As the floodwaters of Cyclone Nargis began to recede from Myanmar's low-lying Irrawaddy Delta this week, at least one regional leader was quick to note that this devastating disaster could have been partially prevented through coastal preservation.
Surin Pitsuwan, secretary-general of the Association of South-East Asian Nations (ASEAN), mentioned in an address in Singapore that expanding coastal populations and widespread mangrove degradation played key roles in worsening the cyclone's impact. "The mangrove forests, which used to serve as buffer between the rising tide, between big waves and storms and the residential area... all those lands have been destroyed," Agence France-Presse reported him saying. "Human beings are now direct victims of such natural forces."
Mangrove forests, salt-tolerant trees and shrubs found mainly in intertidal areas of the tropics, provide critical breeding grounds and habitat for many plants and animals, including several high-value fish species. Ever since the 2005 Indian Ocean tsunami that devastated parts of Sri Lanka, Indonesia, and Thailand, mangroves have received greater attention for their potential role in protecting coastlines against storm surges. But their role as coastal guardians-including in places like the Irrawaddy Delta-is still disputed within the scientific community.
Of the 100,000 people who Myanmar officials say have perished or face imminent death if they do not receive humanitarian aid in the wake of the May 2 cyclone, many built their homes in areas once covered with mangrove forests. Myanmar has some of the highest remaining forest area in Southeast Asia, but the government junta has often encouraged converting mangroves to shrimp aquacultures or rice fields. The U.N. Food and Agriculture Organization estimates that Myanmar lost about 9 percent of its mangrove forests-48,500 hectares-between 1980 and 2005.
Mangrove roots hold together the shifting silt and other debris that flows down a delta and shapes coastal landscapes. By deterring erosion, mangroves prevent the debris from washing inland and damaging agricultural land. "It's pretty...clear, looking around the world, that it is generally accepted that mangroves help stop erosion and protect coastland," said Marc Spalding, a senior marine scientist with The Nature Conservancy.
Mangrove branches and roots may also reduce the surging energy of a massive storm wave as it approaches inland. "There are lots of structures that add friction to the movement of water through this fringing mangrove forest," said Ivan Valiela, a marine biologist with Woods Hole Research Center in Massachusetts.
But to effectively study the role of mangroves in slowing wave action, researchers need to compare a severely damaged mangrove coast with a similar mangrove coast that was not heavily affected. This has proven to be a major limitation and has prevented scientific consensus, said Valiela, editor of the journal Estuarine, Coastal, and Shelf Science.
Finn Danielsen, a senior ecologist with the Nordic Agency for Development and Ecology who has researched the protective power of mangroves during the Asian tsunami, said computer simulations have accurately measured the effect of mangroves. "There is no doubt that mangroves could have absorbed some of the energy of Hurricane Nargis," he said. "It is true that other factors also play a role, but this does not mean that the role of coastal tree vegetation is smaller."
Tom Smith, a research ecologist with the U.S. Geological Survey, considers himself one of the world's few researchers who challenges whether mangroves affect a wave's forces. Data on the subject is "scant and meager," Smith said. He considers studies that have relied upon computer simulations, satellite imagery, and field studies all to be flawed.
Smith concedes that many researchers are uncomfortable with his conclusions, due to concerns that this may slow the momentum of ongoing mangrove conservation efforts. But, he said, more emphasis should instead be placed on relocating people farther inland, which would protect them from dangerous oceanic storms and also help preserve mangrove forests.
According to the United Nations, nearly half of the world's population lives within 150 kilometers of a coast, and more are projected to move there in coming years due to population growth and tourism. Myanmar is no exception to this trend. The recent cyclone flooded the city of Yangôn, home to more than 4 million people, as well as several other cities of between 100,000 and 500,000 people. "Poorly constructed homes in low-lying, incredibly exposed areas... It's just set-up for this sort of disaster," Smith said.
Ben Block is a staff writer with the Worldwatch Institute who covers everything environmental for Eye on Earth. He can be reached at bblock@worldwatch.org.
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