Species that live in mangroves are highly specialized to tolerate and even benefit from the brackish water of coastal lagoons or the salty water of the sea. Excess salt is expelled through glands on the leaves that exude salty water. The plants are also adapted to germinate in an environment frequently battered by waves and periodically flooded by tidal cycles. The most lush mangroves are found in areas influenced by freshwater currents flowing into the sea through infiltration or percolation (coastal swamps or marshes) or directly at river estuaries. Another challenging factor for these plants is the poorly oxygenated soil, which is also often unstable. Reproduction can be asexual, but it is primarily sexual. A notable example of reproduction is found in the genus Rhizophora, which includes viviparous species. Instead of releasing seeds into the soil, they release plantlets or propagules (germinated from seeds on the plant) that reach the ground already formed, thus increasing their chances of taking root in the unstable soil. Given the unique environmental conditions of mangroves, suitable sites are uniformly colonized by such vegetation, with virtually no competitors except for marginal vegetation types. The mangrove biotope has also developed various forms of animal life (insects, amphibians, reptiles, and birds) that have adapted and specialized for this exclusive environment. An example is the red mangrove crab. Due to the discontinuity of the biotopic environment (submerged/dry), the consistency and continuity of the biocenosis, and other structural and functional considerations, there is no consensus on defining mangroves as a full ecosystem.
The mangrove is a type of vegetation (or forest) composed predominantly of woody plants that develops along the low-lying shores of tropical marine coasts, particularly in areas periodically submerged by tides. The WWF considers mangroves as a biome, one of the fourteen major habitat types that the Earth is divided into. The term "mangrove" is also often incorrectly used as a common name for some individual tree species representative of this type of vegetation. Mangroves (or "mangrove forests") typically consist of four zones parallel to the coastline: the first is made up of plants that are almost permanently submerged; the second (the mangrove proper, primarily consisting of species from the genus Rhizophora) is regularly flooded by high tides; the third consists of shrublands and is submerged only by the highest tides; and finally, the fourth, composed of halophytic shrub and tree species, is never submerged and has soil with lower salinity content. However, the last two zones are not always present. The morphological characteristic that distinguishes mangroves, namely the presence of "prop roots" that lift the trunk above the mud, is found only in the second and rarely in the third zone. It is estimated that mangroves cover an area of approximately 150,000 square kilometers worldwide, most of which is in Asia.
Mangroves are found in tropical and subtropical regions of both hemispheres, along the coasts of North America, South America, Africa, Asia, and Oceania. Generally, mangroves on the coasts of the Indian Ocean and the western Pacific are the richest in species, while those in the Americas and the eastern Atlantic coasts have fewer species. The mangrove biome is not present in the Palearctic ecozone. Mangroves do not have a single scientific name because they represent a heterogeneous group of species belonging to different families and botanical genera. However, here are some examples of scientific names of common mangrove species:
- Rhizophora mangle**: (Family: Rhizophoraceae) - Known as the red mangrove.
- Avicennia germinans**: (Family: Acanthaceae, previously Avicenniaceae) - Known as the black mangrove.
- Laguncularia racemosa**: (Family: Combretaceae) - Known as the white mangrove.
- Bruguiera gymnorhiza**: (Family: Rhizophoraceae) - One of the Bruguiera mangrove species.
- Sonneratia alba**: (Family: Lythraceae, previously Sonneratiaceae) - Known as the apple mangrove.
mangrove | global tree biodiversity
