All over the world, industrial sand mining is extracting river sediment much, much faster than Earth's natural cycles can replenish it. Sand mining has progressively altered the Paraná and Tocantins Rivers in Brazil, which are part of the Amazon Basin. "River sand is particularly valued for construction because its grains commonly provide suitable friction and because it is generally non-saline." It's the interlocking grains of river sand that make it particularly suitable for land reclamation. A worker watches a sand excavator along the Mekong River in Laos, dredging sand to make cement.