Coastal vegetation may not offer much protection against tsunamis

Last Plant Standing
Journal Watch Online 10 Dec 09;

After the deadly Indian Ocean Tsunami in December 2004, calls to protect coastlines with more vegetation grew stronger. But according to a review in Conservation Letters, this strategy may not be the best way to prepare for natural disasters – and could end up damaging native ecosystems.

Most research on the effectiveness of coastal ‘bioshields’ is based on eyewitness accounts, surveys performed after the disaster, remote sensing, and mathematical modelling, the authors say. Without controlled scientific experiments, they argue, it’s difficult to know whether other factors – such as topography – have been properly ruled out.

Studies suggest that vegetation does help buffer the land against waves. But tsunamis and storm surges are much more forceful than normal waves and can inundate large areas of the coast for hours, the authors point out. Most people who died during Hurricane Katrina were not killed by waves, they say, but by high inland water levels.

Building up the coast with non-native vegetation can also do ecological harm, according to the review. For instance, India is bulldozing sand dunes in order to plant exotic trees as bioshields. As a result, sea turtles are losing nesting sites, mangroves are at risk of invasion, and the dunes can no longer protect the coast from storms, the team says.

Policymakers should choose their bioshield sites carefully so as to avoid disrupting native ecosystems, the authors write. And if faced with few resources, they say, managers should direct their efforts toward disaster preparation initiatives such as early-warning systems – not bioshields. – Roberta Kwok

Source: Feagin, R., Mukherjee, N., Shanker, K., Baird, A., Cinner, J., Kerr, A., Koedam, N., Sridhar, A., Arthur, R., Jayatissa, L., Lo Seen, D., Menon, M., Rodriguez, S., Shamsuddoha, M., & Dahdouh-Guebas, F. (2009). Shelter from the storm? Use and misuse of coastal vegetation bioshields for managing natural disasters Conservation Letters DOI: 10.1111/j.1755-263X.2009.00087.x