DES MOINES, IOWA — Bill Gates, chairman of Microsoft and joint chair with his wife of the Bill and Melinda Gates Foundation, said the food crisis has forced hunger higher on the world’s agenda. But he cautioned participants in the 2009 Borlaug Dialogue in Des Moines on Oct. 15 that success in efforts to eliminate hunger in our generation required overcoming "an ideological wedge" that splits into two camps those who must work together.

On the one side are those who seek to increase agricultural productivity through technology, while on the other, there are those who advocate an environmental approach that promotes sustainability. The two sides say the world must choose which path to follow.

"It’s a false choice, and it’s dangerous to the field," Mr. Gates said. "It blocks important advances. It breeds hostility among people who need to work together, and it makes it hard to launch a comprehensive program to help poor farmers. The fact is, we need both productivity and sustainability, and there is no reason we can’t have both."

Mr. Gates said many environmental voices rightly point to excesses in the original Green Revolution, warning against the dangers of too much irrigation or fertilizer and cautioning against the consolidation of farms that could squeeze out smallholders.

"These are important points, and they underscore a crucial fact: The next Green Revolution has to be greener than the first," Mr. Gates said. "It must be guided by smallholder farmers, adapted to local circumstances, and sustainable for the economy and the environment." At the same time, it is wrong to restrict the spread of biotechnology to Sub-Saharan Africa "without regard to how much hunger and poverty might be reduced by it, or what the farmers themselves might want," he said.

"Some voices are instantly hostile to any emphasis on productivity," Mr. Gates said. "They act as if there is no emergency, even though in the poorest, hungriest places on earth, population is growing faster than productivity, and the climate is changing."

Mr. Gates referred to a Stanford University study that asserted if farmers in southern Africa plant the same varieties of maize in 2030 as they plant today, harsher conditions from climate change will reduce their productivity by more than 25%.

"Declining yields at a time of rising population in a region with millions of poor people means starvation," Mr. Gates asserted. "The charge is clear. We have to develop crops that can grow in a drought, that can survive a flood, that can resist pests and disease. We need higher yields on the same land in harsher weather. And we will never get it without a continuous and an urgent science-based search to increase productivity, especially on small farms in the developing world."

Mr. Gates said the Gates Foundation doesn’t advocate any particular scientific method but rather supports a range of agricultural techniques.

"In some of our grants, we include transgenic approaches because we believe they can help address farmers’ challenges faster and more efficiently than conventional breeding alone," Mr. Gates said. "Of course, these technologies must be subject to rigorous scientific review to ensure they are safe and effective. It’s the responsibility of governments, farmers and citizens, informed by excellent science, to choose the best and safest ways to feed their countries."

The Gates Foundation has funded several initiatives to support smallholders and follows two principles, Mr. Gates said. First, initiatives must directly benefit smallholders by helping them realize better yields, better soil, a better living and a better life. The second principle calls for improving the value chain. Mr. Gates said in addition to better seeds, smallholders need new tools and training, access to new markets to sell their surplus and stronger organizations to represent their interests.

He pointed to the Gates Foundation’s partnership with the World Food Program in which the W.F.P. buys crops from small farmers in the same countries where the food will be eaten.

"They’ve already purchased 17,000 tonnes of food from small farmers, helping them build the capacity to sell even more to the W.F.P. and other buyers in the future," he said.

Mr. Gates announced nine new grants totaling about $120 million that will assist small farmers span the value chain.