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n-week: Richard Stone ECOLOGY: A Rescue Effort for Tsunami-Ravaged Mangrove Forests Science 2006; 314: 404 [Summary] [Full text] [PDF]

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The Dangerous Myth of Tsunami Greenbelts

Andrew H. Baird, Alexander M. Kerr, University of Guam   (4 April 2007)

The Dangerous Myth of Tsunami Greenbelts 4 April 2007
Andrew H. Baird, Senior Research Fellow James Cook University, Alexander M. Kerr, University of Guam Respond to this E-Letter: Re: The Dangerous Myth of Tsunami Greenbelts	Mangroves have been widely reported as reducing deaths and damage caused by the Indian Ocean tsunami. Consequently, many organizations are advocating the use of mangroves as a natural barrier against future tsunamis. For example, the World Conservation Union is promoting “Mangroves for the Future,” a program highlighted in the article “A Rescue Effort for Tsunami-Ravaged Mangrove Forests” (20 Oct. 2006, p. 404). Discussions to date have concentrated on how to make these replanting programs successful (1). A far more important consideration is whether they will work. The evidence upon which these programs are based is unconvincing, as most of the primary accounts are anecdotal. Quantitative support for the mitigation hypothesis has been mixed. For example, initial work concluded that coastal forests protected communities in Tamil Nadu, India from tsunami damage (2). However, a re-analysis of data from the same area found no relationship between human mortality and the extent of forests fronting coastal hamlets when controlling for differences in elevation and distance from shore (3). The most comprehensive study to date that included 57 sites from throughout the Indian Ocean determined that the distance the tsunami penetrated was best explained by distance from the earthquake epicenter and features of near-shore bathymetry (4). Most importantly, coastal vegetation had no mitigating effect on inundation distance (4). We are concerned that promoting “green belts” as barriers, particularly in preference to tsunami early warning systems, as suggested by some scientists (5), and endorsed by the Food and Agricultural Organisation, may lead to substantial loss of life in a future event. These barriers have yet to be proven effective, and therefore may encourage a false sense of security. Furthermore, these schemes direct time and money away from more effective measures such as early-warning systems, community education, and emergency planning (6). Coastal vegetation can provide communities with many valuable goods and services, and the protection and rehabilitation of these ecosystems is, in general, an endeavor we wholeheartedly support. However, the effectiveness of these barriers in limiting damage from future tsunamis must be questioned. References 1. E. B. Barbier, Front. Ecol. Environ. 4, 124 (2006). 2. F. Danielsen et al., Science 310, 643 (2005). 3. A. M. Kerr, A. H. Baird, S. J. Campbell, Estuarine Coastal Shelf Sci. 67, 539 (2006). 4. B. Chatenoux, P. Peduzzi, Nat. Hazards DOI 10.1007/s11069-006-0015-9 (Oct. 17, 2006). 5. F. Dahdouh-Guebas et al., Curr. Biol. 15, R443 (Jun 21, 2005). 6. K. Sieh, Philos. Trans. R. Soc. A Math. Phys. Eng. Sci. 364, 1947 (2006).