The first nation-wide assessment identifies valuable blue‑carbon seagrass habitat in Indonesia is in moderate condition

Seagrasses help mitigate climate change by capturing and storing carbon for a very long time. Despite their sig- nificance, multiple threats are putting pressure on this valuable habitat. Seagrass conservation and restoration is essential to maintain the carbon sequestration service, along with the other ecosystem services (e.g., fisheries production). Information on the status of seagrass habitat is required to enable proactive management strategies. In this study, we assessed the ecological status of seagrass meadows in Indonesia, a globally significant hotspot of blue carbon habitat, using five resilience parameters: seagrass species richness, seagrass cover, macroalgal cover, epiphyte cover, and water transparency. We collected data on these parameters from 18 locations across Indonesia and developed the Seagrass Ecological Quality Index (SEQI, range 0–1) that summarises the parame- ters into a standard seagrass assessment. We recorded that Thalassia hemprichii and Enhalus acoroides were the most common species in the sampling locations. Seagrass cover was on average 39 ± 3.6% (mean ± SE) which was lower than measured 3 years before (46%). Macroalgal cover and epiphyte cover were relatively low with mean values 10 ± 1.8% and 22 ± 4.4% respectively. Most locations had clear water. Our analysis showed that Indonesia's seagrass meadows are generally in moderate condition, indicated by the mean value of SEQI 0.68 ± 0.02. These findings provide a baseline for seagrass conservation and management. It enables setting up of specific goals for management action plans, at both the local, national and international level, and where appropriate, track the progress of management actions based on threat mitigation or restoration over time. The SEQI is a useful tool to summarise the condition of tropical seagrass meadows in Indonesia and could be ap- plied across Southeast Asia or the Tropical Indo-Pacific bioregion.