The U.N.'s environment program is warning about the overuse of sand resources, saying a three-fold increase in demand over the last 20 years amid increasing population, urbanization and building work has contributed to beach erosion, flooding and drought.

In a new report launched Tuesday, UNEP urged a re-think about the use of the world's second-most extracted resource, after water, by industry, governments and the public.

UNEP said demand for sand and gravel amounts to 40-50 billion tons every year, and pointed to the need for conservation, recycling and a look for alternatives like sawdust.

Pascal Peduzzi, director of a UNEP program with the University of Geneva, said more thought needs to be taken: "We aren't very smart about how we use sand, because we think: This is just sand."