A site suitability index framework for mangrove afforestation in dynamic coastal char lands of Bangladesh

Successful mangrove afforestation in newly accreted coastal char lands depends strongly on appropriate site selection. The assessment based on individual environmental variables may not capture the multiple factors influencing mangrove establishment. Eighty-five sampling units across 157 uniform 25 ha grids were selected using stratified random sampling. These sites were distributed across 18 pre-screened potential mangrove afforestation sites in Barguna, Bhola, and Patuakhali districts of Bangladesh. The present study developed a field-based Site Suitability Index (SSI) using five sub-indices: Land Cover Index (LCI), Ecological Condition Index (ECI), Soil-Hydrology Index (SHI), Sediment Stability Index (SedI), and Disturbance Index (DI). Sensitivity analysis examined how changes in sub-index weights affected SSI classifications. About 92% of the assessed area was classified as Suitable or Highly Suitable, about 7% as Unsuitable, and the remaining area consisted of existing mangrove plantations. Soil-hydrological conditions and sediment stability were important components of overall suitability, whereas sandy substrates represented a major constraint in unsuitable areas. SSI classifications were relatively stable under alternative weighting scenarios, with 91.8–100% of sampling units retaining their baseline classes under ±20% changes in individual sub-index weights. The high proportion of suitable areas should be interpreted in the context of the preliminary screening of the study sites. The SSI provides a structured field-based approach for assessing potential mangrove afforestation sites; however, follow-up monitoring of plantation establishment, survival, growth, and natural regeneration is required to validate and, where necessary, refine the framework.