WITH the world’s aid resources concentrated on the immediate needs of survivors, little has so far been done to address the tsunami’s environmental impact. But the recovery of coastal ecosystems will be crucial as fractured communities try to piece their lives back together.
Along the Indonesian coast, for example, habitats change rapidly as you move inland from the water’s edge. “A kilometre will take you through at least two zones,” says Lisa Curran, director of the Tropical Resources Institute at Yale University. This means that the waves could have torn out entire ecosystems along vast stretches, leaving little from which they could regenerate. Moreover, Aceh, the most heavily hit province of Sumatra, was also one of the most biologically rich. The less damaged regions to the south are far more densely settled so they support less natural vegetation to recolonise devastated areas.
Only when fishermen return to the sea in numbers will the impact on fish stocks become clear. In some places, the waves have probably pounded coral reefs to rubble, ripped out mangroves and buried habitats under a blanket of sediment. In most cases this will reduce fish numbers, but in deeper waters, nutrient-rich sediment might increase fish stocks by fertilising plankton says Serge Garcia, director of the fisheries resources division of the UN Food and Agriculture Organization.
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The US National Oceanic and Atmospheric Administration predicts that some coastal ecosystems “could take centuries to fully recuperate” – typically shallow bays normally protected from high-energy waves. However, the NOAA expects estuaries, mangroves and seagrass habitats to recover within a few months or years.
Masses of man-made debris from fishing nets to cars will have been washed out to sea. Much of this will contain chemicals such as oils and paints that could kill corals and other filter feeders. And its impact might not be apparent for years.
“The waves will have torn out entire ecosystems along vast stretches, leaving little from which they could regenerate”
Navigation at sea will be more hazardous. Buoys have been torn out or shifted by the waves, and harbours may need to be remapped before ships can enter them, since shifting sediments and shipwrecks may now be blocking former channels. “It’s been surprising to me how much shoreline change there has been,” says Chris Andreasen, chief hydrographer for the US National Geospatial-Intelligence Agency.
The destruction on land may also promote the spread of mosquito-borne diseases such as malaria. Only a few mosquito species can breed in salty water, so the tsunami will have initially reduced their numbers. However, the devastated landscape will form an excellent breeding ground. “Where you have debris, you have lots of opportunity for water to pool in cup-sized depressions. That’s ample for mosquitoes,” says William Schaffner, an infectious-disease expert at Vanderbilt University in Nashville, Tennessee.
But the tsunami’s biggest effect on terrestrial ecosystems may be an indirect one, Curran says. Hundreds of thousands of homeless coastal dwellers will need to find new places to settle, at least for a few months or years. That will bring damage to ecosystems far beyond the reach of the waves.
