US drought and dust storms affect crops
2 July 2014 Last updated at 22:11 BST
Parts of the United States are experiencing the worst drought for decades, with farmers warning that harvests are being badly hit.
The state of Oklahoma has endured persistent drought for the past three-and-a-half years and people there are fearful of a return of the so-called Dust Bowl conditions of the 1930s.
The BBC's science editor David Shukman visited one of the worst-affected areas, known as the Oklahoma Panhandle.