But another result was that some traditional crops were lost.

CHRISTOPHER CRUISE: The Food and Agriculture Organization says about two hundred fifty thousand plant species are now known to exist. The FAO notes that today, thirty thousand plant species could be eaten. Still, it says, only seven thousand have been used for food.

About one hundred twenty crops are grown to feed humans. The FAO says nine of those crops provide seventy five percent of human food. Rice, wheat and maize are said to supply more than half of human food.

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MARIO RITTER: Not all experts agree that a decrease in cultivated food crops is a crisis. A recent study showed a different situation, at least in the United States. The study examined records of plant varieties in America during the past century.

The study was the project of Paul Heald of the University of Illinois College of Law and Susannah Chapman of the Anthropology Department at the University of Georgia. They found that the total number of vegetable and apple crop varieties in the United States did not fall over the past century. Instead, Professor Heald says, the study may show a small increase in the number of varieties

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CHRISTOPHER CRUISE: Professor Heald and Ms. Chapman examined records of forty-two thousand vegetable crops. The crops were grown from nineteen three to two thousand four. They also studied apple variety records from nineteen hundred to two thousand.