This process of desertification is particularly acute in China, where more than 400 million people are affected by problems that include the loss of valuable agricultural land and huge sandstorms that batter Beijing.
But now the country is fighting back.
Adam Shaw heads to Doulun County, Inner Mongolia, where the authorities have turned to a low-tech approach to keep the Gobi Desert at bay.
They are building the Great Green Wall, which involves planting millions of trees to block the advancing tide. But will it be enough?