Managing stream restoration: Framing and assessing the stream ecosystem services and biodiversity index (SESBI)

Streams and rivers worldwide are heavily affected by human intervention and are often degraded despite the numerous ecosystem services they provide. The degradation is particularly severe in water-stressed regions and arid and semi-arid areas. Various indices have been developed to assess the health of streams and rivers and the ecosystem services they provide. However, existing indices need improvement to provide a straightforward tool for assessing the complexity of stream ecosystems in water-stressed climates while also accounting for the ecosystem services provided by streams and rivers. To achieve this goal, we developed the Stream Ecosystem Services and Biodiversity Index (SESBI), which evaluates the health of streams based on six ecosystem services they provide: biodiversity conservation, water purification, riparian buffer zones, flood mitigation, recreation/ecotourism, and landscape ecology. The SESBI framework was developed based on existing literature, experts' in-depth interviews, and questionnaires, focusing on ES indicators that reflect ecological functioning and management priorities in water-stressed climates. We applied the SESBI to three streams in Israel and validated its performance using expert assessments and available data. Comparisons with local experts' ratings showed strong alignment, confirming the index's reliability and adaptability. To our knowledge, this study is the first to use ecosystem services as proxies to assess stream health in arid and semi-arid climates as a tool to monitor changes before and after rehabilitation. While designed for streams, this approach can be adapted for rivers with appropriate modifications. The index methodology developed in this research provides a valuable tool for planners, stakeholders, and decision-makers, offering an accessible yet scientifically robust approach to assessing and prioritizing ecosystem rehabilitation plans. This research contributes to the sustainable management of ecosystems on theoretical, empirical, and practical levels by simplifying the complexity of stream ecosystems into a practical and easy-to-apply framework.