Mangrove

The intertidal challenge

Mangrove trees solve a problem most plants can’t: how to grow with roots that flood twice a day with full-salinity seawater, in soft anoxic mud, in habitats periodically smashed by storms. The solutions are convergent across families:

• Salt management. Mangroves either exclude salt at the root membrane (filtering it out of the water taken up by the roots — Rhizophora) or secrete salt through specialized leaf glands (Avicennia) or concentrate salt in old leaves that are then dropped (Excoecaria) — or some combination.
• Aerial roots. Anoxic mud has no oxygen for root respiration. Mangrove root systems extend above the mud as pneumatophores (vertical “snorkel” roots in Avicennia) or prop roots (arching aerial roots in Rhizophora) or knee roots (looped above-mud roots in Bruguiera). These let the tree breathe.
• Vivipary. Many mangroves germinate seeds on the parent tree, the embryo growing into a torpedo-shaped propagule (10–30 cm long) that drops, floats, and lodges in suitable mud — a strategy adapted to dispersal in tidal water and to immediate establishment in soft substrate.

The convergent adaptations have evolved at least 16 independent times across unrelated plant families. “Mangrove” is therefore a functional category, not a taxonomic one.

Functions

Fishery nursery. Mangrove root systems shelter juvenile fish, shrimp, crabs from offshore predators. A large fraction of tropical commercial offshore fisheries depends on mangrove nursery habitat — estimated at 70–80% of offshore fish caught in some tropical regions.

Storm and tsunami buffer. Mangrove forests reduce wave energy and storm-surge inundation. The 2004 Indian Ocean tsunami caused dramatically less damage on coastlines with intact mangrove than on coastlines that had been cleared. Vietnamese mangrove-restoration work specifically motivated by typhoon-defense has been substantial since the 1990s.

Carbon storage. Mangrove forests are one of the most carbon-dense ecosystems on Earth — most of the carbon stored not in the trees themselves but in the deep peat-like mangrove sediments, accumulating for thousands of years. Per hectare, mangroves store 3–5 times more carbon than typical tropical terrestrial forest. The disturbance of mangrove sediments releases this carbon at scale.

Major mangrove regions

• Sundarbans. The Ganges-Brahmaputra delta mangroves spanning the India-Bangladesh border — the world’s largest contiguous mangrove forest at ~10,000 km². Home to the Bengal tiger and central to the cultural identity of the surrounding Bawali (mangrove-honey gatherers) and Mawali (fishers) communities.
• Cà Mau, Vietnam. The southern tip of the Mekong Delta, Vietnam’s largest mangrove complex.
• Sundarbans-like coastlines around the Indian Ocean. The mangrove arcs of the East African coast (Mozambique, Tanzania, Kenya, Madagascar), Sri Lanka, Myanmar’s Ayeyarwady delta, Indonesian Borneo, the Philippines.
• Caribbean and Atlantic Americas. Florida Everglades mangroves, Cuban and Hispaniolan mangroves, Belizean Caribbean coast, Brazilian Pará-Maranhão coast.
• West Africa. Senegal, Sierra Leone, Nigeria, Cameroon mangroves of the Gulf of Guinea.
• Australian-Pacific. Northern Australia, Papua New Guinea, the Pacific island chains.

See also

Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.

• Demonstrated by: [[mekong-delta]] · [[indo-gangetic-plain]]

Sources

• Spalding, Mark, World Atlas of Mangroves (2010)
• Global Mangrove Alliance — annual State of the World’s Mangroves
• Wikipedia — Mangrove

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A concept entry in the 0mn1.one wiki.