NAIROBI, April 26( Xinhua)--Extraction of sand along oceans' shorelines as well as riverbeds must be capped to limit damage to fragile ecosystems and shield coastal communities from storm surges, the UN Environment Programme( UNEP) said in a report. The report, titled" Sand and Sustainability: 10 Strategic Recommendations to Avert a Crisis" and compiled by UNEP's GRID-Geneva team, reveals that sand was the most exploited resource globally after water, with 50 billion metric tons being harvested