The Earth has 2,149 barrier islands, 657 more than was believed ten years ago, the researchers from Duke University and from Meredith College in Raleigh (USA) have discovered, informes Livescience.com.
The latest study, completed in 2001, based on satellite images has identified 1492 islands. Now, scientists have used, in addition, topographic maps.
Barrier islands are long and narrow sand and sediment deposits, lying parallel to the coast, but separated by gulfs, estuaries or lagoons. Unlike ordinary islands, the barrier ones are alternatively formed and eroded because of the waves, tides and marine currents.
The 2,149 barrier islands spread over 21,000 km, representing 10% of the total length of the coastline in the world, concludes the 2011 study. Researchers have found this type of islands across all continents (except Antarctica) and in all oceans of the world. It is also mentioned that 74% of these islands are located in the northern hemisphere.
The barrier islands protect shores from erosion and storm damage, and can be the habitat to numerous wild animals. “This study proves that the barrier islands are present in any climate and in any sea, regardless of the waves level or tides”, said Orrin Pilkey from Duke University.
“The 657 islands newly discovered, have not taken shape in the last ten years”, explains Matthew Stutz from Meredith College. “They are old, but they could not be identified using the old technology, or they have been considered in the old studies as being something else”, said Stutz.
For example, in the past, researchers believed that the barrier islands can not exist in the seas with tides higher than 4 meters. However, the new study reveals that the longest chain of barrier islands – counting 54 islands and extended on 571 km – is in Brazil, a place where the tides reach a height of 7 meters.