How will climate change influence phosphorus systems? -- an expert elicitation workshop

Phosphorus (P) sustainability is a 'wicked problem' due to environmental and societal challenges. This may be further exacerbated by climate change, although within-discipline literature is lacking. Our knowledge of how climate change may impact P dynamics is challenged by our understanding of baseline vs managed system response signals, complex biophysical and societal process interactions and thresholds. This challenge was discussed at the 10th International P Workshop, where experts from academia and industry gathered. We asked international experts to discuss the impacts of climate change on P across three topics: soils, waters, and human systems. Participants discussed knowledge and data availability on these topics, and positioned their responses on a matrix with importance (relevance of the impact according to their understanding and knowledge) and confidence (about the data availability regarding that impact) as axes. The 320 statements were digitized and categorized into themes, and we report them in context with the current literature. Our analysis emphasizes that phosphorus must become more visible in climate change discourse and addressed through transdisciplinary approaches. We recommend further data collection regarding circular economy and climate adaptation, as well as modelling and policy development to anticipate risks and support adaptive P management. This includes attention to thresholds and socio-economic linkages, where consequences of inaction may be abrupt and widespread. We provide suggestions for research and practice, including forthcoming International Phosphorus Workshops.