Intact mangroves could have reduced Nargis damage
Mangrove forests could have reduced damage resulting from the waves caused by cyclone Nargis in Myanmar, the UN Food and
Agriculture Organization (FAO) said recently.
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.
ENDS