After water, sand and gravel are the most used natural materials in the world. But a looming global shortage has led to a boom in clandestine sand mining and even outright theft. In the southern Indian state of Tamil Nadu, authorities are battling a so-called “sand mafia” who supply the construction industry through illegal dredging of riverbanks. Last year Malaysia became the latest country in the region to ban the sale and export of its sand, demand for which has soared as Singapore seeks to reclaim land from the sea. A decade ago an entire beach, 500 truckloads, was stolen from a resort in northern Jamaica and, it is believed, sold to rival operators.