A ground-truthed national atlas of mangroves in Mauritius: spatial baselines, blue carbon significance, and implications for climate resilience in Small Island Developing States

Abstract

Mangroves provide coastal protection, nursery habitat, nutrient retention and long-term carbon storage, yet national-scale mangrove information remains incomplete in many Small Island Developing States (SIDS), where forests are often narrow, fragmented and difficult to resolve using medium-resolution satellite products alone. This study presents a comprehensive national mangrove atlas for mainland Mauritius, developed from island-wide ground surveys, GPS-referenced site documentation, manually digitised mangrove polygons and district-level geospatial synthesis. Mangrove coverage maps were baseline-validated using 2019 field data and Google Earth Pro imagery. Subsequent 2026 update integrated latest available remote sensing data with sporadic field-truthing visits. The atlas identifies 244.5 ha (~2.445 km²) of mangroves distributed across the seven coastal districts, with strong spatial concentration in the eastern coastal areas, namely, Riviere du Rempart and surrounding islets (~92.80 ha; ~38.0%), Flacq and surrounding islets (~60.62 ha; ~24.8%) and Grand Port (~55.73 ha; ~22.8%). Boundary sensitivity analysis produced an indicative boundary-derived area envelope of ±24.9 ha (~10.2%). Field validation confirmed that mangroves occur as estuarine stands, lagoon fringes, hypersaline or saltpan-associated patches, islet mangals and restored stands. The atlas provides a reproducible spatial baseline for environmental impact assessment, restoration prioritisation, post-disaster monitoring and future national blue carbon accounting. We show that field-validated ecological atlases remain essential scientific infrastructure for SIDS, where mangrove systems are small in area but disproportionately important for coastal resilience and climate governance. Recent mapping upgrade indicates that the mapped mangrove extent increased by ~12.81% as compared to data captured in 2019. Using stable, mature stands as a predictive proxy, the mangrove extent yields an overall screening-level estimate of approximately 21,829.3 t AGB, corresponding to ~33,617.5 t CO₂e, and ~10,234.3 t BGB, corresponding to ~15,775.2 t CO₂e. Surface sediment carbon was estimated separately at ~0.25 t organic C per tonne of surface sediment, corresponding to ~0.71 t CO₂e.