Most of Australia is also classified as drylands, along with much of the western U.S., parts of southern Africa, and patches of desert in South America.

CNN: Growing deserts 'a global problem'

Drylands, which range from "dry sub-humid" to "hyper-arid" regions, make up more than 40 percent of the world's land surface and are home to two billion people.

CNN: Growing deserts 'a global problem'

Desertification has also been linked to health problems caused by dust storms, poverty and a drop in farm production, with infant mortality in drylands double the rate elsewhere in developing nations.

CNN: Growing deserts 'a global problem'