Scientists estimate there are at least 7.5 x 1018, or seven quintillion, five hundred quadrillion, grains of sand on the Earth. This unimaginably high number isn't surprising, however.

What few people realize is that the ability to pin a number on a natural resource means this resource is finite -- and will be used up one day. Right now, the 7.5 x 1018 grains of sand will become an endangered natural resource in the future because of excessive sand mining and extraction.

In short, the world is running out of sand and it just doesn’t know it.

What the world urgently needs now is a global agenda to prevent sand from being overused, said a group of scientists from the University of Colorado Boulder, the University of Illinois, the University of Hull and Arizona State University.

A commentary by these concerned scientists published in the journal Nature argues that more information is urgently needed to assess the actual extent of sand scarcity. It said sand and gravel are being extracted faster than they can be replaced.

Fueling this huge demand for sand is rapid urbanization and global population growth. It’s estimated anywhere from 32 billion to 50 billion tons of sand is extracted globally each year.

Then there’s the little known problem of illegal sand mining that’s now been documented in 70 countries. There have been deadly battles over sand that’s killed hundreds of people in recent years, including local citizens, police officers and government officials.

"The fact that sand is such a fundamental component of modern society, and yet we have no clear idea of how much sand we remove from our rivers every year, or even how much sand is naturally available, makes ensuring this industry is sustainable very, very difficult" said Chris Hackney, research fellow at the University of Hull's Energy and Environment Institute.

"It's time that sand was given the same focus on the world stage as other global commodities such as oil, gas and precious metals."

Unrestricted sand mining from rivers and beaches has massive impacts on ecology, infrastructure and national economies.

"From 2000-2100 it is projected there will be a 300 percent increase in sand demand and 400 percent increase in prices," said Mette Bendixen, a researcher at CU Boulder's Institute of Arctic and Alpine Research (INSTAAR).

"We urgently require a monitoring program to address the current data and knowledge gap, and thus fully assess the magnitude of sand scarcity. It is up to the scientific community, governments and policy makers to take the steps needed to make this happen."

The concerned scientists say a lack of oversight and monitoring of sand resources is leading to unsustainable exploitation, planning and trade.

"Politically and socially, we must ask: If we can send probes to the depths of the oceans or the furthest regions of the solar system, is it too much to expect that we possess a reliable understanding of sand mining in the world's great rivers, and on which so much of the world's human population, rely?" asked Jim Best, a professor at the University of Illinois Department of Geology.

The scientists argue current extraction rates and sand needs are unsustainable. There is now a need to recycle concrete and develop alternative to sand such as crushed rocks or plastic waste.