Intact mangroves could have reduced Nargis damage

Rome – Mangrove forests could have reduced damage resulting from the waves caused by cyclone Nargis in Myanmar, the UN Food and Agriculture Organization (FAO) said today.

Parts of Myanmar’s coast have been largely cleared of mangrove forests in recent decades and coastal communities are now more exposed to cyclone damage. «Mangroves have been converted to
agricultural land and fish ponds. Settlements have been established closer to the sea and the combination of proximity to coastal hazards and lack of a protective forest buffer has increased
the risks to human populations in many countries, including Myanmar,» said Jan Heino, the Assistant Director General of the FAO Forestry Department.

The mangrove area in the Ayeyarwady Delta, severely hit by the cyclone, is now less than half the size it was in 1975 or just over 100 000 hectares. Of equal concern is over-exploitation of the
mangrove resource, which has led to a decrease in the density of the forest cover.

Waves associated with the storm surge were reported to be up to 3.5m high. Although porous barriers such as coastal trees and forests cannot prevent inundation and inland flooding associated
with storm surge, there is considerable potential for intact and dense coastal vegetation to reduce the impacts of waves and currents associated with the storm surge. Coastal forests can also
act as windbreaks in reducing devastation in coastal communities resulting from cyclones.

A wide area of forest with higher densities of stems, branches and stilt roots will provide greater protection than a degraded forest or a forest in which stems are widely spaced or there are
few branches. Ground vegetation is also important in the case of smaller waves.

Healthy mangrove forests are particularly good at reducing the force of waves because of the resistance provided by stilt roots as well as the trees’ trunks and branches. Mangroves also trap
and stabilise sediment and reduce the risk of shoreline erosion – which brings waves closer to habitation – by dissipating surface wave energy.

During cyclone Sidr that struck southern Bangladesh in November 2007, the Sunderbans forests played a crucial role in the mitigation of the deadly effects of the cyclone. However, mangroves are
not only buffers for cyclones they are critical ecosystems harbouring biodiversity and fisheries breeding grounds.

In the future, sea level rise and increased frequency and intensity of storms arising from climate change are expected to put coastal areas at greater risk of damage. Lessons learned following
the 2004 Indian Ocean tsunami and earlier efforts to conserve and rehabilitate the mangroves of the Ayeyarwady Delta suggest that much can be done to improve the sustainability of coastal
development in the region.

Discouraging further expansion of settlements close to the coast and maintaining healthy mangroves and other coastal forests will be important measures to protect coastal assets and
populations. Reestablishment of the damaged infrastructure and communication facilities is urgently required and measures should be put in place to facilitate sound coastal area planning to
maintain the resilience of coastal areas and reduce the vulnerability of coastal communities and ecosystems.

Coastal planning to avoid development in vulnerable areas and maintenance of coastal vegetation as buffers are important measures, but will not be enough to protect against all such storms.
Early warning systems, evacuation plans, effective communication and transport infrastructure, and storm shelters should also be implemented as necessary measures to protect lives in the future
from cyclones such as Nargis.

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