India's Unnatural Disaster Caused by Mangrove Forest Loss
11/6/99
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Title: INDIA, An Unnatural Disaster, Clearing India's Mangrove
Forests Has Left The Coast Defenseless
Source: New Scientist
Status: Copyright 1999, contact source for permission to reprint
Date: November 6, 1999
The cyclone came ashore from the Bay of Bengal and ripped through the
coastal state of Orissa, with winds of up to 300 kilometers per hour.
Early reports said that the accompanying tidal surge, coupled with
torrential rain and burst river banks, flooded the flat coastal region
and the delta of the River Mahanadi in head height for up to 13
kilometers inland. Slums in the state capital, Bhubaneshwar, 50
kilometers from the coast, were washed away.
"This coastline was once covered by mangrove forests," says Tom
Spencer of the Cambridge Coastal Research Unit at Cambridge
University. "In the past, the mangroves would have dissipated the
incoming wave energy." Mangroves grow on tidal coasts between the high
and low-water marks. They trap sediment in their roots, which gives
the seabed a shallow shape. This absorbs the energy of waves and tidal
surges, protecting the land behind. The trees themselves also form a
barrier against wind.
In the past 40 years, India has lost more than half of its mangrove
forests. "The mangroves in Orissa have been mostly destroyed, says
Spencer. This has left it wide open to attack by the wind and waves of
the cyclones that regularly lash the coast of eastern India and
neighboring Bangladesh.
"I am quite sure the loss of the mangroves was a contributory factor
in the extent of the damage," says Spencer. The problem is that the
mangroves make ideal places for conversion into ponds for shrimp
farming. This lucrative form of aquaculture is one of the fastest
growing businesses in the world, and India is one of the top four
exporters, with production growing by 15% a year. Orissa, a major
centre of the business, specializes in raising tiger prawns.
Three years ago, India's Supreme Court ordered the closure of large
shrimp farms within 500 meters of the high tide mark (New Scientist
21, December 1996, p. 8). It ruled that they were encouraging the
penetration of salt into coastal water supplies and rice paddies, as
well as polluting the lands with pesticides. But despite the move, the
lucrative business continues to grow. The death and destruction in
Orissa may prompt a reappraisal.