Salt Marsh and Mangroves (for Coastal Defence) - Essay Example

? Salt Marsh and Mangroves (for Coastal Defence) 20 May Introduction Mangroves in coastal areas present a gooddefence against tidal waves that cause the erosion of sand from beaches. They are considered as critical tools which are quite cheap too compared to other coastal defensive measures such as masonry barriers (which can cost up to $2,200 per linear metre). A mangrove stand can achieve the same results at a mere fraction of the cost using a simple earthen bund behind the stand (Spalding, Kainuma & Collins 232). It also provides a good source of livelihood for fishermen as it is a good sanctuary for types of fishes that live close to the shore. Mangroves provide a good site for fisheries as the nursery grounds for young fish (fingerlings) and for laying their eggs. Mangrove forest cover is a crucial part of the bio-diversity of a locality such as giving a good habitat for a host of marine life. This is proven by the presence of three types of fauna found in mangroves which are resident species (living primarily among the mangroves), the seasonal migrants and the occasional species which visit the mangrove stands once in a while (Schwartz 608). The scientific study of mangroves and salt marsh as part of the conservation efforts is now a recognized field in engineering and of studies in ecology and oceanography. Mangrove forests are natural ecosystems in many coastal areas around the world and provide a natural coastal defence system which is often overlooked by country planners. Mangroves are a good deterrent against erosion caused by higher sea levels due to global warming and a changed wind pattern from various directions and velocities (Drunen, Lasage & Dorland 91). Unfortunately, mangroves are under threat today from human activities and expansion. Discussion This paper will discuss how mangroves and salt marsh are crucial components in the coastal defence of areas threatened with erosion from tides and strong winds. It will then also tackle other issues concerning mangrove forests such as clearing them for firewood, charcoal and the other human needs such as for certain coastal developments like resorts (Crossland & Kremer 47). Humans today are increasingly seen as major catalysts for change among coastal processes which had not been examined very closely before. Human interventions in areas of the coast form part of the larger anthropocene in which larger ecosystems are impacted. Various threats to Mangrove Forests – mangroves are under pressure from us humans especially in developed mangrove areas of the world such as those located along the Niger and delta areas of the Ganges-Brahmaputra and the Irrawaddy in Burma (Kathiresan 476). Other threats identified are degradation and destruction of the mangroves, plant disease and global warming from climate changes. Some 90% of identified global mangroves are located in developing countries which make these mangrove forests particularly vulnerable to human exploitation and expansion of human activities. The estimated 18 million kms2 of mangroves in 1997 has since been reduced to a mere 15 million square-kilometres; it takes a long time for mangrove forests to recover once these are destroyed. Human Encroachments – this is perhaps the greatest threat to mangroves due to the various activities of humans such as urbanization (like in Singapore), Bangkok, Rangoon and in India (Calcutta and Bombay). Another is agricultural expansion from reclamation activities and for aquaculture purposes such as building ponds for shrimps. Other reasons are cutting the mangroves for firewood, charcoal and lumber (mangrove timber is highly resistant to the usual deterioration of wood because of high phenol content). The mangrove areas are usually drained of their salt water content using rain water and protected from salt water intrusions. Degradation – this results when the health and productivity of the mangrove areas had deteriorated significantly from various causes. Among identified causes are oil pollution, dumped solid wastes, industrial effluents, mining activities, diseases, pests, parasites and the nature-induced changes such as cyclones, tropical storms and tsunami (ibid. 478). Increased soil salinity resulting from reduced water flows and blocked periodic inundations result into nutrient imbalances and pathogenic cankers. Introduction of non-native species also causes a degradation of the native species like what happened in Nigeria. Proposed Solutions – coastal salt marshes and mangrove forests respond similarly to an accelerated sea-level rise by a landward-directed horizontal expanded colonisation. This development has significant implications because many coastal areas are heavily populated. Heavy human presence makes these coastal areas are vulnerable to inundation, subsidence, shoreline recession and sediment starvation (Crossland & Kremer 47). Mangroves are very hardy plants with deep roots and greatly help in the prevention of soil erosion in the coastal areas. In particular, mangrove plantations contribute to accelerated soil accretion and to the stabilisation of exposed soft sediments (Schwartz 608). Some studies seemed to indicate the mangrove forests aid in control of pollutants by acting as bio-chemical barriers. Coastal wetlands such as mangrove forests and salt marshes provide the first defence against storm surge flooding. The American Society of Civil Engineers (ASCE) realized this fact and taken steps to avert similar experiences like what happened during Hurricane Katrina in New Orleans back in 2005. The society supports protection and restoration of the wetlands through appropriate engineering designs (such as construction of stronger levees), technology and land use zoning through flood-plain management (ASCE 1). An example of engineering technology application is the so-called “coastal squeeze” in which man-made structures are used to halt the advance inland of these coastal wetlands (Glazer 17). The United Kingdom has adopted a slightly different approach with regards to these wetlands located in and around England and Wales. It first conducted a Risk Assessment of Coastal Erosion (RACE) and integrated this into the National Coastal Erosion Risk Mapping (NCERM) to identify the areas of high risk to erosion and flooding from the expected rise in sea level from global warming (Hosking 1). The UK government passed regulations requiring any coastal engineering designs to take into account the distinct probability of a 1-metre rise in sea levels for the next century. In this regard, non-structural approaches are also preferred to the usual engineering works which are found to be unsustainable in the long term (ibid.). The long-term “change options” involve crafting a new “Coastal Change Policy.” The use of seawalls and breakwaters are considered as temporary at best, similar to the use of the beach nourishment technique of using sand to replace the sediment in shorelines (Dean 123). Conclusion Various studies have suggested that integrated adoption strategies with regards to the conservation and preservation of wetlands are the best approaches (Campbell et al. 56). This is termed as Integrated Coastal Zone Management (ICZM). Hard structures built without the consideration of impacts on buffering can result into maladaptation such as mangroves trying to move inland due to rising sea levels but cannot do so because of the “coastal squeeze” in which there is very little land for moving inwards. Wrong coastal preservation strategies can lead to land subsidence like what happened in Louisiana despite ample evidence of such from happening in the case of the Netherlands (ibid.) due to the drainage of wetlands. The utility and value of mangrove forests and salt marshes are only recently recognized after so much of mangroves had been destroyed either directly or inadvertently. Efforts to slow the destruction still need constant monitoring as the causes of destruction vary from habitat to habitat. There is still enough time to preserve these precious eco-systems if efforts are consistent. Works Cited American Society of Civil Engineers. “Policy Statement 514 - Reconstruction of New Orleans and the Gulf Coast.” ASCE, 10 July 2010. Web. 15 May 2011. Campbell, Alison et al. Review of the Literature on the Links between Biodiversity and Climate Change. Cambridge, UK: World Conservation Monitoring Centre, 2010. Print. Crossland, Christopher J. and Hartwig H. Kremer. Coastal Fluxes in the Anthropocene: The Land-Ocean Interactions in the Coastal Zone Project of the International Geosphere-Biosphere Programme. Berlin, Germany: Springer, 2005. Print. Dean, Robert G. Beach Nourishment: Theory and Practice. Singapore: World Scientific Publishing Company Limited, 2002. Print. Drunen, M. A. Van, Lasage, R. and C. Dorland. Climate Change in Developing Countries. Oxfordshire, UK: CAB International, 2006. Print. Glazer, Mark P. New Frontiers in Environmental Research. New York, USA: Nova Science Publishers, Incorporated, 2006. Print. Hosking, Adam. “Sea Level Rise: UK Model for Sustainable Shoreline Management (Part 2).” ASCE, 2 March 2010. Web. 16 May 2011. Schwartz, Maurice L. Encyclopaedia of Coastal Science. New York, USA: Springer, 2005. Print. Spalding, Mark, Kainuma, Mami and Loma Collins. World Atlas of Mangroves. London, UK: Earthscan Limited, 2010. Print. Appendix Figure 1: A Shrimp Aquaculture Pond (Source: http://mangroveactionproject.org/) Note: Artificially-raised shrimps are greatest threats to mangrove ecosystems today. Figure 2: Mangroves are Forests of the Tide (Source: National Geographic) Figure 3: A typical Mangrove Swamp is shown below (Source: Google Images) Figure 4: Extent of Mangrove Forest Losses as of 2007 (Source: http://maps.grida.no/go/graphic/the-world-is-losing-its-mangroves) Figure 5: A Student Tour of Mangrove Swamps in Costa Rica (Source: http://www.marietta.edu/~biol/biomes/mangroves.htm) Figure 6: Wetlands Provide Habitats for Various Species and other Benefits such as store of floodwaters and improving water quality Source: (http://water.epa.gov/type/wetlands/) Figure 7: Shoreline Modification to Protect Upland Property from Population Growth (Source: http://www.southalabama.edu/cesrp/Tide.htm) Figure 8: Beach Sand Losses and a Beach Nourishment Project (Source: National Oceanic and Atmospheric Administration) Read More