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Many of you will have heard that “there are more stars in the universe than grains of sand on our beaches”. And it is true, despite the fact that imagine this material many times, almost as an infinite resource. However, it is not so. But, how many grains of sand there are on Earth exactly? A new study points out that we are doing a count “misleading” of this basic raw material in the construction and that, in addition, may be affected by climate change and the rise of the oceans.

“Not all sand is equal,” explains Ana Vila-Concejo , associate professor of the Faculty of Geosciences of the University of Sydney and one of the authors of the study which is now published in “Nature Scientific Reports”. “However, the models to assess the sand and how it moves is mainly based on one of the types . This means that we have an inaccurate image of what is happening, especially in coastal areas that are vulnerable to climate change.”

Amin Riazi , of the University of the Eastern Mediterranean, she worked with Vila-Council to develop new systems that take into account the different forms of the grains of sand. The standard models assume that the sand grains are spherical, what is good for the sands common compound of silica and rocks of quartz. But for the composite carbonate derived from shells, corals and skeletons marine animals not served : they tend to be grains ellipsoidal, less dense and with more holes and edges. Taking this into account, the researchers estimated that has not been taken into account for 35% of the surface of the sands carbonate .

And that is not all. The team has shown that engineering models standard also overestimate the transport of the sands of carbonate in the bottom of the sea in more than 20% and underestimate the transport suspended in at least a 10% . “This means that we are not counting the arena correctly,” says Vila-Concejo. “Although this has an impact on construction and manufacturing, could also have a great effect on the management of coastal areas affected by climate change.”

The “dirty war” by the sand

sand is used throughout the industry. From the glass of the mobile phones to the highways, the grains are used in all of our economy . In fact, the sand and gravel are the materials most extracted raw material on the planet, even surpassing fossil fuels. And, therefore, there is a kind of “war” by the sand that is extracted illegally this raw material (an article published in “Nature” revealed that this traffic occurs in 70 countries around the world and that hundreds of people have died because of these battles.

“If the wars of sand do not occur in Australia, we have areas with coastal erosion and chronic loss of sand, as in beach Jimmys in Port Stephens,” says Vila-Concejo.

New mathematical models

The team took sand of carbonate near Heron Island , in the Great Barrier Reef, and observed how it responded in the experimental conditions. On the basis of these measurements, they developed new mathematical equations that predict much better how to move the sands of carbonate. After, we compared with existing data on the movement of sand, carbonate accumulated during six years of observations on the north coast of Oahu, Hawaii.

professor Ana Vola-Council collecting samples in the Bay of Tomales, California – University of Sydney

“to Do a follow-up of the sand of carbonate will be increasingly important,” says Tristan Salles also of the Faculty of Geosciences. “If the islands and atolls are at risk from the erosion caused by the sea level rise, will be vital to understand how the sands that protect them will respond to ocean currents, the waves and the energy of the sea that hit”. In addition, these new equations can be used for other sediments.

“This means that we can develop an image much more accurate of how the changing ocean will affect the marine ecosystems where the sands of carbonate are dominant,” says Vila-Concejo. “ to Understand how, why and when to move sediment it is crucial to manage and predict the effects of climate change and our new work will help in the development of strategies for mitigation and adaptation”.