ecosystem service assessments in catchments elsewhere. The results summarised here for the Mitchell catchment are valuable for assessing the potential implications of using a simplified representation of this ecosystem service.