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Archive for March, 2013

Recovery status of Aceh mangroves after the 2004 Indian Ocean Tsunami

1Onrizal and 2Mashhor Mansor

1Forestry Sciences Department, Faculty of Agriculture, University of Sumatera Utara [onrizal@gmail.com; onrizal@usu.ac.id]

2School of Biological Sciences, Universiti Sains Malaysia

 

Abstract

 

The recovery status of Aceh mangrove after the 26 December 2004 Indian Ocean tsunami was examined. The field researches were conducted during January 2005 to December 2011 in more than 70 km of Aceh coast to (1) look at plant species that are resilient to the onslaught of up to 50-meter tsunami waves, (2) observe and record the emergence of several existing plant species as well as new ones that were caused by the tsunami, and (3) examine the survival of the rehabilitated mangroves after the tsunami disaster. The natural hazards caused catastrophic destruction to Aceh coastal communities, and also caused environmental changes such as landscape change, land subsidence, land uplift, etc. Disturbance is an important factor in structuring ecological communities, exerting its influence through changes to the physical environment and to the trajectories of succession processes. For natural succession, the main result shows that (1) mangrove coasts may not recover at all to their former state as their topography has been greatly altered and hydrologic and sedimentary conditions differ from their previous state, (2) most of mangrove trees dead due to change in habitat environments, mainly in land subsidence coasts, (3) some mangrove species in land subsidence coasts were found to migrate land-ward via seedling recruitment, naturally, (4) some mangrove plants species seemed to thrive well in the natural stands with mother trees survived against tsunami, (5) new species such as Typha latifolia are widely colonizing along the intertidal coastal zone, and (6) mangrove fern Acrostichum aureum population occupy the open areas left by mangrove plant communities or unmanaged aquaculture pond. For rehabilitation activities, the true mangrove species such as Rhizophora apiculata and Rhizophora mucronata are most popular selected in mangrove rehabilitation after tsunami disaster. The successful level of rehabilitation are varied from low to middle survival due to some reason such as mistakes in the selection of planting sites, unsuitable choice of plants, insufficient preparation, inadequate guidance, no tending of the plants, and the low capacity of human resources. It should be noted that before 26th December 2004, most of the Aceh mangroves had been destroyed to make way for aquaculture ponds. Since the mangroves provide a natural barrier, more human lives could probably be saved during the tsunami. Unfortunately, due to high demand of aquaculture products such as shrimps, prawns and fish, the widespread destruction of these mangrove forests was unmanaged. Therefore, mangrove forests should be rehabilitated and conserved very well in the future. Based on the results, the impact and natural recovery processes provide valuable lessons for coastal management, for example, in the replanting of mangroves in the modified coastal environments following and the questionable construction of seawalls on accreting coasts.

 

Keywords: mangroves, natural succession, rehabilitation, tsunami impact, coastal management, Aceh

*presented at the Regional Symposium on Mangrove Ecosystem Management in Southeast Asia: Mainstreaming Mangrove, held in Surabaya, 27 Feb-1 March 2013

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