Environmental Description:  Soil/substrate/hydrology: Mangroves (mangal, mangle) are tidal, estuarine forested wetlands that occur along the (sheltered) coasts of tropical latitudes of the Earth. They are commonly found on the intertidal mudflats along the shores of estuaries, usually in the region between the salt marshes and sea-grass beds. Where tidal amplitude is relatively low, they form narrow bands along the coastal plains, and rarely penetrate inland more than several kilometers along rivers. Where tidal amplitude is greater, mangroves extend farther inland along river courses forming extensive stands in the major river deltas. Mangrove cays occur also within the lagoon complex of barrier reefs (Stoddart et al. 1982). In general, mangroves fall within two categories: mangroves of oceanic islands and inland mangroves. The latter need to adapt to a pronounced variation in salinity due to the variations in freshwater carried from the interior streams, while the former owe the salinity gradient to the rate of evaporation in the shallow ponds and mudflats and the rainfall on site, especially in the case of small to very small islands.

Gilmore and Snedaker (1993) described five distinct types of mangrove forests based on water level, wave energy, and pore water salinity: (1) mangrove fringe forests, (2) overwash mangrove islands, (3) riverine mangrove forests, (4) basin mangrove forests, and (5) dwarf mangrove forests. Dwarf forests are most commonly observed in south Florida, around the vicinity of the Everglades, but occur in all portions of the range where physical conditions are suboptimal, especially in drier transitional areas.

Rainfall plays an important role in distribution and species composition because rainfall regulates salt concentrations in soils and plants, as well as providing a source of freshwater for the mangroves. This is an important factor when propagules begin to take root and when mature individuals bloom and fruit. If high rainfall occurs over a short period and other months of the year are prone to drought, the conditions can be considered unfavorable for the growth and distribution of mangroves.

Mangroves provide habitats for commercially important crustaceans; are important nursery grounds for juvenile fish; filter and trap pollutants and sediments from land runoff thus maintaining estuarine water quality; provide barriers and buffer zones to stabilize shorelines and prevent coastal erosion; and are also a major producer of organic material. Mangroves protect the coast against erosion, but monsoons and storms cause large waves and winds to erode the coast, destroying many mangrove areas. Sea level rise, together with monsoons or hurricanes and storms, accelerates the speed of mangrove coastal erosion.

Mangroves cannot tolerate frost, especially in the seedling stage, but mangroves are also regulated by sea temperatures, rarely occurring outside the range delimited by the winter position of the 20°C isotherm (Hogarth 2007). It is not entirely clear why mangroves are limited to the tropics. Given their pan-tropical distribution and the wide availability of muddy, saline habitats in temperate regions, there would seem to be many suitable opportunities to spread into these latitudes. Hogarth (2007) suggests that perhaps the combination of being a tree, tolerating salt, and coping with waterlogging creates a metabolic cost that is difficult to sustain in lower temperatures and shorter day lengths.