Mangroves

Mangroves (generally) are trees and shrubs that grow in saline (brackish) coastal habitats in the tropics and subtropics. The word is used in at least three senses: (1)most broadly to refer to the habitat and entire plant assemblage or mangal, for which the terms mangrove swamp and mangrove forest are also used, (2)to refer to all trees and large shrubs in the mangal, and (3) narrowly to refer to the mangrove family of plants, the Rhizophoraceae, or even more specifically just to mangrove trees of the genus Rhizophora. Mangals are found in depositional coastal environments where fine sediments, often with high organic content, collect in areas protected from high energy wave action.
Mangroves protect the coast from erosion, storm surges (especially during hurricanes), and tsunamis. Their massive root system is efficient at dissipating wave energy. Likewise, they slow down tidal water enough that its sediment is deposited as the tide comes in and is not re-suspended when the tide leaves, except for fine particles. As a result, mangroves build their own environment. Because of the uniqueness of the mangrove ecosystems and their protection against erosion, they are often the object of conservation programs including national Biodiversity Action Plans.
Despite their benefits, the protective value of mangroves is sometimes overstated. Wave energy is typically low in areas where mangroves grow, so their effect on erosion can only be measured in the long-term. Their capacity to limit high-energy wave erosion is limited to events like storm surges and tsunamis. Erosion often still occurs on the outer sides of bends in river channels that wind through mangroves, just as new stands of mangroves are appearing on the inner sides where sediment is accreting.