Revealing performance and environmental thresholds of mangrove nature-based solutions: A nonlinear blue carbon...

Mangroves are a cornerstone coastal nature-based solution (NbS), providing long-term carbon sequestration, shoreline stabilization, and ecosystem regulation services. However, the ability to precisely estimate mangrove blue carbon storage and to identify its nonlinear responses and environmental factor thresholds under interacting environmental gradients remains very limited. Here, we developed an integrated analytical framework and applied it to the Qinglan Mangrove Provincial Nature Reserve in Hainan, China. Integrating field sampling and remote sensing inversion, a resolution (50 m × 50 m) dataset was established to examine spatial patterns, key environmental drivers, and nonlinear responses of mangrove blue carbon. The results show the total blue carbon stock of mangroves in the study area was 0.1362 Tg C, with an average blue carbon storage of 373.43 ± 17.76 Mg C/ha. Spatial analysis revealed distinct clusters where above- and below-ground biomass carbon co-varied, reflecting strong environmental controls across soil, hydrological, and topographic gradients. Predictive modelling further revealed strong spatial variability in the relative importance of environmental drivers. Soil nutrients played a dominant promotive role in high-carbon zones, whereas salinity and redox factors constrained carbon accumulation in lower-value zones. Nonlinear response analysis clearly identified the thresholds of environmental factors regulating mangrove carbon accumulation, revealing the potential vulnerability of mangrove NbS under environmental change. These findings provide a transferable analytical framework for identifying environmental factor thresholds and blue carbon performance disparities in mangrove ecosystems, offering practical guidance for adaptive coastal management, targeted mangrove restoration, and long-term blue carbon governance.