"In the next few decades, a major international effort is needed to feed the world when the population soars from six to nine billion. We might call it a second Green Revolution," Diouf told the World Affairs Council in a speech in San Francisco.

A copy of the speech was released in the FAO's Rome headquarters Wednesday.

The original Green Revolution of the 1950s and 60s doubled world food production by bringing the power of science to agriculture, but "relied on the lavish use of inputs such as water, fertilizer and pesticides," the FAO chief said.

"The task ahead may well prove harder," Diouf warned. "We not only need to grow an extra one billion tonnes of cereals a year by 2050 but do so from a diminishing resource base of land and water in many of the worlds regions, and in an environment increasingly threatened by global warming and climate change."

The FAO can play a leading role in bringing about this second Green Revolution, Diouf explained, by ensuring that it be based on the wise and efficient use of available natural resources rather than on the introduction of new varieties of wheat or rice.

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