Mangroves are woody trees or shrubs that grow in mangrove habitats or mangal (Hogarth, 1999). The mangrove is often considered a type of biome. Mangrove habitat is exclusively tropical and tidal, and therefore having soil or sediment that is water-logged and saline or of variable salinity. Areas where mangal occurs includes estuaries and marine shorelines. A wide variety of plant species can be found in mangrove habitat, but some 54 species in 20 genera, belonging to 16 families constitute the "true mangroves" — species that occur exclusively in mangrove habitats and rarely elsewhere (Hogarth, 1999).