Assessment of Mangrove Ecosystem Health, Blue Carbon Stocks, and Restoration Potential in São Tomé and Príncipe

Mangrove ecosystems are critical for climate resilience, coastal protection, biodiversity conservation, and carbon sequestration. Despite their importance, information on mangrove extent, condition, and restoration opportunities remains limited in many Small Island Developing States (SIDS), including São Tomé and Príncipe (STP). This study provides the first national assessment of mangrove ecosystem health, blue carbon stocks, and restoration potential in STP to support conservation planning and sustainable blue economy development. Mangrove mapping was conducted using Sentinel satellite imagery, Geographic Information Systems (GIS), and field verification. Ecological assessments were undertaken in 24 randomly distributed plots (100 m² each) across mangrove sites on São Tomé and Príncipe islands. Data collected included species composition, stand density, tree height, stem diameter, biomass, carbon stocks, harvesting pressure, and natural regeneration. Potential restoration sites were evaluated using hydrological, ecological, and land-use suitability criteria. Mangroves in STP were estimated to cover 183 ha distributed across 21 sites, with six mangrove species recorded. Mean stand density was 2,170±366 stems ha⁻¹, basal area 25±3.9 m² ha⁻¹, and total biomass 337.2±53.1 Mg ha⁻¹. Mean biomass carbon was estimated at 157.9±24.9 Mg C ha⁻¹, while total ecosystem carbon density reached approximately 938.1 Mg C ha⁻¹, demonstrating the significant blue carbon value of these ecosystems. However, localized overexploitation, altered hydrology, pollution, and inadequate natural regeneration were observed in several sites. Approximately 26.5 ha were identified as priority areas for restoration. Experimental restoration efforts achieved an average seedling survival rate of 82% six months after planting, indicating strong potential for ecosystem recovery. The findings provide a critical baseline for mangrove conservation, climate adaptation, and blue carbon initiatives in STP. Targeted restoration and community-based management can enhance coastal resilience while supporting sustainable blue economy opportunities in Small Island Developing States.