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Trees protected villages from tsunami waves

In India, trees growing along the coastline helped to protect villages from the "walls of water" or tsunami waves that were triggered by a powerful earthquake that struck beneath the Indian Ocean on 26 December 2004, scientists have discovered.

Along parts of the 21-kilometer stretch of coastline in southeastern India that the scientists studied, special wetland forests called "mangroves" grow. Along other parts of this short chunk of Indian Ocean coastline, beach-forest trees grow. In still other areas, most or all of the trees have been cut down.

Villages behind trees generally suffered much less destruction from tsunami waves than villages not protected by trees, according to new research from Finn Danielsen from the Nordic Agency for Development and Ecology in Copenhagen, Denmark and his team of scientists.

"We wanted to understand if human activities such as cutting down trees along the coastline worsened the destruction caused by the tsunami waves," Danielsen said.

This is just what the researchers think they found. It appears that the trees absorbed some of the energy from the tsunami waves -- energy that might otherwise have destroyed whatever was behind the trees. But Danielsen was quick to mention that the area in India they studied was not the hardest hit by the tsunami.

Trees growing along the coast would probably not have protected against the horrible destruction that occurred in Indonesia, and other areas where the tsunami waves were the strongest, Danielsen explained.

Along the stretch of coastline the researchers studied, the tsunami waves appear to have hit the entire area with about the same strength. The tallest tsunami waves in this area were probably about 4.5 meters in height.

Mangrove forests are one of the world's most threatened tropical ecosystems in the world. The trees and shrubs that make up mangrove forests grow in salty, wetlands in tropical and subtropical areas of the world. Protecting or replanting coastal mangroves may help communities shield themselves from future tsunamis and storms, according to the authors.

This research appears in the 28 October 2005 issue of the journal Science.