Streambank erosion and phosphorus loading to surface waters: knowns, unknowns, and implications for nutrient loss reduction research and policy.

To monitor and meet water quality objectives, it is necessary to understand and quantify the contribution of non-point sources to total phosphorus (P) loading to surface waters. However, the contribution of streambank erosion to surface water P loads remains unclear and is typically unaccounted for in many nutrient loading assessments and policies. As a result, agricultural contributions of P are overestimated, and a potentially manageable non-point source of P is missed in strategies to reduce loads. In this Perspective, we review and synthesize the results of a special symposium at the 2022 ASA-CSSA-SSSA annual meeting in Baltimore, MD that focused on streambank erosion and its contributions to P loading of surface waters. Based on discussions among interdisciplinary researchers and policy experts, we overview the knowns and unknowns, propose next steps to understand streambank erosion contribution to P export budgets, and discuss implications of the science of streambank erosion for policy and nutrient loss reduction strategies. This article is protected by copyright. All rights reserved.