Due to intensive land management practices and land use changes worldwide, the quality and quantity of freshwater resources have deteriorated globally. The management of freshwaters is challenging due to the concurrent action of multiple stressors and drivers that alter freshwater ecosystems’ structural and functional integrity. Moreover, management lacks science-based thresholds that mark the critical transition from an ecosystem capable of compensating for human impacts to an ecosystem where the loss of ecosystem functioning follows increased stressor intensity.

The OperaSOS project aims to operationalize the SOS concept for stream ecosystem functioning by accounting for the variation in agricultural land use intensity in catchments. The project combines fieldwork with data analysis in a theory-driven approach to facilitate adaptive land use management of streams and rivers. We focus on agricultural land use, as the conversion of pristine areas and the intensification of pasture into arable land still constitute the most important pressure on terrestrial and freshwater ecosystems. The project quantifies responses of ecosystem structure and functions along the entire agricultural gradient from pristine to intensive crop farming in river catchments across Germany. We will develop an agricultural Land Use Intensity index for Stream ecosystems (LUIS) for this. By testing the predictive power of LUIS for the stream network-dependent ecological status (ecosystem structure) and ecosystem functioning, we will be able to upscale ecosystem functions based on LUIS to large scales and scenario analysis for land management practices.