Restoration versus natural regeneration in a neotropical mangrove: Effects on plant biomass and crab communities

Mangrove restoration is a powerful tool for reconstructing degraded tropical estuaries worldwide. The level of intervention necessary for rebuilding a mangrove area is still under study because this system is quite dynamic and some degraded areas are able to recover by themselves. We compared a Restored Area planted with Rhizophora mangle and a Self-recovered Area, to investigate how they would differ in respect to their plant and crab assemblages. In each area, 10 plots were randomly sampled for measuring tree richness, density, diameter at breast height and biomass, as well as crab richness and density after five years from recover. Plant height and biomass, as well as crab density, were significantly higher in the Restored in relation to the Self-recovered Area. However, tree richness was higher in the Self-recovered Area and crab assemblage reached in five years a similar composition in assisted, naturally recovered and natural areas, showing the high resilience of this important functional group. Active planting of R. mangle propagules can significantly improve mangrove recovery in sites with high propagule predation, increasing tree biomass and accelerating the return of animal functional groups such as crabs. However, if resources for active restoration are scarce, passive recovery can be a successful low cost alternative for mangrove restoration that preserves tree diversity and crab assemblages.