This is the VOA Special English Development Report.

The United Nations says more than 850 million people do not have enough food. For this year's World Food Day observance last week, VOA reporters examined the current causes of hunger.

Poverty, disease and conflict have historically threatened food security. Now, rising food prices and issues like climate change add to these threats.

A new study warns of future losses in world food production because of crop damage from changes in the weather. William Cline wrote the study from the Center for Global Development in Washington. He says countries closest to the equator will be hardest hit.

For example, he predicts that if nothing is done, global warming could cut India's food production by up to forty percent by the year 2080. Africa and Latin America could lose twenty percent or more.

Governments concerned about global warming and dependence on oil are investing in biofuels from corn and other plants. But Lester Brown at the Earth Policy Institute in Washington says demand for fuel crops is pushing up food prices. He says the world's 860 million automobile owners are now in direct competition with the two billion poorest people.

This comes as grain supplies are at their lowest level in years. Experts see a number of reasons. These include not enough investment in agricultural technology. A loss of farmland to development. Droughts and floods made worse by climate change. And, growing competition for water.

Population growth also means a greater demand on food supplies. The United Nations predicts a population of more than eight billion by the year 2030.

By that time, demand for animal products could double, led by growing economies like China and India. Francois Le Gal of the World Bank says climate change and the globalization of trade raise the risk of spreading animal diseases. Experts say most countries are not ready for a health crisis caused by a disease jumping to humans.

And, finally, they say the growing population of cities is adding to the world's hunger problem. Danielle Nierenberg at the Worldwatch Institute in Washington says the poor can spend fifty to eighty percent of their money on food.

She points out that city people do not have farm animals to sell in times of need. So they are especially threatened when prices go up.

And that's the VOA Special English Development Report, written by Jill Moss.