Asia Relies on Mangroves as Coastal Safety Nets

By Frederick Noronha

GOA, India, December 10, 2004 (ENS) - Some call them the sentinels of the coast. Others see them as a vital but often overlooked life saver. Scientific research in India is now confirming the importance of mangroves for the environment of the region.

The millennium's worst super-cyclone that hit the eastern Indian coastal state of Orissa in 1999 killed more than 10,000 people and damaged three million houses. Almost all beaches in Orissa were affected except for the Nasi Island in Kendrapara district.

"One reason attributed for this miraculous exception was the presence of an army of mangroves that dissipated the cyclonic power," says S.R. Bhat, a scientist with the National Institute of Oceanography at Goa (NIO-Goa), a mangrove expert.

A mangrove is a tropical maritime tree or shrub of the genus Rhizophora. (Photo courtesy OAR)

In India, the western state of Gujarat has afforested over 13,000 hectares with mangroves, and the tiny state of Goa on India's west coast has replanted 700 hectares.

Bangladesh is taking shelter from the frequent cyclones that strike the low-lying country behind a permanent mangrove cover that workers have newly created along the coast.

In 1985, the government of Pakistan began a mangrove replanting program, and more than 9,000 hectares were planted around the Indus delta with the cooperation of the state of Sindh and UN agencies.

Further east, Indonesia lost most of its vast mangroves during the Second World War, but Indonesians have restored the area over the past two decades.

Mangroves are unique plants, both by their habitat and function. Living in salt water, mangroves grow on sheltered coastlines, and fringe the edges of deltas, estuaries and lagoons. They vary in height according to species and environment, from shrubs to 40 meter (130 foot) tall trees.

Of 70 mangrove species belonging to 20 families, 59 species are found in India.

Says Bhat, "Though a precise figure is not available, estimated world coverage is 17 million hectares - with Asia seven million hectares, America 5.5 million hectares, and Africa 3.5 million hectares." One hectare equals about 2.5 acres.

Where land meets sea at the southern tip of West Bengal lies the Indian Sunderbans - the world's largest mangrove forest - part of the world's largest delta formed by the rivers Ganges, Brahmaputra and Meghna. The Sundarbans of Bangladesh are also covered with a protective forest of mangroves.

The Andaman and Nicobar Islands off India's east coast have vast mangrove forests. Goa has some 2,000 hectares of mangroves including 16 species. Based at NIO-Goa, Bhat is right at home amongst them.

"To cope up with the hostile conditions, many mangroves have undergone selective adaptations," he says. "The soil in which they grow is often water-logged, bears a rotten-egg type of smell, is oxygen deficient, and offer least mechanical support. To overcome this, mangroves have developed aerial roots, tilted, hooped and sometimes of buttress form, enabling them to stand upright in that unstable soil."

Mangroves in Indonesia (Photo credit unknown)

This root system, together with aerial roots, form a mesh-like barrier. Scientists point out that this root system dissipates the force of even a cyclonic storm and negates the eroding force of waves.

"That's one of the major reasons why we should have more mangroves along the coast to protect our shoreland," urges Bhat.

Mangroves have adapted to their saline environment, but they are still vulnerable to excessive buildup of salt in their tissues. To balance the salt in their systems, most mangroves exclude excess salt through their roots and special leaf salt glands. Salt patches can be seen on lower surface of their leaves.

Mangrove areas have loads of organic matter, which serves to support the aquatic food chain. Mangroves act as a nursery ground for mollusks, crabs, shrimps and many commercial marine fishes.

In India, the annual yield from the mangrove supported estuarine fisheries is estimated to be 30,000 metric tons of fish and 130,000 tons of crabs and prawns.

Booms of mangrove wood await transport to a newsprint mill from the Sundarbans of Bangladesh. (Photo courtesy Ramsar Convention)

Mangrove honey is now produced in Pakistan. In 1992 to 1994, IUCN - The World Conservation Union and the Pak-Beekeepers Society initiated the Mangrove Honey Production Project for the villagers in the northern part of the Indus delta to provide an alternative source of income during the time of the year when fishing is banned in the harbor. The project has grabbed the attention of many villagers and seems to be on the road to success, says IUCN Pakistan.

Mangroves have also traditionally been used for medicinal and therapeutic purposes - with bark, fruit, tender leaf and latex from about 34 species being reported for use in curing ulcers, rheumatic disorders, malaria, stomach troubles, and skin abscesses.

Says Bhat, "We have to understand our environment well, if it is to be managed well. Mangroves are not isolated plants, but are vital component of coastal ecosystem.

"They have been silently safeguarding our lives from the fury of cyclones and storms, curbing coastal erosion, providing timber, honey, medicine, tannin, oxygen, nursing a variety of commercial fishes, and providing a lovely green canopy housing monkeys and birds."