Spatial-temporal patterns and environmental controls of soil organic carbon stocks in global tidal wetlands since 2009

Dataset and Code for "Spatial-temporal patterns and environmental controls of soil organic carbon stocks in global tidal wetlands since 2009" Abstract: Tidal wetlands are important blue carbon sinks and a global research priority for climate mitigation due to their high carbon storage. While current global estimates of tidal wetland soil organic carbon (SOC) stocks mainly focus on individual wetland types and calculate changes based on wetland area changes, comprehensive assessments of SOC stocks across tidal wetland types and their dynamics remain scarce. By jointly accounting for spatio-temporal changes in both SOC density and wetland extent, this study provides the first spatially explicit and temporally resolved global assessment of SOC stocks and decadal changes across major tidal wetland types: mangroves, salt marshes, and tidal flats. Using a spatio-temporal digital soil mapping (ST-DSM) framework, we integrated global soil observations (5,489 locations, 42,154 soil layer records) with 62 environmental covariates to generate 90 m SOC maps at three depth intervals (0 ~ 30 cm, 30 ~ 60 cm, and 60 ~ 100 cm) for two time periods (2009-2014 and 2015-2020). Results reveal a global SOC decline from 8.80 (±0.09) Pg to 8.26 (±0.09) Pg (-6.1%), with greater losses in deeper layers. Low-latitude regions such as southern Asia and Africa were key loss hotspots. Mangroves showed the largest losses, mainly driven by decrease in SOC density. Tidal flats lost both SOC density and area, whereas salt marshes exhibited moderate gains caused by area expansion and SOC density increase. SOC losses were more pronounced in countries at lower-middle and upper-middle income levels. Driver analysis indicated that oceanographic and climatic factors were the dominant controls on SOC dynamics, although the key drivers for the three wetland types differed. Quantifying spatial and temporal variability of SOC at a global scale, this work reveals the magnitude and drivers of blue carbon change and underscores the need for targeted wetland conservation to support sustainable management and climate mitigation. File Description: Each .7z file contains multiple results for UL, mean, and LL for two time periods: 2009-2014 and 2015-2020. "mosaic.7z" contains SOC density results (Mg/ha); "mosaic_pg.7z" contains SOC stocks results (Pg), categorized by different depths (0 ~ 30 cm, 30 ~ 60 cm, 60 ~ 100 cm). Taking 0030_2014_LL.tif as an example: 0030 represents the soil depth range (0-30 cm; other depths include 30-60 cm and 60-100 cm). 2014 refers to the time period (2014 = 2009-2014; 2020 = 2015-2020). LL represents the lower prediction limit (0.05 quantile), while UL and mean represent the upper prediction limit (0.95 quantile) and the mean estimate, respectively. The mean is used as the primary result.