The dangerous myth of tsunami greenbelts

Future tsunamis may have a higher death toll than necessary as a consequence of dangerous myths being circulated about the effectiveness of "green belts" and buffer zones as protective barriers during the 2004 Indian Ocean event.

The Australian people gave generously to support the reconstruction effort in Indonesia following the tsunami. The money has largely been well spent, on roads, schools, hospitals and other essential infrastructure.

Governments in Scandinavia have chosen a different path for much of their reconstruction aid, funding fanciful schemes to reduce loss of life in future tsunamis by planting a coastal barrier of mangroves. These schemes will lead to a greater loss of life in future tsunamis and are resulting in major social injustice in many of the countries affected, an issue which should be of major concern to all Australians given the susceptibility of our neighbours to the threat of tsunamis.

After the tsunami of December 26, 2004 some scientists and institutions promoted the idea that healthy ecosystems, such as coastal forests and coral reefs, had reduced the damage to coastal communities. The evidence to support the idea consists of a number of reports presenting anecdotal evidence which is often incorrect, plus a series of high profile articles in scientific journals, all of which suffer statistical flaws.

Studies which challenge, or indeed, contradict these findings, have routinely been rejected or ignored. In fact, a recent paper in the journal Natural Hazards that included data from 50 sites in the regions affected found that coastal vegetation had no mitigating effect on the distance the tsunami penetrated, and that this distance was actually greater in areas fronted by coral reefs. And, in the historic Krakatoa eruption, tsunamis penetrated eight kilometres inland through dense primary rainforest.

If saving lives from tsunamis is the intent of these schemes, then every cent may be wasted. Worse still is the plight of tens of thousands of impoverished fisher folk in India, Thailand and Sri Lanka, who are being prevented from rebuilding their homes in buffer zones demarcated in the name of tsunami protection.

Fig. 1. View looking south over the villages of Lhoknga and Lampuuk Aceh, Indonesia. A. November 1987, B. December 2005. Almost all coastal vegetation was stripped away by the tsunami of December 26, 2004 and every structure in both villages was entirely destroyed, with the exception of the mosque (not visible).

The simple fact is that, to be effective against tsunamis, buffer zones would need to be many kilometres wide - far wider than those currently proposed, and almost impossible to institute without high social and economic costs.

Bad science is being used to justify worse policy, with the potential for major social injustice and future loss of life. The promotion of green belts and buffer zones as protective barriers, particularly in preference to tsunami early-warning systems, as irresponsibly suggested by some scientists, and recently endorsed by the Food and Agriculture Organization, will lead to substantial loss of life in a future event. These barriers have not been proved effective and will therefore encourage a false sense of security.

Furthermore, schemes such as "Mangroves for the Future", a $US72 million World Conservation Union (IUCN), introduced by Bill Clinton, the UN Ambassador for tsunami reconstruction in New York on October 31, must direct time and money away from more effective measures, such as well co-ordinated early-warning systems, education and planning.

More than 18 months after the Boxing Day disaster, the Indonesian Government has yet to deploy an early warning system south of Sumatra. The tsunami of July 17, 2006 demonstrated the tragic consequences of this oversight. Tremors from the tsunami were felt and it was preceded by a tell-tale "draw-down" - yet amazingly people did not know to run. Government officials were given precise warnings of the likelihood of the tsunami and failed to act.