This is due to the pattern of hot and cold ocean currents (Pinet, 1998 Hogarth, 1999 ).Īs a result of global warming, the area with a suitable settling climate for mangroves is currently expanding in the polar direction. In the Southern Hemisphere, mangals generally occur further south on the eastern edges of landmasses than on the western side.
The number of species tends to decrease with distance from the equator. The isotherm of 20 ☌ in winter is a good indicator of the distribution limit. Their occurrence is most closely related to seawater temperature. They do not tolerate frost, but can cope with air temperatures down to 5 ☌. Mangroves are almost exclusively tropical, but also occur in the subtropics. A species overview is given in the Mangrove Species Database. Over the world, 54-70 species and hybrids in 20-27 genera and 16-19 families are found (Berness et al., 2001 ). The most highly developed and most species-rich mangals are found in Indonesia, Australia and Malaysia. The global distribution of mangroves is shown in Fig. The distribution, density and species composition are determined by the water and air temperatures during the winter, exposure to wave action and tidal currents, the range of the tide, the type of sediment and the chemistry of the seawater. The buttonwoods are not really a mangrove species, but are a transition species between the mangrove and the terrestrial vegetation.Įstimates of the area covered by mangroves worldwide range between 84,000 and 136,000 km 2 (Hamilton and Casey, 2016 Worthington and Spalding, 2018 ). The upper limit of the mangroves is occupied with white mangroves and buttonwoods. These areas receive only shallow flooding during high tide. More landwards are the black mangroves ( Avicennia). Red mangroves ( Rhizophora) are usually found closest to the edge of the water, where the greatest degree of tidal flooding occurs. Each of the zones is dominated by a different mangrove species and associated fauna and flora. Deposition of sediments by small-moderate waves and tides.ĭue to these processes, a well-marked zonation is seen.
Saline water they are facultative halophytes.
Shores must be free of strong wave action and strong tidal currents.Exceptions are the development of mangroves on corals, as for example in Papua New Guinea and Kenya. Average temperature of the coldest month higher than 20☌ the seasonal temperature range should not exceed 5☌.Requirements for the development of mangroves are: Mangroves are frequently associated with saline lagoons and are regularly found on protected sides of islands, atolls and tropical estuaries (Karleskint, 1998 ). Mangals therefore fulfill an important coastal protection function. Wave energy reduction can be greater than 50% on average and increases with increasing offshore wave heights (Horstman et al., 2014 ). While growing, mangal forests further reduce waves and increase sedimentation. They settle where there is little wave action and where muddy sediments accumulate. The dominant vegetation are several species of mangrove: woody trees and shrubs with a thick, partially exposed network of roots that grow down from the branches into the water and sediment. They are salt-tolerant forested wetlands at the interface between the terrestrial landscape and the marine environment. They replace salt marshes in tropical and subtropical regions. The word mangrove is derived from the Portugese word mangue which means “tree” and the English word grove which is used for trees and shrubs that are found in shallow, sandy or muddy areas (Karleskint, 1998 ). Mangrove forests or mangals are a type of intertidal wetland ecosystems. North and South America, Africa and Middle-East, Asia and Oceania (incl. They are represented on all continents with tropical and subtropical coasts, i.e. They form unique intertidal forests at the edge of land and sea, see Fig. Mangroves are the only trees that are capable of thriving in salt water. 9.2 Principles of Ecological Mangrove Restoration (EMR).9 Mangrove restoration and rehabilitation.