Mangrove forests are the only forests situated at the sea-land interface in tropical and subtropical latitudes. They are often called as ‘marine tidal forests', ‘coastal woodlands' or ‘oceanic rainforests'. The Mangrove forest ecosystem supports biologically diverse groups of organisms. This is due to diversified habitats such as core forests, litter forest floors, mudflats, adjacent coral reefs and seagrass ecosystems as well as the contiguous water bodies that consist of the rivers, bays, inter tidal creeks, channels and backwaters. The mangroves can exist under wide ranges of salinities, tidal amplitudes, winds, and temperatures, even in muddy and anaerobic soil conditions. Over a long period of time the mangroves and their components have been studied extensively but still remain poorly understood.
Mangroves possess unique characteristics. They are one of the world's most productive vegetation communities with capacity for high rate of primary productivity (~ 24 tons /hectare / year) and accumulation of atmospheric CO2 (0.055 g C/cm2 soil). Standing crop in the mangrove forest is greater than any other aquatic systems in the world. No other groups of plants have high adaptation to extreme environmental conditions. They significantly contribute to oceanic carbon (25 billion kg of carbon to ocean per year in northern Brazil). The mangroves are live sea walls, more effective than concrete wall structures to keep away the seawater.
Mangroves are of valuable ecological and economic resources, securing life and providing livelihood to the coastal people. The mangroves offer coastal protection against erosion, waves, currents and storms as well natural calamities. They serve as breeding sites and nursery grounds for crabs, prawns, mollusks, other shellfishes, finfishes, birds, reptiles and mammals. They are source of wood, poles, firewood, charcoal, fodder, medicines, honey and other forest products. They are accumulation sites of sediment, carbon, nutrients and pollutants and playing a central role in biogeochemical cycles in the coastal environment. Mangroves protect other marine ecosystems such as coral reefs and seagrass. Economic value of mangroves is more than US$ 10,000 /ha/yr, which is greater than that of coral reefs, continental shelves and opens sea. Endowed with arching roots, breathing roots, salt-vomiting leaves, mud-dancing fishes, and breath-taking beauty, the mangroves are sites of education, recreation and ecotourism.
About 90% of the global mangroves are growing in developing countries and they are under the condition of critically endangered and nearing extinction in 26 countries. The rate of mangrove is 1-2 % per year which is greater than the declines of coral reefs and tropical rain forests. The mangroves continue to disappear globally due to growing pressure of urban and industrial developments along the coast, combined with climate change and sea level rise. The world mangrove experts are of the opinion that the long term survival of mangroves is at great risk due to fragmentation of the habitats and that the services offered by the mangroves may likely to be lost totally within 100 years. In this context, better understanding of mangrove forest ecosystems by the people world over will ensure increased care for mangroves. Bearing this in mind, the present online course of mangroves is designed for their better understanding among the people around the world.