Mangroves
Mangroves are communities of plants and animals existing within swampy intertidal mudflats in the Tropics, mainly at estuaries, riverbanks, and coastal regions subject to brackish water. Asia has 46 percent of the world's mangroves.
Diverse communities are found in mangroves. Frequent inundation and continual silting make the soil soft and clayey in texture, lacking aeration. Mangrove flora are uniquely adapted to such conditions. The red mangrove (Rhizophora mangle) has prop roots growing from the trunk for stability and bears germinated seedlings with long radicles. The white mangrove (Laguncularia racemosa) develops a dense network of cable roots within the soft mud for stability. A feature of this and several other species is spongy vertical structures growing from the cable roots, protruding several centimeters above the soil surface. These breathing roots (pneumatophores) help the plants obtain air. The black mangrove (Avicennia germinans) achieves stability by a massive growth of knee-shaped pneumatophores around the collar of the tree.
An abundance of animal species inhabits mangroves, including mollusks, crustaceans, insects, and fish. The fauna feed on organic matter mainly derived from leaf litter. The group of crabs called sesarmids may rely on fresh mangrove leaves as a food source.
Humans also benefit from mangroves. In countries such as Bangladesh, mangroves are the main source of livelihood for coastal populations. They derive fuel, medicines, and building materials from mangrove trees. Mangroves are also reliable sources of food: fruit such as Nipah palm nuts, and crabs, prawns, snails, and bivalves are constantly harvested. The complex structure of pneumatophores and fallen branches, and the abundant detritus, make mangroves nursery grounds for commercial varieties of fish, prawns, and crabs. Mangroves also help prevent erosion of the shore or riverbanks as their dense root networks help stabilize the soil.
More than 75 percent of the coastlines of tropical and subtropical countries were once covered with mangrove forests, which help to protect the shorelines. However, it is estimated that fewer than 50 percent of these remain today. The loss of mangroves in several countries is caused largely by urbanization, land reclamation, deforestation for charcoal and timber, mounting pollution problems, as well as the recent pressure from commercial shrimp farming. Industrial shrimp aquaculture has led to the clearing of large tracts of mangrove forest in Southeast Asia, Latin America, Africa, and the Pacific Islands. Furthermore, the pollution caused by organic waste from shrimp is an additional problem. In view of the importance of mangroves, several initiatives are being implemented in several of the countries mentioned to restore degraded mangrove forests and regenerate these on new mudflats. Active research is also being conducted internationally to develop sustainable models on how to derive benefits from the mangrove forests without destroying the ecosystem.
Further Reading
Lee, S. K., W. H. Tan, and S. Havanond. (1996) "Regeneration and Colonisation of Mangrove on Clay-Filled Reclaimed Land in Singapore." Hydrobiologia 319: 23–35.
Mangrove Action Project. (1990) "Mangrove Ecosystems." Retrieved 30 November 2001, from: http://www.earthisland.org/map/mngec.ht m.
Ng, P. K. L., and N. Sivasothi, eds. (1999) A Guide to the Mangroves of Singapore. 2 vols. Singapore: Singapore Science Centre.
Tomlinson, P. B. (1986) The Botany of Mangroves. Cambridge, U.K.: Cambridge University Press.
Watson, J. G. (1928). "Mangrove Forest of the Malay Peninsula." Malayan Forest Records 6: 1–275.
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