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Some 70 species of mangrove plants (trees and shrubs) are recognized from various regions of the world. They stand on riverbanks and coastlines of tropical and subtropical regions, with their characteristic roots in salt water where they are regularly subjected to tidal influences. In actuality, the species of plants known as mangroves belong to a number of plant families. The common characteristic, which they all possess, is tolerance to salt and brackish waters, achieved through the evolution of a variety of survival and reproductive strategies to tolerate the muddy, shifting, saline environment. Mangrove plants support a complex food web and provide a unique habitat for a diversity of animals. Traditionally, mangroves have supplied people with building materials, firewood, charcoal, food and medicine. They additionally provide a stabilizing effect for the riverbanks and coastlines, and may play an important role in the healthy functioning of adjacent ecosystems, such as terrestrial wetlands, salt marshes, seagrass beds and coral reefs.
The total area of mangrove in the world is some 181,000 square kilometres, with more than 40 percent occurring in Asia. Mangroves are largely confined to the regions between 30N and 30S of the equator, with notable extensions beyond this to the north in Bermuda and to the south in Australia, New Zealand and the east coast of South Africa. Within these confines they are widely distributed, although their latitude development is restricted along the western coasts of the Americas and Africa, as compared to the equivalent eastern coasts. In the Pacific Ocean natural mangrove communities are limited to western areas, and they are absent from many Pacific islands. There are two main centres of diversity for mangrove communities. The eastern group broadly corresponds with the Indo-Pacific. The western group fringes the African and American coasts of the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico, and also includes the eastern Pacific coast of the Americas. These two groupings have distinct characteristics separating them. However, their distribution patterns are similarly the result of a combination of historical factors, temperature and rainfall.
In recent years, the pressures of increasing population, food production and industrial and urban development have led to the destruction of a significant proportion of the world's mangroves. The shortage of productive land in developing countries has led to the clearance of many areas for agricultural purposes or for fish and shrimp ponds for commerial production. Mangroves have also been logged for timber, fuel wood and charcoal production, chipped for paper production and destroyed to provide land for the construction of mines, ports, tourist resorts and housing. The limited data that is available show that significant decreases in the global mangrove area have already occurred. In Southeast Asia, for example, the loss figures for four countries are: Malaysia - 12 % from 1980-1990; the Philippines - 4,000 sq km originally to 1,600 sq km, today; Thailand - 5,000sq km in 1961 to 2,470 sq km in 1986; and Vietnam - 4,000 sq km originally to 2,525 sq km, today. These figures suggest a total of some 7,445 sq km of mangrove loss, representing over 4% of the current global total.