Infrastructure holds civilization together. Transportation and housing require lots of concrete. Concrete requires sand. As China builds and much of the world repairs, the demand for concrete has created a demand for sand. Our buildings and roads are piles of sand held together chemically. We stack beaches into buildings.The demand is so great that pirating is happening, as are turf wars. As our population grows we approach and reach resource limits for things than water and land. Sand may become expensive, limiting growth and repair.