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Scientists discover 657 new islands

The Earth has many more barrier islands than previously thought, a global survey has found.

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Previously, for instance, scientists believed barrier islands couldn't exist in locations with seasonal tides of more than 13 feet (4 meters). Yet the new survey identifies the world's longest chain of barrier islands along a stretch of the equatorial coast of Brazil, where spring tides reach 23 feet (7 meters).

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The 54-island chain extends 355 miles (571 kilometers) along the fringe of a mangrove forest south of the mouth of the Amazon River. Past surveys didn't recognize it as a barrier island coast partly because older, low-resolution satellite images didn't show a clear separation between the islands and mangrove, Stutz says, but also because the chain didn't match the wave-tide criteria used to classify barrier islands in the United States, where most studies have been conducted.

Scientists failed to consider that supplies of replenishing sand are so plentiful along the equatorial Brazilian coast that they can compensate for the erosion caused by higher spring tides.

Under threat

The new findings illustrate the need for a new way to classify and study barrier islands, so that scientists can predict which of today's islands might be in danger of disappearing in the near future, the researchers say.

The potential for significant climate and sea level change this century "underscores the need to improve our understanding of the fundamental roles these factors have played historically in island evolution, in order to help us better predict future impacts," Pilkey said.

Barrier islands are under tremendous development pressure, which unfortunately is timed to a period of rising sea levels and shoreline retreat, Pilkey said. A developed barrier island, held in place by seawalls, jetties or groins, can't migrate and "essentially becomes a sitting duck unable to respond to the changes occurring around it."

The study is detailed in the March edition of the Journal of Coastal Research.

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