In the world of events occur, which many of us have not even heard of. We are talking about hundreds of new islands have been discovered by researchers all over the place in the recent past. On Earth, there are 657 on the barrier islands than previously thought, according to a new global survey conducted by researchers at Duke University.
Researchers have identified a total of 2,149 barrier islands worldwide using satellite images, topographical maps and navigational charts. The new result is much higher than the 1,492 islands identified in a 2001 survey conducted without the aid of publicly available satellite images.
The barrier islands or reefs are often shaped in the form of chains of long, low, narrow coastal deposits of sand and sediment, extending parallel to the coast, but separated from them by bays, estuaries or lagoons. In contrast to fixed landforms, barrier islands are built, destroyed and re-created and migrate through time in response to waves, tides, currents and other physical processes in the open ocean environment.
Earlier always reported that the barrier islands around the world reaching about 21,000 kilometers in length. They are found along all continents except Antarctica and in all oceans, and they make up about 10% of the continental coasts of the earth. On the northern hemisphere is 74% of the islands.
Barrier reefs provide protection for low-mounted mainland coast from erosion and storm damage, and also can serve as a habitat for some species. The country with the largest number of islands (405) are the United States, including those that are found along the Alaskan Arctic coast.
"This provides proof that barrier islands exist in every climate, providing a combination of tides" - said research team member Orrin Pilkey of Duke University. "We found that the barrier reefs exist wherever there is a flat piece of land near the shore, a rational supply of sand, enough waves to move sand or sediment and slightly elevated level of the sea, which forms a curved coast."
Recently opened the barrier island miraculously appeared in the last decade. They have long existed, but were ignored or not included in the classification in past studies. First, for example, scientists believed that barrier islands could not exist in areas with seasonal ebb and flow of the value of more than 4 meters. But now, a new survey has identified banks the world’s longest chain of barrier islands that stretches along the equatorial coast of Brazil, where spring tides reach seven meters.
The chain’s 54 islands stretches for 571 km along the edge of the mangrove forest, south of the mouth of the Amazon River. Past studies did not recognize them as a coastal barrier islands as older satellite systems with low-resolution images did not show a clear separation between the islands and mangrove forests. They have also been ignored as the chain does not meet the criteria of the wave tides used to classify barrier islands in the United States, where most studies have been conducted.
The scientists were wrong, considering that the supply of additional sand is so plentiful along the equatorial Brazilian coast that they can compensate for the erosion caused by higher spring tides. New findings illustrate the need for a new method of classification and study barrier islands, so that scientists can predict which of today’s islands may be threatened with extinction in the near future.
"The potential for significant climate change and sea level rise in this century, emphasizes the need to improve our understanding of the fundamental roles these factors have played historically in island evolution, in order that we can better and more accurately predict the future impact," - said Pilkey.
Barrier islands are under tremendous development pressure, which unfortunately, as reported by Pilkey is synchronized with the period of sea level rise and coastal retreat. Formed a barrier island that hold seawalls and breakwaters, can not migrate and essentially become sedentary, not being able to react to the changes taking place around him.
The assay is described in detail in the March edition of the journal "Journal of Coastal Research".
Original: LiveScience Translation: M. Potter