“If the world population continues to increase at the same rate, we will destroy the species,” he declared.

Traveling to Norway, the land of his ancestors, to receive the award, he warned the Nobel audience that the struggle against hunger had not been won. “We may be at high tide now, but ebb tide could soon set in if we become complacent and relax our efforts,” he said. Twice more in his lifetime, in the 1970s and again in 2008, those words would prove prescient as food shortages and high prices caused global unrest.

His Nobel Prize was the culmination of a storied life in agriculture that began when he was a boy growing up on a farm in Iowa, wondering why plants grew better in some places than others. His was also an unlikely career path, one that began in earnest near the end of World War II, when Dr. Borlaug walked away from a promising job at DuPont, the chemical company, to take a position in Mexico trying to help farmers improve their crops.

The job was part of an assault on hunger in Mexico that was devised in Manhattan, at the offices of the Rockefeller Foundation, with political support in Washington. But it was not a career choice calculated to lead to fame or honor.

Indeed, on first seeing the situation in Mexico for himself, Dr. Borlaug reacted with near despair. Mexican soils were depleted, the crops were ravaged by disease, yields were low and the farmers could not feed themselves, much less improve their lot by selling surplus.

“These places I’ve seen have clubbed my mind  they are so poor and depressing,” he wrote to his wife after his first extended sojourn in the country. “I don’t know what we can do to help these people, but we’ve got to do something.” The next few years were ones of toil and privation as Dr. Borlaug and his colleagues, with scant funds or equipment, set to work improving yields in tropical crop varieties.