|
|
|||
|
|
|||
|
|
|||
|
|||
|
|
|||
BIODIVERSITY AND MANGROVESMANGROVES: A CRUCIAL LINK BETWEEN LAND AND SEAImagine a tree so well adapted to shoreline conditions that its roots can filter salt water. These trees, known as mangroves, have a unique system of slit like roots which protect coastlines from storms and filter sediments that would otherwise smother sea grasses and corals. Leaves falling from the canopy form the basis of an incredibly productive food chain, with detritus directly and indirectly nourishing thousands of life forms. Mangroves once covered 3/4 of the world's tropical coastlines, often in conjunction with coral reefs. Asia contains most of the world's mangroves with 46%, followed by America with 35% and Africa with 17% (MAP, 1990). Mangroves either exclude or excrete silt from their tissues, and have special upright roots which "breathe" in stagnant shallows. Some species produce spike like seedlings, which drop off the parent and land upright in the mud, ready to grow. A BIODIVERSE HABITATSeveral reef and oceanic species, including shrimp, depend on mangrove habitats during various stages of their life cycles. Species such as the endangered olive Ridley turtle, the white breasted sea eagle, the tree climbing fish, the proboscis monkey, the dugong, and even the Bengal tiger use mangrove forests in their daily lives (MAP, 1990, Subramania et Krishnamurthy, 1990). Prawn fries require copper for their body fluid during development and thus mangroves soils provide an excellent source for this mineral (Subramania et al., 1990). In the United States, half of the commercial marine fisheries are dependent on coastal wetlands for spawning and as nurseries (Mathias et Moyle, 1992). Of the species studied in one mangrove community in Belize, 10 percent of the crustaceans were previously unrecorded, and 20 30 percent of the microbes, algae, sponges and worms may also have been new to science (Feller and Rutzler, 1006). Researchers in Venezuela found that mangroves are one of the most widely used winter habitats of Near Arctic warbler species (Lefebvre et al., 1994). The shallow mangrove waters, abundance of food, and absence of predators are ideal for young organisms to thrive. Underneath the mangroves, soft soils provide an excellent habitat for burrowing prawns and other mud dwellers. The nutrient humic layer provides food for the herbivores found in the mangroves. Through continuous tidal movements, these nutrients also supply species in surrounding estuaries and coral reefs. This release of excess nutrients is essential for resources such as oysters. It is estimated that US$ 8 million is generated by the oyster industry in Thailand (Ambio, 1991). DESTRUCTION OF MANGROVES FOR SHRIMP PONDSUnfortunately, because of their high productivity, mangrove areas are targeted for shrimp pond development. When a mangrove area is cut down for shrimp aquaculture, the intricate and productive system is destroyed. In Ecuador, it is estimated that 25 percent to 40 percent of the mangroves have been lost due to extensive shrimp aquaculture (MAP, 1990). Removing mangroves also destroys habitat for all sorts of life forms and has in some cases led to a reduction in wild shrimp populations (Lee, 1992). Shrimp farmers must then use artificially cultured larvae, which are less hardy and require fertilizer and antibiotics. Further devastation occurs when exotic shrimp species introduce foreign pathogens into the system (Primavera, 1994). Indigenous species are incapable of combating foreign diseases resulting in decreased populations. Mangroves are a type of wetland and are one of the most threatened habitats worldwide. Habitat loss is the primary reason for species endangerment. Sedimentation downstream and along coral reefs occur when mangrove roots no longer hold soil in place. In many countries seasonal storms are more intense when the protective layer provided by the forests are removed. In 1991, thousands of people were killed by a tidal wave in Bangladesh where shrimp farms had replaced mangroves. In 1960, a tidal wave of similar magnitude passed over the same area without loss of human life (Barraclough et al., 1995). Mangroves: A Source of LivelihoodMangroves are so productive that they are the source of livelihood for many people. Basic necessities such as food, shelter, fuel, and medicines are all obtained from mangroves. The traditional way of life is being slowly altered by commercial shrimp aquaculture. In Thailand, sustainable charcoal production, using wood from mangroves, generates an annual income of approximately US$22.4 million (Ambio, 1991). Unfortunately, it is estimated that since 1989, 25 percent of mangrove loss is due to shrimp farm conversion (FAO, 1995). Loss of mangroves will inevitably lead to loss of livelihood and eventual displacement all for short term profits of shrimp aquaculture. Large faceless corporations are reluctant to stop these unsustainable practices. The generation of export dollars is attractive to many countries but environmental and social destruction are not tabulated into the value of the gross national product. It is therefore necessary to realize the importance of mangroves and the need to restore and conserve these ecosystems.
FOR MORE INFORMATION:Sierra Club of Canada References:Mangrove Action Project. (1990) Mangrove Ecosystems. www. earthisland.org/scripts/imagemap/eil?373,141. Subramania, P., Krishnamurthy, K. (1990). Mangroves: The Diplomats of Neptune's Court. Environment and Ecology. 8(2): 659 663. Mathias, M., Moyle, P. (1992). Wetland and Aquatic Habitats. Agriculture, Ecosystems and Environment. 42:165 176. Feller, I., and K Rutzler. (1996). Caribbean Mangrove Swamps. Scientific American. 274(3):94 99. Lefebvre, G. (1994) Abundance, Feeding Behavior and Body: Condition of Near Arctic Warblers Wintering in Venezuelan Mangroves. Auk. 3(2):405 416. Biological Diversity. (1991) Ambio. 20(2). Mangrove Action Project. (1990) Mangrove Ecosystems. www. earthisland.org/scripts/imagemap/eil?373,141 Lee, S. (1992) The management of traditional tidal ponds for aquaculture and wildlife conservation in southeast Asia: Problems and prospects. Biol. Cons. 63:113 118. Primavera, J. (1994) Environmental and socioeconomic effects of shrimp farming: The Philippine experience. Infofish Int. 1:44 49. Barraclough, S., Finger Stich. (1995) Some Ecological and Social Implications of Commercial Shrimp Farming in Asia. United Nations Research Institute for Social Development in collaboration with the World Wide Fund for Nature. Switzerland. Biological Diversity. (1991) Ambio. 20(2). FAO. (1995). World Fisheries: Problems and Prospects, 21st Session. Rome: Italy. March 10 15.
|
|||
|
|
|||
|
© Copyright and
Fair Use . SDNP Bangladesh holds the ©
copyright to its publications and web pages but |
|||
