Often, it takes a catastrophe to make us realise the importance of the environment. Reports are coming in from Malaysia, India, Sri Lanka, Thailand and Sumatra that those coastal areas still covered by mangroves were relatively less affected by the tsunami.

ONE of the emerging lessons of the earthquake-tsunami disaster is that mangroves and coral reefs are vital barriers that can prevent or at least soften the damage caused by tsunamis and high tidal waves. Unfortunately, many mangrove forests have been cleared, including in the areas affected by the Dec 26 tsunami, thus opening them to the full blast of the waves.

As our understanding of the value of reefs and mangroves as natural barriers against tsunamis, tidal waves and hurricanes increases, this should inspire projects to replant the mangroves as one of the key actions in the region’s rehabilitation plan. In Penang, the fishermen had planted 25,000 mangrove saplings in several areas, and where the mangrove swamps were more abundant, there was less damage to the houses.

Many fishermen clung tight to the mangrove trees when the first waves came, and some others took refuge in the mangrove swamps and were shielded, said the Penang Inshore Fishermen Welfare Association. Friends of the Earth International compiled reports of how places with extensive coral reefs and mangroves forests suffered fewer deaths and less damage. “The ring of coral in crystal waters around the Surin Island chain off Thailand's west coast forms a sturdy defence against the sea. So when the tsunami struck on Sunday it punched a few holes in the reef, but the structure mostly held firm,” according to a Wall Street Journal article on Dec 31. The reef, says Thai marine environmentalist Thon Thamrongnavasawadi, may have saved many lives. Only a handful of people on the islands are known to have perished.

A report by the Science and Development Network in India said: “When the tsunami struck Tamil Nadu, areas with dense mangroves suffered fewer human casualties and less damage to property compared to areas without mangroves.” Hemantha Withanage from the Centre of Environmental Justice in Sri Lanka also reported that in areas where there were “green belts” the damage was less or none at all. Friends of the Earth said: “The full fury and wrath of the tidal waves were felt in areas where nature's green belts of coral reefs and mangroves no longer exist or were never present in the first place.

“In many parts of the affected areas where dense mangroves and coral reefs once acted as natural buffers between the sea and coast, other developments have taken place, such as construction of hotels, shrimp farms, coastal highways, housing and commercial development.”

Another organisation, Global Environment Centre, reported two cases in and off Sumatra where the mangroves limited the tsunami’s damaging effect. Simeuleu island is only 40km from the earthquake’s epicentre, but it was saved by the wide belt of mangroves, and only four people there died. Five villages in Julok near Banda Aceh were also saved by extensive mangroves in the area.

In previous natural disasters, a similar observation had been made. For example, Indian scientists noted that mangrove forests had reduced the impact of a “super-cyclone” in October 1999 in Orissa on India's east coast, killing at least 10,000 people.

“Mangroves often served as a barrier to the fury of water,” says M.S. Swaminathan, head of the M.S. Swaminathan Research Foundation in Chennai, India. “If a killer tsunami wave hits Orissa's coast, we estimate that at least 100,000 people would die since the damage will be more extensive than what happened in Andhra Pradesh and Tamil Nadu,” said Biswajit Mohanty, secretary of the Wildlife Society of Orissa, as reported by news agency Indo-Asian News Service.

The state's coastline was once covered by luxuriant mangrove forests. “However, due to rampant proliferation of prawn farms along the coast and estuarine areas, these forests are now reduced drasticaly,” he said.

Mangrove is an efficient soil binder and has a dense root and branch structure, which can combat the most violent of cyclones and tidal waves. Tsunamis can easily be arrested and slowed down by thick mangrove.

Afsar Abbas, a scientist at the Institute of Physics added: “Massive and continuing loss of greenery has contributed significantly to the frequent disasters.” Unfortunately, up to half the world’s mangrove swamps have vanished in the last 30 years. The role they play in guarding the coastlines from natural disasters should lead to a re-evaluation of the alternative uses (hotels, shrimp farms and so on) that have killed off the mangroves.

“Coastal zones and green belts such as mangroves, coral reefs and other natural barriers must be protected, regenerated and managed,” says Friends of the Earth. “Only through this can coastal communities can be protected in the long run.”