This undated file photo shows Sudanese farmer, in the capital Khartoum's district of Jureif Gharb. (ASHRAF SHAZLY / AFP)

Roughly 40 percent  of the world’s people live in farming areas facing large water shortages, and scarce supplies pose an increasing risk to food security as populations swell and the climate changes, the United Nations said.

Of the total, 1.2 billion people - a sixth of the global population - are in areas with severely constrained water supplies, and the amount of freshwater available per person has dropped 20 percent in the past two decades, according to a UN report

About 3.2 billion people live in agricultural areas with “high to very high” water shortages and competition over resources is rising, the UN’s Food and Agriculture Organization said in a report. Many farms that depend on rain are at risk as severe droughts become more common, and bigger global incomes are spurring demand for water-intensive foods like meat and dairy.

Of the total, 1.2 billion people - a sixth of the global population - are in areas with severely constrained water supplies, and the amount of freshwater available per person has dropped 20 percent in the past two decades, according to the report. Swaths of Asia and North Africa have been most affected, while small amounts of people in Europe and the Americas have seen extreme restrictions.

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Agriculture accounts for 70 percent of the world’s freshwater withdrawals, and the UN called for better management to keep resources in check and boost agricultural yields. Earlier this year, CME Group Inc announced its first futures contracts on water supplies in California, which has been afflicted by droughts and wildfire.

READ MORE: Achieving zero hunger

Almost two-thirds of the world’s population is expected to face water shortages by 2025, according to the bourse.