Post-Tsunami Hazard: Reconstruction and Restoration
Ch 19: Observations of Natural Recruitment and Human Attempts at Mangrove Rehabilitation After Seismic (Tsunami and Earthquake) Events in Simeulue Island and Singkil Lagoon, Aceh, Indonesia
The December, 2004 tsunami and March 2005 earthquake along the Sunda Megathrust off the Western Coast of Aceh, Sumatra , Indonesia not only resulted in catastrophic losses of life and livelihood, but also changed the very shape of the land and coast. The effects of this rapid change in coastal geomorphology are well expressed in a pair of locations, the remote Island of Simeulue, relatively unknown even in Indonesia before the tsunami, and the district of Singkil, which includes a mainland section as well as the Banyak (Many) Islands. Simeulue and Singkil effectively straddle the Sunda Megathrust, yet experienced the cumulative effects of the tsunami and earthquakes differently, with Simeulue Island undergoing seismic uplift while coastal mainland Singkil subsided. After the seismic events, at least 163 separate institutions (government agencies, local and international non-governmental organizations) planned and implemented mangrove rehabilitation activities in Aceh, including over a dozen in Simeulue and Singkil districts. (Brown and Yuniati 2008)
Despite a great deal of commitment from such organizations to bringing back mangroves in the affected areas, the majority of the rehabilitation attempts, which mainly relied on hand planting methods, failed to restore mangrove forests. All the while, mangroves were naturally recruiting seismically repositioned intertidal surfaces, and growing well. Near to total mortality was observed in 6 out of 7 planting sites in the two districts, while recruitment rates, stem densities and species diversity in nearby intertidal zones indicated that natural recovery was well underway. When comparing the “success” of natural recovery versus planted sites, we see that practitioners are still faced with signifi cant challenges. This paper makes the case that observation and monitoring of natural regeneration, and calculation of rates of recruitment after a major disturbance event is equally or more important than mangrove planting, from not only ecological but also social and economic points of view.