The general distribution of mangroves corresponds to that of tropical forests, but extends further north and south of the equator, sometimes beyond the tropics. However, over the past several decades, the global area in mangroves has increasingly diminished as a result of a variety of human activities, such as overharvesting, freshwater diversion and conversion to other uses. Mangrove forests are vital for healthy coastal ecosystems. A primary factor of the natural environment that affects mangroves over the long term is sea level and its fluctuations. Other shorter-term factors are air temperature, salinity, ocean currents, storms, shore slope, and soil substrate.
Most mangroves live on muddy soils, but they also grow on sand, peat, and coral rock.
If tidal conditions are optimal, mangroves can flourish far inland, along the upper reaches of coastal estuaries. Evolutionary adjustments to varying coastal marine environments have produced some astounding biological characteristics within mangrove plant communities. Certain species of mangroves exclude salt from their systems, others actually excrete the salt they take in via their leaves, roots, or branches. In salt excluding mangrove species , the mangrove root system is so effective in filtering out salt that a thirsty traveler could drink fresh water from a cut root, though the tree itself stands in saline soil. The mangroves as a resource Most people have thought of mangroves as noxious impenetrable swamps full of diseases, and they used to be destroyed as a public health measure, but now we know better.