The protective role of coastal forests in human security – fact or illusion?

After the 26 December 2004 Indian Ocean tsunami, the protective role of mangroves and other coastal forests and trees in saving lives and property received considerable attention, both in the press and in academic circles. Many forest rehabilitation efforts were launched with coastal protection cited as one of the rationales. However, controversy arose over the effectiveness of forests in coastal protection. Many eyewitnesses reported that coastal forests had saved lives and villages from destruction, but some people claimed that forests could not provide significant protection from hazards of a certain magnitude. Others asserted that land elevation and distance from the coast were more significant determinants of protection than forest cover. It became clear that a better understanding of the degree to which forests and trees could provide protection from different types of coastal hazards was needed to provide an improved basis for formulation of coastal management plans and disaster mitigation strategies.

With this need in mind, the FAO Forestry Programme for Early Rehabilitation in Asian Tsunami Affected Countries, funded by the Government of Finland, sponsored a regional technical workshop entitled “Coastal Protection in the Aftermath of the Indian Ocean Tsunami: What Role for Forests and Trees?”. The workshop, held in Khao Lak, Thailand from 28 to 31 August 2006, aimed at contributing to improved coastal area planning, coastal forest management and disaster mitigation by increasing the knowledge and understanding of the role of trees and forests in protecting populations and assets from the most common and destructive natural hazards affecting coastal areas of Asia, namely cyclones, erosion, tsunamis, wind and salt spray.

The workshop provided a rare opportunity for multidisciplinary analysis of this issue. Coastal engineers and oceanographers, forest ecologists and managers, disaster management specialists, coastal planners and social scientists brought together their combined experience. The 63 participants included government representatives from the eight tsunami-affected countries (Bangladesh, India, Indonesia, Malaysia, the Maldives, Myanmar, Sri Lanka and Thailand) and other experts from 15 different countries and from national, regional and international organizations.

The workshop confirmed that forests and trees can act as bioshields for protection of people and other assets against tsunamis and other coastal hazards, but they do not provide effective protection against all hazards (e.g.extremely large tsunami waves, flooding from cyclones, and certain types of coastal erosion). The degree of protection they offer depends on a number of variables, including the characteristics of the hazard itself (e.g. type, force, frequency), the features of the site and the characteristics of the bioshield (type of forest or trees, density, height, etc.). Care must be taken not to generalize and to avoid creating a false sense of security. In cases where bioshields are not a feasible option or sufficiently effective, provision must be made for other forms of protection, including hard engineering solutions and a hybrid of “hard” and “soft” solutions. In extreme events, evacuation may be necessary.

In planning the development of bioshields, it is important to match the species with the site. Some forest types and tree species cannot survive or thrive in areas exposed to specific coastal hazards. Furthermore, development of bioshields is not possible in all situations because of biological limitations, space constraints, incompatibility with priority land uses, prohibitive costs, etc. It is important to recognize that many years are required to establish and grow bioshields to a size and density that could offer protection against coastal hazards.

Additional attention is needed for further understanding of the protective potential of coastal forests and trees, for example research on non-mangrove coastal forests and data collection and development of models on the interactions between physical and ecological parameters.

Detailed information on the workshop and its conclusions and recommendations may be found at: www.fao.org/forestry/tsunami/coastalprotection

Post-tsunami mangrove replanting at Ban Nam Khem, Phang Nga, Thailand

S. Fortuna