Mangroves are trees and shrubs that grow in saline coastal habitats in the tropics and subtropics. The many species of trees and shrubs adapted to these conditions may not be closely related, yet are still grouped by the term "mangrove".
Mangroves typically form a woodland or shrubland habitat. Tropical mangrove forests occur in both estuaries and open coastland environments. To flourish they need deposits of sediment, high in organic content which is sheltered by the wave action of the sea.
The type and success of a mangrove forest is influenced by a number of factors. These include climate, salt tolerance, water level fluctuation, nutrients and wave energy.
Mangroves can be surprisingly resilient to water salinity. The saline conditions tolerated range from brackish water, through seawater up to over twice the salinity of seawater, where the salt has become concentrated by evaporation.
They are not so resilient to temperature stresses and only grow in areas where the temperature remains above 19°C. Growth of mangrove habitats is also restricted when there are temperature variations of more than 10°C.
Mangrove coastal protection
Mangrove forests protect tropical coastal areas from erosion. The massive root system of a mangrove forest dissipates wave energy, especially from storm surge and Tsunami.
Mangrove roots slow down the tidal water with the roots trapping the ocean sediment during the daily tidal cycle. In this way they stabilise land elevation by promoting sediment buildup in tidal areas. This filtering effect of mangrove forests also plays a vital role in protecting seagrass beds and coral reefs from damaging siltation.