Global demand for sand and gravel, used extensively in construction, is about 50 billion tons or an average of 18 kg (40 lb) per person per day, according to a report published by the UN Environment Program (UNEP).

Extraction in rivers and beaches has increased pollution and flooding, lowered groundwater levels, hurt marine life, and exacerbated the occurrence and severity of landslides and drought, it said.

"We are spending our sand 'budget' faster than we can produce it responsibly," Joyce Msuya, UNEP's acting executive director, said in a statement.

"For one of the most traded commodities on the planet, it is one of the least regulated activities, and there is very low general awareness about extraction impacts."

Growing populations, increasing urbanization, land reclamation projects, and rapid infrastructure development in countries such as China and India have increased demand for sand three-fold over the last two decades, the UNEP said.

Meanwhile, damming of rivers and excessive extraction have reduced the sediment carried by rivers to coastal areas, leading to reduced deposits in river deltas and faster beach erosion.

"Communities in the Asian deltas are the biggest losers, with the combined effect of sand mining, hydropower dams and groundwater extraction causing large areas of land to sink and shrink," said Marc Goichot at the Worldwide Fund for Nature.

"But as long as demand for sand remains high and no alternative sourcing is available, enforcement is close to impossible, as the economy is based on sand," said Goichot, a water expert who contributed to the UNEP report.

Current legal frameworks are not sufficient, and "sand mafias" comprising builders, businessmen and dealers in countries such as Cambodia, Vietnam, India, Kenya and Sierra Leone regularly flout existing laws, said the UNEP.

The science to support responsible consumption and extraction is lagging, it said, adding that new technologies and materials that can substitute or limit the use of traditional concrete are growing in use, but still limited.

In India, a 2017 Thomson Reuters Foundation investigation revealed that workers were drowning while illegally mining sand in some parts of the country.

While awareness of the impacts of sand mining have grown, and more laws are in place, greater efforts are needed to map supply and demand for effective regulation, said Sumaira Abdulali of environmental advocacy group Awaaz Foundation.

"Communities are losing their land and their homes because of sand mining, but they are split over the issue because some people make a living from it, while others say it is ruining their lives," she told the Thomson Reuters Foundation.

"Sand is too plain, too ubiquitous to get the sort of attention that illegally mined diamonds have. But it deserves just as much attention, because its impact is so tremendous."