There are sixty-eight million hectares of genetically engineered crops. This is about five percent of all cropland in the world, and expanding. But debate over how best to use this biological technology continues.

Experts compare the rise of biotechnology to the period of change in the nineteen-sixties and seventies. The Green Revolution produced the modern systems and chemicals of agriculture. Productivity increased in many countries.

Today, the United Nations and others are calling for a Gene Revolution. Experts say the world must find new ways to fight hunger and feed its growing population.

But, unlike the Green Revolution, biotechnology has been supported mainly by private investment. Businesses are unwilling to share trade secrets with countries that do not recognize their property rights. Companies also want to earn a profit, so they develop crops for large markets.

Ninety-nine percent of genetically engineered crops are either soybeans, corn, cotton or canola. The U.N. Food and Agriculture Organization says little research has been done on food crops like wheat, rice, potatoes and cassava. An F.A.O. report last month expressed concern that biotechnology is not helping developing nations.

Six countries grew ninety-nine percent of all biotech crops last year: Argentina, Brazil, Canada, China, South Africa and the United States. Almost all these crops have special genes to resist damage by insects or by chemicals used to kill unwanted plants. The F.A.O. says there is little research on biotech plants that could resist crop failure in poor countries, or provide extra vitamins.

Director-General Jacques Diouf says scientists generally agree that foods made from genetically engineered crops are safe to eat. But he adds that little is known about their long-term effects. He also says there is less scientific agreement on the environmental effects, so each product must be carefully observed.

Public opinion is a big issue in the debate. Opponents say there may be unknown health dangers. Some poor nations have refused any food aid that contains genetically engineered products.

Yet the industry has had some successes recently. Last month the European Union ended a six-year suspension of approval for new biotech foods. And Brazil has been moving to let farmers plant genetically engineered soybeans.

This VOA Special English Agriculture Report was written by Mario Ritter. This is Steve Ember.