2. Varadero, Cuba
People walk on a beach in Varadero, a 12-mile-long peninsula of white-sand beaches lined with resorts in the province of Matanzas around 135 kilometres (84 miles) from Havana May 5, 2010. REUTERS/Desmond Boylan

Sand appears to be almost limitless. In fact, researchers from the University of Hawaii have estimated that there may be roughly seven quintillion, five hundred quadrillion individual grains on the Earth's surface.

But humanity is using up sand faster than almost any other resource, regardless of the fact that it takes thousands, if not millions, of years for the material to replenish itself through erosive processes.

Sand and gravel account for the "largest volume of solid material extracted globally" according to a recent report from the United Nations Environmental Programme, which suggests that humans go through more than 40 billion tons of the stuff every year.

The material's versatility makes it incredibly important to a huge range of industries, including the electronics and agricultural sectors. However, by far the most prolific consumer is the construction industry which uses sand to produce everything from bricks and roads, to glass and concrete.

The production of concrete – which is made from cement, water, sand and gravel – alone consumes huge quantities. For every ton of cement produced – a total of 3.7 billion tons were produced in 2012 - the construction industry needs six to seven times the amount of sand and gravel.

This is not to mention the vast quantities of sand that are required for land reclamation projects, which are common in places such as Dubai and Singapore – the biggest sand importer in the world.

While we may not run out of accessible sand for a very long time, we are causing damage to the environment in the process

Cambodia, Vietnam, Malaysia and Cambodia have all banned sand exports to Singapore due to the havoc the practice wreaks. Globally, the environmental problems caused by sand extraction are wide-ranging, according to the report.

"The volume being extracted globally is having a major impact on rivers, deltas and coastal and marine ecosystems, resulting in loss of land through river or coastal erosion, lowering of the water table and decreases in the amount of sediment supply," the authors write.

These problems can be particularly acute in countries where environmental regulations are less stringent.

Ocean sand mining involves the use of suction dredge barges, which essentially work like giant vacuum cleaners. This process can be devastating for both the marine environment and the flora and fauna that call the seabed home.

Similarly, the extraction of sand from rivers has led to severe damage to river basins, including pollution and changes in pH levels.

Furthermore, the removal of sand from beaches – which often occurs due to illegal activity – can leave shorelines unprotected against the power of the waves, a particularly significant problem in a world of rising sea levels.

"Despite the colossal quantities of sand and gravel being used, our increasing dependence on them and the significant impact that their extraction has on the environment, this issue has been mostly ignored by policy makers and remains largely unknown by the general public," the authors say.