Supplementary materials for A New Optic on Mangrove Conservation: Blue Nitrogen

Nitrogen (N) pollution is a primary driver of widespread coastal ecosystem collapse, and mangrove forests represent an undervalued natural mitigation solution for nitrogen removal. Through a comprehensive meta-analysis, we reveal that globally, mangroves remove 870 Gg N annually, which represents only 15% of their theoretical maximum capacity of 5,670 Gg N yr-1. The economic value of this service reaches 8.7 billion annually via N credit-based valuation, more than 12 times the annual carbon credits value of mangrove carbon sequestration, yet this remains entirely unrecognized in current conservation frameworks. We also highlight critical environmental thresholds demonstrating that this service is vulnerable: extreme eutrophication, rising mean annual temperature above 22°C, and hypersalinity all suppress mangrove nitrogen removal capacity. Our findings provide the scientific foundation for “Blue Nitrogen” credits, offering a transformative financing mechanism for coastal water quality management that could reshape both mangrove conservation and nitrogen pollution mitigation strategies, worldwide.