Mangrove rehabilitation projects often fail completely or fail to meet their objectives. This study examines village-level rehabilitation planting carried out in 13 villages (119 rehabilitation attempts at 74 sites) across two countries in southeast Asia, to assess village-level rehabilitation effectiveness, and to identify what factors influenced outcomes. Mean propagule survival across all rehabilitation attempts was 20% with a median of 10%. Sixty six percent of attempts had a survival rate of less than 20%. Mid mangrove zone projects were more successful (mean 30%) than rehabilitation projects at other elevations. Planting on mudflats, representing 32% of rehabilitation/afforestation attempts, achieved only a 1.4% propagule survival rate.
The overall low success rate was due to several inter-related factors. Poor site/species matching on high and low elevation sites was common; for example, Rhizophora spp. was used alone or in combination at least 65% of the time, including on mudflats where this genus is ecologically unlikely to establish. Site selection was often driven by the desire to achieve centrally defined area or propagule planting targets, rather than survivorship targets, and thus required large, uncontested project areas. Conversely, the presence of natural regeneration, even if in small amounts, was associated with higher than average success. Therefore, it was estimated that only 16% of planting attempts were actually necessary.