(January 2005) Last month's tsunami damaged or destroyed countless coastal fishing communities along the Eastern and Western Indian Ocean, from Somalia to Indonesia. The waves also did substantial damage to the ecosystems upon which these communities depend.
PRB asked the WorldFish Center in Panang, Malaysia, about the extent of the ecological destruction. The WorldFish Center is a nonprofit research center of the Consultative Group on International Agricultural Research (CGIAR).
PRB: Coastal fisheries and their ecosystems seem at special risk from a tsunami. Were coral reefs affected, and how badly?
WorldFish Center: Reports on coral reef status are being collected by the WorldFish Center ReefBase operation in cooperation with the Global Coral Reef Monitoring Network (GCRMN).1 Preliminary results suggest that the impacts were very variable, even along the same stretch of coastline. Some areas show considerable damage, others only minimal. Overall, preliminary assessment reports from Thailand and the Seychelles are encouraging. Around Phuket and the Phi Phi Islands (Thailand), it has been estimated that not more than 20 percent of coral reefs were damaged by the tsunamis.
Tsunamis can have serious negative impacts on coral reefs. Although reefs in deeper water or at distance from the coastline may escape unharmed—as the tsunami passes across as a pressure wave with only slight changes in water depth (perhaps a meter or so)—near-shore reefs stand to take a considerable pounding.
Shallow reefs close to the shoreline can help protect the coast by absorbing some of the energy—at cost, however. Reports from the 1883 tsunami following the eruption of Krakatoa say that giant coral heads weighing many tons were tossed hundreds of feet inshore. The degree and nature of the impact will vary depending on the shore topography and the hydrodynamics of the wave itself.
The wave is a double-whammy. First, there is the direct destructive force. Second (and perhaps more importantly within the region), returning water carrying mud, sediments, and debris back into the reefs will have caused significant impacts, including physical damage to the reef structure through both breakage and smothering. Debris, lying over a reef, will slide to and fro with the constant movement of the water continually grinding and abrading the reef structure, rubbing out the underlying organisms. Mud and silt settling on the corals' surface will tend to smother them. It is possible that these sediments have buried entire reefs.
Corals are, in general, slow growing. However, if the underlying reef structure is broken, the reef becomes more susceptible to further breakages, and full recovery and restoration will be measured in hundreds of years rather than decades. Preliminary reports indicate that the tsunamis have resulted in some localized physical damage caused by land-based debris, with some reef areas observed to be covered by over one meter of sand.
All the countries in the region affected by the devastating tsunamis have coral reefs. These fragile natural resources have been of great importance to their economies, providing livelihoods to many coastal villages, through fisheries and tourism as well as coastal protection.
PRB: What about the region's coastal mangrove forests?
WorldFish Center: It is likely that mangrove trees and their associated ecosystems suffered considerable damage. Mangrove ecosystems form an important habitat for a number of juvenile fish, many of them commercial species. Hence there is likely to be a concomitant impact to the coastal fisheries. The extent of this damage is, at present, unknown, though preliminary area estimates are probably being made from satellite image data. Results from image analysis will have to be verified by field surveys.
PRB: Has human activity put these resources at risk from damage by such natural disasters?
WorldFish Center: Indirectly, human activities have put these valuable resources at risk. Tom Hourigan, a coral reef expert for the U.S. National Marine Fisheries Service, has said that coral formations throughout the Indian Ocean were severely damaged by the El Nino warming event in 1997 and 1998 and were just beginning to recover when they were slammed by the tsunami last month. Coral reefs may also suffer extra damage as pollutants previously on land such as chemicals, oils from cars and garages, paints, and others will have been washed into their local environment.
In some parts of the world, developers and others have cut down mangroves without perhaps taking into account the true value of mangroves as coastal protection, fisheries' nurseries, and a sustainable source of timber. Although it is unlikely that coastal mangroves would have been able to fully protect coastal developments from the impact of these waves, their presence would have meant that other more population intensive activities would not have been taking place there.
Most coastal fisheries' resources in the region are overfished and severely depleted. The impact of a natural disaster such as the tsunami on these depleted stocks may have been greater than on stocks not as heavily fished. The resilience of overfished stocks to natural disasters is likely to be lower.
PRB:Are there freshwater fishing resources that might also have been damaged?
WorldFish Center: Freshwater fisheries may have been damaged in the short term, but it is more likely that they will recover rapidly due to the flushing effects of new fresh water. Perhaps more significantly, freshwater wells have been contaminated with salt water and the coastal soils covered with salt. The wells may recover if the water is pumped out and the salt water has not penetrated the underlying aquifer that delivers the water. The salty soil may take much longer to recover, putting an extra burden on coastal agriculture.
PRB: What about the destruction of boats and fishing gear by the tsunami? Could you discuss how devastating this might be for fishing livelihoods?
WorldFish Center: The loss of fishing boats and fishing gear will be very damaging to the local communities affected. However, such infrastructure can, in the long run, be replaced with outside assistance. In Andhra Pradesh state in India alone, some 2,000 fishing boats and 47,370 nets are reported lost. Nearly 300,000 fishermen were rendered jobless and they are estimated to be losing 50 million rupees in income a day. Many of the affected fisherfolk may have purchased their boats on a hire-purchase type of arrangement, and it is not clear what the effects will be now that the debts remain and the means of servicing the debt has been destroyed.
Also important is damage to harbors, jetties, ice plants, and the necessary infrastructure necessary to process and sell the fish once they have been landed. Worse, however, is the loss of individual families' breadwinners, and the effects this will have on the health and nutritional status of mothers and their children as well as the ability of the family to send children to school.
PRB: Have there been comparable disasters that have affected fisherfolk in South Asia, or is this a unique experience?
WorldFish Center: This is a unique experience within South Asia, within our lifetime, purely on its scale; the magnitude of the loss of life, the destruction to property. However, the 1998 flooding in Bangladesh is comparable; that "flood of the century" covered more than two-thirds of Bangladesh, causing crop losses of 2.04 million tons of rice, an amount equal to 10.5 percent of the country's target production in 1998-99. This flood threatened the health and lives of millions through food shortages caused by crop failure, loss of purchasing power, and the spread of waterborne disease.2
References
- Accessed online at www.reefbase.org/Tsunami.asp, on Jan. 14, 2005.
- Carlo del Ninno et al., "The 1998 Floods in Bangladesh: Disaster Impacts, Household Coping Strategies, and Responses," Research Report 122 (Washington, DC: International Food Policy Research Institute, 2001.)