Baseline carbon emission factors for Indonesian seagrass ecosystems derived from a chronosequence modeling approach

Carbon biogeochemical dynamic in seagrass ecosystems is strongly influenced by disturbance, and consequently emission factors (EF) are needed for national greenhhouse-gas accounting. Indonesia is home to vast seagrass meadows, but EF values have been poorly constrained and presently use global Tier-1 defaults. This study applies a chronosequence approach to estimate EF using a national dataset of seagrass condition, carbon stock, and degradation status. The EF values at the site level and country-wide varied between 0.53 and 3.25 tC ha^-1 yr^-1. Higher EF values were generally observed in areas along the southern coasts of Java and parts of Bali and Sumatra, whereas lower values were more common in Sulawesi, Maluku, and Papua. Despite temporal variability, regional EF patterns were assessed descriptively across five oceanographic regions, with spatial contrasts remaining consistent across reference scenarios and sensitivity analyses. Sensitivity testing further revealed that the EF estimates remain robust using a fixed biogeochemical baseline. This study provide the country-specific estimates of seagrass carbon emissions factors for Tier-2 reporting within Indonesia and identify those regions considered to be a priority area in need of targeted management to minimise seagrass carbon loss.