BOMA, South Sudan—Tim Schilling trudged through the African wilderness, trailing a barefoot tribeswoman named Nyameron.

A sort of Indiana Jones of coffee, Mr. Schilling, 59 years old, was seeking wild strains of coffea Arabica, the fragrant beans used to make most of the world's lattes and cappuccinos. The Texas A&M University agronomist heads World Coffee Research, a nonprofit financed by Folgers coffee maker J.M. Smucker Co. , Peet's Coffee & Tea Inc. and others.

The group's goal is to expand the global coffee crop's tiny gene pool. But after four days of hiking on this plateau west of Ethiopia, Mr. Schilling's 15-member expedition—which included a coffee taxonomist, a Green Mountain Coffee Roasters Inc. executive, agriculture students and hired porters—still hadn't found any specimens that seemed new. They were hoping that Nyameron, a wild-coffee connoisseur they had met through a Murle tribal chief, could help.

Companies are turning to exploration to ensure future coffee supplies because production has leveled off even as demand has increased, causing coffee-bean prices to quadruple since 2001.

The world consumed 17.6 billion pounds of coffee beans last year, up from 2.6 billion in 1982, according to the U.S. Agriculture Department. But production in Colombia, which provides 10% of the world's Arabica beans, has dropped 36% since 2005. Output in Brazil, the world's leading Arabica producer, recently hit a four-year low.