Mangroves occur in the waterlogged, salty soils of sheltered tropical and subtropical shores. They are subject to the twice-daily ebb and flow of tides, fortnightly spring and neap tides, and seasonal weather fluctuations. They stretch from the intertidal zone up to the high-tide mark. These forests are comprised of 12 genera comprising about 60 species of salt-tolerant trees.
With their distinctive nest of stilt and prop-like roots, mangroves can thrive in areas of soft, waterlogged, and oxygen-poor soil by using aerial and even horizontal roots to gain a foothold. The roots also absorb oxygen from the air, while the tree's leaves can excrete excess salt.
Associated with the tree species are a whole host of aquatic and salt-tolerant plants. Together they provide important nursery habitats for a vast array of aquatic animal species.
Mangrove ecosystems are most diverse in South Asian seas and least diverse in the Caribbean. Mangrove forests on the western coast of Madagascar support a number of endemic bird species that are endangered. In some tropical countries, such as India, the Philippines, and Vietnam, over 50% of mangrove ecosystems have been lost in this century.
Most species typically have relatively widespread distributions; low diversity floras but overall alpha diversity very high when terrestrial and aquatic species are considered; very low beta diversity and low ecoregional endemism; some highly localized species exist; strong zonation along gradients; several distinct mangrove habitat formations.
Mangroves require relatively intact hydrographic and salinity regimes, without these conditions remaining within natural ranges the persistence or restoration of mangroves is difficult or impossible.
Sensitivity to Disturbance
Alterations of hydrography and substrate have considerable impact, but restoration potential is high; mangroves are susceptible to pollution, particulary oil and other petroleum compounds; alteration of salinity levels can have dramatic impacts on mangroves.