Impact of Tsunamis on Ecosystems

General impacts

The impact of the recent Asian tsunami on ecosystems from Indonesia to East Africa will take a long time and significant resources to assess. The first major report Status of Coral Reefs in Tsunami Affected Countries: 2005 has just been completed and confirms the earlier predictions about likely damage, made on this page, as follows:

There is likely damage to the structure and function of the coastal ecosystems (coral reefs, mangroves, sea grasses, estuarine mudflats):
  • The physical structure has been damaged by the force of the wave itself, physical removal of flora and fauna and increased sediment load which will have killed sediment sensitive corals and sea grasses by smothering. The extent of this damage is being assessed and will likely vary considerably depending on the local topography and hydrology.
  • Chemical changes have included saltwater intrusion, eutrophication (enrichment) of the water resulting from increased runoff, raw sewage and decomposition of flora and fauna including unrecovered bodies. There will be the slower decomposition of timber from mangroves, fishing boats and buildings.
  • Non biodegradable waste such as plastics has contributed to a build up in marine debris.
  • Toxic wastes, which were inadequately stored, may have been dispersed, as has been reported on beaches in Somalia.
  • Exotic (introduced) species used for aquaculture have escaped.
Finally, the biological structure of the ecosystem could be disrupted as various species at different trophic levels were differentially removed. With the structure altered, ecosystem functions could be altered.

Tropical Ecosystems

Coral reefs have been thought of as “nature's defense” and there is an early suggestion that the ecosystems in areas in which reefs were largely intact, such as the Surin Island chain off Thailand's west coast, may have survived better than areas where the coast has been modified by urban development, aquaculture and tourism. Keeping the reefs intact around the Maldives is credited with reducing the loss of life.

Mangroves are an important natural barrier as well as a profitable timber resource. Areas in Pichavaram and Muthupet, in the state of Tamil Nadu, India with dense mangroves suffered fewer human casualties and less damage to property compared to areas without mangroves. On Penang Island, the worst affected area in Malaysia, representatives of the Penang Inshore Fishermen Welfare Association observed that in areas where the mangrove forests were intact, there was reduced property damage and less impact on the coast.

Sandy beaches have been seriously damaged by the tsunami in some areas and sea turtle nesting sites have been destroyed. Coconuts are an integral part of the economy for many coastal communities and feature prominently in tsunami survival stories: people surviving by eating coconuts, people who survived by clinging on to coconut trees so as not to be washed away, and the Acehenese man who clung to a coconut palm and survived at sea for 9 days. Replanting coconuts to restore the sandy beach ecosystem will be an important part of the recovery process.

Long Term Ecological Research (LTER)

 
Long term ecological research (LTER) will be needed to assess the damage of the Asian tsunami on ecosystems. The focus will be on sites that have already been intensively studied over many years, such as southern India (Kerala and Tamil Nadu), Sri Lanka, west coast peninsular Malaysia and western Thailand. Attention should also be given to the changes in fisheries resources, taking note of observations from fishers on the changes that have occurred. There are many precedents for LTER following natural disasters such as tsunamis in Japan, hurricanes in the Caribbean and the damage caused by the oil spill from the Exxon Valdez in Alaska. LTER will be a useful adjunct to other efforts by the international community to restore the fisheries and livelihood of the coastal dwellers of the affected region.
 
 
Selected Sources: Science and Development Network in India, 30 December 2004 (not cited); Andrew Browne, Wall Street Journal, 31 December 2004, p A5; Meryl Williams (pers comm). Recent information is found in theStatus of Coral Reefs in Tsunami Affected Countries: 2005. The partners in the International Coral Reef Initiative requested that the Global Coral Reef Monitoring Network in partnership with Reef Check, ReefBase and the CORDIO (Coral Reef Degradation in the Indian Ocean) program update their report on the Status of Coral Reefs of the World: 2004 with a focus on the tsunami affected countries.

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