Along with gravel, sand is the most extracted natural resource on the planet, exceeding fossil fuels. Between 32 billion and 50 billion tonnes of the stuff is used every year to produce concrete for construction, glass for our mobile phones, and even our toothpaste includes an ingredient made from sand. As Kiran Pereira, founder of SandStories.org once said: “It's almost become like air, the air we breathe. We don't think too much about it, but you can't live without it.”

Sand’s universal appeal, however, has led to the unregulated and illegal mining of the resource in around 70 countries. “Sand mafias” who control some of these extractions and subsequent transactions have been known to threaten and even kill activists who speak out against their activities. In the last decade, battles over sand in the so-called “sand wars” have led to the loss of hundreds of lives in countries such as India and Kenya. If the unsustainable exploitation of sand continues, we could see demand outstrip supply by the middle of this century, according to a Nature comment piece. 

Part of this resource’s protection rests on our ability to keep track of it, but a new study has found that we have been measuring sand the wrong way.

“Not all sand is the same,” Associate Professor Ana Vila-Concejo from the University of Sydney, Australia, said in a statement. “Yet the models for assessing sand and how it moves mostly rely on one type. This means we have an inaccurate picture of what is happening…"

Whilst standard models assume that sand grains are spherical, which is the case for common sands made up of ground-down silica and quartz rocks, other types of sand go against the grain. Carbonate sands, for example, which come from shells, corals, and skeletons of marine animals, are better described as elliptical, less dense, and have more holes and edges.

As described in the study, published in Nature’s Scientific Reports, when this is accounted for, current models were found to have underestimated the surface area of carbonate sands by 35 percent. This has a substantial impact on the transport of these sands on the seafloor, which existing models overestimate by more than 20 percent.

“This means we are not accounting for sand correctly,” Vila-Concejo said.

Not only is our ability to accurately monitor sand important for its protection, but in areas where climate change threatens coastal erosion, its predicted response is crucial knowledge.

“Keeping track of carbonate sand will become increasingly important,” Dr Tristan Salles, also from the University of Sydney, said in a statement. “If islands and atolls [ring-shaped coral reefs] are at risk from erosion caused by sea-level rise, it will be vital to understand how the sands protecting them will respond to the ocean currents, waves and high-energy sea swells battering them.”

Based on observations of carbonate sand taken from near Heron Island on the Great Barrier Reef, the team have created a new transport for areas where that type is dominant.

“Understanding how, why and when sediments move is crucial to managing and predicting the effects of climate change and our new work will help in the development of mitigation and adaptation strategies,” Vila-Concejo concluded.