A mangrove is a shrub or tree that grows mainly in coastal saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen and remove salt, allowing them to tolerate conditions that kill most plants. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse due to convergent evolution in several plant families. They occur worldwide in tropical and subtropical coastal areas, mainly between latitudes 30° N and 30° S, with the greatest mangrove area within 5° of the equator. Mangrove plant families first appeared during the Late Cretaceous to Paleocene epochs and became widely distributed in part due to the movement of tectonic plates. The oldest known fossils of mangrove palm date to 75 million years ago. Mangroves are salt-tolerant (halophytic) and are adapted to live in harsh coastal conditions. They contain a complex salt filtration system and a complex root system to cope with saltwater immersion and wave action. They are adapted to the low-oxygen conditions of waterlogged mud, but are most likely to thrive in the upper half of the intertidal zone. The mangrove biome, often called the mangrove forest or mangal, is a distinct saline woodland or shrubland habitat characterized by depositional coastal environments, where fine sediments (often with high organic content) collect in areas protected from high-energy wave action. The saline conditions tolerated by various mangrove species range from brackish water, through pure seawater (3 to 4% salinity), to water concentrated by evaporation to over twice the salinity of ocean seawater (up to 9% salinity). Beginning in 2010, remote sensing technologies and global data have been used to assess areas, conditions and deforestation rates of mangroves around the world. In 2018, the Global Mangrove Watch Initiative released a new global baseline which estimates the total mangrove forest area of the world as of 2010 at 137,600 km2 (53,100 sq mi), spanning 118 countries and territories. A 2022 study on losses and gains of tidal wetlands estimates a 3,700 km2 (1,400 sq mi) net decrease in global mangrove extent from 1999 to 2019. Mangrove loss continues due to human activity, with a global annual deforestation rate estimated at 0.16%, and per-country rates as high as 0.70%. Degradation in quality of remaining mangroves is also an important concern. There is interest in mangrove restoration for several reasons. Mangroves support sustainable coastal and marine ecosystems. They protect nearby areas from tsunamis and extreme weather events. Mangrove forests are also effective at carbon sequestration and storage. The success of mangrove restoration may depend heavily on engagement with local stakeholders, and on careful assessment to ensure that growing conditions will be suitable for the species chosen. In 2025, the area of mangroves globally is estimated at 15.9 million hectares. Asia has the largest area, at 6.10 million ha, and Europe reported no mangrove area. Among countries and areas, Indonesia has the world's largest extent of mangroves, at 3.40 million ha, followed by Brazil (1.39 million ha), Australia (1.11 million ha), Nigeria (976,000 ha) and Mexico (947,000 ha). Collectively, these five countries host almost half (49%) of the global mangrove area. The International Day for the Conservation of the Mangrove Ecosystem is celebrated every year on 26 July.
Etymology
Etymology of the English term mangrove is speculative and disputed. The term may have come to English from the Portuguese mangue or the Spanish mangle. Further back, it may be traced to South America and Cariban and Arawakan languages such as Taíno. Other possibilities include the Malay language manggi-manggi. The English usage may reflect a corruption via folk etymology of the words mangrow and grove. The word "mangrove" is used in at least three senses:
Most broadly to refer to the habitat and entire plant assemblage or mangal, for which the terms mangrove forest biome and mangrove swamp are also used; To refer to all trees and large shrubs in a mangrove swamp; and Narrowly to refer only to mangrove trees of the genus Rhizophora of the family Rhizophoraceae.
Biology According to Hogarth (2015), among the recognized mangrove species there are about 70 species in 20 genera from 16 families that constitute the "true mangroves" – species that occur almost exclusively in mangrove habitats. Demonstrating convergent evolution, many of these species found similar solutions to the tropical conditions of variable salinity, tidal range (inundation), anaerobic soils, and intense sunlight. Plant biodiversity is generally low in a given mangrove. The greatest biodiversity of mangroves occurs in Southeast Asia, particularly in the Indonesian archipelago.
Adaptations to low oxygen The red mangrove (Rhizophora mangle) survives in the most inundated areas, props itself above the water level with stilt or prop roots and then absorbs air through lenticels in its bark. The black mangrove (Avicennia germinans) lives on higher ground and develops many specialized root-like structures called pneumatophores, which stick up out of the soil like straws for breathing. These "breathing tubes" typically reach heights of up to 30 cm (12 in), and in some species, over 3 m (9.8 ft). The roots also contain wide aerenchyma to facilitate transport within the plants.
Nutrient uptake Because the soil is perpetually waterlogged, little free oxygen is available. Anaerobic bacteria liberate nitrogen gas, soluble ferrum (iron), inorganic phosphates, sulfides, and methane, which make the soil much less nutritious. Pneumatophores (aerial roots) allow mangroves to absorb gases directly from the atmosphere, and other nutrients such as iron, from the inhospitable soil. Mangroves store gases directly inside the roots, processing them even when the roots are submerged during high tide.
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