Development of a mapping framework for ecosystem services: The case of sediment control supply at a watershed scale in Newfoundland, Canada

Abstract Mapping the supply of ecosystem services (ESs) is essential for communicating the importance of ESs to policy makers and to demonstrate that sustainable development is being applied with due diligence by forest managers. ES mapping facilitates the integration of ES assessments into the decision-making process. To that end, the main objective of this study was to provide a mapping framework for a specific water-related regulating ES – the sediment control service (SCS) – developed for a forest-dominated watershed in western Newfoundland, Canada (640 km2). The mapping framework proposes the development of composite indicators (referred to as an index), based on a proxy variables causal relationship approach, which is less complex to implement than physical models and less subjective than expert opinions. Two composite indicators used to rank sub-watersheds on a relative scale were developed: one using equal weights among proxies and a second using expert opinion to assign weights to proxies. The use of an index for mapping addresses the multidimensional and complex nature of ESs. The proxy variables represent ecosystem function indicators (FI) that are necessary to describe the causal relationship between ecological functions and SCS. The validation of ESs map results is often lacking in the literature. Therefore, we propose comparing the SCS relative scales with a sediment-yield classification that is simulated using the hydrological model SWAT (Soil Water Assessment Tool). To that end, the semi-distributed hydrological SWAT model has been developed. The overall agreement of the classification ranged from 35 to 81% depending upon the timeframe and weighting schemes that were applied, with better results being obtained for periods with more forest management operations and the expert-based weighting scheme. Results of the framework implementation show the potential supply of SCS at a sub-watershed scale and highlight those sub-watersheds most likely to be affected by forest management operations.