Shelter from the storm? Use and misuse of coastal vegetation for managing natural disasters
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R. A. Feagin, N. Mukherjee, K. Shanker, A. H. Baird, J. Cinner, A, M. Kerr, N. Koedam, A. Sridhar, R. Arthur, L.P. Jayatissa, D. L. Seen, M. Menon, S. Rodriguez, Md. Shamsuddoha, & F. Dahdouh-Guebas


Vegetated coastal ecosystems provide goods and services to billions of people. In the aftermath of a series of recent natural disasters, including the Indian Ocean Tsunami, Hurricane Katrina and Cyclone Nargis, coastal vegetation has been widely promoted for the purpose of reducing the impact of large storm surges and tsunami. In this paper, we review the use of coastal vegetation as a “bioshield” against these extreme events. Our objective is to alter bioshields policy and reduce the long-term negative consequences for biodiversity and human capital. We begin with an overview of the scientific literature, in particular focusing on studies published since the Indian Ocean Tsunami in 2004 and discuss the science of wave attenuation by vegetation. We then explore case studies from the Indian subcontinent and evaluate the detrimental impacts bioshield plantations can have upon native ecosystems, drawing a distinction between coastal restoration and the introduction of exotic species (extinction) in inappropriate locations. Finally, we place bioshield policies into a political context, and outline a new direction for coastal vegetation policy and research.

Main Results and Conclusions:
  • Bioshield plantations in the wrong habitat can do more harm than good if the sites are not properly surveyed and/or analyzed prior to their creation:
    • “In India, the concept of bioshields has moved actively to developing vast plantations of exotic trees (mainly Casuarina equisetifolia L.) to act as bioshields, despite a range of issues including the selective application of science to support predetermined agendas, violations of indigenous land rights, and loss of biodiversity (extinction) (Shanker et al. 2008)”(4).
    • “If done effectively, Casuarina plantations can be an important supplemental livelihood for marginalized coastal communities, but should be pursued as such. In their current form, Casuarina plantations appear to have little support from communities”(5).
    • “Bioshield plantations have displaced native vegetated ecosystems in many areas. In some locations, exotic Casuarina plantations have been promoted as a better alternative to native vegetation species… The use of exotic rather than native species, for protection and stabilization, is common practice in many other coastal areas as well. In India, sand dunes have been flattened to make way for these plantations (Figure 3), destroying sea turtle nesting habitat and reducing the natural effectiveness of coastal dune topography to provide protection from storms… Moreover, plantation projects often demand the displacement of indigenous peoples from the coast (e.g., Sri Lanka, Ingram et al. 2006; Wong 2009a), allowing their undocumented land rights to disappear while filling the coast with new (coastal) developments (e.g., India, Rodriguez et al. 2008).”(6).
    •  “… we conducted a site-selection analysis for planting mangrove forests in Sri Lanka in response to the country’s interest in using vegetation for potential protection (see Supporting Information material online for detailed Methods and Results). We found that two-thirds of the vulnerable coastline did not have the appropriate environmental settings for mangrove forests to develop (Figure 5). Their introduction in the wrong settings would have replaced other native ecosystems, particularly sand dunes; although for previously degraded mangrove sites, we strongly advocated their restoration provided that the physico-chemical conditions were suitable”(8).
  • Recommendations for future bioshields projects:
    • “The best ways to reduce the impact of extreme episodic events are: (1) to reduce physical exposure by promoting sensible coastal development; (2) to develop adequate disaster preparation; and (3) to enhance the capacity of social-ecological systems to cope with and adapt to surprise”(8-9).
    • “Coastal vegetation such as mangrove ecosystems is critical to the resilience and vitality of many coastal social-ecological systems and we believe that their conservation is necessary. In the long-term, the goods and services (e.g., carbon storage, increased fisheries production, or water purification) provided by mangrove forests are likely to be more valuable than gains from unsustainable agriculture or aquaculture (Huitric et al. 2002), even without the protection service values included”(9).
Works Cited:

Cronk, Q.C.B., Fuller J.L. (2001) Plant invaders: the threat to natural ecosystems. Earthscan Publications, London, UK.

Huitric, M., Folke C., Kautsky N. (2002) Development and government policies of the shrimp farming industry in Thailand in relation to mangrove ecosystems. Ecol Econ 40, 441–455.

Ingram, J.C., Franco G., Rumbaitis-del Rio C., Khazai B. (2006) Post-disaster recovery dilemmas: challenges in balancing short-term and long-term needs for vulnerability reduction. Environ Sci Pol 9, 607–613.

Rodriguez, S., Balasubramanian G., Peter S.M., Duraiswamy M., Jaiprakash P. (2008) Beyond the Tsunami: Community Perceptions of Resources, Policy and Development, Post-Tsunami Interventions and Community Institutions in Tamil Nadu, India. UNDP/UNTRS, Chennai and ATREE, Bangalore.

Shanker, K., Namboothri N., Rodriguez S., Sridhar A. (2008) Beyond the tsunami: social, ecological and policy analyses of coastal and marine systems on the mainland coast of India. in K. Shanker, N. Namboothri, S. Rodriguez, A. Sridhar, editors. Post Tsunami Environment Impact Report. UNDP/UNTRS, Chennai and ATREE, Bangalore.

Wong, P.P. (2009a) Rethinking post-tsunami integrated coastal management for Asia-Pacific. Ocean and Coastal Management 52, 405–410.