About 10 percent of the crops grown in the world’s major food production regions are irrigated with groundwater that is non-renewable. In other words, aquifers are being drained faster than they’re refilling—a problem which will only get worse as the world continues to heat up, explained Michael Puma, director of Columbia’s Center for Climate Systems Research.

This is happening in major food producing regions such as the U.S. Great Plains and California’s Central Valley, and in Pakistan, India, northeastern China, and parts of Iran and Iraq.

Climate projections show that droughts will become more common in much of the U.S., especially the southwest. In other parts of the world, drought and water shortages are expected to affect the production of rice, which is a staple food for more than half of the people on Earth. During severe drought years, rainfed rice yields have decreased 17 to 40 percent. In South and Southeast Asia, 23 million hectares of rainfed rice production areas are already subject to water scarcity, and recurring drought affects almost 80 percent of the rainfed rice growing areas of Africa.

A recent study of global vegetable and legume production concluded that if greenhouse gas emissions continue on their current trajectory, yields could fall by 35 percent by 2100 due to water scarcity and increased salinity and ozone.