Under the Microscope: It is now clear that the damage caused by the tsunami that struck south-east Asia last St Stephen's Day would have been much less had natural coastal protective barriers in the form of mangrove swamps and coral reefs not been greatly reduced by human interventions on behalf of fisheries and tourism.
And of course it was clear right from the very start that an effective tsunami-warning system would have greatly reduced the carnage. Much good can be salvaged from the disaster if lessons are learned and obvious solutions implemented.
Mangroves are woody trees or shrubs that grow in mangrove habitats. These habitats are tropical and tidal, with soil or sediment that is waterlogged and saline - estuaries and marine shoreline. A wide variety of plant species are found in these habitats and 54 species occur exclusively there. The roots of the mangrove plants stabilise the sand and the mud. Mangrove forests naturally occur along coasts that rim the Indian Ocean where the earthquake occurred that triggered the recent tsunami.
Coral is a limestone formation made in the sea by million of tiny animals called polyps that mostly live together in colonies, connected to each other by flat sheets of tissue. The polyps remove calcium from the seawater to build their limestone skeletons. When the animals die they leave limestone skeletons that become the foundation of barriers and ridges called coal reefs. As new polyps grow, the mass of the reef grows larger and larger. The coral formations come in diverse shapes - branching trees, large domes, small pipes, etc. The polyps can colour the formations in beautiful hues of orange, yellow, purple and green. Polyps cannot live in water cooler than 180C and coral reefs are found mostly in warm, shallow coastal tropical water, such as the coastal waters that rim the Indian Ocean.
The tsunami St Stephen's Day killed about 220,000 people in Indonesia and left more than a million survivors destitute. Much destruction was also caused in Thailand, Sri Lanka, India, Myanmar, Somalia, the Maldives Islands and many other areas around the Indian Ocean and more than 300,000 people have died altogether. We now know that the losses suffered were much exacerbated by human activities in these regions.
Coastal regions around the Indian Ocean are naturally protected against the worst excesses of typhoons and tsunamis by mangrove forests and coral reefs. When the wave hits the mangroves, the forest itself is pretty much levelled, but the impact takes the energy out of the wave thereby protecting the territory behind the mangrove swamp. The coral reef also acts as an effective buffer against the lethal effect of the tsunami, breaking up and slowing down the wave. Unfortunately both of these natural buffers against lethal waves, the mangrove forests and the coral reefs, have been increasingly destroyed over the past 50 years leaving the coastal populations around the Indian Ocean unprotected.
More than half the mangrove population in Thailand, India and elsewhere in south-east Asia has been chopped down to clear the way for shrimp farms, towns and tourist resorts. One fifth of the world's coral reefs have been destroyed by human activity. Sources of damage range from sewage pollution to quarrying coral for building material. Half of the reefs still remaining in the Indian Ocean are at risk.
Preserving the mangrove forests and coral reefs would not have prevented the massive earthquake that triggered the tsunami, but it would have mitigated the effects as the statistics now show. For example, the Maldive Islands were totally exposed to the tsunami and were particularly vulnerable because very little of the land there rises more than a couple of metres over sea level. The wave passed right over the islands, briefly submerging them, but just 100 people died on the 1,190 islands. This has been attributed to the protective effect of the healthy coral reefs that surround the islands, protected by regulations in support of the tourist industry. The reefs weakened the wave. Most people were able to hold on, or, if swept out to sea, to get back again to land.
The story is much the same where mangrove forests remain intact. Kerala State reported much less damage in areas where mangroves remained than in places where they had been cleared for fish farming, or on open beaches. Past experience also reinforces this effect. In 1960, when a tsunami hit Bangladesh with its mangroves intact, not a single person drowned. In 1991, a tsunami drowned thousands in the same area, but, by then, most of the mangroves had been removed.
When the earthquake sent the tsunami roaring towards Asian coasts last December, some scientists knew the onslaught was coming but had no way of communicating the news to people on the ground. An effective warning system must now be put in place and this must be done in full consultation with people on the ground. The warning system must be tailored for local use and make use of simple familiar technology such as pole-mounted loudspeakers and bells.
Clearly, in addition to a warning system, coral reefs and mangroves will have to be preserved and, where feasible, regenerated. However, the danger is that developers will move in to exploit the land newly cleared by nature, and create areas of even greater vulnerability.
William Reville is associate professor of biochemistry and director of microscopy at UCC